Displays

In-situ oil burning (isOB) is one of the oil-spill mitigation measures and has been used after some major oil-spill events such as the Deepwater Horizon oil spill in the Gulf of Mexico. Although the ecological impact of oil spills and mitigation measures on the marine ecosystem are of great interest, the toxicity and biodegradation potential of isOB by-products have been poorly addressed and mainly are an unknown.

We investigated the effects of burned oil residue and soot deposition on the marine plankton communities of the oligotrophic Eastern Mediterranean Sea using a mesocosm experimental approach. Coastal water (collected at 300 m from the coast, north of Crete, Greece) was incubated in 3.5 m³ mesocosms for 26 days. Three different treatments in triplicates were tested. In one treatment, 2 L of Iranian Crude Oil were added and burned (Burned treatment) while soot was collected and deposited in the form of artificial rain in more mesocosms (Soot treatment) using a custom-designed soot collection apparatus. The third treatment served as the non-contaminated control (Control treatment). Samples were collected at 9 time points (from Day 0 to Day 26) and the plankton, from viruses to micro-plankton, was studied using flow cytometry and inverted microscopy.  

Although the abundance of prokaryotes was slightly decreased in Burned and Soot treatments compared to the Control, the percentage of active heterotrophic bacteria and their relative size (based on their cytometric characteristics) was higher, which is an indication of increased bacterial activity in the contaminated treatments. Viral to Prokaryote Ratio and pico/nano-eukaryotic abundance were significantly increased in the Burned treatment compared to the Control, which could explain the lower bacterial abundance, despite the estimated increased activity, in the Burned treatment. Also, ciliate abundance was significantly lower in the Burned treatment while the opposite was observed in the Soot treatment (up to three orders of magnitude difference between Burned and Soot) compared to Control. Moreover, soot deposits seem to have had a positive effect on the abundance of dinoflagellates and diatoms.

To our knowledge, this is the first experiment to study the effects of isOB on whole marine plankton communities. It is evident that the in-situ oil burning has a significant effect on the plankton communities not only at the event site but also on distant areas through the soot deposition.     

How to cite: Magiopoulos, I., Chantzaras, C., Symiakaki, K., Antoniou, E., Pavloudi, C., Romano, F., Piperakis, G., Zanaroli, G., Kalogerakis, N., and Pitta, P.: To burn or not to burn? Impact of in-situ oil burning by-products on marine plankton: A mesocosm experimental approach , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14807, https://doi.org/10.5194/egusphere-egu2020-14807, 2020.

The coastal systems are among the most dynamic natural systems, being extreme complex zones in which chemical, physical and biological processes interact at different spatial and temporal scales. A holistic approach, based on the integration of multiple monitoring tools for data collection (i.e. satellite imagery, numerical models and in situ observations), may provide different information about coastal ecosystems, at different spatial and temporal scales. Of course, none of these tools is perfect, being each characterized by intrinsic errors and therefore specific uncertainty, the latter also considered as an important subject of investigation.

In this context, our goal is to understand the spatial and temporal distribution of phytoplanktonic biomass in coastal waters in order to evaluate the phytoplankton dynamics in a polluted coastal area located in the northern Tyrrhenian Sea. Long-term high-resolution observations (weekly sampling from 2015 to 2017) of phytoplankton biomass at a coastal site from the C-CEMS observing system (central Tyrrhenian Sea offshore Civitavecchia) are presented, discussed and integrated with the analysis data provided by the Copernicus Marine Environment Monitoring Services (CMEMS) for the Mediterranean Sea, generated by the MedBFM model system, and with satellite observations (from CMEMS Ocean Colour database). The focus of this work is twofold: on one side, to analyse the phytoplankton bloom dynamics of the Civitavecchia coastal ecosystem by adopting a multi-platform approach which integrates CMEMS products and C-CEMS in situ data, on the other side, to propose best practices to integrate multi-platform data streams that may be adopted also in other similar contexts of coastal ecosystems.

The analysis of the time series of phytoplankton provided by in situ, satellite and model data show the typical dynamics of temperate climate, characterized by spring and autumn blooms, together with a significant interannual variability. The EOF analysis has shown consistency among multi-platform datasets. Notwithstanding the incongruences, specifically related to the chlorophyll model outputs, which underestimate the in situ and satellite data and that may be related to some representativeness error (i.e. river nutrient inputs based on climatological information and grid resolution), the intercomparison is beneficial to provide information at different temporal and spatial scales of the phytoplankton dynamics.

How to cite: Salon, S., Martellucci, R., and Cossarini, G.: Proposed best practices for the integration of in situ observations and large scale analysis and forecast systems: case study of the phytoplankton blooming off a Tyrrhenian coastal site, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14041, https://doi.org/10.5194/egusphere-egu2020-14041, 2020.

Natural climate variability influences phytoplankton community both directly and indirectly by altering ocean stratification and availabilities of nutrient and light, or grazing pressure. The world’s largest ecosystem, North Pacific Subtropical Gyre (NPSG), is largely controlled by basin-scale decadal climate variability, such as the North Pacific Gyre Oscillation and the Pacific Decadal Oscillation. These indices have two phases, known as warm phase and cool phase, respectively. Previous studies reported that warm phase was related to the dominance of pico-phytoplankton induced by warm temperature anomaly (i.e., strong stratification) while cool phase was related to the dominance of nano-phytoplankton induced by cold temperature anomaly (i.e., weak stratification). Besides the impact of natural climate variability, anthropogenic global warming has accelerated in recent years and it might have abnormal impact on marine ecosystems. However, there is little information about the responses of phytoplankton community to recent climate change in the NPSG. Here, we present the temporal variations of deseasonalized and normalized NPSG phytoplankton community using phytoplankton pigment concentrations and cell densities, obtained on monthly intervals over the period 1988−2018 at Station ALOHA (22°45’N, 158°W). These variations were compared with the variations of climate indices, physical, and biogeochemical parameters from Station ALOHA. The NPSG climate indices showed five phase transitions; warm (~1997) – cool (1998−2002) – warm (2003−2006) – cool (2007−2013) – warm (2014~). Before 2006 year, the phase transitions of phytoplankton community (pico→nano→pico) were coincident with physical factors (e.g., stratification; strong→weak→strong) and biogeochemical factors (e.g., particle export; low→high→low), coupling with phases of climate indices. However, interestingly, following the recent rapid rise in greenhouse gas emission (since 2007), phytoplankton community, even under continued coupling of climate indices and physical factors, showed only dominance of pico-phytoplankton, decoupling with the phases of climate indices. These findings suggest that the contribution of pico-sized plankton to NPSG phytoplankton community will increase gradually in response to the acceleration of the global warming.

How to cite: Yoon, J.-E. and Kim, I.-N.: Climate-driven phytoplankton community shifts in the North Pacific Subtropical Gyre, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6754, https://doi.org/10.5194/egusphere-egu2020-6754, 2020.

The stock of nekton resources and spatiotemporal variation of community in the gulf of estuary area are closely related to the quality of habitat and ecological environment (e.g., habitat degradation, freshwater input, eutrophication, and water exchange). However, their relative importance in shaping the spatial heterogeneity of nekton in bay of China estuary remains rarely reported. In this study, the spatiotemporal dynamics of the nekton assemblage structure were investigated in Hangzhou Bay (HZB), a semi-enclosed bay of China estuary. It was based on a comprehensive survey constituting 40 collections from 10 stations over 4 seasons within a year. A wide taxonomic diversity was encountered during the nekton survey, including 57 taxa distributed among 23 families. Average nekton biomass was significantly higher in winter which dominated by the fish biomass than in summer with the shrimp biomass had the higher proportion. The average nekton abundance was significantly higher in warm seasons with the especially high abundance of shrimp than in cold seasons which the abundance of shrimp relatively low. Nekton of HZB were mainly composed of small near-shore species. Little differences between subtropical (27 species) and warm-temperate (30 species) species of nekton were surveyed on the basis of thermal adaptability, but the seasonal variation was obvious. The number of demersal species in warm seasons (54 species) was higher than that in cold seasons (43 species). The dominant species (IRI>1000) were fishes such as Miichthys miiuy, Collichthys lucidus and shrimps such as Exopalaemon annandalei, Palaemon gravieri and crabs such as Portunus trituberculatus. The biomass diversity index (H'), evenness index (J') and richness index (d) of nekton in HZB were higher in summer and autumn (warm seasons) than in winter and spring (cold seasons). Nevertheless, the abundance diversity index (H') and evenness index (J') of nekton were showed opposite seasonal variation characteristics. The seasonal alternate index (AI) and migrate index (MI) of nekton community varied from 94 to 218 and -73 to 35 respectively, which meant that the nekton community in the survey waters were in large variation and unstable comfortably. The survey stations could be divided into 3~4 groups in the 55%~65% similarity levels by the clustering and NMDS sequencing analysis of nekton during four seasons. Important environmental correlates of assemblage structure were identified using redundancy analysis (RDA). Strong physical gradients in salinity, water temperature, dissolved oxygen and depth correlated predominantly with nekton assemblage structure, and reflected substantial spatiotemporal variation. And chemical variables like DIP and Chla were also highly correlated with nekton community structure. Estuarine embayments in the central bay of China, like Hangzhou Bay, might be viewed appropriately as landwardmost sections of the wider, highly productive spawning and nursery grounds of this region with the good fisheries monitoring and management strategies adapted to the needs of ecosystems and national conditions.

How to cite: Zhang, D., Chen, L., and Jia, G.: Spatio-temporal distribution of nekton community structure and diversity change in Hangzhou Bay, CHINA, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2306, https://doi.org/10.5194/egusphere-egu2020-2306, 2020.

The Antarctic toothfish (Dissostichus mawsoni), commonly known as Chilean Sea Bass, has a critical role in Southern ecosystems as a top fish predator. Simultaneously, it represents the most lucrative Antarctic fishery.

Its fishery is managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), which introduced the world’s largest Marine Protected Area (MPA) in the Ross Sea region of the Southern Ocean in 2016.

Since 2013, scientists at the Alfred Wegener Institute in Germany have been proposing the creation of an even more expansive MPA in the Weddell Sea region of the Southern Ocean, in order to protect unique ecosystems in this region, which has largely escaped the exploitation seen in the Ross Sea, due to its historic inaccessibility. However, CCAMLR, whose 25-member country composition functions by consensus, has failed to arrive at unanimous support for the various forms of a Weddell Sea MPA (WSMPA) proposed over recent years.

A remaining impediment to the design and acceptance of a WSMPA, is a near total lack of knowledge of the life history and population structure of Antarctica toothfish in the Weddell Sea. Much of the data regarding connectivity and ontogenic movement of Antarctic toothfish derive from the Ross Sea, given the presence of an active fishery there since 1997. Based on the hypotheses that have arisen from the Ross Sea (which remain contentious), a possible life cycle of Antarctic toothfish comprises juvenile development on nutrient rich continental shelf areas, followed by passive transport via gyre systems to offshore sea mounts, where spawning occurs, prior to completion of the cycle as fish are passively transported back towards the coast.

The combination of population genetics and otolith chemistry, methodologies which define population structure via metrics of relatedness and provenance respectively, offers the possibility to fill many of the existing knowledge gaps with regards to Antarctic toothfish life history connectivity in the Weddell Sea region of the Southern Ocean. The integration of hydrographic data on water mass movement which informs both the passive transport of Antarctic toothfish at various life stages, as well as the location of important prey sources, is an integral third point of consideration, completing the development of life history connectivity hypotheses testable via the aforementioned metrics.

Tissue samples from the present study derive from otoliths (fish ear bones), which are a standard tissue extract by CCAMLR observers on Antarctic fishing vessels, historically collected for age determination. Otoliths provide both a source of DNA for genetics work, via tissue traces dried on the otolith exterior, as well as a source for chemistry analysis, via trace element analysis of otolith ring layers from the nucleus (earliest) to edge (latest) elemental depositions.

The aim of the present study is to utilize this readily available tissue source (otoliths) in order to apply both aforementioned methodologies, with the ultimate aim to test between hypotheses of single or multiple populations within the Weddell Sea, while also contextualizing those Weddell Sea population(s) within the greater Southern Ocean distribution of Antarctic toothfish.

How to cite: Caccavo, J., Mazzoni, C., and Brey, T.: A multidisciplinary approach to understanding the population structure of an exploited Southern Ocean top predator, the Antarctic toothfish, to improve sustainability and marine spatial planning, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-894, https://doi.org/10.5194/egusphere-egu2020-894, 2020.

The European flat oyster (Ostrea edulis, EFO) has been common in the North Sea at least throughout the late Holocene. Aside from its important ecological function as a reef builder the EFO has been of high economic value ever since man invented commercial fishery. During first half of the 20th century CE the EFO became functionally extinct in the German Bight. It is commonly agreed that industry-style overexploitation using dredges and trawls destroyed the habitats and eventually caused the extirpation of the EFO. Today, the EFO is a severely endangered and protected species.

Recently, an as yet uncharted fossil EFO bed was encountered close to the island Helgoland (German Bight, SE North Sea), that does not reveal any obvious signs of the physical disturbances typical for heavily harvested sites. This suggests possible environmental forcing behind the decline of this particular EFO bed, which could also have contributed to the fall of the entire oyster population of the German Bight.

The area was surveyed using drift videos along with grab samples to locate the EFO bed, measure its perimeter and evaluate characteristics, such as the density of shells. A total of 590 shells from 17 locations were measured (length, width) and weighed. A total of 19 shell samples from 17 locations were AMS radiocarbon dated to obtain absolute age control.

The EFO bed is located on a rocky slope to the west of Helgoland, its area is about 0.6 km² and the water depth ranges between 32 and 43 m. The shallower parts are characterized by rubble whereas the EFO bed disappears under muddy sediments in the deeper parts. A rough estimation reveals around 200,000,000 single oyster shells in this bed. The oldest shell dated to about 4000 years BP, the youngest age dates to the beginning of the 19th century CE. Most shell ages are between 2700 and 2000 years BP. A hiatus occurs between 1300 and 300 years BP, and only one measurement reveals an age younger than 1300 years.

This EFO bed had perished already 1300 years ago, hence intense fishery as a reason can be ruled out. Today, the deeper part of the EFO bed is affected by muddy sediment that temporally buries the seafloor and occasionally forms turbid clouds of suspended matter. The sediment likely originates from large rivers (e.g. Rhine, Weser, Elbe) and the mudflats of the Wadden Sea. Climatic/oceanographic fluctuations that had modified the discharge and transport of muddy sediments in combination with increased influx of sediment from fluvial sources as a result of land-use changes in early medieval central Europe may have been a major stressor for the oyster habitats, albeit biological stressors cannot be ruled out.

How to cite: Hass, H. C., Michaelis, R., Sander, L., Hausen, T., and Pogoda, B.: The Rise And Fall Of An Oyster Bed In The German Bight (North Sea) Before The Dawn Of Industrial Fishery, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7082, https://doi.org/10.5194/egusphere-egu2020-7082, 2020.

Coral reefs are increasingly threatened by climate change and mass bleaching events. Predicting how corals will respond to rapid ocean warming requires a better understanding of how they have responded to environmental change in the past – information that can be reconstructed from coral skeletal records. However, significant knowledge gaps remain in our understanding of how coral biomineralization and the incorporation of geochemical tracers is impacted by heat stress and bleaching, particularly since the physiological status of corals used for reconstruction of past stress events is often unknown. Using boron-based geochemical tracers (δ¹¹B, B/Ca), we investigated how heat stress caused by a marine heatwave impacted the carbonate chemistry of the coral calcifying fluid as well as skeletal trace element composition in the branching coral Acropora aspera. Importantly, we recorded in situ temperature and coral health status during the bleaching event and after 7 months of recovery. We show that heat-stressed Acropora corals continued to upregulate the pH of their calcifying fluid (cf); however, dissolved inorganic carbon upregulation inside the cf was significantly disrupted by heat stress. Similarly, we observed suppression of the typical seasonality in the temperature proxies Sr/Ca, Mg/Ca, Li/Ca and Li/Mg, likely due to a combination of reduced growth rates, disruption of key enzymes involved in calcification and Rayleigh fractionation. Anomalies in TE/Ca ratios were still observed 7 months after peak bleaching, even though symbiont densities and chlorophyll a concentrations were fully restored at this point. Interestingly, the response to heat stress did not differ between the thermally variable intertidal and the thermally more moderate subtidal environments whose coral populations are known to have a different heat tolerance, nor between colonies with varying degrees of bleaching. Our findings suggest that coral biomineralization mechanisms are highly sensitive to heat stress, and that the biogeochemical stress response of branching Acropora corals is remarkably consistent with that of massive Porites corals.

How to cite: Schoepf, V., D'Olivo, J.-P., Rigal, C., Jung, M., and McCulloch, M.: Impacts of heat stress on the calcifying fluid chemistry and trace element composition of corals from thermally variable reefs, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19080, https://doi.org/10.5194/egusphere-egu2020-19080, 2020.

To evaluate the anthropogenic impact in surface sediments of the Northern and Central Adriatic Sea, dissolved fluxes at the sediment water interface of heavy metals and nutrients on the sea bottom in front of the Po River mouths and along the western side of the Northern and Central Adriatic Sea have been determined. The fluxes have been measured by benthic chamber deployments and calculated by pore water modelling. Pore waters composition have been used also to understand the early diagenesis processes generating the benthic fluxes.

Benthic chamber deployments and sediment core collection for pore water extraction have been carried out in three cruises in spring and autumn 2013 and autumn 2014.

The study stations have been chosen on the base of previous research results indicating a decreasing heavy metal and organic matter surface content leaving from the Po River mouths (Pérez-Albaladejo et al., 2016). The data obtained have been compared with previous studies carried in the Adriatic Sea (Spagnoli et al. 2010).

Results of the 2013 and 2014 cruises and of previous investigations indicate a consistent and rapid dissolved benthic flux decreasing going away from the Po River mouths both southward, eastward and northward.

The decreasing regards the final electron acceptors and the organic matter degradation products and some heavy metals.

On the whole, different early diagenesis environments have been recognized in the Northern and Central Adriatic Sea: they embrace two end members: from the Po River Prodelta to the Mid Adriatic Depression (MAD) (Spagnoli et al., 2014). In front of the Po River sediments are characterized by high sedimentation rate and by high inputs of fresh marine organic matter, continental organic matter and Fe-oxyhydroxides. These inputs produce high concentrations of organic matter degradation products, strong anoxic environment in the pore waters and high dissolved benthic fluxes. In the MAD the diagenetic environments are characterized by low sedimentation rate and low inputs of reactive organic matter that produce low concentrations of pore-water organic matter degradation products with oxic conditions near the surface and weak benthic fluxes.

As regard the two major metals involved in the early diagenesis processes (Fe and Mn), they too show dissolved benthic fluxes decreases from the Po River mouths. Also in this case, this trend is attributed to the high Po River dissolved and particulate, anthropogenic and natural, metal inputs that deposit in the surface sediments of the Po Prodelta (Spagnoli and Bergamini, 1997).

The dissolved benthic fluxes of trace heavy metals (Co, Ni, Zn, Cu, Cd, Pb) indicate that some elements, such as Co and Pb, are clearly adsorbed by the sediment that act, for these two elements as sink. Other elements, such as Cu, don’t show a clear north–south trend s, while other elements, such as Cd, indicate a southward decreasing trend suggesting a behavior affected by the Po River inputs and Fe-Mn-oxyhydroxide cycle.

How to cite: Spagnoli, F., De Marco, R., Giuliani, G., Penna, P., Campanelli, A., Kaberi, E., Zeri, C., Bortoluzzi, G., Giordano, P., Ravaioli, M., and Martinotti, V.: Dissolved heavy metal fluxes at sediment-water interface in polluted sediments of the Adriatic Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19366, https://doi.org/10.5194/egusphere-egu2020-19366, 2020.

The main goal of this study is to investigate the anthropic influence on benthic habitats in the Punta Campanella Marine Protected Area (MPA). This area is located at the western end of the Sorrento Peninsula in the Bay of Naples, southern Italy. It is a rocky coast consisting of vertical or near vertical limestone cliffs of structural control, with marine areas characterized by suboutcropping rocky substrate. Seabed sediments are mainly coarse and biogenic in origin with skeletal grains and coralligenous bioconstructions occurring widely [1].

The Punta Campanella seabed habitats have been characterized and mapped on the base of geophysical and sedimentological data together with results from benthic communities. In addition, several environmental components both marine and terrestrial have been analysed in order to evaluate the anthropic influence on the recognized benthic habitats. Such environmental components include foraminiferal assemblages, water column features and inorganic pollutants (heavy metals) as well as terrestrial biota, fresh water supply and quality, land use and natural hazard.

First results indicate 1) anomalous values of specific heavy metals (Ni, Hg) in the marine sediments, 2) the presence of benthic foraminiferal assemblages distinctive of human-impacted environmental conditions, and 3) the occurrence of morphological deformities affecting some foraminiferal species. At present, as next step of this study, we are applying a methodology based on the Environmental Functional Analysis (EFA) in order to combine and analyse terrestrial and marine environmental components together with territorial data and selected socio-economic components of the coastal zone (i.e. human pressure, land use, etc.) [2]. This method was originally developed by Cendrero and Fischer (1997) [3] and successively employed as management tool and monitoring technique for coastal areas [4] and terrestrial protected areas [5]. Such a holistic-based approach can be used to evaluate the anthropic disturbance in the Punta Campanella MPA and to compare the potential for conservation and the potential for use of the study area.

References

[1] D'Argenio B., Violante C., Sacchi M., Budillon F., Pappone G., Casciello E., Cesarano M., 2004: Capri, Bocca Piccola and Punta Campanella (southern Italy), marine and onland geology compared. In: G. Pasquarè and C. Venturini (Eds), Mapping Geology in Italy, APAT, Roma, 35-42.

[2] Hopkins, T.S., Bailly, D., Støttrup, J.G., 2011. A Systems Approach Framework for Coastal Zones. Ecol. Soc. 16(4), 25.

[3] Cendrero A., Fischer D.W., 1997: A procedure for assessing the environmental quality of coastal areas for planning and management. Journal of Coastal Research 13(3), 732-744.

[4] Giordano L., Ferraro L., 2020. Conservation or development? An environmental function analysis assessment of the Volturno River coastal zone (central Tyrrhenian Sea - Italy). Journal of Coastal Conservation, 24(6), 5-12.

[5] Calado H., Bragagnolo C., Silva S., Vergílio M., 2016: Adapting environmental function analysis for management of protected areas in small islands e case of Pico Island (the Azores). Journal of Environmental Management 171, 231-242.

How to cite: Violante, C., Buonocunto, F. P., Esposito, E., Ferraro, L., Giordano, L., and Milia, A.: Anthropic disturbance to seabed habitats in the Punta Campanella Marine Protected Area, southern Italy, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22036, https://doi.org/10.5194/egusphere-egu2020-22036, 2020.

Shelf sea ecosystems are amongst the most productive on Earth. A large proportion of the nutrients required to sustain this productivity is supplied via the remineralization of organic material in the underlying sediments. Industrial fisheries trawling at the seafloor, the most intense form of anthropogenic disturbance in shelf seas, has the potential to influence the release of sediment and nutrients from the seafloor and hence shelf-scale primary production. However, the absence of data on the concentrations and composition of the materials resuspended by benthic trawling hinders our ability to robustly assess the wider ecosystem effects of this industrial activity. We addressed this key knowledge gap by conducting the first in-situ experiments to quantify the concentrations of particles and nutrients released by different benthic trawling gears.

Our results demonstrate that the composition of resuspended particles and nutrients are both influenced by sampling height above the seafloor and the amount of drag exerted by the trawl gear, although the relative importance of these factors differs between the two response variables examined. These differences likely reflect that sediment particles adhere to physical laws of a solid in a fluid with associated weights, while dissolved nutrients follow the physical laws of fluids and dilution.  

Our findings demonstrate that trawl gear design strongly influences the amount of dissolved and particulate material resuspended. This suggests that gear design could be modified to reduce the impacts on shelf ecosystems. Future work will upscale our observations to assess the potential effects of benthic trawling activities on primary production at the shelf-scale.

How to cite: Breimann, S., O'Neill, B., Stinchcombe, M., and Mayor, D.: The level of hydrodynamic drag as a main component in explaining concentrations of nutrients and particle loads at different heights of a fisheries trawl plume, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5521, https://doi.org/10.5194/egusphere-egu2020-5521, 2020.

The abyssal seafloor is at some locations covered with polymetallic nodules that provide hard substrate for sessile organisms. Extraction of these mineral-rich nodules will likely severely modify the trophic and non-trophic interactions within the abyssal food web, but the importance of nodules and their associated sessile fauna in supporting this food web remains unclear. Here, we present highly resolved interaction webs with ~200 (Peru Basin) and ~450 (Clarion-Clipperton Zone, CCZ) food-web compartments based on an extensive literature research. Compartments were connected with ~3,100 (Peru Basin) and ~8,500 (CCZ) trophic and non-trophic (e.g. substrate-providing nodules) links. The webs were used to assess how nodule extraction would modify the number of network compartments, number of links, link density and web connectance. We showed that nodule removal would reduce the number of food-web compartments and links by ~25% and ~35%, respectively, in the Peru Basin and by 21% and 20%, respectively, in the CCZ. Subsequent analysis identified stalked sponges, living attached to the nodules, as key structural species that support a high diversity of commensal and mutualistic fauna. We conclude that nodules are critical for food-web integrity and suggest the deployment of artificial sponge stalks as a potential mitigation strategy for deep-sea mining.

How to cite: Stratmann, T., Amptmeijer, D., Kersken, D., Soetaert, K., and van Oevelen, D.: Polymetallic nodules are essential for food-web integrity of Pacific abyssal plains, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6794, https://doi.org/10.5194/egusphere-egu2020-6794, 2020.

Bottom trawling is one of the most important anthropogenic disturbances affecting marine ecosystems and there has been increased attention to its impacts on seabed habitats as well as the structure and functioning of benthic ecosystems. The impact of bottom trawling is well-known with regard to benthic organisms. However, we still have a poor understanding of its effects on bentho-pelagic coupling and biogeochemical cycling in the sediment. In the Baltic Sea, the study area of the present investigation, there is a particular lack of data.
Here, we present new results from field experiments to quantify changes in sediment properties, macrofauna and biogeochemical cycling after the passage of a benthic dredge. To put the results in a broader context, a field survey was conducted in six areas of different commercial trawling intensities in the Bornholm Basin. Acoustic geophysical mapping, isotope profiling, functional categorization of macrofauna and sediment-water nutrient and oxygen flux measurements were used to evaluate the physical disturbance of the seabed. Preliminary results suggest a range of ecological, biogeochemical and physical impacts of trawling in the Baltic Sea, with implications for benthic ecosystem functioning.

How to cite: Morys, C., Jakobsson, M., Sköld, M., Masqué, P., Brüchert, V., Bonaglia, S., and Bradshaw, C.: Addressing the effects of bottom trawling on benthic processes using experimental and field studies in the Baltic Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22362, https://doi.org/10.5194/egusphere-egu2020-22362, 2020.

For several decades the Belgian Continental Shelf (BCS) has been exploited for its sand. As this exploitation intensified over the years, according with the environmental regulation both on national and European levels, evaluating the extraction impact on the seabed bathymetry and morphology as well as on the sediment nature itself is a legal obligation.

The impact assessment of sand extraction is based on multiple types of data: statistics derived from the extraction registers, data from the Electronic Monitoring Systems (EMS = “black-boxes”) on board the dredging vessels, bathymetric and backscatter time series derived from regular MBES surveys, and ground truth data. In this framework, the most extracted areas have been surveyed several times each year for more than 15 years, enabling the development of well-controlled highly valuable and informative time series. In addition to this local approach, regular but less frequent surveys along straight lines, parallel and perpendicular to the sandbanks and the gullies, provide valuable information on the global evolution of the bathymetry and the sediment allowing a comparison between extracted and non-extracted areas. This multi-scale approach combining various types of data provides a 4D (space and time) overview of the evolution of the extraction and leads to robust and pragmatic conclusions about the impact of the sand extraction on the bathymetry, the morphology and the seabed habitats.

The long MBES bathymetric and BS time series on several monitoring areas inside the extraction sectors demonstrate the direct and non cumulative impact of the extraction on the bathymetry of the sandbanks and the unsustainable character of the sand resource. However, several questions remain regarding how the extraction impacts the seabed morphology and sedimentology in real time. Dredging by suction generates fine sediment plumes which could, after transport and sedimentation, modify the habitats within a certain radius around the extraction sites. Although the plumes generated during dredging operations have been the subject of numerous publications, few projects have been attempted to visualize these plumes and quantify the volume of fine sediment by using MBES water column amplitude data.

Specific series of acoustic measurements using the Kongsberg EM2040 MBES installed on the RV Simon Stevin were carried out following dredging vessels on the Belgian Continental Shelf. The resulting high quality dataset allows the evaluation of the real time impact of the extraction on the seabed and the water column in a 4D visualization. Another goal of this research is to evaluate the feasibility to use the MBES water column amplitude data to characterize and quantify the sediment plumes generated by the dredging operation. In a second experiment the scope was extended to plumes from fishing vessels and an evaluation of the impact of tidal currents on the water column measurements. The results of the simultaneous measurements with several acoustic and optical instruments and water sampling will contribute to the establishment of a methodology which will extend the present monitoring program to include the important impact on the seabed from the extraction technique itself.

How to cite: Degrendele, K. and Roche, M.: Monitoring the impact of sand extraction on the bathy-morphology and the seabed sediment in the Belgian part of the North Sea: Lessons of fifteen years of MBES measurements and current innovation. , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10428, https://doi.org/10.5194/egusphere-egu2020-10428, 2020.

Industrial-scale harvesting of deep-sea mineral resources, such as polymetallic nodules, is likely to have severe consequences for the natural environment. However, the effects of mining activities on deep‑sea ecosystems, sediment geochemistry and element fluxes are still poorly understood. Predicting the environmental impact is challenging due to the scarcity of environmental baseline studies and the lack of mining trials with industrial mining equipment in the deep sea. Thus, currently we have to rely on small-scale disturbances simulating deep-sea mining activities as a first-order approximation to study the expected impacts on the abyssal environment and ecosystem.

We have investigated surface sediments in disturbance tracks of seven small-scale benthic impact experiments, which have been performed in four European contract areas for the exploration of polymetallic nodules in the Clarion-Clipperton Zone (CCZ) in the NE Pacific Ocean. These small-scale disturbance experiments were performed 1 day to 37 years prior to our sampling program in the German, Polish, Belgian and French contract areas using different disturbance devices, such as dredges and epibenthic sledges. We show that the depth distribution of solid-phase Mn in the upper 20 cm of the sediments in the CCZ provides a reliable tool for the determination of the disturbance depth. We found that the upper 5–15 cm of the sediments were removed during various small‑scale disturbance experiments in the different contract areas. Transient transport‑reaction modelling for the Polish and German contract areas reveals that the removal of the surface sediments is associated with the loss of reactive labile organic carbon. As a result, oxygen consumption rates decrease significantly after the removal of the surface sediments, and consequently, oxygen penetrates up to tenfold deeper into the sediments inhibiting denitrification and Mn(IV) reduction. Our model results show that the return to steady state geochemical conditions after the disturbance is controlled by diffusion until the reactive labile TOC fraction in the surface sediments is partly re‑established and the biogeochemical processes commence. While the re-establishment of bioturbation is essential, steady state geochemical conditions are ultimately controlled by the burial rate of organic matter. Hence, under current depositional conditions, new steady state geochemical conditions in the sediments of the CCZ are reached only on a millennium-scale even for these small-scale disturbances simulating deep-sea mining activities.

How to cite: Volz, J., Haffert, L., Haeckel, M., Koschinsky, A., and Kasten, S.: Impact of simulated deep-sea polymetallic nodule mining on sediment and pore-water geochemistry in prospective mining areas in the NE Pacific Ocean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3729, https://doi.org/10.5194/egusphere-egu2020-3729, 2020.

Deep bottom trawling often occurs in the vicinities of submarine canyons since these morphological features act as nursery areas for commercial species. Previous studies in the submarine canyons incising the NW Mediterranean margin have highlighted that bottom trawling resuspends large volumes of sediment which are partly transported downcanyon as sediment gravity flows. To assess the contribution of downward particle fluxes in La Fonera Canyon (NW Mediterranean) linked to natural sediment transport events and bottom trawling, a near-bottom mooring equipped with a 24-cup sediment trap, a current meter, and a turbidimeter was deployed during 2017 in its axis (1200 m water depth), next to a trawling ground. Temporal variations in the quantity and composition of trapped particulate organic matter were assessed through the analysis of organic carbon (OC), total nitrogen (TN) and several biomarkers (lignins, cutin acids, p-hydroxybenzenes, benzoic acids, amino acid-derived products, dicarboxylic acids, and fatty acids).

High downward particle fluxes (60-100 g·m^-2·d^-1) were registered in autumn and winter associated to torrential river discharges, seasonal storms and dense shelf water cascading. During these natural events, sediment transported downcanyon had high organic matter contents that were mostly terrigenous in origin. However, the highest downward particle flux (>140 g·m^-2·d^-1) was recorded in the onset of the bottom trawling season in March, after a 2-month seasonal trawling closure. During the following summer months no major natural sediment transport events occurred, but the high frequency of bottom trawling activities (10-26 hauls·week^-1) near the sediment trap caused considerably high downward particulate fluxes (80-125 g·m^-2·d^-1) during this season. Compared to autumn and winter months, sediment transferred downcanyon caused by trawling had lower organic matter contents, mostly consisting in refractory compounds (i.e. lignins, p-hydroxybenzenes and benzoic acids) with similar concentrations to those observed in the bottom sediments of the trawling grounds, confirming that this material originates from these areas. During periods with less trawling activity, lower sediment fluxes (30-50 g·m^-2·d^-1) with higher organic matter contents enriched in labile compounds (i.e. amino acid-derived products, di-carboxylic acids, and fatty acids) were recorded. These results highlight how bottom trawling activities on the flanks of submarine canyons modify the supply of sediment and organic matter downcanyon. The low-quality of organic matter transferred by bottom trawling activities may ultimately affect the fragile ecosystems dwelling in these deep environments.

How to cite: Paradis, S., Arjona-Camas, M., Goñi, M., Masqué, P., and Puig, P.: Natural vs. trawling-derived transport of sediment and particulate organic matter in a submarine canyon, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-978, https://doi.org/10.5194/egusphere-egu2020-978, 2020.

Ongoing erosion at coasts, beaches and dunes accompanied by a climate change-induced sea-level rise requires extensive protection measures. At the Island of Sylt (SE North Sea) beach nourishments were conducted for almost 50 years to protect the exposed western coast against erosion. Since 1984, the materials for the sand replenishments were dredged from an offshore excavation site approx. 7 km west off Sylt in the German Bight. In this study, we investigate the long-term effects of sand extraction on the local geomorphology, the associated benthic habitats and fauna. Hydroacoustic surveys and grab sampling revealed that after more than 35 years changes in bathymetry (with dredging pits of down to ~15 m below sea floor) and also changes in habitat characteristics are still present. Additionally, the sediment and benthic faunal compositions have changed. A comparison between dredged areas and undisturbed seafloor revealed significant differences in mud content (increasing), the number of individuals and species of macrozoobenthic organisms (decreasing). This indicates that the benthic communities in the dredging areas are in a persistent successional stage. Mud-loving species (e. g. Notomastus latericeus and Kurtiella bidentate) profit from the changed habitats, however sand-preferring organisms (e.g. Pisione remota and Aonides paucibranchiata) largely disappeared. Because of the slow backfill rates, we conclude that a complete backfill of the deep dredging pits is likely to take centuries. The same is expected to apply for the regeneration of the benthic communities. However, since rather coarse-to-medium sand was removed from this area and re-accumulation of this Pleistocene material is not possible because of weak transport rates, a re-establishment of benthic communities that prefer coarser sand seems to be unlikely. Since benthic communities are strongly linked to the habitat characteristics, habitat mapping using hydroacoustic techniques is an efficient and cost-effective measure to monitor the state of regeneration in this study site.

How to cite: Mielck, F., Michaelis, R., Armonies, W., and Hass, H. C.: Impact of marine sand extraction on benthic communities west off Sylt (SE North Sea), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5084, https://doi.org/10.5194/egusphere-egu2020-5084, 2020.

The impacts of bottom trawling on the structure of benthic communities can be relatively non-selective, hitting biodiversity as a whole. This holds true also in the deep sea, where the impacts of trawling can be more severe and long-lasting than in shallow-waters, due to the reduced capacity for recovery and greater vulnerability of deep-sea organisms. For years, our knowledge of the impact of trawling on deep-water ecosystems has remained limited and has focused mainly on fish stocks and hard bottom systems. More recently, a number of studies have addressed the impacts of bottom trawling in the deep-sea sedimentary environments, and very few of them have focused on the impacts on meiofauna, though it is a key faunal component of deep-sea ecosystems.

We investigated the impact of bottom trawling on the quantity, biochemical composition and nutritional value of sedimentary organic matter and meiofauna along the Sicilian Margin (Gulf of Castellammare, southwestern Mediterranean) at ca. 550 m depth, during the summer of 2016. Amount, biochemical composition and freshness of sedimentary OM, as well as the abundance and community composition of meiofauna were determined in sediment cores taken at both trawled and untrawled grounds. The continuous erosive processes in the trawled site have led, generally, to the depletion of OM contents (20-60% lower than those in the untrawled site), as well as to statistically significant differences from the untrawled site in its biochemical composition. Nevertheless, the upper 2 cm of the trawled site consisted of recently accumulated sediments, enriched in phytopigments, and bulk OM contents similar to those in the untrawled one, interpreted as a very recent input of fresh OM from the upper water column. The abundance of meiofauna in trawled grounds was significantly higher than that in untrawled ones, whereas no differences were observed between trawled and untrawled grounds deeper in the sediment. Differences in the meiofaunal community composition among sediment layers in each site were larger than those among sites.

As previously reported, deep bottom trawling in the Gulf of Castellammare erodes large volumes of sediment, exposing old compacted sediment that is depleted in OM. This erosive action generally prevents the accumulation of fresh sediment. However, the episodic short-lived deposition of fresh organic detritus between hauls can lead to a temporary accumulation of fresh and bioavailable OM which, in turn, can induce a positive response in meiofauna abundance.

These results pinpoint the need of considering the impacts of bottom trawling on the benthic communities of deep-sea sedimentary environments at temporal scales shorter than previously done.

How to cite: Pusceddu, A., Paradis, S., Moccia, D., Puig, P., Masque, P., Russo, T., Meloni, M. C., and Lo Iacono, C.: Impacts of bottom trawling on benthic trophic status and meiofauna in a deep-sea sedimentary environment (Gulf of Castellammare, southwestern Mediterranean Sea), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9804, https://doi.org/10.5194/egusphere-egu2020-9804, 2020.

Industrial-scale mining of deep-sea polymetallic nodules will remove nodules in large areas and impact the physical integrity of the seafloor. However, environmental standards for seafloor integrity and studies of recovery from environmental impacts are still largely missing. Further we have only a poor understanding of the role of nodules in shaping benthic microbial diversity and element cycles. We revisited the deep-sea disturbance and recolonization experiment carried out with a towed plough harrow in 1989 in the Peru Basin nodule field within a circular area of approx. 3.5 km diameter (>4100 m water depth). In the experimental area, the 26 years old plough tracks were still visible and showed different types and levels of disturbance such as removal and compaction of surface sediments. Microbial communities and their diversity were studied in disturbance tracks and undisturbed sites and related to habitat integrity, remineralization rates, and carbon flow. Locally, microbial activity was reduced up to 4 times in the impacted areas. Microbial cell numbers were reduced by ~50% in fresh, and by <30% in the old tracks. Our data suggest that microbially-mediated biogeochemical functions need more than 50 years to return to undisturbed levels in the sediments. In areas with nodules (i.e., outside the disturbance tracks) microbial communities in the nodules themselves were studied. Nodule communities were distinct from sediments and showed a lower diversity and a higher proportion of sequences related to potential metal-cycling bacteria (i.e. Magnetospiraceae, Hyphomicrobiaceae), bacterial and archaeal nitrifiers (i.e. AqS1, unclassified Nitrosomonadaceae, Nitrosopumilus, Nitrospina, Nitrospira), as well as bacterial sequences typically found in ocean crust, hydrothermal deposits and sessile fauna. Our results confirm that nodules host specific microbial communities with potentially significant contributions to organic carbon remineralization and metal cycling. This study contributes to developing environmental standards for deep-sea mining and highlights the limits for maintaining and recovering ecological integrity and functions during large-scale nodule mining.

How to cite: Molari, M., Vonnahme, T. R., Janssen, F., Wenzhöfer, F., Haeckel, M., Tischack, J., and Boetius, A.: Impact of deep-sea polymetallic nodule mining on benthic microbial community and mediated biogeochemical functions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13789, https://doi.org/10.5194/egusphere-egu2020-13789, 2020.

Concerns about future access to strategic raw materials for the high-tech industry have led to a renewed interest in mining of mineral resources from the deep-sea as a potential alternative for land-based mining. Polymetallic nodules, especially abundant in the eastern equatorial Pacific Ocean in water depths of 4000-6000 m, are a likely target of future deep-sea mining. However, many questions exist about the environmental sustainability of deep-sea mining, as it would involve the removal of hard substrate, disturbance of the surface sediment layer and dispersion of mobilised sediment over large areas of seabed adjacent to the mining sites. Anticipating on full-scale industrial mining tests, which are likely to start in the near future in the deep Pacific Ocean, we tried approaches for environmental monitoring of mining activities during two industry field tests in relatively shallow water offshore southern Spain, carried out in the framework of the European Blue Nodules project. The aim of these field tests was to assess technical and environmental performance of a scaled polymetallic nodule mining vehicle developed by the Dutch shipbuilder and maritime technology provider Royal IHC. Although the tests were performed in only 300 m water depth, much less than the depth where future deep-sea mining will take place, the weakly stratified bottom water, tide-dominated near-bed currents with mean magnitude around 5-10 cm s^-1, and gently sloping seabed covered with fine muddy sediment are fairly comparable to operational conditions in the deep-sea. The plume of suspended sediment mobilised by the mining vehicle, considered to represent a major environmental pressure which may extend far beyond the actual mining area, was monitored with turbidity sensors deployed with ship-operated ROV and CTD, as well as in a static array of moored sensors. It was found that the generated sediment plume extended not more than 2 m above the seabed close to the disturbance (< 100 m), but increased in height with distance away from the disturbance site. Turbidity decreased rapidly with increasing distance from the source, but a distinct signal could still be distinguished above background turbidity at 350 m away from the source. In this near-coast setting, plume monitoring suffered significant interference by bottom trawling activities in neighbouring areas. The monitoring setup proved to be well designed and the findings on the plume size and dispersion can be significantly extrapolated to account for a more realistic mining situation. Seabed surveys with ROV-based video and scanning sonar showed that the tracks of the test vehicle, exerting an average pressure of 3 kPa on the seabed, left impressions of 4±0.8 cm deep in the surface sediment. In sediment cores collected from the path of the vehicle, geotechnical testing showed an increase in undrained shear strength and bearing capacity, as compared to undisturbed sites, indicating compaction of the surface sediment. Surveys revealed ubiquitous signs of bottom trawling, including furrows of approximately 10 cm deep produced by trawl doors. 

How to cite: de Stigter, H., Haalboom, S., Mohn, C., Vandorpe, T., Smit, M., de Jonge, L., and Reichart, G.-J.: Monitoring environmental effects of a deep-sea mining test in shallow water, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7710, https://doi.org/10.5194/egusphere-egu2020-7710, 2020.

The globally increasing demand for metals and rare earth elements has raised the interest for potential mining of deep-sea mineral resources such as polymetallic nodules. One important field of polymetallic nodules is located within the Clarion-Clipperton Fracture Zone (CCZ) in the northeastern equatorial Pacific. To date, the International Seabed Authority (ISA) has granted 25 licenses for the exploration of polymetallic nodules in the CCZ. However, the impact of potential future mining activities on the deep-sea environment is only insufficiently known. To assess the environmental impacts of potential future mining activities, a nodule pre-prototype collector test is scheduled to occur in the German license area within the CCZ in autumn 2020, and will be accompanied by an extensive environmental monitoring program (joint effort between BGR and the European research project JPI-Oceans “MiningImpact2”). However, to assess the environmental impact of mining activities, for example due to the development of an operational sediment plume on the seafloor, prior knowledge on the bottom current regime and variability of particle flux and composition within the CCZ under natural conditions is a prerequisite. In order to analyze the bottom current regime and background particle fluxes, BGR deployed Ocean Bottom Moorings (OBM) equipped with current and turbidity meters (4 years between 2013 and 2019), and a sediment trap (2018-2019). Here, we present preliminary results and analyses of these oceanographic and sedimentological time-series data, and compare the results with other available information deriving from the region.

How to cite: Hollstein, M., Vink, A., Schmidt, K., Lahajnar, N., Lückge, A., and Purkiani, K.: Time series of near-bottom currents and particle fluxes from Ocean Bottom Moorings in the NE equatorial Pacific, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4653, https://doi.org/10.5194/egusphere-egu2020-4653, 2020.

Shelf and coastal seas hold vast quantities of sedimentary carbon which contribute to atmospheric carbon dioxide removal and long-term carbon storage. However, the stability and resilience of this key component of global natural capital remains poorly quantified, particularly under anthropogenic stressors. Demersal trawling activity is the most significant cause of widespread anthropogenic disturbance to the seabed, leading to massive sediment resuspension events and wide scale impact to benthic communities. The impacts of trawling on benthic ecosystems and biodiversity are well reported and understood within the literature (e.g. Jones, 1992; Rijnsdorp et al., 2016); however, a knowledge gap remains regarding the post-trawl fate of sedimentary carbon (van de Velde et al., 2018).

In order to gain a better understanding of the post-disturbance effects of carbon cycling in marine sediments, an experimental trial to mimic fishing impacts was created. Over a 21-day period, a series of closed-tank incubation experiments investigating the impact of simulated benthic fishing gear penetration depth in soft sediments was conducted. Here, marine sediments underwent an artificial disturbance event every 24 hours, with a series of varying depth regimes used. We hypothesise that the large-scale resuspension events caused by trawling may contribute towards an enhancement in localised carbon cycling, and thus a reduction in the net carbon storage within these sediments. The aim of this experiment was to better understand the biogeochemical processes which occur in marine sediments during massive resuspension events, with a particular emphasis on the fate of resuspended organic carbon matter and its potential vulnerability. Dissolved organic carbon and various macronutrients of interest (e.g. PO₄, SiO₂, NH₄, NO₂, NO₃) were also measured.

Jones, J.B., 1992. Environmental impact of trawling on the sea bed: a review. New Zeal. J. Mar. Freshw. Res. 26, 59–67. https://doi.org/10.1080/00288330.1992.9516500org/10.1080/00288330.1992.9516500

Rijnsdorp, A.D., Bastardie, F., Bolam, S.G., Buhl-Mortensen, L., Eigaard, O.R., Hamon, K.G., Hiddink, J.G., Hintzen, N.T., Ivanović, A., Kenny, A., Laffargue, P., Nielsen, J.R., O’Neill, F.G., Piet, G.J., Polet, H., Sala, A., Smith, C., Van Denderen, P.D., Van Kooten, T., Zengin, M., 2016. Towards a framework for the quantitative assessment of trawling impact on the seabed and benthic ecosystem. ICES J. Mar. Sci. 73, i127–i138. https://doi.org/10.1093/icesjms/fsv207

van de Velde, S., Van Lancker, V., Hidalgo-Martinez, S., Berelson, W.M., Meysman, F.J.R., 2018. Anthropogenic disturbance keeps the coastal seafloor biogeochemistry in a transient state. Sci. Rep. 8. https://doi.org/10.1038/s41598-018-23925-y

How to cite: Black, K., Austin, W., and Norkko, J.: Assessing the Influences of Large-Scale Disturbance on Sedimentary Marine Carbon Stores, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5682, https://doi.org/10.5194/egusphere-egu2020-5682, 2020.

Coasts are extremely sensitive areas and are internationally considered “hotspot” of environmental contamination. The presence of multiple human activities in these areas frequently lead to the potential increase in organic and inorganic pollutants. In particular, industrial and maritime activities, tourism, recreational activities, aquaculture and fishing contribute to the pollutants release in the coastal environments. In this context, northern Latium coastal area (northern Thyrrenian Sea, Italy) hosts several industrial activities of national and international relevance, located in a very restricted seaside area: the Port of Civitavecchia, one of the most important hub for cruise and commercial traffic in the Mediterranean Sea, the Torrevaldaliga Nord coal-fired power plant of the national energy company (ENEL), and the Tirreno Power combined cycle (gas-fueled) power plant. All these activities strongly contribute to the increase of pollutant load to the land as well as marine coastal environment. For this reason, a research project aimed at understanding the main source for the pollution has been undertaken in the last years. The project is particularly aimed at designing and testing of reliable low-cost devices (Gozzi et al., 2015, 2017) able to provide both the amount and typology of solid particles spread in the environment.

As a first step, the air quality inside the Civitavecchia harbor has been monitored for six months by measuring the content of PM1, PM2.5, and PM10 simultaneously to environmental parameters such as air temperature and humidity. The sensing station (Della Ventura et al., 2017) was equipped with a filtering set-up able to collect the solid load in the atmosphere with dimension > 400 nm. The filters were periodically removed from the station and studied by combining microscopic (optical and electron), spectroscopic (IR, Raman) and microchemical (SEM-EDS) techniques for a full characterization of microparticles typologies. Collected information, augmented by environmental (wind, rain) data from local broadcasting stations provides a valuable tool for assessing the contribution of anthropic (industrial and maritime) activities to the pollution in this coastal area.

References

Gozzi, F., Della Ventura, G., Marcelli, A. (2015) Mobile monitoring of particulate matter: State of art and perspectives. Atmospheric Pollution Research, 7, 228-234. DOI:10.1016/j.apr.2015.09.007.

Gozzi, F., Della Ventura, G., Marcelli, A., Lucci, F. (2017) Current status of particulate matter pollution in Europe and future perspectives: a review. Journal of Materials and Environmental Science, 8, 1901-1909. ISSN: 2028-2508

Della Ventura, G., Gozzi, F., Marcelli, A. (2017) The MIAMI project: design and testing of an IoT low-cost device for mobile monitoring of PM and gaseous pollutants. Superstripe Press, Science Series, 12, 41-44, ISBN 9788866830764.

How to cite: Piazzolla, D., Terribili, A., Bonamano, S., Scanu, S., Marcelli, M., Della Ventura, G., Conte, A., Lucci, F., and Marcelli, A.: Monitoring coastal pollution by using an integrated low-cost device, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1946, https://doi.org/10.5194/egusphere-egu2020-1946, 2020.

Sound is the most widespread and pervasive kind of anthropogenic energy that human activities introduce into the marine environment. Sound energy input can be highly variable both in time and space, becoming an important part of the total ocean acoustic background. Moreover, the underwater sound plays an ecologically important role in marine ecosystems, being a critical sensory modality for many marine organisms that can be useful for both sensing the environment and communication. With the Marine Strategy Framework Directive (MSFD) (2008/56/EC, EU 2008), underwater noise has been recognized as pollution and included in the qualitative high-level descriptors to achieve good environmental status, GES.

During recent years, passive acoustic monitoring in the ocean has become a standard technique across the oceanographic community and is used to address biological, geological and meteorological issues. Due to the highly spatio-temporal variability of the ocean noise, a large number of the observing systems would be needed. Extended marine monitoring would require a reduction in the cost of platforms and instruments, without compromising data quality. Despite, a significant effort has been invested by the scientific community in the development of low-cost PAM recorders, much work still remains. Most of the problems are related to the pressure to which the devices are exposed, the battery pack limits, storage memory limits, and sensibility of the sound sensor once waterproofing and so on.

Here, we present a low-cost underwater sound recorder for coastal applications developed to be applied in both background noise monitoring and bioacoustic monitoring. This recorder consists of a high-performance USB-based microcontroller development system with an audio adapter that guarantees high audio quality. Additionally, test were conducted using both an ECM (Electret Condenser Microphone) and a MEMS microphone (Micro-Electro-Mechanical System) for a wide frequency range recordings to find the better solutions for good data quality. Compact and small in size, it can be easily installed on various oceanographic platforms for different types of sampling.

Here we present the first results of the laboratory and field tests, comparing our assembled device with a commercial recorder and a pre-calibrated hydrophone.  

How to cite: Cafaro, V., Terribili, A., Pasculli, L., Piermattei, V., Marcelli, M., and Zimmer, W. M.: Low-Cost Underwater Sound Recorder for coastal applications., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6746, https://doi.org/10.5194/egusphere-egu2020-6746, 2020.

The coastal marine system is characterized by multiple uses and it represents a vulnerable area highly subjected to anthropogenic pressures. Coastal marine ecosystems monitoring therefore requires an integrated multidisciplinary approach. The modeling of marine coastal dynamics and processes and the development of new observational technologies are fundamental in order to increase the available amount of data needed for the application of integrated approaches. New technologies and coastal observation networks are therefore a priority of the Global Ocean Observation System (GOOS) and of the Agenda 2030 strategy to improve the sustainable management of marine ecosystems and to contribute to future climate change scenarios. In this context a big effort is carried out by existing observing programs (ARGO, DPCP, GO-SHIP, OceanSITES, SOOP), which focus on open ocean waters and do not cover coastal areas. To do this, a significant reduction in the costs of platforms and instruments is necessary while maintaining sufficient measurement precision and consequently data quality. To face this issue, an Arduino based technology has been developed starting from the Tree-Talker-Cloud Technology (TT-Cloud board), a data acquisition and transmission system to monitor the health of trees and the impacts of climate change. From this technology, a new low-cost board, TT-Marine, has been developed, characterized by a high modularity allowing to manage the sensors by different types of communication protocols: RS232, UART, i2c, RS485; analog sensors can be managed by 16 and 24 bit AD converters. Depending on the characteristics and opportunities of the site, the system can manage LoRa, WiFi, gprs/gsm or cable data transmission systems. The TT-Marine is designed to be used in different modes: autonomous, ship-like as a profiler, on buoys and other measuring platforms.Here we present several operating modalities, with different missions and instrumental configurations.

How to cite: Piermattei, V., Marcelli, M., Cafaro, V., Madonia, A., Terribili, A., and Valentini, R.: TT-MARINE: a new open modular cost-effective board to monitor coastal ecosystems, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10405, https://doi.org/10.5194/egusphere-egu2020-10405, 2020.

This paper describes the technological development of an innovative Autonomous Surface Vehicle designed to meet the requirement of accessing the extremely shallow waters peculiar of the Wetlands. Wetlands are those geographic areas where water meets the earth and cover between 5 and 8 % of the Earth's surface. Wetlands include mangrove zones, swamps, bogs and marshes, rivers and lakes, alluvial plains and flooded forests, shallow coasts and coral reefs. In recent years, their importance is becoming more and more recognized and various international conventions, directives and projects work on the protection of these fundamental ecosystems. Wetlands are considered among the world’s most productive environments for their biological diversity. Nevertheless the number, quality and spacial resolution of surveys in these peculiar environments is reduced due to the absence of suitable tools expressly addressed to work in these areas. This reduces the possibilities of monitoring and protecting the Wetlands. In this paper the first prototype of an innovative class of reliable modular re-configurable lightweight ASVs for extremely shallow water and remote areas applications is presented. SWAMP (Shallow Water Autonomous Multipurpose Platform) is a fully electric, modular, portable, lightweight, and highly-controllable Autonomous Surface Vehicle (ASV). It is a catamaran equipped with azimuth pump-jet actuators, and it is characterized by small draft soft-foam, unsinkable hull structure with high modularity and a flexible hardware/software architecture. The main advantage of pumpjet motors is that they are flush with the hull, thus minimizing the risks of damages due to possible grounding. This system is used to increase the manoeuvrability in narrow spaces and to increase the special resolution also in extremely shallow waters. The introduction of a soft hull structure is suitable for working in coastal areas and in riverine environment where impacts can affect the survival of the robot. The foam of the hulls is drilled in order to make SWAMP a completely modular catamaran that is able to host various types of tools, such as intelligent systems, samplers, and sensors, together with thrusters that are, in this way, protected by the foam. A preliminary study is shown related to the bathymetry carried on with a single beam sonar in a Ligurian river after a series of floods. Liguria is one of the European regions where extreme events related to anthropic changes have had the greatest number of negative effects. In this kind of areas the use of suitable robots can improve the assessment and monitoring the impact of anthropogenic pressure in wetland ecosystems.

How to cite: Odetti, A., Bruzzone, G., Bibuli, M., Ferretti, R., Zereik, E., and Caccia, M.: An innovative ASV for the monitoring of anthropogenic pressure on Wetlands, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11920, https://doi.org/10.5194/egusphere-egu2020-11920, 2020.

Plastic pollution is a globally concerning issue in marine environments. There is currently little research about the seasonal changes in microplastics in coastal areas. Here, we report a seasonal study on the concentrations and characteristics of microplastics in the surface seawater and zooplankton of Jiaozhou Bay, a typical bay in the west Yellow Sea. The concentrations of microplastics in the surface water of Jiaozhou Bay were 0.063, 0.174, 0.094, and 0.050 pieces/m³ in February, May, August and November, respectively, with an annual average concentration of 0.095 pieces/m³, a low value compared with the plastic concentrations of other coastal areas. The size of the collected microplastics ranged from 346 to 155200 μm, with an average of 5093 μm. The overall percentages of fibers, fragments and plastic foams were 29%, 55% and 16%, respectively. Fragments were the most dominant shape in four seasons. Nine plastic polymers were detected from the surface water of Jiaozhou Bay. The dominant chemical composition was polypropylene (PP), accounting for 51.04% of polymers, followed by polyethylene (PE), accounting for 26.04% of polymers. The seasonal variation of plastic characteristics in Jiaozhou Bay, including the shape, color and chemical composition, was significant. The highest concentration of plastics occurred in May and the lowest concentration of plastics occurred in November. Strong rainfall resulted in an increase in the plastic concentration in May, and winds and eddies affected the spatial distribution of plastics in Jiaozhou Bay. Focused on the dominant zooplankton groups in Jiaozhou Bay, the morphology, color, size, chemical composition and quantity of MPs in zooplankton were investigated in Jiaozhou Bay. The results showed that the MPs in zooplankton of the Jiaozhou Bay were dominated by fibers. The proportions of fiber in February, May, August and November were 91%, 88%, 89% and 88%, respectively. The average size of MPs in zooplankton was 441±2, 468±2, 576±2, and 379±4μm in the four seasons. For the 2 common zooplankton groups in the 4 seasons, the MP/zooplankton was 0.3, 0.26, 0.17, 0.19 for copepod, and 0.22, 0.19, 0.17, 0.45 for chaetognath, respectively.

How to cite: Sun, X.: Seasonal variation of microplastics in seawater and zooplankton in Jiaozhou Bay, the Yellow Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3892, https://doi.org/10.5194/egusphere-egu2020-3892, 2020.

How to cite: Bonamano, S., Madonia, A., De Luca, A., Lazzara, L., Becagli, S., Piermattei, V., and Marcelli, M.: Development and application of Phyto-VFP model (Variable Fluorescence Phytoplankton Production) to estimate primary production in highly vulnerable marine pelagic ecosystems, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7438, https://doi.org/10.5194/egusphere-egu2020-7438, 2020.

This work analyzes and quantifies the value of ecosystem services in the P.oceanica meadows of the Italian seas, defining methodological approaches and creating synoptic maps through the use of GIS. Ecosystem Services can be defined as benefits provided to mankind by natural ecosystems. Their contribution is essential for human progress and of fundamental importance in the long run.

Posidonia oceanica was chosen as the object of study because its meadows represent one of the Mediterranean "climax community". P. oceanica is, therefore, one of the most important ecosystem in the Mediterranean and has been indicated as "priority habitat" according to the Habitat Directive (Dir. N. 92/43 / EEC), which groups together all the Sites of Community Importance (SCI) that need to be protected.

The method of evaluating the ecosystem services for P.oceanica is derived from what reported in Costanza et al. (1997) applying the specific site approach for the definition of benefits and services (Marcelli et al. 2018).

The identified benefits for P.oceanica are carbon sequestration, oxygen production, erosion protection, bioremediation and food production.

P.oceanica data are organized from the dataset collected by the Italian Institute for the Protection of the Environment and Research (ISPRA) for the Marine Strategy Framework Directive and include parameters such as coverage and shoots number (m²), average leaf area, leaf area index, average number of leaves, average height of the rhizomes, average foliar and rhizomes production. The data were used for the calculation of the benefits of P. oceanica which are represented in synoptic maps through GIS with the creation of the Atlas of the values ​​of ecosystem services in the Italian seas.

How to cite: Scanu, S., Mellini, S., Piazzolla, D., Bonamano, S., Mancini, E., and Frattarelli, F. M.: Synoptic representation of P.oceanica ecosystem services in the Italian seas, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15329, https://doi.org/10.5194/egusphere-egu2020-15329, 2020.

Today, biological invasions represent a threat to endemic animal and plant communities and a major cause of biodiversity loss worldwide. In the Mediterranean Sea, there are about 100 species of macrophytes, introduced intentionally or accidentally, most of which are highly invasive. Among these, the macroalga Caulerpa cylindracea Sonder, 1845, entered in the Mediterranean basin since 1990 through the Suez Canal and now it is widespread along the Italian coasts. This species is able to colonize a high number of coastal substrates and it can affect the density of some seagrasses, such as Cymodocea nodosa (Ucria) Ascherson, 1870 and Posidonia oceanica (L.) Delile, 1813. Its colonization ability is enhanced in environments with a high concentration of nutrients and its growth can modify the redox potential of the substrate making it unsuitable for the establishment of other seagrasses and algae. This work aimed to analyse and describe the potential interaction between the C. racemosa and P. oceanica in the coastal area of Civitavecchia. The potential effects of this interaction were studied inside of two different P. oceanica patches, located at a depth of 3-5 m and characterized by the presence/absence of the invasive alga, through the morphostructural analysis of the two species. In particular, the seagrass growth and primary production were analysed using some direct and indirect techniques (phenology and lepidochronology), while for the alga were analysed the phenological characteristics and the percentage of coverage of the substrate. The sampling campaigns were carried out in two different months of the same year, June and October 2019, in order to observe both the growth phase and the maximum bloom phase of the C. racemosa.

How to cite: Boschi, M., Caporale, G., Pasculli, L., Piazzolla, D., and Mancini, E.: Evaluation of the effects of Caulerpa cylindracea on Posidonia oceanica through the analysis of primary production and morphometric characteristics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17439, https://doi.org/10.5194/egusphere-egu2020-17439, 2020.

Adélie penguin (Pygoscelis adeliae) are known as an eco-indicator species of the Southern Ocean marine ecosystem. Environmental variability drives penguin population dynamics through its effects on vital rates (e.g., survival, dispersal, or breeding success). Recent studies suggested that inter-annual variation strongly affected Adélie penguin abundance in individual colonies, and aggregating abundance across space provided more reliable trends of population dynamics. By considering the similarity of the regional sea-ice concentration, we divided the Ross Sea region into six areas to investigate the effects of environmental changes on penguin population dynamics from 1982–2013. Time lagged analysis of 0–6 years between penguin abundance and environmental factors were conducted in our study. We found that penguin abundance was significantly correlated with environmental factors at different lag times (p <0.05). In the western Ross Sea region, penguin abundance was positively correlated with temperature over the past 5 years (p <0.05), and positively correlated with sea-ice concentration at a lag of 4–6 years (p <0.05). In the northernmost region of the Ross Sea, penguin abundance was significantly correlated with chlorophyll concentration 4 years earlier (p <0.01). Generalized additive model (GAM) results showed that in mid-Victoria Land, the relationship between sea-ice concentration and penguin abundance was quadratic. Penguin abundance peaked when sea-ice concentration was approximately 40%. On Franklin Island, temperature positively affected penguin abundance when temperature was lower than -3°C, and the contribution decreased considerably when temperature was higher than -2.5°C. Optimal ranges of environmental factors for Adélie penguin population might exist and differ spatially in the Ross Sea. Our study highlighted the lagged response of penguin population to environmental factors to further understand the effects of climate changes on the Antarctic biosphere.

How to cite: Chen, X. and Li, X.: Lagged response of Adélie penguin population dynamics to environmental variability in the Ross Sea, Antarctica, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21001, https://doi.org/10.5194/egusphere-egu2020-21001, 2020.

The barrier reef lagoon of Noumea (New Caledonia) is potentially influenced by Ni and black carbon (BC) rich aerosols (the two latter originating from a Ni power plant).  Experiments were performed with lagoon water collected close to the reef crest to assess the effect of anthropogenic influences on bacterial abundance (BA), production (BP), respiration (BR), growth efficiency (BGE) and community composition (BCC) in artificial produced aggregates. In both treatments, BA were not affected or enhanced compared to the unamended control (up to 40% for BA and 180% for VA). BP was not or negatively affected (up to 70%). No clear trend was found for BR in the Ni treatment; in the BC treatment BR was enhanced by 63-69%. BGE was reduced in both treatments. The strongest effects on BCC profiles as determined by 16S rDNA denaturing gradient gel electrophoresis were due to incubation time treatment particularly for BC. A phylotype corresponding to a specific BC band was closely related to Acinetobacter oleivorans DR1. Thus, this experimental study confirms potential anthropogenic influences on the bacterial community on aggregates in the Bay of Noumea.

How to cite: Weinbauer, M.: Ni and black carbon influence bacterial production, respiration and community composition in the barrier reef Lagoon of Noumea (New Caledonia): an experimental study, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8867, https://doi.org/10.5194/egusphere-egu2020-8867, 2020.

Heavy metals are considered to be among the most potent environmental contaminants, and their release into the environment is increasing rapidly since the last decades from various sources and activities and may enter into the environment by a wide range of pathways and processes. They can be translocated, disperse in the environment, and bio-concentrate in aquatic organisms, causing increase ecosystem degradation and leading to biodiversity loss. Furthermore, they may enter the food chain, creating health risks for both humans and animals. This study aimed to evaluate the ecotoxicological effects of anthropogenic pressure in semi-enclosed artificial lagoon ecosystems in the Gulf of Aqaba, Red Sea. Our findings with regard to heavy metal contamination showed that the area is contaminated by significant amounts of several potentially toxic heavy metals (such as Cd, Cr, Cu, and Fe). The anthropic intervention in the area impacted heavily the natural environment. We found that the biological test (lipid peroxidation) was a useful assay for assessing the overall health condition and response (stress level) towards natural and anthropogenic forces in the studied areas. The selected marine organisms (Holothuria atra, Tripneustes gratilla, Ulva lactuca and Halophila stipulacea) have the ability to accumulate several levels of heavy metals in their tissue with different trends of bioaccumulation. Therefore, they can be used as promising bioindicators for such research. The results obtained permit to assess the environmental effects of anthropogenic pressure and can be a useful basis for planning possible remediation projects.

How to cite: Wahsha, M. A. and Al-Najjar, T.: Ecotoxicological effects of anthropogenic pressure in semi-enclosed artificial lagoon ecosystems in the Gulf of Aqaba, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16480, https://doi.org/10.5194/egusphere-egu2020-16480, 2020.

Environmental monitoring of highly anthropised areas demands for deep survey of different environmental compartments (water, sediment, soil and biota) and determination of numerous bio-geo-chemical parameters, due to the huge impact of natural and anthropogenic organic substances constantly released into these environments. However, the interpretation of the large amount of data is not straightforward task due to their complexity that require a very tricky elaboration especially for the decision making processes. Chemo-metrics tools based on the multivariate statistical data analysis seems to be a powerful tool in addressing such complexity (Mali et al., 2017). In this work they are performed to get insight the occurrence of organic pollutants within a highly populated area such as the Gulf of Naples.

The Gulfs of Naples, located along the Eastern Tyrrhenian Sea, is semi-enclosed by the Ischia-Procida Islands to NW, Campi Flegrei and the Campanian Plain in NE, the Sorrento peninsula in SE, and Capri island in W. The Campania region has one of the highest population densities in Italy. The Gulfs of Naples are the receiving environment for persistent toxic substances from the Campania Plain (Albanese et al., 2010; Arienzo et al., 2017). Montuori and Triassi (2012) reported that the discharges of PAHs from the Sarno River to the Gulf of Naples is approximately 8530 g/d. The main goal of this work is to establish the influence of the Campania Plain on the present sedimentation in the Naples bay continental shelf by evaluating organic matter contribution and pollution. For this purpose, superficial sediment samples collected from 158 sites located offshore the Gulf of Naples between Sarno River and Capri Island, were analyzed for total nitrogen and phosphorus, total organic carbon (TOC), grain size, metals, priority polycyclic aromatic hydrocarbons (PAHs), total petroleum hydrocarbon (TPHs), volatile organic compounds (VOCs), polychlorinated biphenyls (PCBs), pesticides and organotin compounds (OTs). The adopted multivariate approach allowed, through a clear spatial representation of score plots, a deep dive into the large dataset generated by the investigation campaign, highlighting the influence of some main factors controlling the contamination pattern, such as organic matter content and depositional environment.

References

Albanese, S., De Vivo, B., Lima, A., Cicchella, D., Civitillo, D., Cosenza, A., 2010. Geochemical baselines and risk assessment of the Bagnoli brownfield site coastal sea sediments (Naples, Italy). J. Geochem. Explor. 105, 19–33.

Arienzo, M., Donadio, C., Mangoni, O., Bolinesi, F., Stanislao, C., Trifuoggi, M., Toscanesi, M., Di Natale, G., Ferrara, L., 2017. Characterization and source apportionment of polycyclic aromatic hydrocarbons (pahs) in the sediments of gulf of Pozzuoli (Campania, Italy). Mar. Pollut. Bull. 124, 480–487.

Mali, M., Dell'Anna, M.M., Notarnicola, M., Damiani, L., Mastrorilli, P., 2017. Combining chemometric tools for assessing hazard sources and factors acting simultaneously in contaminated areas. Case study: "Mar Piccolo" Taranto (South Italy). Chemosphere 184, 784-794.

Montuori, P., Triassi, M., 2012. Polycyclic aromatic hydrocarbons loads into the Mediterranean Sea: estimate of Sarno River inputs. Mar. Pollut. Bull. 64, 512–520.

How to cite: buonocunto, F. P., cardellicchio, N., di leo, A., esposito, E., ferraro, L., giandomenico, S., milia, A., spada, L., violante, C., and mali, M.: Multivariate tools to investigate the occurrence of pollutants in a highly anthropised marine area, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21954, https://doi.org/10.5194/egusphere-egu2020-21954, 2020.

Coastal areas are under compounding pressures from urbanization, industrialization, infrastructure growth, and aquaculture.  There is hence an urgent need for developing solutions for coastal pollution and ecosystem safety. In this work, based on our long-term and multidisciplinary ecosystem monitoring data, we develop tools to translate the observing data into management information to sustainable coastal use and development. From the existing data and experimental studies, we develop approaches to understand key processes and factors controlling coastal ecosystems and to define thresholds and guidelines values of ecological parameters to determine. With focus on marine ecosystem health assessment, we use the integrating data to describe ecosystem condition, its potential trend and the impact of existing pressures. This present study initially focused on the coastal area of the Yellow Sea, in the JIAOZHOU Bay. The technique of the structured research can be applied to other coastal regions as well to understand how these ecosystems respond to local and global pressures.

How to cite: Hu, Z., Logan, M., Sun, X., Brinkman, R., and Sun, S.: Assessment of cumulative impacts and coastal ecosystem health in the JiaoZhou Bay, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22276, https://doi.org/10.5194/egusphere-egu2020-22276, 2020.

Coastal zone is of great importance in the provision of various valuable ecosystem services. However, it is also sensitive and vulnerable to environmental changes due to high human populations and interactions between the land and ocean. Major threats of pollution from over enrichment of nutrients, increasing metals and persistent organic pollutants (POPs), and climate change have led to severe ecological degradation in the coastal zone, while few studies have focused on the combined impacts of pollution and climate change on the coastal ecosystems at the global level. A global overview of nutrients, metals, POPs, and major environmental changes due to climate change and their impacts on coastal ecosystems was carried out in this study. Coasts of the Eastern Atlantic and Western Pacific were hotspots of concentrations of several pollutants, and mostly affected by warming climate. These hotspots shared the same features of large populations, heavy industry and (semi-) closed sea. Estimation of coastal ocean capital, integrated management of land-ocean interaction in the coastal zone, enhancement of integrated global observation system, and coastal ecosystem-based management can play effective roles in promoting sustainable management of coastal marine ecosystems. Enhanced management from the perspective of mitigating pollution and climate change was proposed.

How to cite: Lu, Y., Yuan, J., Lu, X., Su, C., Zhang, Y., Quan, Y., and Xie, W.: Major threats of pollution and climate change to global coastal ecosystems and enhanced management for sustainability, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22316, https://doi.org/10.5194/egusphere-egu2020-22316, 2020.

Trace metals are important micronutrient for marine microbial life. They support many metabolic reactions necessary for bacteria, phytoplankton and zooplankton, however, some trace metals such as Cu or Zn may have toxic effects at high concentrations. The processes shaping trace metals distribution and cycling in the ocean are still poorly understood. Furthermore, the evolution of trace metals distributions as a consequence of climate change has never been investigated.

This work aims at characterizing the potential impacts of climate change on the global biogeochemical cycling of essential trace metals. We use a state-of-the-art global ocean biogeochemical model representing a suite of trace elements (Fe, Cu, Zn, Co, Mn) to investigate how their distribution and inventories may change in response to the RCP8.5 climate change scenario. The changing ocean circulation in this scenario may result in surface stratification, resulting in changes in biological pump strength, oxygen distribution and particle loadings. In regions affected by external inputs, surface concentration of micronutrient may increase as a result of surface stratification. On the other hand, surface micronutrient concentrations may decrease in the open ocean as a result of the decline in vertical supply of nutrients. We use an extended Redfield ratio calculation in order to characterise the changes in trace metal concentrations and highlight the regions where trace metal cycling is the most affected by climate change. Results show that cobalt and manganese concentrations display important evolutions in the Arctic whereas zinc is mostly impacted in the Southern Ocean. Our results suggest that changes to the ocean physics and productivity will impact trace metals differently depending on their role and biogeochemical drivers.

How to cite: Richon, C. and Tagliabue, A.: Will climate change impacts the biogeochemical cycles of essential micronutrients?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19136, https://doi.org/10.5194/egusphere-egu2020-19136, 2020.

Artificial fish reefs are the underwater structures placed on the ocean floor to simulate some characteristics of natural reefs. The onshore current can be transformed into upwelling under the influence of artificial fish reefs, thus the nutrient at the bottom of the near shore can be raised, which increases the prey of plankton and fish yield. In order to investigate this phenomenon, a 3D large eddy simulation (LES) of the ocean boundary layer was combined with four different types of artificial fish reef terrains (square, convex-fan, isosceles right triangle, concave-fan). In the near surface, almost only the square terrain can uplift the nutrient, which brings about the most uniform nutrient distribution. Based on the size of integral values of nutrient concentration in the upper part of the four reefs, they are listed as follows: square terrain, convex-fan terrain, isosceles right triangle terrain, concave-fan terrain decreases (from largest to smallest). What is more, the integral values of the four terrains reduce exponentially. Because the nutrient flow encounters the square terrain’s vertical plane, it has a larger vertical velocity. Nevertheless, for convex-fan terrain and isosceles right triangle terrain, their slopes are smoothly, resulting in poor lifting effect. Meanwhile, compared with the other three types of terrains, the concave-fan terrain can prevent the overflow of nutrients better. Among those four reefs, it can be found the square-shaped artificial fish reef is the best one for uplifting the nutrient.

How to cite: Wang, Z. and Li, S.: A large eddy simulation study of the inshore nutrient uplift process: The role of topography, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12913, https://doi.org/10.5194/egusphere-egu2020-12913, 2020.