BG4.4 | Biogeochemistry of coastal seas and continental shelves
EDI
Biogeochemistry of coastal seas and continental shelves
Co-sponsored by JpGU
Convener: Helmuth Thomas | Co-conveners: Hiroshi Kitazato, Alberto V. Borges, Craig Smeaton, Katarzyna Koziorowska-Makuch, Arthur Capet, Petra Heinz
Orals
| Thu, 27 Apr, 08:30–12:30 (CEST)
 
Room 2.17
Posters on site
| Attendance Thu, 27 Apr, 16:15–18:00 (CEST)
 
Hall A
Posters virtual
| Attendance Thu, 27 Apr, 16:15–18:00 (CEST)
 
vHall BG
Orals |
Thu, 08:30
Thu, 16:15
Thu, 16:15
The coastal ocean has been increasingly recognized as a dynamic component of the global carbon budget. This session aims at fostering our understanding of the roles of coastal environments and of exchange processes, both natural or perturbed, along the terrestrial / coastal sea / open ocean continuum in global biogeochemical cycles. During the session recent advancements in the field of coastal and shelf biogeochemistry will be discussed. Contributions focusing on carbon and nutrient and all other element's cycles in coastal, shelf and shelf break environments, both pelagic and sedimentary, are invited.

This session is multidisciplinary and is open to observational, experimental, modelling and theoretical studies in order to promote the dialogue. The session will comprise subsections on coastal carbon storage, on benthic biogeochemical processes and on biological and ecological experimental approaches in marine bogeosciences.

The session is co-sponsored by JpGU.

Orals: Thu, 27 Apr | Room 2.17

Chairpersons: Petra Heinz, Helmuth Thomas, Katarzyna Koziorowska-Makuch
08:30–08:35
08:35–08:45
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EGU23-976
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Virtual presentation
Malcolm Hart, Christopher Smart, Giulia Molina, and Claire Widdicombe

The Western Channel Observatory (Smyth et al., 2015) was established by the Natural Environmental Research Council (NERC), with Plymouth Marine Laboratory managing the two autonomous buoys that are located to the south of Plymouth in the English Channel (Stations L4 and E1). These two locations are now monitored continually and there is regular sampling of the water column and the sea floor at Station L4. At this location, despite it being located in water with a depth of 50 m, benthic foraminifera are regularly found in the surface water plankton samples. Some of these benthic foraminifera appear to contain algal symbionts, indicating that they may have been living at the time of capture. If benthic foraminifera can be entrained in the water column, while still living, then this provides a mechanism for dispersal or migration that is much more rapid and efficient than the rate at which protists could migrate within, or on, the sediment surface. Re-colonization by foraminifera, following disturbance, could well be facilitated by this mechanism which has only rarely been reported in the literature (Murray, 1965). It is clearly limited to depths impacted by fair weather (~30 m) or storm wave base (80–100 m).

Observations of vertical plankton tow (20 μm mesh) samples collected at Station L4 during the three winters (2015–2018) have shown that, following significant storms, the numbers of benthic foraminifera in the plankton tows are increased (Hart et al., 2017). Some of the specimens contain sediment, indicating that they have been picked up from the sediment surface and are in the process of being re-deposited. Such assemblage mixing has significant implications for the interpretation of both modern, and ancient, environments. Analysis of sea floor samples in the area has shown that the recorded species are from the area of Station L4 or Hillmars (in 50 m water depth) although some may have been transported from shallower-water settings by increased run-off during the storm events.

Clearly, re-distribution of foraminifera in the environment might make subsequent interpretations of ecology less accurate if the ‘living’ assemblage is not identified (by staining), but in the fossil record such changes could go completely un-detected and lead to inaccuracy in interpretations of palaeoecology.

 

Hart, M.B., Molina, G.S., Smart, C.W. and Widdicombe, C.E. 2017. The Western Channel Observatory: benthic foraminifera in the plankton following storms. Geoscience in South-West England, 14(1), 39–45. [for 2016]

Murray, J.W. 1965. Significance of benthic foraminiferids in plankton samples. Journal of Paleontology, 39, 156–157.

Smyth, T., Atkinson, A., Widdicombe, S., Frost, M., Allen, I., Fishwick, J., Queiros, A., Sims, D. and Barange, M. 2015. The Western Channel Observatory. Progress in Oceanography, 137, 335–341.

 

How to cite: Hart, M., Smart, C., Molina, G., and Widdicombe, C.: Benthic foraminifera in the plankton: how might this impact on palaeoecological interpretations?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-976, https://doi.org/10.5194/egusphere-egu23-976, 2023.

08:45–08:55
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EGU23-10163
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ECS
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On-site presentation
Han Wang, Diana Ruiz-Pino, Silvia Gardin, Ian Probert, and Gerald Langer

The magnesium/calcium ratio of seawater has oscillated throughout the geological time between aragonite seas (>2) and calcite seas (<2), which strongly influenced coccolithophores biocalcification, along with the variation of ocean temperature and pH. Here we proposed to analyze in a concomitant way the effect of temperature and pH together with Mg/Ca on coccolithophores. 

In this study, we cultured Emiliania huxleyi (RCC963) under a range of Mg/Ca ratios (Mg/Ca: 0.2, 1, 5), temperature (15, 21.5, 28) and pH (7.4, 7.8, 8.2) to evaluate the cell adaption and calcification sensitivity by measuring the growth rate(μ), Photosystem efficiency (Fv/Fm), calcification rate and coccolith morphology. We have found that in the calcite sea, E. huxleyi is more vulnerable to changes of temperature and pH than it is in the aragonite sea. The coccolith morphology also supports the different response to the Mg/Ca ratio variation where more malformed and incomplete coccoliths were observed with the decreasing of temperature and pH. Further exploration is needed to understand the multi-changes in environmental parameters in the distribution of Mg in coccoliths of E. huxleyi and morphogenesis. 

How to cite: Wang, H., Ruiz-Pino, D., Gardin, S., Probert, I., and Langer, G.: Calcification response of Emiliania huxleyi under calcite and aragonite sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10163, https://doi.org/10.5194/egusphere-egu23-10163, 2023.

08:55–09:05
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EGU23-16323
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Virtual presentation
Takashi Toyofuku and Nagai Yukiko

Calcareous foraminifera is a unicellular protist that possesses calcium carbonate shells and is commonly found in the oceans. Biomineralization of these organisms has been extensively studied, as the shells of these organisms hold valuable information about past environmental conditions. In particular, the evolution of foraminiferal assemblages in different environments has been well-documented throughout geologic time, and they are often used as facies fossils and reference fossils.

In this study, we aimed to estimate the calcification rate of the species Spirillina vivipara, which is known for its fast generational turnover and rapid shell growth rate. Foraminifera samples were collected from the Enoshima Aquarium in Fujisawa City, Japan, and kept in an incubator with a 12-hour light/dark cycle and a constant temperature of 20°C. The foraminifera was reared in filtered seawater with a salinity of 35 and fed twice a week with live Dunaliella sp.
To observe the calcification process, we recorded the elongation rate of testes by time-lapse observation using differential interference microscopy and calcein-containing seawater to mark the shells. We then used multiple techniques, including a focused ion beam (FIB)-SEM, to measure the thickness of the shells. In this presentation, we will present the results of our study on the shell growth rate of foraminifera and compare them with previous studies.

How to cite: Toyofuku, T. and Yukiko, N.: Estimation of calcification rate of Spirillina vivipara, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16323, https://doi.org/10.5194/egusphere-egu23-16323, 2023.

09:05–09:15
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EGU23-7935
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ECS
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On-site presentation
Laurie Charrieau, Claire Rollion-Bard, Anja Terbrueggen, David Wilson, Philip Pogge von Strandmann, Sambuddha Misra, and Jelle Bijma

The chemical weathering of continental silicate rocks removes CO2 from the atmosphere and exerts a fundamental control on the Earth’s climate over geological timescales. Characterizing silicate weathering in the past is therefore crucial for understanding the climate system. The lithium isotopic composition (δ7Li) of carbonates is considered to be a reliable archive of past seawater δ7Li values, which are useful as a tracer of silicate weathering. However, the Li isotopic fractionation during biogenic carbonate formation is complex, and local conditions such as carbonate system parameters could impact δ7Li values in marine calcifiers. For example, δ7Li values have been shown to be dependent on either pH or DIC in two studies using large benthic foraminifera. Those results are enigmatic, since both studies used similar species of the genus Amphistegina but reported differing controls on δ7Li values.

The aim of this study was to address the earlier contradictory results on the Li isotope behaviour in the hyaline species Amphistegina lessonii. We performed culture experiments under decoupled pH/DIC conditions, and analysed the δ7Li values and Li/Ca ratios in the foraminifera tests. Two different light treatments (light/dark and dark) were also implemented to investigate the potential role of the symbionts.

Contrary to the two previous studies, no links between either pH or DIC and δ7Li or Li/Ca values were observed for any of the treatments in our experiments. Additionally, growth rates also did not seem to influence the Li incorporation or isotopic fractionation. However, an effect of different light treatments was observed, probably due to different physiological processes of the symbionts occurring in dark conditions. Overall, these findings appear to support the use of Li isotopes in large benthic foraminifera to reconstruct past seawater chemistry and to infer changes in chemical weathering during carbon cycle perturbations over the last several hundred million years of Earth history.

How to cite: Charrieau, L., Rollion-Bard, C., Terbrueggen, A., Wilson, D., Pogge von Strandmann, P., Misra, S., and Bijma, J.: Lithium incorporation and isotopic fractionation in large benthic foraminifera under decoupled pH/DIC conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7935, https://doi.org/10.5194/egusphere-egu23-7935, 2023.

09:15–09:25
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EGU23-3402
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ECS
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On-site presentation
Yaroslav Trubin and Martin Langer

The Line Islands rank among the most isolated in the tropical Pacific, hold a biogeographic key position for the translocation of taxa across the Pacific, and constitute the ultimate stepping stone for the dispersal of species from east to west and vice versa. Because benthic foraminifera have limited dispersal capabilities, these isolated stepping stones are crucial for ecological and biogeographic studies. Mapping large-scale biogeographic patterns is vital for setting conservation priorities by revealing biogeographic variability and enabling the identification of species richness hot- and coldspots. Here we present the first results of a comprehensive survey of modern benthic foraminiferal assemblages from the Line Islands and compare the foraminiferal assemblages to other regions in the Pacific Ocean. We also document the diversity and composition foraminiferal biotas from inhabited and uninhabited islands to assess the impact of anthropogenic activities.

The large number of species identified allow us to place the Line Islands into a biogeographic context and to assess the role of these remote islands as a stepping stone for the translocation of species across the Pacific Ocean. Our study provides novel insights into underlying mechanisms that promote species richness patterns in different shallow-water habitats.

The sediments analyzed includes material from the inhabited Tabuaeran Island, also known as Fanning and the uninhabited Palmyra Island. The environments of the island comprise a multitude of habitats including coral reef areas, lagoons, and algal covered shallow bays.

The foraminiferal associations from coral habitats are dominated large benthic foraminifera (LBF) such as Amphistegina, Sorites, and Peneroplis and low amounts of various miliolids. The preservation of nearshore assemblages revealed predominantly abraded and broken individuals. The assemblages from nearshore beaches and reef flats are composed of miliolids, numerous perforate-hyaline, and variable amounts of diverse LBF. The foraminiferal assemblages from algal covered beaches comprise a suite of diverse smaller miliolids and rare, mainly juvenile forms of Sorites. Our survey provides novel insight into the preservation, habitat-preferences, diversity and biogeography of benthic foraminifera across the tropical Pacific.

How to cite: Trubin, Y. and Langer, M.: Benthic foraminifera from extremely shallow-water habitats of Line Islands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3402, https://doi.org/10.5194/egusphere-egu23-3402, 2023.

09:25–09:35
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EGU23-1332
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ECS
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On-site presentation
Tania L. Maxwell, Mark Spalding, and Thomas A. Worthington and the global marsh soil C team

Tidal marshes are a threatened coastal ecosystem valued for their capacity as a carbon sink. Given that effective action on climate change includes the protection, enhancement and restoration of natural carbon sinks, it is crucial to accurately quantify and map the current soil carbon stocks in this ecosystem. We aim to produce the first globally consistent map of soil carbon storage in tidal marshes.

A globally distributed soil carbon core dataset was compiled by a systematic literature review (n = 2,127 locations), supplemented by data from the Coastal Carbon Research Coordination Network database (n = 1,798 locations). We then developed a list of global landscape-level environmental drivers that are important in determining variation in soil carbon, including vegetation indices, elevation, flow accumulation, water occurrence, tidal amplitude, and other climatic variables. 

Using the carbon cores as training data and the environmental driver data as covariate layers, we are developing a machine learning model to map global marsh carbon stocks and their uncertainties at 0-30 and 30-100 cm depths, at a high resolution, and applying these to a new globally consistent tidal marsh extent map. The model and the global map will be easily updatable when new information (i.e. additional soil cores) becomes available. This map will be valuable to support conservation efforts, compliment blue carbon studies, and Nationally Determined Contributions.

How to cite: Maxwell, T. L., Spalding, M., and Worthington, T. A. and the global marsh soil C team: Global map of soil carbon in tidal marshes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1332, https://doi.org/10.5194/egusphere-egu23-1332, 2023.

09:35–09:45
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EGU23-1520
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ECS
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On-site presentation
Sara Pino Cobacho, Sjoerd Janssen, Mabel Brekelmans, Ingrid van de Leemput, Milena Holmgren, and Marjolijn Christianen

Mangrove forests provide a wide range of benefits for natural and human communities in tropical and subtropical coastlines. Mangrove restoration using seedlings is vital to counteract the loss of mangrove forests, currently estimated at 3.4% over the past 24 years, with mangroves disappearing at a rate twice as large as their gain. Restoration success depends on the successful establishment of seedlings in the new environment, which may be influenced by unexplored factors such as nutrient status and temperature in selected sites. In order to determine the role of these two factors on mangrove seedling growth and development once they have been outplanted, we set up a laboratory experiment consisting of two climate rooms at 25ºC and 30ºC mimicking a standard and a future global warming scenario. These two temperature levels were combined with two different nutrient levels representing a standard and an eutrophication scenario. We assessed the influence of increased nutrients and temperature on the development and photosynthetic performance of black mangrove seedlings over a period of 10 weeks, and studied their responses to the individual and combined effects of these drivers. Seedling growth was measured as leaf area, plant length and above/ below biomass development. In addition, we determined the photosynthetic performance of seedlings by applying the Pulse Amplitude Modulated (PAM) fluorometry technique. Our results showed reduced root growth and disproportionally long, bent stems, with lower net assimilation rates under the combined effects of high temperature and nutrient concentrations. These outcomes, specially the nearly-negligible root growth suggest a low stability as the seedlings fail to anchor themselves to the sediment, which may translate into a greater vulnerability to physical disturbance leading to their dislodgement. On this basis, we recommend that local hydrodynamic conditions and nutrient status are taken into consideration for improving future site selection and increasing restoration success under a warming climate. Our results also suggest that the impacts of global-scale processes such as global warming could be dampened by the implementation of local policies, such as preventing coastal eutrophication.

How to cite: Pino Cobacho, S., Janssen, S., Brekelmans, M., van de Leemput, I., Holmgren, M., and Christianen, M.: Higher temperature and nutrient concentrations may decrease black mangrove seedling stability during coastline recovery   , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1520, https://doi.org/10.5194/egusphere-egu23-1520, 2023.

09:45–09:55
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EGU23-8734
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On-site presentation
Joonas Virtasalo, Peter Österholm, and Eero Asmala

Among the most important processes affecting the global biogeochemical cycles of carbon, nutrients and trace metals is the physicochemical transformation of terrestrial dissolved and colloidal material into suspended particles in estuaries. The gradient of increasing salinity and pH towards seawater induces the flocculation of riverine dissolved organic matter to the particulate form, providing a mechanism for the capture of dissolved metals to the newly formed particles. The role of pH is particularly relevant in the context of acid sulphate (AS) soils that can generate extremely low pH conditions and high soluble trace metal concentrations in river waters.

This study investigated organic matter flocculation, and trace metal (Al, Fe, Co, Mn and Cu) association with the newly formed organic particles, by the mixing of natural acidic river water and synthetic seawater in the laboratory. River water was collected from the Laihianjoki and Sulvanjoki rivers that are among the most AS-soil-impacted rivers in Finland and Europe. Continuous bucket experiments with an in situ LISST-100X particle size distribution analyser and YSI EXO2 multiparameter water quality sonde were run to simulate the development of suspended particle pool over the local salinity gradient from 0 to 6. Jar experiments with discrete salinity treatments were carried out to investigate metal behaviour with the collection of flocculated material on glassfibre filters. The filter samples were subjected to persulfate digestion of organic particles and metal oxyhydroxides (pH <2.3) and the digestion supernatants were analysed for metal concentrations by ICP-MS.

It was found that Al and Fe were strongly transferred to the particle pool and captured in large (>80 µm) organic flocs already in the lowest salinity range from 0 to 2, with a slightly lower transfer rate at higher salinities. The increasing concentration of small (median 11 µm) flocculi particles above pH ca. 5.5 (salinity 1 in Laihianjoki, salinity 2 in Sulvanjoki) indicate that the precipitation of Al and Fe oxyhydroxides contributed to the particle pool as a minor component. Co and Mn were weakly associated with organic complexes and relatively persistent in solution; however, the transfer of Co to the particle pool was roughly twice of that of Mn, indicating at least partial decoupling of Co from Mn oxyhydroxide precipitation. Cu to a significant proportion (<60 %) was bound to organic particles in the acidic and humic-rich rivers, and this proportion did not change significantly during mixing with seawater. The findings of this study demonstrate that salinity and pH in the estuarine mixing are important controls for the seaward transport and environmental impacts of metal loading from boreal AS-soil-impacted rivers.

How to cite: Virtasalo, J., Österholm, P., and Asmala, E.: Flocculation of trace metals from boreal acid sulphate soils over an estuarine gradient, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8734, https://doi.org/10.5194/egusphere-egu23-8734, 2023.

09:55–10:05
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EGU23-11942
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ECS
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On-site presentation
Hannah Muir, Jacqui Keenan, Rowan Henthorn, James Strong, David G. Reading, Peter Duncan, Martin W. Skov, Jan G. Hiddink, Richard K. F. Unsworth, Phillip E. Warwick, and Claire Evans

Shelf sea sediments are natural, long-term carbon sinks that may be managed for Blue Carbon (BC) storage to offset greenhouse gas emissions and contribute to nations ‘Net Zero’ ambitions. The Isle of Man in the Irish Sea has territorial waters equivalent to approximately 85% of its total jurisdiction, and significant potential for BC offsetting through seabed management. The Island’s Government is developing a comprehensive BC management plan to maximise carbon sequestration and restore seabed biodiversity and wider ecosystem services. We determined the effects of disturbance on sedimentary carbon stocks and accumulation rates in the western territorial sea, a region of mud-dominated sediment with elevated disturbance from Nephrops norvegicus bioturbation and bottom-contact fishing activities. Sediment cores were collected from approximately 5 to 12 nautical miles off the west coast of the Isle of Man, at depths from 60 m to 120 m. The cores were sectioned and analysed using: elemental analysis and isotope ratio mass spectrometry to quantify organic and inorganic carbon stocks; and gamma-ray spectrometry and alpha spectrometry to identify and quantify radionuclides of Cs-137, Pb-210, Am-241 and Po-210 to determine sedimentation rates. Complete sediment cores were scanned using X-ray to generate radiographs and laminographs, to determine internal core structure and identify N. norvegicus burrows. The results show that organic/inorganic carbon and sedimentation rates in offshore sediments vary over time and space. Analysis is ongoing to ascertain if these variations are related to disturbance of the sedimentary system, using indicators of fishing intensities and N. norvegicus bioturbation. Results of this analysis will be presented to elucidate the effects of disturbance on sedimentary carbon stocks and accumulation.

How to cite: Muir, H., Keenan, J., Henthorn, R., Strong, J., Reading, D. G., Duncan, P., Skov, M. W., Hiddink, J. G., Unsworth, R. K. F., Warwick, P. E., and Evans, C.: Influence of Disturbance on Sedimentary Carbon Stocks in a Temperate Seabed, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11942, https://doi.org/10.5194/egusphere-egu23-11942, 2023.

10:05–10:15
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EGU23-12822
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ECS
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On-site presentation
Yord Yedema, Francesca Sangiorgi, João Trabucho Alexandre, Jorien Vonk, and Francien Peterse

River-dominated continental margins receive large inputs of terrestrial organic matter (TerrOM). This TerrOM can potentially form a long-term sink for atmospheric CO2 upon burial in continental margin sediments, thereby forming a key component of the global carbon cycle. However, only part of the TerrOM that is delivered to the coastal zone is preserved on the seafloor, as its sequestration efficiency depends on its properties and composition. The composition and quality of TerrOM on the seafloor is usually not determined, hampering estimates of its contribution to carbon sequestration on the continental margin. Moreover, TerrOM is thought to form associations with mineral surfaces that protect it from degradation, but it is not fully known to which extent these associations persist in the marine realm and if different types of TerrOM preferentially bind to certain minerals.  

Here, we investigated the TerrOM composition in different grain size fractions (>250, 250–125, 125–63, 63–30, 30–10 and <10 μm) of surface sediments along a land-sea transect (15–600 m water depth) in the northern Gulf of Mexico, using bulk properties (TOC, TN, δ13Corg) and lipid biomarkers for plant- (long-chain n-alkanes), fluvial- (long-chain C32 1,15-diol) and soil-microbial derived OM (branched glycerol dialkyl glycerol tetraethers; brGDGTs). In addition, we used mineral surface area analysis and X-ray diffraction (XRD) to assess whether different TerrOM types have an affinity for certain minerals.

We found that along the land-sea transect, the concentrations and mineral loading of n-alkanes remained constant, while the concentrations of both brGDGTs and the C32 1,15-diol rapidly decreased. Moreover, the concentrations of lipid biomarkers, in particular the n-alkanes, were highest in the smaller (<30 μm) size fractions along the transect. This suggests that n-alkanes likely form associations with clay minerals, in particular smectite, as shown by our XRD results.

However, n-alkanes might also be more resistant against degradation than the brGDGTs and diols,  further explaining their presence offshore. While brGDGT concentrations also increase towards smaller grain sizes, their molecular signature is constant among size fractions at each site, suggesting that they are not bound to a specific grain size fraction. Furthermore, an increase in the degree of cyclisation of the brGDGTs between 50 and 150 m water depth indicates that the initial soil-derived signal is strongly overprinted by an in situ marine contribution in this zone.

Our results show that in coastal waters, plant-derived OM is more likely to remain associated with mineral (smectite) surfaces than soil-microbial and fluvial OM, thereby facilitating its transport further offshore through hydraulic sorting and preferential burial on the shelf.

How to cite: Yedema, Y., Sangiorgi, F., Trabucho Alexandre, J., Vonk, J., and Peterse, F.: The influence of mineral associations on terrestrial particulate organic matter transfer and dispersal in the northern Gulf of Mexico, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12822, https://doi.org/10.5194/egusphere-egu23-12822, 2023.

Coffee break
Chairpersons: Craig Smeaton, Arthur Capet, Helmuth Thomas
10:45–10:50
10:50–11:00
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EGU23-645
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ECS
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On-site presentation
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Dunia Rios Yunes, Justin C. Tiano, Emil De Borger, Dick van Oevelen, and Karline Soetaert

Coastal areas are subjected to several anthropogenic stressors with much of the world’s intertidal areas receding due to human activities, coastal erosion, and sea level rise. The Eastern Scheldt (ES) tidal bay in The Netherlands is predicted to lose around 35 % of intertidal areas by 2060. Our study investigated differences between biogeochemical fluxes of intertidal and subtidal sediments of the ES and assessed how ongoing intertidal loss may modify the sedimentary ecosystem functioning of this tidal bay in the coming decades. Monthly fluxes and porewater concentrations of dissolved inorganic nitrogen (DIN), phosphorous (DIP), silica, carbon and oxygen (O2) as well as organic matter characteristics were measured from intertidal and subtidal sediments from June 2016 – December 2017. O2 fluxes were 37% higher in the intertidal, and these sediments exhibited influxes of nitrates (-1.2 mmol m-2 d-1) and DIP (-0.03 mmol m-2 d-1). In contrast, subtidal sediments exhibited an average efflux of nitrates (0.28 mmol m-2 d-1) and DIP (0.09 mmol m-2 d-1). Intertidal areas removal of DIN and DIP was 34 % and 38% higher than in the subtidal suggesting stronger denitrification and phosphorus adsorption to solid particles. The potential loss of biogeochemical functionality due to intertidal area loss by 2060 was estimated. In the next 40 years, the ES tidal bay may experience a reduction of 11 % and 8 % for respective nitrogen and phosphorus removal. Given the global observations of eroding intertidal areas and rising sea levels, we suggest that the predicted habitat loss may cause significant changes for coastal biogeochemistry and should be investigated further to understand its potential consequences for coastal ecosystems.

How to cite: Rios Yunes, D., Tiano, J. C., De Borger, E., van Oevelen, D., and Soetaert, K.: Differences between subtidal and intertidal benthic biogeochemistry: implications of intertidal area loss for ecosystem functionality, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-645, https://doi.org/10.5194/egusphere-egu23-645, 2023.

11:00–11:10
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EGU23-9006
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Virtual presentation
David González Santana, Aridane G. González, Veronica Arnone, Melchor González-Dávila, and J. Magdalena Santana-Casiano

The interaction between lava and seawater has received significant interest, since multiple reactions can take place which act as sources or sinks of elements, consequently changing the chemical properties of the surrounding seawater. However, most of these studies are based on underwater hydrothermal vent sites. On the 19th of September 2021, 6 km away from the coast, the Tajogaite volcano in La Palma, Canary Islands started its eruptive phase.

Lava flows reached the shoreline during three events on September 28th, November 10th, and November 22nd, strongly affecting the seawater properties as they interacted with the seawater. The evolution of surface and water column physicochemical properties (temperature, salinity, carbonate system variables, dissolved oxygen), iron concentrations (soluble (sFe), dissolved (dFe) and total dissolvable (TdFe)) concentrations, and iron ligands were characterized during 13 visits to the frontal zone of the newly formed deltas. A large volume of hot (50°C measured on November 12th) and high salinity seawater promoted pH values in the frontal zone of 7.0 with important decreases in alkalinity and total dissolved inorganic carbon. These waters were also characterised by high iron concentrations reaching 18 nM, 117 nM, and 2024 nM for sFe, dFe, and TdFe, respectively. The affected waters travelled in the top meter of the water column over 1 km away from the coast, naturally fertilising the surrounding photic layer.

How to cite: González Santana, D., González, A. G., Arnone, V., González-Dávila, M., and Santana-Casiano, J. M.: Subaerial lava as a source of coastal hydrothermal iron, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9006, https://doi.org/10.5194/egusphere-egu23-9006, 2023.

11:10–11:20
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EGU23-14229
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ECS
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On-site presentation
Silvia Placitu, Sebastiaan van de Velde, Elizabeth K. Robertson, Per O. J. Hall, and Steeve Bonneville

Burial of organic carbon (OC) in marine sediments controls atmospheric CO2 and O2 concentrations and is a key process in the global carbon cycle. Marine sediments bury ~160 Tg C yr-1 globally, of which ~90% in continental shelf sediments, which makes these sites a burial hotspot. It is generally assumed that OC is buried more efficiently in sediments underlying anoxic bottom waters. Recently, however, sediments of the Gotland Basin (Baltic Sea) have been shown to have unusually low OC burial efficiencies (~10%) considering their sediment accumulation rates, despite being overlaid by anoxic bottom waters.  

To investigate the reason for this lower-than-expected OC burial efficiency, we sampled five sites along a transect (including two sites for Fe-OM assessment) across the Western Gotland Basin. Sulphate reduction rate measurements showed that the OC reactivity was much higher than was expected for the age of the OC. Subsequent analysis of iron-organic matter associations and OC-to-surface area ratios showed that the potential for physical protection via either coprecipitation with iron minerals or mineral adsorption was very low (below the detection limit in one core and a maximum of 7% of OC linked to Fe in the other, which is low compared to the global average of ~20%). Our results suggest that in the Western Gotland Basin, the absence of physical protection seems to allow for unusually high mineralisation rates (low OC burial efficiency) despite anoxic conditions. Consequently, the link between oxygen exposure and OC mineralisation rate is likely not as universal as currently assumed.

 

How to cite: Placitu, S., van de Velde, S., Robertson, E. K., Hall, P. O. J., and Bonneville, S.: Unexpectedly low organic carbon burial efficiency in anoxic sediments is linked to the absence of physical protection: lessons from the Western Gotland Basin (Batic Sea), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14229, https://doi.org/10.5194/egusphere-egu23-14229, 2023.

11:20–11:30
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EGU23-3898
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On-site presentation
Johannes Paetsch, Vlad A. Macovei, Yoana G. Voynova, Wilhelm Petersen, and Lennart Möller

The partial pressure of carbon dioxide (pCO2) in surface waters is influenced by physical, chemical and biological variables. The interplay of these environmental variables is shown along a section in the central North Sea between Immingham (UK) and Halden (Norway) for the year 2013. Both, underway measurements by ships of opportunity and the results of a high resolution 3D – biogeochemical model show very high pCO2 values near the UK coast and reduced values near the Norwegian coast. This pattern is due to high UK river loads at the western part and the outflow of Baltic water along the Norwegian coast at the eastern part of the section. Seasonal variations within the central North Sea off the coastal waters exhibit both the influence of temperature and biological activities. During the phytoplankton growth seasons, the pCO2 is considerably lowered by the biological uptake of dissolved inorganic carbon and concurrently increased by higher sea surface temperatures.

The model is able to reproduce observed winter pCO2 values using a variety of different bulk air-sea flux formulas. However, during spring and summer, the use of these formulas results in overestimated simulated pCO2 values. Only the application of a formula which takes the presence of surfactants into consideration improved the simulated pCO2 values. The latter formula exhibits lower piston velocities for the exchange of CO2 between atmosphere and ocean than the common formulas.

How to cite: Paetsch, J., Macovei, V. A., Voynova, Y. G., Petersen, W., and Möller, L.: Observed and simulated variations of marine partial pressure of CO2 within the central North Sea: The choice of the bulk air-sea flux formula matters, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3898, https://doi.org/10.5194/egusphere-egu23-3898, 2023.

11:30–11:40
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EGU23-1403
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On-site presentation
|
David Kaiser, Yoana Voynova, and Holger Brix

In 2018, Europe experienced an unprecedented heatwave and drought, especially in central and northern Europe, which caused decreased terrestrial production and ecosystem health. The effects on the marine environment are yet unclear. Here we investigate the biogeochemical response to the event in the German Bight of the North Sea. Using time series data from FerryBoxes, research cruises, monitoring programs and remote sensing we compare conditions in 2018 to climatological values. We hypothesize that (1) the heatwave caused unusual warming of surface waters, (2) the drought reduced river discharge and nutrient loads to the coast, and (3) the combined effects altered coastal biogeochemistry and productivity. During 2018, both water discharge and nutrient loads from rivers discharging into the German Bight were extremely low from March onward. Throughout the study domain, water temperature was unusually low in March 2018, but extremely high in May 2018, representing the fastest spring warming on record. This extreme warming period saw concurrent unusually high peaks in chlorophyll a, dissolved oxygen and pH values, consistent with the development of a strong spring bloom. It appears that productivity was unusually strong in near-shore regions, while offshore it was unusually low in 2018. The drought related low discharge limited nutrient supply from the rivers, but likely enhanced near-shore water residence time, where a burst of effective nutrient utilization during the spring depleted nutrients available for transport off shore. There, the heatwave related rapid surface water warming resulted in the establishment of a stable thermal water column stratification, hindering vertical nutrient supply to the surface layer during the summer.

How to cite: Kaiser, D., Voynova, Y., and Brix, H.: Effects of the 2018 European heatwave and drought on coastal biogeochemistry in the German Bight, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1403, https://doi.org/10.5194/egusphere-egu23-1403, 2023.

11:40–11:50
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EGU23-2517
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ECS
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Highlight
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On-site presentation
Sarah Seabrook, Cliff Law, Matt Druce, Vonda Cummings, Stacy Deppeler, Simon Cox, Rogier Westerhoff, Jess Hillman, Adina Paytan, Jill Mikucki, Yoann Ladroit, Alicia Maurice, Erica Spain, and Karl Safi

Climate warming is increasing glacial melt on the Antarctic continent, in turn shifting hydrostatic pressure on subglacial and surface lakes. This has a direct impact on the rates ofgroundwater discharge, with feedbacks to local and regional ocean and climate dynamics, as well as ice sheet retreat rates. The magnitude and diversity of Antarctic subglacial flux and its interaction with the marine realm is currently unknown, yet it may be critical to projecting hydrologic dynamics and the fate of coastal ecosystems in the Ross Sea under future climate change scenarios. Here, we report the first holistic quantification of the magnitude, composition, and impact of subglacial fluxes documented in the Antarctic region. With extensive water column, sediment, and ecological sampling we have explored the magnitude, biogeochemical composition, and temporal variability of subglacial water and dissolved constituent fluxes in the Ross Sea. We will highlight initial findings from this research, including the magnitude and spatial variability of subglacial fluxes from the Victoria Land coast, and the sphere of influence of these fluids on the coastal marine ecosystem in the Ross Sea.  We will place discoveries to date in the context of this emerging field, including incorporation into ice sheet and oceanographic models of the region. With this, we provide the first direct evidence of land-sea connectivity in the Ross Sea coastal environment through submarine groundwater discharge (SGD) and establish a critical baseline for measuring and predicting future change.

 

How to cite: Seabrook, S., Law, C., Druce, M., Cummings, V., Deppeler, S., Cox, S., Westerhoff, R., Hillman, J., Paytan, A., Mikucki, J., Ladroit, Y., Maurice, A., Spain, E., and Safi, K.: Antarctic subglacial flux: a driver of climate sensitivity on coastal margins, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2517, https://doi.org/10.5194/egusphere-egu23-2517, 2023.

11:50–12:00
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EGU23-16078
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On-site presentation
Karol Kulinski, Fernando Aguado Gonzalo, Laura Bromboszcz, Magdalena Diak, Katarzyna Koziorowska-Makuch, Przemyslaw Makuch, Izabela Palka, Piotr Prusinski, Seyed Reza Saghravani, Beata Szymczycha, and Aleksandra Winogradow

Rising CO2 concentrations in the atmosphere have a multidimensional influence on marine ecosystems. Through amplifying the greenhouse effect they lead to seawater temperature increase, which initiates cascade changes in the environment. In addition to this climatic pathway, increasing atmospheric CO2 concentrations cause also an overall increase of CO2 concentrations in surface seawater and, consequently, a pH decrease – a mechanism called Ocean Acidification (OA). OA is already fairly well understood and traceable in the open ocean waters, where large-scale projects and actions supply an enormous amount of observations and experimental data and where the magnitude of OA is to a large extent thermodynamically consistent with the increase in atmospheric pCO2. In the coastal and shelf seas, OA is still a considerably understudied phenomenon despite their high socio-economic importance and potentially great vulnerability of these regions to acidification due to often lower salinity and corresponding lower buffer capacity of waters as compared to open ocean.

In the present study, we underline the importance of total alkalinity (TA) as the key factor shaping the OA dynamics and pH fields in the coastal and shelf seas. The extensive research performed in 2018-2022 extended from the brackish Baltic Sea through the open waters of the eastern Fram Strait to the Spitsbergen fjords affected by the high inflow of meltwaters. It revealed extremely high variability in the marine CO2 system structure and significantly different influences of freshwater input in the investigated regions. The observed overall spatial and temporal (seasonal) variability in TA extended in the broad range between <350 and 4,320 µmol kg-1. This makes TA a fundamental variable for studying the large-scale pH and pCO2 changes and forecasting the development of OA in the coastal zone in the future high-CO2 world. This large-scale study can be considered as the reference for future OA research in the investigated regions and simultaneously calls for action to include TA in the routinely observed parameters in the coastal waters.

How to cite: Kulinski, K., Aguado Gonzalo, F., Bromboszcz, L., Diak, M., Koziorowska-Makuch, K., Makuch, P., Palka, I., Prusinski, P., Saghravani, S. R., Szymczycha, B., and Winogradow, A.: Climate-related changes in total alkalinity as a key to understanding ocean acidification in the coastal zone, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16078, https://doi.org/10.5194/egusphere-egu23-16078, 2023.

12:00–12:10
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EGU23-13978
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Highlight
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On-site presentation
Tina Sanders, Martina Heineke, Flöser Götz, Vanessa Russnak, Eva Husmann, Kirstin Dähnke, Andreas Schöl, Fabian Große, and Yoana G. Voynova

The Elbe Estuary is strongly impacted by anthropogenic activities such as dredging and eutrophication. Together, these cause oxygen minimum zones (OMZ) regularly during summer in the Hamburg Port area, within the tidal freshwater region of the estuary. Over the last years, this OMZ has expanded spatially and temporally. We present an analysis of an extraordinary oxygen minimum event in June 2022, when an all-time lowest oxygen concentration was observed upstream of the Hamburg Port.

We combine data from six transect cruises (early May -late June, 2022) and monitoring stations (2016-2022), to show the decrease of oxygen, and the increasing number of oxygen minimum events. In June 2022, the OMZ moved upstream due to the collapse of a phytoplankton bloom upstream of the tidal weir. This was accompanied by particularly warm temperatures and low river discharge, providing a glimpse into the potential future changes of central European estuaries under climate change.

How to cite: Sanders, T., Heineke, M., Götz, F., Russnak, V., Husmann, E., Dähnke, K., Schöl, A., Große, F., and Voynova, Y. G.: Increasing of oxygen minimum events in a temperate estuary caused by warming and reduced discharge, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13978, https://doi.org/10.5194/egusphere-egu23-13978, 2023.

12:10–12:20
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EGU23-11848
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ECS
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On-site presentation
Vlad Macovei, Louise Rewrie, and Yoana Voynova

The land-ocean continuum is a key component of the biogeochemical cycling of carbon and nutrients. At the same time, the rapidly changing conditions at the river-sea interface make the nearshore regions highly dynamic and variable. For better understanding of the drivers of this variability, high temporal and spatial frequency observations are needed. Here, we use ship-of-opportunity measurements in the outer estuaries of the Humber (UK) and Elbe (Germany) rivers to show that essential ocean variables in these regions vary with a periodicity that matches the spring-neap tidal cycles. The tidal disturbance was observed up to 10 km offshore from the river mouth. While at neap tide, the conditions at this location were typical of the open North Sea, during spring tide, the salinity dropped below 15, the turbidity was high (>50 FTU), dissolved oxygen dropped to under-saturated values and the partial pressure of carbon dioxide (pCO2) in seawater rose above 700 µatm. Since neap tide seawater pCO2 values were below 400 µatm, lower than atmospheric levels, the near-shore area shifts between being a sink and a source of carbon dioxide to the atmosphere on roughly one-week timescales. This behaviour is currently not resolved in some biogeochemical models. Correctly integrating the drivers of this variability into regional assessments is essential for the accurate evaluation of shelf sea carbon budgets.

How to cite: Macovei, V., Rewrie, L., and Voynova, Y.: Spring-neap tidal cycles are major drivers for biogeochemical variability in two large outer estuaries, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11848, https://doi.org/10.5194/egusphere-egu23-11848, 2023.

12:20–12:30
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EGU23-16578
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On-site presentation
Laure Resplandy, Alizée Roobaert, Goulven Gildas Laruelle, Enhui Liao, and Pierre Regnier

Significant progress has been made regarding the spatial distribution of sources and sinks of atmospheric CO2 within the global coastal ocean. The physical and biochemical drivers that govern these CO2 sources and sinks as well as their variability on seasonal timescales are, however, poorly understood. In this study we aim at filling this knowledge gap and assess to what extend the CO2 dynamics in the coastal ocean is controlled by the adjacent open ocean or conversely is dominated by continental influence. We use the global ocean biophysical model MOM6-COBALT, carefully evaluated against a well-established coastal data-product (Laruelle et al., 2017), to quantify the individual influences of the oceanic transport, thermal changes, freshwater influence, and biological activity on the annual mean spatial distribution of CO2 sources and sinks as well as their seasonal variability for the coastal ocean worldwide. Our analysis reveals complex spatial and temporal dynamics, depending on the coastal region and/or the time scale investigated (seasonal or annual) resulting from interactions and compensations between the different processes. We identify five typical behaviors of coastal systems (i.e., coastal regions under biological drawdown, vertical transport, imprint of land, dominated by intracoastal alongshore currents, and weak CO2 sources and sinks coastal regions) and propose a processed-based typology of the coastal ocean based on the processes that control the spatial and seasonal air-sea CO2 dynamics. 

How to cite: Resplandy, L., Roobaert, A., Laruelle, G. G., Liao, E., and Regnier, P.: Process-based typology of the global coastal ocean based on physical and biogeochemical controls of the sea surface CO2 dynamics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16578, https://doi.org/10.5194/egusphere-egu23-16578, 2023.

Posters on site: Thu, 27 Apr, 16:15–18:00 | Hall A

Chairpersons: Craig Smeaton, Arthur Capet, Katarzyna Koziorowska-Makuch
A.265
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EGU23-4182
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ECS
Zelong Yan, Shaofeng Wang, Yongfeng Jia, Xiangfeng Zeng, Xu Ma, Guoqing Zhang, and Yuanbi Yi

   Sediment dissolved organic matter (DOM) on the coast of China plays a critical role in the terrestrial and marine carbon cycle process of the global environment. In this study, surface sediment samples were collected from coastal areas including the Bohai Sea (BS), Yellow Sea (YS), East China Sea (ECS), and South China Sea (SCS) in China (Figure 1). We considered environmental factors, sediment sources, and the molecular compositions of sedimental DOM on coast of China in combination with the stable isotopic analysis and FT-ICR-MS. We analyzed the δ13C and δ15N stable isotopic compositions and DOM molecular characteristics of sediments collected from coastal areas spanning the BS, YS, ECS, and SCS by using the isotope ratio mass spectrometry and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Stable isotope (δ13C and δ15N) analysis and the MixSIAR model showed that the sediments on the coast of China are affected by three main end-members. 

    Isotopic analysis indicated that most of the C and N in coastal sediments of the BS, YS, and ECS came from terrigenous sources (45.0%~73.3%), whereas anthropogenic sources were the main end-members in the SCS (49.8%). There were no significant regional differences in the concentrations of DOM(Figure 2). The major molecular compounds detected in the DOM on the coast of China were lignins (22.17%~25.83%) and proteins/amino sugars (47.95%~54.35%). The sources of the sediments affect the composition of DOM molecules, and mainly terrigenous inputs to the DOM were affected. The terrigenous DOM present in the sediments is mainly affected by the dissolution of sediments, and the DOM molecules in this fraction are mainly condensed aromatics and unsaturated hydrocarbons. Environmental factors play a vital role in the molecular composition of DOM. Lignin molecules in DOM increase with increasing salinity and depth. Autochthonous sediment sources likely contribute to the O-poor and unsaturated compounds present in the coastal DOM(Figure 2). Baased on a combination of Spearman’s correlation analysis and stable isotopic analysis, it was found that DOM molecular chemodiversity was influenced by spatial environmental factors (mainly salinity, depth, and temperature.) and by the origin of coastal sediments. DOM molecules containing nitrogen were mainly influenced by marine sources in the sediments (p<0.05). Our findings are of significance for understanding the carbon cycle on the coast of China. These findings can facilitate a better assessment of the contribution of DOM sources and highlight the importance of maintaining a balance between development and coastal ecosystem sustainability under increasing human disturbances.

          

                                                                       

 

 

How to cite: Yan, Z., Wang, S., Jia, Y., Zeng, X., Ma, X., Zhang, G., and Yi, Y.: Environment and Sources Affect the Molecular Composition and Characteristics of Sediment Dissolved Organic Matter in Coastal Environments in China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4182, https://doi.org/10.5194/egusphere-egu23-4182, 2023.

A.266
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EGU23-6160
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ECS
Peiyuan Zhu, Xiaogang Chen, Yan Zhan, Xinyu Chen, and Ling Li

Saltmarshes in estuaries with intensive human activity regulate coastal nutrient biogeochemistry, however, limited studies have quantified porewater-derived nutrient fluxes and identified the implication on coastal nutrients cycling. Here, we hypothesize that porewater-derived nutrient fluxes may contribute to coastal water quality issues. Spatial investigation was conducted in a saltmarsh-fringed estuary with multi-species saltmarshes. Based on a radon mass balance model, porewater-derived fluxes of nitrogen (including total nitrogen, nitrate, nitrite, and ammonium), phosphorus (total phosphorus and orthophosphate) and silicate were estimated. While nitrate was absorbed by saltmarshes, ammonium was export from porewater to surface water. Nitrate flux was supposed to provide nitrogen for saltmarsh species and ammonium flux was considered as the production of organic nitrogen mineralization. Furthermore, obvious inorganic phosphorus sink and silicate source were observed in the saltmarsh. According to nutrient fluxes and related N/P ratio, porewater-derived nitrogen and phosphorus fluxes can significantly mitigate the eutrophication in nearby water body.

How to cite: Zhu, P., Chen, X., Zhan, Y., Chen, X., and Li, L.: Porewater-derived nutrient biogeochemistry in a saltmarsh-fringed estuary under intensive human activity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6160, https://doi.org/10.5194/egusphere-egu23-6160, 2023.

A.267
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EGU23-12459
Ed Garrett, Craig Smeaton, W. Roland Gehrels, Natasha Barlow, Will Blake, Martha B. Koot, Lucy Miller, Glenn Havelock, Lucy McMahon, Cai Ladd, and William Austin

Saltmarshes play a key role in sequestering and storing carbon, as well as providing a wide range of other ecosystem services. Assessments of both total carbon stocks and rates of carbon accumulation are vital for quantifying saltmarsh contributions to climate-change mitigation and for guiding efforts to protect and restore coastal wetlands. Current assessments of the rates at which UK saltmarshes accumulate carbon are based on a small and spatially limited dataset. To address this knowledge gap, we estimate sedimentation rates and assess organic carbon density from 22 saltmarshes distributed around the UK. Bayesian modelling quantifies the relationship between depth and age from 210Pb and 137Cs activity data. We combine these sedimentation rates with centimetre-resolution organic carbon density measurements to quantify carbon accumulation rates through time. By upscaling these estimates to the total UK saltmarsh area and fully quantifying uncertainties, we conclude that UK saltmarsh carbon burial rates are lower than previously thought.

How to cite: Garrett, E., Smeaton, C., Gehrels, W. R., Barlow, N., Blake, W., Koot, M. B., Miller, L., Havelock, G., McMahon, L., Ladd, C., and Austin, W.: Sedimentation and carbon accumulation rates in UK saltmarshes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12459, https://doi.org/10.5194/egusphere-egu23-12459, 2023.

A.268
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EGU23-13776
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ECS
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Daniel Müller, Bo Liu, Walter Geibert, Elda Miramontes García, Hei­di Taubner, Moritz Holtappels, Susann Henkel, Jessica Volz, and Sabine Kasten

Fine-grained coastal and marine sediments represent the largest permanent sink for carbon on our planet. They harbor large stocks of particulate organic carbon (POC) derived from marine plankton, land plants and coastal vegetation that build POC via photosynthesis and in this way take up CO2 from the atmosphere. The Helgoland Mud Area (HMA) represents the main depocenter for fine-grained and organic-rich sediments in the German Bight, North Sea. It covers a seafloor area of approximately 500 km2 off the island of Helgoland with a sediment thickness of up to 21 m and water depths between 11 and 27 m. In order to be able to quantify the long-term storage of carbon and its turnover during mineralization in the sediments of the HMA, we reconstruct sedimentation rates for the past decades and determine POC contents and origin. These results on the natural POC dynamics in the HMA are fundamental in order to understand how on-going anthropogenic activities (e.g., bottom trawling, dredging, offshore infrastructure) may affect the POC storage capacity of the HMA. Complementing existing estimates of sedimentation rates, we have determined 210Pbxs and 137Cs activities from the upper ~ 30 cm of the sediments in a high spatial and vertical resolution across the HMA. Based on this new dataset, we establish age models and describe the variation of depositional conditions across the HMA. The source of POC is determined by using the pore-water dissolved inorganic carbon concentrations (DIC) and respective stable carbon isotopic compositions with Keeling and Miller-Tans plot analysis as well as thermal gravimetric analysis (TGA). Published sedimentation rates for the HMA range from 0.5 to 11 mm yr-1 with strong lateral variations. The highest rates have been reported for the NW and central HMA. Our first results on sedimentation rates show ~ 2 mm yr-1 for these high accumulation areas within the HMA. POC contents in these areas are at ~ 1 wt% throughout the upper ~ 30 cm of the sediments. The source isotopic composition of POC ranges from -2.6 to -28.2 ‰ throughout the study area and needs to be complemented by on-going TGA analyses in order to reliably determine the origin of the POC. Once these analyses are completed, we aim to better understand the sources of organic carbon in this depocenter and to assess how the variation in depositional processes controls the mineralization and long-term burial of POC in the sediments of the HMA.

How to cite: Müller, D., Liu, B., Geibert, W., Miramontes García, E., Taubner, H., Holtappels, M., Henkel, S., Volz, J., and Kasten, S.: Depositional processes, particulate organic carbon contents and origin across the Helgoland Mud Area, SE German Bight., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13776, https://doi.org/10.5194/egusphere-egu23-13776, 2023.

A.269
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EGU23-16931
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ECS
Abduljamiu Amao, Fabrizio Frontalini, and Michael Kaminski

This study  investigated the scientific production and impact of research on Foraminifera, a marine organism that has made significant contributions to understanding our planet and its evolution. Bibliometric data from Web of Science and SCOPUS was used to analyze 22,372 published works on Foraminifera between 1841-2020. The United States topped the list of countries conducting research on Foraminifera, followed by the United Kingdom, France, and Germany. The most productive journals were found to be Palaeogeography Palaeoclimatology Palaeoecology and Marine Micropaleontology. The majority of research focuses on Foraminifera's role in paleoceanography, paleoclimate, and biostratigraphy. Foraminifera was found to be a reliable material for age calibration in radiocarbon dating, as evidenced by the inclusion of one of the most cited reference materials in the top 20 most cited documents. The study provides insights into the scientific production and impact of research on Foraminifera and highlights the continued significance of this organism in the field of earth and environmental sciences

How to cite: Amao, A., Frontalini, F., and Kaminski, M.: Foraminifera Research Evolution: A Bibliometric Analysis of Scientific Production and Impact from 1841-2020, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16931, https://doi.org/10.5194/egusphere-egu23-16931, 2023.

A.270
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EGU23-14951
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ECS
Sören Iwe, Bernd Schneider, and Oliver Schmale

Nitrogen fixation by cyanobacteria is a common phenomenon in the Baltic Sea. It occurs in the absence of dissolved inorganic nitrogen (DIN) during mid-summer (June – August) mainly in the central Baltic Sea and the Gulf of Finland. The contribution to the N budget is significant and enhances the eutrophication of the Baltic Sea. Current input estimates range between 300 kt-N/yr and 800 kt-N/yr and are in the same order of magnitude as the sum of the riverine and airborne DIN input. The huge range of the different estimates is a consequence of both the considerable interannual variability of the N2 fixation and huge uncertainties associated with the different approaches (15N incubation; total N budget; pCO2 records; phosphate excess) for the quantification of the N2 fixation and with extrapolating the results from local studies to entire basins.                                                                               

To overcome some of these limitations, we have developed a new methodological approach to quantify the contribution of N2 fixation to the N budget of the Baltic Sea. Our approach is based on large-scale records of the surface water N2 depletion during a cyanobacteria bloom, complemented by Ar measurements to account for the air-sea N2 gas exchange. The N2 and Ar concentrations will be determined continuously by means of mass spectrometric analysis of N2 and Ar in air equilibrated with a continuous flow of surface water (MIMS, Membrane Inlet Mass Spectrometry). In our first pilot study, we have performed measurements on a voluntary observation ship (VOS, „Finnmaid“) for a period of six weeks in summer 2022 between the Mecklenburg Bight and the Gulf of Finland. The results demonstrate that our new approach is able to identify the areal distribution of cyanobacterial bloom events and to quantify the nitrogen fixation in a very precise way with a high temporal and spatial resolution (2 – 3 days, ~0.7 km).                                                                              

Within in future studies, we will perform further ship-based investigations and use the high-resolution dataset to set up a N budget for the Baltic Proper. In addition, we are aiming for the identification of the different factors which trigger and possibly limit the cyanobacteria growth such as temperature, phosphor availability and meteorological/hydrographic conditions. 

                                                      

How to cite: Iwe, S., Schneider, B., and Schmale, O.: Continuous nitrogen and argon measurements for the quantification of nitrogen fixation in the Baltic Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14951, https://doi.org/10.5194/egusphere-egu23-14951, 2023.

A.271
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EGU23-15838
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ECS
The influence of transient oxygen exposure on dissimilatory nitrate reduction to ammonium and sulfate reduction
(withdrawn)
Olivia Bourceau, Marit van Erk, and Dirk de Beer

Posters virtual: Thu, 27 Apr, 16:15–18:00 | vHall BG

Chairpersons: Petra Heinz, Hiroshi Kitazato
vBG.10
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EGU23-7100
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ECS
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Rafał Nawrot, Martin Zuschin, Adam Tomašových, Michał Kowalewski, and Daniele Scarponi

The youngest fossil record is an indispensable source of data on long-term human impact on marine ecosystems. However, human actions alter not only marine communities and their habitats but also sedimentary and biotic processes controlling the formation of the stratigraphic archives recording those changes. Based on literature data and our own field studies we provide a conceptual framework for understanding the impact of anthropogenic processes on the completeness and spatiotemporal resolution of the fossil record forming on continental shelves. Such processes are diverse and include, among others, changes in sediment fluxes due to reshaping of alluvial and coastal landscapes, seabed disturbance by bottom trawling and ship traffic, ocean acidification and anoxia, removal of native species, and introduction of invasive ecosystem engineers. These physical, geochemical, and biological disturbances can modify sedimentation rates, depth and intensity of sediment mixing, pore water saturation state, and preservation potential of skeletal remains. The resulting taphonomic and stratigraphic signatures can pinpoint historical changes in ecosystem functioning but can also lead to systematic changes in the quality of the record complicating paleoecological and paleoclimatic reconstructions based on the data from sediment cores and surface death assemblages. We highlight the complex feedbacks between human impacts on the ecosystem processes and their preservation in the marine stratigraphic record and suggest research strategies that can maximize the informative value of the geohistorical data.

How to cite: Nawrot, R., Zuschin, M., Tomašových, A., Kowalewski, M., and Scarponi, D.: Anthropogenic processes alter the completeness and resolution of the marine fossil record, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7100, https://doi.org/10.5194/egusphere-egu23-7100, 2023.

vBG.11
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EGU23-7741
Ulrike Löptien, Heiner Dietze, Britta Munkes, Robinson Hordoir, and Matthias Renz

In the Baltic Sea, cyanobacteria regularly form massive blooms in late summer. These blooms can produce toxins and have the potential to counteract management efforts to limit eutrophication because they add bioavailable nitrogen (fixed from the atmosphere) to an already over-fertilized system. Despite their critical role and substantial research progress, the controls on cyanobacteria are still not comprehensively understood. This can limit the accuracy of model-based projections. Our study adds to the ongoing discussion by providing a comparison of existing contemporary model formulations. This comparison is supplemented by a unique combination of satellite estimates of cyanobacteria blooms, in-situ nutrient observations and output of a high-resolution general ocean circulation model (MOMBA). We retrace bloom origins and conditions by calculating the trajectories of respective water parcels backwards in time. In an attempt to identify drivers of bloom development, we find that blooms originate and manifest themselves predominantly offshore. Potential implications for contemporary modelling approaches are discussed. 

How to cite: Löptien, U., Dietze, H., Munkes, B., Hordoir, R., and Renz, M.: Cyanobacteria blooms in the Baltic Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7741, https://doi.org/10.5194/egusphere-egu23-7741, 2023.

vBG.12
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EGU23-10812
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ECS
|
Avinash Dahakey, Om Adarsh, Vedanth Prasanna Kumar, and Devapriya Chattopadhyay

Biotic interactions, such as predation, is an important evolutionary force reshaping the shallow marine community in the geologic past. Benthic mollusks are ideal groups to study the deep time record of predation because they preserve the predation record (drilling and durophagous) on the shell and are known to respond to evolutionary triggers. The physical environment also influences shallow marine molluscan communities. It is important to evaluate the influence of physical factors on biotic interactions to understand the true mechanism of the evolution of shallow marine fauna in deep time. To evaluate the effect of abiotic factors on biotic interaction in the marine realm, we need a setting with distinct environmental patterns inhabited by diverse community with recognizable biotic interaction. The recent shallow marine bivalve community of the Andaman island provides such a setting.  

The Andaman island is part of Andaman–Nicobar archipelago in the Indian Ocean marking the western margin of the Andaman Sea. It represents a sediment-dominated accretionary wedge associated with a convergent margin. The east coast of Andaman island receives significant riverine input from Irrawaddy delta in the north and is located in the vicinity of well-developed reef system of south-east Asia. The east coast of Andaman also has diverse molluscan fauna. We collected samples from 19 localities along the east coast. These localities represent of diverse depositional environments and substrate types including muddy tidal flats, mangroves, sandy beach and coral reef. We collected grab samples from water depths between 1-15m. We characterized the drilling frequency (DF) and prey selectivity across environments, family and depth. Drilling predator–prey systems have been explored using cost–benefit models in modern and fossil assemblages. In this study, we also tried to establish a relationship between the benefit to cost ratio (BCR) of drilling attempts across depositional environments and compared them with global data.

We studied ~3000 bivalve specimens of which 291 have drill holes. The overall drilling frequency (DF) is 0.19. A total of 21 prey families were identified and the DF ranges between 0 to 0.5. Three families (Crassatellidae, Isognomonidae, Placunidae) show the highest DF. There is a significant variation in DF across environments. Coral sand shows the highest DF and muddy substrate shows the lowest.

The benefit to cost ratio (BCR) of drilling is positively correlated with predator size for the muddy substrate for the Andaman specimens. The Andaman BCR is lower than the global average for the shallow marine environment. In contrast, the BCR is higher for the mangrove community of the Andaman compared to the global data. The BCR declines with increasing predator size for the Andaman and global data. This implies a possible role of increasing metabolic cost of larger predators.

The record of predation in the geologic record has been thought to be influenced primarily by the interaction between organisms where the role of the physical environment is largely ignored. Our study demonstrates the significant influence of the physical environment in shaping predation intensity and prey selection which in turn changes BCR of predation events.

How to cite: Dahakey, A., Adarsh, O., Prasanna Kumar, V., and Chattopadhyay, D.: Spatial variation in marine predation pattern across depositional environments: Insights from the drilling predation records of the recent bivalve fauna of Andaman Islands, India., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10812, https://doi.org/10.5194/egusphere-egu23-10812, 2023.