SSP4.3

Diel Vertical Migration (DVM) is a key feature of pelagic and mesopelagic ecosystems, mainly driven by predator-prey interactions along a time-varying vertical gradient of light. Marine organisms including meso-zooplankton and fish typically hide from visual predators at depth during daytime and migrate up at dusk to feed in productive near-surface waters during nighttime. Specific migration patterns, however, vary tremendously, for instance in terms of residency depth during day and night. In addition to environmental parameters such as light intensity and oxygen concentration, the migration pattern of each organism is intrinsically linked to the patterns of its conspecifics, its prey, and its predators through feedbacks that are hard to understand—but important to consider.

DVM not only affects trophic interactions, but also the biogeochemistry of the world’s oceans.  Organisms preying at the surface and actively migrating vertically transport carbon to depth, contributing to the biological carbon pump, and directly connecting surface production with mesopelagic and demersal ecosystems.

Here, we present a method based on a game-theoretic trait-based mechanistic model that enables the optimal DVM patterns for all organisms in a food-web to be computed simultaneously. The results are used to investigate the contributions of the different food-web pathways to the active component of the biological carbon pump. We apply the method to a modern pelagic food-web (comprised of meso- and macro-zooplankton, forage fish, mesopelagic fish, large pelagic fish and gelatinous organisms), shedding light on the direct effects that different trophic levels can have on the DVM behaviours of each other. The model is run on a global scale to assess the carbon export mediated by different functional groups, through fecal pellet production, carcasses sinking and respiration.

Finally, the model output is coupled to an ocean inverse circulation model to assess the carbon sequestration potential of the different export pathways. Results indicate that the carbon sequestration mediated by fish is much more important than presently recognised in global assessments of the biological carbon pump. The work we present relates to contemporary ecosystems, but we also explain how it can be adapted to fit any pelagic food-web structure to assess the contribution of the active biological pump to the global carbon cycle in past ecosystems.

How to cite: Pinti, J., DeVries, T., Norin, T., Serra-Pompei, C., Proud, R., Siegel, D. A., Kiørboe, T., Petrik, C. M., Andersen, K. H., Brierley, A. S., and Visser, A. W.: Diel Vertical migration of marine organisms and the biological carbon pump, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-198, https://doi.org/10.5194/egusphere-egu21-198, 2021.

Introduced predators currently threaten endemic animals on Madagascar through predation, facilitation of human-led hunts, competition, and disease transmission, but the antiquity and past consequences of these introductions are poorly known. We use radiocarbon and stable carbon and nitrogen isotope data from the bone collagen of introduced dogs (Canis familiaris) and endemic fosa (Cryptoprocta spp.) in central and southern Madagascar to test for competition between introduced and endemic predators. Isotopic evidence indicates little overlap in diet between ancient dogs and fosa in these regions but leaves open the possibility that dogs competitively exclude fosa. Radiocarbon dates confirm that dogs have been present on Madagascar for at least a millennium and suggest that they briefly co-occurred with the island’s extinct megafauna, which included giant lemurs, elephant birds, and pygmy hippopotamuses. Dogs share a mutualism with pastoralists who also at least occasionally hunt, and this is reflected in deposits at several Malagasy paleontological sites that contain dog and livestock bones along with butchered bones of extinct megafauna and extant lemurs. Dogs on Madagascar have had a wide range of diets during the past millennium, but relatively high stable carbon isotope values suggest few individuals relied primarily on forest bushmeat. The absence of distinct dietary differences between dogs from archaeological and paleontological sites may reflect the absence of discrete feral populations. Our data suggest that dogs were part of a suite of animal introductions beginning over a millennium ago that coincided with widespread landscape transformation and megafaunal extinction.

How to cite: Hixon, S., Douglass, K., Godfrey, L., Eccles, L., Crowley, B., Rakotozafy, L., Clark, G., Haberle, S., Anderson, A., Wright, H., and Kennett, D.: Ecological Consequences of a Millennium of Introduced Dogs on Madagascar, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-927, https://doi.org/10.5194/egusphere-egu21-927, 2021.

Current and future climate change is a serious threat to biodiversity and ecosystem stability. With a rapid increase of global temperatures by 1.5°C since the pre-industrial period and a projected warming of 1.5-4°C by the end of this century, plant species are forced to either adapt to these changes, shift their distribution range to higher elevation, or face population decline and extinction. Today, there is an urgent need to better understand the responses of mountain vegetation to climate change in order to predict the consequences of the human-driven global change currently occurring during the Anthropocene and maintain species diversity and ecosystem services. However, most predictions are based on short-term experiments. There is, in general, an insufficient use of longer time scales in conservation biology to understand long-term processes. Palaeoecological data are a great source of information to infer past species responses to changing environmental factors, such as climate or anthropogenic disturbances.

The last climate change of a similar magnitude and rate as projected for this century was the transition between the last Ice Age and the Holocene interglacial (ca. 11,700 years ago). By analyzing subfossil plant remains such as plant macrofossils, charcoal and pollen from natural archives, we can study past responses to climate change. However, until recently it was not possible to reconstruct changes at the population level. With the development of new methods to extract ancient DNA (aDNA) from plant remains and next generation DNA-sequencing techniques, we can now infer past population dynamics by analyzing the genetic variation through time. Ancient DNA might also be able to reveal if species could adapt to climatic changes by identifying intraspecific variation of specific genes related to climatic adaptations.

We are currently investigating a palaeoecological archive from a high-altitude mountain lake, Lai da Vons (1991 m a.s.l), situated in Eastern Switzerland. We are presenting preliminary macrofossil, pollen and charcoal results to reconstruct local to regional vegetation and fire dynamics with high chronological precision and resolution. In a next step, we will use novel molecular methods, in order to track adaptive and neutral genetic diversity through the Holocene by analyzing aDNA from subfossil conifer needles. The overarching goal of this large-scale, multiproxy study is to better understand past vegetation dynamics and the impact of future climate change on plants at multiple scales; from the genetic to the community level.

How to cite: Dziomber, L., Gurtner, L., Leunda, M., and Schwörer, C.: A multiproxy reconstruction of vegetation dynamics in the Eastern Alps (Switzerland): combining paleoecological and paleogenetic approaches., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14457, https://doi.org/10.5194/egusphere-egu21-14457, 2021.

This study aims at checking the quality of the sedimentary record preserved on the deltaic seafloor by analyzing the deposits preserved in 4 shallow cores. These have been collected by scuba diving at four different depths (10m, 20m, 30m and 40m) just in correspondence of the delta of the Entella river, in the Gulf of Tigullio (Western Ligurian Sea - Italy).

The Entella river runs through several onshore sites that can have been potential source of pollution or contamination of the marine system in the past and thus potentially preserved in the sedimentary sequence. Among those sites the possible contamination sources could be caused by extensive human activities such as production and processing of thermoplastic material, vegetable oils, junkyards, several quarries (limestone and slate), landfill of solid urban waste.

The core subsampling was directly performed onboard of the support vessel immediately after underwater collection. In total four cores, with a length comprised between 26 and 44 cm, have been collected. Each core was cut into 2-cm slices, which were then further divided in half.

The first half of sediment has been placed in a plastic bag in order to perform the followed analyses: granulometry, content of organic/inorganic matter by thermogravimetric method, XRPD analyses, C14 radiometric dating and chemical component analysis.

The second half of sediment, stored into a glass jar (to prevent plastic contamination), has been used to search for both agglutinated microplastics on picked agglutinated foraminifera and further microplastics on filters. Filters have been prepared using density separation in supersalty aqueous solution and filtration. Investigations have been performed by optical microscopy and µRaman spectroscopy. Since the analysis of the whole filter is extensively time-consuming, due to the high number of items present, we have tested a statistical approach to optimize the filter investigation.

All the data obtained were processed using the statistical software R. Multivariate analyses have been performed for the granulometry dataset as well as for other data. The results seem to point to specific trends characterized by possible seasonal fluctuations registered in the sedimentary sequence. The mineralogy dataset, investigated by cluster analysis, points to a clear separation of the mineralogical composition of the shallower versus the deeper cores. Interestingly, agglutinated foraminifera (i.e., mostly textulariids) seem to agglutinate large amount of carbon grains and plastics have been not yet observed.

How to cite: Altieri, C., Briguglio, A., Carbone, C., Consani, S., Cutroneo, L., Geneselli, I., Malatesta, A., Reboa, A., and Capello, M.: What do shallow cores tell us when drilled in an anthropogenically active delta from northwest Italy?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3484, https://doi.org/10.5194/egusphere-egu21-3484, 2021.

Benthic communities in the Northern Adriatic Sea experienced major environmental and ecological changes during the late Holocene, particularly in the late 20^th century due to anthropogenic induced stressors such as hypoxic events. These events lead to mass mortalities and changes in benthic communities. Here, we assess stratigraphic changes in bulk sediment geochemistry and sedimentological attributes to quantify the magnitude and timing of environmental changes and to correlate them to ecological changes. We focus on the reconstruction of the micro- to macrobenthic community composition (foraminifera, ostracods, bivalves and gastropods) prior and after major anthropogenic impacts. We investigate the differences in responses of these taxonomic groups to environmental changes and account for the impact of time-averaging.

The 3-m-long gravity core was collected at 31 m water depth, off the Po prodelta in the western part of the northern Adriatic Sea. The upper 60 cm of the core represent a condensed record determined by sediment bypassing and winnowing during the early and late sea level highstand. In total, 50 shells of the common bivalve Corbula gibba were dated by ¹⁴C-calibrated amino acid racemization (AAR) from the upper 30 cm and plant remains were dated by ¹⁴C from deeper parts. These analyses show that median shell ages of Corbula decline downcore, from ~50 years in the top 2.5 cm to 1,400 years in the 5-7.5 cm increment, 2,900 years in the 10-12.5 cm increment, and 4,500 years in the 17.5-20 cm increment. Median age in the 28-33 cm increment is again 3,600 years, indicating effects of mixing. The youngest shell corresponds to 24 years BP in the top 2.5 cm and the oldest shell to to 7800 years BP at the base at 30 cm.  The 60 cm-long highstand record can be divided in 4 major intervals:

(1) Early-highstand sediments cover the development of a baseline community. Total abundances of micro-and macrobenthic species increase upwards (2) In the late-highstand sediments (around 12.5-15 cm), micro-and macrobenthic absolute species abundance are highest. Increase in eutrophication and heavy metal pollution is indicated by rising N levels and Pb content in bulk sediments. (3) At 5 cm depth, a major anthropogenic environmental shift indicated by strong pollution (Pb and Hg) and eutrophication (TOC) coincides with a strong decline in micro-and macrobenthic abundance and diversity (4) The surface-mixed layer yields a slight increase in micro-to macrobenthic abundances, next to a slight decrease of heavy metal pollution and eutrophication.

¹⁴C-calibrated AAR shell ages indicate a relatively limited, centennial time averaging (measured by interquartile age ranges) of Corbula in the uppermost increment but then show a millennial-scale time-averaging below the uppermost surface-mixed layer. This can be linked to a decrease in bioturbation in the 20^th century and to a slight increase in sedimentation rate. Although the record is affected by time-averaging, the micro-and macrobenthic community abundances show a distinct pattern that can be related to environmental changes from geochemical sediment proxies. Benthic foraminifers, ostracods and mollusks abundance show similar responses to sedimentological and geochemical tracers in these condensed sediments.

How to cite: Berensmeier, M., Tomašových, A., and Zuschin, M.: Micro- and macrofaunal responses to major environmental changes in Holocene highstand sediments from the Northern Adriatic Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15320, https://doi.org/10.5194/egusphere-egu21-15320, 2021.

Fish otoliths are incrementally growing aragonitic elements found in the inner ear of most fishes. They have species-specific morphology that enable species level identification and they are excellent high-resolution recorders of ambient water conditions, enabling the reconstruction of past fish faunas and their environment. Although they have been studied as fossils for almost 150 years, and they are very useful tools for tracking lifestyle and population changes in modern fishes, otolith death assemblages recovered from sea bottom sediments have been studied only much more recently. Still, these fish remains can provide valuable insight into past fish faunas before most anthropogenic impacts, such as climate warming, habitat modification and biological invasions. Here, we present an overview of research done until now on otolith death assemblages highlighting their applications for marine conservation.

How to cite: Agiadi, K. and Albano, P. G.: Addressing challenges in biodiversity conservation with fish otolith death assemblages: the state-of-the-art, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-879, https://doi.org/10.5194/egusphere-egu21-879, 2021.

The Lessepsian invasion – the largest marine biological invasion – followed the opening of the Suez Canal in 1869 (81 years BP). Shortly afterwards, tropical species also distributed in the Red Sea appeared on Mediterranean shores: it was the dawn of what would become the invasion of several hundred tropical species. The time of the Suez Canal opening coincided with an acceleration in natural history exploration and description, but the eastern sectors of the Mediterranean Sea lagged behind and were thoroughly explored only in the second half of the 20^th century. Many parts are still insufficiently studied today. Baseline information on pre-Lessepsian ecosystem states is thus scarce. This knowledge gap has rarely been considered by invasion scientists: every new finding of species belonging to tropical clades has been assumed to be a Lessepsian invader.

We here question this assumption by radiocarbon dating seven individual tests of miliolids – imperforated calcareous foraminifera – belonging to five alleged non-indigenous species. Tests were found in two sediment cores collected at 30 and 40 m depth off Ashqelon, on the Mediterranean Israeli shelf. We dated one Cribromiliolinella milletti (core at 40 m, 20 cm sediment depth), three Nodophthalmidium antillarum (core at 40 m, 35 cm sediment depth), one Miliolinella cf. fichteliana (core at 30 m, 110 cm sediment depth), one Articulina alticostata (core at 40 m, 35 cm sediment depth) and one Spiroloculina antillarum (core at 30 m, 110 cm sediment depth). All foraminiferal tests proved to be of Holocene age, with a median calibrated age spanning between 749 and 8285 years BP. Only one test of N. antillarum showed a 2-sigma error overlapping the time of the opening of the Suez Canal, but with a median age of 1123 years BP. Additionally, a thorough literature search resulted in a further record of S. antillarum in a core interval dated 1820–2064 years BP in Turkey.

Therefore, these foraminiferal species are not introduced, but native species. They are all circumtropical or Indo-Pacific and in the Mediterranean distributed mostly in the eastern sectors (only S. antillarum occurs also in the Adriatic Sea). Two hypotheses can explain our results: these species are Tethyan relicts that survived the Messinian salinity crisis (5.97–5.33 Ma) and the glacial periods of the Pleistocene in the Eastern Mediterranean, which may have never desiccated completely during the Messinian crisis and which may have worked as a warm-water refugium in the Pleistocene; or they entered the Mediterranean Sea from the Red Sea more recently but before the opening of the Suez Canal, for example during the Last Interglacial (MIS5e) high-stand (125,000 years BP) when the flooded Isthmus of Suez enabled exchanges between the Mediterranean and the Indo-Pacific fauna. The recognition that some alleged Lessepsian invaders are in fact native species influences our understanding of the invasion process, its rates and environmental correlates.

How to cite: Albano, P. G., Sabbatini, A., Lattanzio, J., Steger, J., Szidat, S., Hua, Q., Kaufman, D., Zuschin, M., and Negri, A.: Radiocarbon dating of individual foram tests show that alleged Lessepsian species are of Holocene age, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6206, https://doi.org/10.5194/egusphere-egu21-6206, 2021.

Coral reefs throughout the world are well known for the dominance of scleractinian corals. However, one group of hydrozoan corals can be very common in modern tropical coral reefs as well: Millepora, the fire coral. The modern Red Sea is particularly well known for its high abundances of Millepora, where the fire coral is dominant on current-exposed reefs. Yet, this hydrozoan has been described as rare in the fossil record throughout the world and the documented abundances in fossil reefs do not match the numbers from modern reefs. The main interpretation to explain this phenomenon so far has been a lower preservation potential of milleporids compared to scleractinians due to differences in skeletal structure.

During an investigation of six Eemian Egyptian reef sites (29 line intercept transects, typically of 20 m length) we found Millepora in 69% of the fossil reef transects. The abundances were comparable to the adjacent modern reefs (65.13% to 0.26%). Preservation of fossil Millepora was good to excellent and in some cases well-preserved pore characters allowed for identification to species level. Our findings seem to be in stark contrast to results and interpretations of earlier studies, which suggest that Millepora is very rare in the fossil record globally. To understand the reason for this mismatch, we compared the associated scleractinian fauna between fossil reefs with and without Millepora presence. Furthermore, as a differentiation between shallower habitats close to the reef edge and deeper habitats along the reef slope was possible, we were able to investigate habitat preferences. Porites abundances were higher in fossil reefs without Millepora. Based on a comparison with modern communities, this suggests that the exposure to water energy might be a decisive factor for Millepora presence in the fossil reef. Therefore, preservation and consecutive investigation of appropriate fire coral-habitats is a pre-requisite for valid comparisons.

Another factor for the mismatch between our results and earlier studies might be a difference in diagenetic conditions that allow preservation of hydrozoan skeletons in the fossil record. Preservation of the investigated Egyptian sites is favored by their young geological age and their geographic location in a desert climate, reducing dissolution by aggressive meteoric waters. Furthermore, the extremely high abundance of Millepora in modern Red Sea coral reefs may in part mitigate the lower preservation potential of the hydrozoan skeleton in comparison with that of scleractinian corals.

How to cite: Ivkić, A., Kroh, A., Mansour, A., and Zuschin, M.: Unexpected abundance: Millepora corals in Late Pleistocene reefs of Egypt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10057, https://doi.org/10.5194/egusphere-egu21-10057, 2021.

Many studies focus on modern coral reefs and their associated invertebrate fauna, but not much is known about the paleoecology and diversity of molluscs of Late Pleistocene coral reefs, which were formed during the last interglacial MIS5e. This study is investigating the molluscan assemblage of a Late Pleistocene coral reef in southern Egypt, at the locality Sharm El Luli, in the area of Marsa Alam. The locality is characterized by a variety of reef- and reef associated habitats, including a reef flat, reef slope, a patch reef, and soft bottoms of a lagoon and in the backreef area. We quantitatively and qualitatively sampled 10 sites with a total of 79 samples and collected 2126 shells, which belong to 177 taxa, mostly identified to the species level.   Most taxa were found with the qualitative sampling approach. The most abundant bivalves taxon was the epifaunal, encrusting Chama spp., the most abundant gastropod species was the cerithiid Rhinoclavis vertagus. Regarding the life habitats most bivalve species are infaunal filter feeders, while most gastropods are epifaunal carnivores.    Alpha diversity is highest in the coral patch and in the upper reef region, which implies the reef slope, the reef flat as well as the transition between reef slope and the lagoon. Preliminary statistical results suggest a division in coral-patch, lagoon and backreef as well as a cluster of upper-reef habitats. From these two broad environments can be distinguished: hard bottoms associated to reefs and reef-associated soft bottom environments. The former are best characterized by encrusting taxa such as Chama spp. and Spondylus spp., and by Tridacna maxima and Perigylypta spp., which are well-known reef associates. Gastropods in this environment are predatory conids and cypraeids. All of these species live on - or occur cryptically in - structured hard bottoms. Reef associated-soft bottom environments are best characterized by infauna, such as the tellinid Quidinipagus palatam and the lucinids Anodontia kora and Pillucina vietnamica. Furthermore, many soft bottom gastropod species such as the strombid Gibberulus gibberulus albus, the cerithiid Rhinoclavis vertagus, both with an herbivorous diet, and the nassariid Nassarius fenistratus, a scavenger, can be found here.  A comparison with modern datasets from the Red Sea indicates strong similarities in faunal composition and habitat diversity between fossil and recent reefs.  Furthermore, our preliminary results suggest that Late Pleistocene molluscan assemblages can aid in reconstruction of associated fossil reef habitats. 

How to cite: Haider, A., Ivkić, A., Kroh, A., Mansour, A., and Zuschin, M.: Fossil molluscan fauna reflects zonation of a Late Pleistocene reef of the Red Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16060, https://doi.org/10.5194/egusphere-egu21-16060, 2021.

In order to reveal the response of benthic foraminifera to Cretaceous-Paleogene (K/Pg) boundary event, a high-resolution benthic foraminiferal study was carried out from a land-based Haymana section which is biostratigraphically complete, and once located in the northern branch of the Tethyan Ocean. To this end, 25 samples collected from deep marine succession of the Haymana Basin were quantitatively assessed along with the utilization of quantification of species, morphogroup analysis and diversity indices to establish remarkable changes in biofacies which resulted from the boundary event.

Depositional environment is inferred as upper bathyal (200-600 m) throughout the studied section based on foraminiferal associations. Bathymetric marker species include mainly bi- to triserial forms in Maastrichtian, which favor this interval. Calcareous taxa including Bolivinoides draco,  Eouvigerina subsculptura, Nonionellina sp. 1, Pseudouvigerina plummerae, Pyramidina minuta, as well as species belonging to Gyroidinoides, Laevidentalina, Lagena, Lenticulina, Pullenia, and Sitella are together forming 30% of the whole assemblage in this study, which are also attributed as Shallow Bathyal Assemblage of Widmark and Speijer (1997b) from the upper bathyal environment. Accompanied agglutinated taxa are consisting of Clavuinoides trilatera, Arenobulimina sp., as well as species of Dorothia, Gaudryina, Verneuilina, and Heterostomella, which are reported from low and mid-latitude Slope Deep Water biofacies of Kuhnt et al. (1989). There was probably no paleobathymetric change in the Danian, as it is concluded from the structure of the faunal assemblage. Besides, calcareous taxa are found to be more abundant with respect to agglutinated taxa within the whole section, offering deposition over Carbonate Compensation Depth (CCD) level.

With this study, Eouvigerina subsculptura Acme Zone is newly offered for the uppermost Maastrichtian, and also aligned with Bolivinoides draco Zone, since it is existing as very abundant in all samples. Besides, Angulogavelinella avnimelechi-Anomalinoides rubiginosus Interval Zone (BB1) is assigned for the lowermost Danian section based on marker Paleocene species.

Based on this benthic foraminiferal record, a highly diverse foraminiferal assemblage is observed in the Maastrichtian, then it is replaced with a poor to moderate diversity assemblage in the Danian. This finding is presented by diversity indices (Fisher alpha, Shannon H and Berger Parker). Presence of diverse morphogroups together in the upper Maastrichtian section along with taxa preferring high nutrient levels including E. Subsculptura (11-23%), Sliteria varsoviensis (0-6%), Praebulimina reussi (2-9%), Heterostomella spp. (4-11%) and Sitella spp. (1-13%) suggests meso- to eutrophic conditions in this section. A sudden change in the faunal composition right after the K/Pg boundary offers depleted food flux into the bottom of the basin. Infaunal morpogroups decline after the boundary in the Danian section, whereas epifaunal morphogroups including mostly opportunistic Cibicidoides spp. (17%), increased in number in this section. The timing of this record is coinciding with the worldwide primary productivity collapse and planktonic foraminiferal mass extinction during the K/Pg boundary event.

Keywords: K/Pg boundary, deep sea benthic foraminifera, quantitative assessment, paleoenvironment, Haymana Basin

How to cite: Vardar, E. and Özkan-Altıner, S.: Deep sea benthic foraminiferal record from the Haymana Basin (Turkey): changes in abundance patterns and diversity across Cretaceous-Paleogene boundary, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15764, https://doi.org/10.5194/egusphere-egu21-15764, 2021.