BG4.1

With rising atmospheric pCO₂, ocean acidification is an increasing threat to carbonate-secreting biota. As the diffusion of CO₂ from the atmosphere into the oceans is relatively slow, it is the surface water plankton and the shallow water benthos that are most at risk. In some quite restricted environments, naturally sourced CO₂ and NH₄ are bubbling to the sediment surface, creating reduced pH environments. Near the Italian island of Ischia (Dias et al., 2010), locally derived CO₂ is emerging into sea grass meadows, and reducing pH from 8.17 to 7.5 and this is causing a progressive loss of calcareous taxa and reducing the foraminiferal assemblage to only agglutinated taxa, with a distinct reduction in species richness. In the Gulf of California (Petit et al., 2013) the pH in surface sediments is being reduced from normal values to 7.5 and while the assemblage of living benthic foraminifera seems to be little affected, once dead the tests of calcareous taxa begin to be dissolved (as witnessed by enlarged pores and holes in the carbonate test material). In the plankton, especially the pteropods and heteropods, there is increasing evidence of shell dissolution and fragility with reducing pH and – in the Late Pleistocene of the Caribbean Sea – one can see a reduction in shell quality during interglacial conditions and concentrations of well-preserved shells in the glacial intervals. These records demonstrate that ocean acidification is not a new process and that variations in pH and shell mineralisation extend through the fossil record. In areas such as SW England, maerl (rhodophyte algae) accumulations are potentially at risk and may be overtaken by increases in sea grass meadows.

          Evidence of short-duration, surface-water acidification events are known from the earliest Jurassic (Hettangian) and the earliest Paleocene (following the K/Pg boundary; see Hart et al., 2019) based on the interpretation of calcareous nannofossil distributions and benthic foraminifera.

DIAS, B.B., HART, M.B., SMART, C.W. & HALL-SPENCER, J.M. 2010. Modern seawater acidification: the response of foraminifera to high CO₂ conditions in the Mediterranean Sea. Journal of the Geological Society, London, 167, 843–846.

PETTIT, L., HART, M.B., MEDINA-SANCHEZ, A.N., SMART, C.W., RODOLFO-METALPA, R., HALL-SPENCER, J.M. & PROL-LEDESMA, R.M. 2013. Benthic foraminifera show some resilience to ocean acidification in the northern Gulf of California. Marine Pollution Bulletin, 73, 452–462.

Hart, M.B., Leighton, A.D., Hampton, M. & Smart, C.W. 2019.Global bioevents and the Cretaceous/Paleogene boundary in Texas and Alabama: stratigraphy, correlation and ocean acidification. Global and Planetary Change, 175, 129–143.

How to cite: Hart, M. B. and Smart, C. W.: Ocean acidification: past, present and future., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13163, https://doi.org/10.5194/egusphere-egu22-13163, 2022.

Ocean acidification is a consequence of current anthropogenic climate changes. The concomitant decrease in pH and carbonate ion concentration in sea water may have severe impacts on calcifying organisms, such as foraminifera. The composition of the shells (called tests) of these cosmopolitan unicellular organisms roughly reflects environmental conditions at the calcification time, and they can fossilise. Thus, foraminifera are widely used as proxy for past environmental parameters, including for the carbonate system.

The aim of this study was to evaluate the effects of varying pH on calcification and test geochemistry of the symbiont-bearing species Peneroplis spp. We performed culture experiments to study their resistance to ocean acidification conditions, as well as their calcification recovery once placed back under open ocean pH 7.9.

After 3 days at pH 6.9 and dark conditions, strongly decalcified specimens were observed, with the inner organic lining clearly appearing. These specimens were still alive, as attested by cytoplasm streaming. Some of the specimens were then placed back at pH 7.9, in light/dark conditions. After one month, a new calcification phase started for the majority of the specimens, by addition of new chambers. The trace elements concentrations of the new calcite were analysed by LA-ICPMS. The incorporation of B and Zn appeared to have been rapidly impacted by changes in the culture conditions. Moreover, the newly formed chambers were most of the time abnormal, and the general structure of the tests was altered, which has potential impacts on reproduction and in situ survival of the specimens. In conclusion, if symbiont-bearing foraminifera show some resistance and recovery abilities to short term lowered pH conditions, they will remain strongly affected by ocean acidification.

How to cite: Charrieau, L., Nagai, Y., Kimoto, K., Dissard, D., Below, B., Fujita, K., and Toyofuku, T.: Calcification recovery after exposure to ocean acidification conditions - results from culture experiments and geochemical signature, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11564, https://doi.org/10.5194/egusphere-egu22-11564, 2022.

Insights into past marine carbon cycling and water mass properties can be obtained with reconstructions of the seawater carbonate system (C-system) through controlled experiments with accurate C-system manipulations. Benthic foraminifera (marine calcifying microorganisms) incorporate various elements into their biogenic calcium carbonate shells as a function of specific environmental parameters. We explore the use of Sr/Ca ratio of the calcite shells as a potential sea water C-system proxy after a controlled growth experiment with two deep-sea foraminiferal species (Bulimina marginata and Cassidulina carinata) and one intertidal species (Ammonia T6). To this aim, we decoupled carbonate chemistry in controlled growth experiments, i.e., changing pH at constant dissolved inorganic carbon (DIC) and changing DIC at constant pH. These experiments were performed for the first time with a new generation of environmental ecological experiment simulators (Ecolab system) allowing a precise control and monitoring of pCO₂, temperature and humidity. Four climatic chambers were used with different concentrations of atmospheric pCO₂ (180 ppm, 410 ppm, 1000 ppm, 1500 ppm). Preliminary results describe a positive correlation between Sr/Ca and the C-system (DIC/bicarbonate ion concentration) for Ammonia T6 and B. marginata, whereas no correlation with any of the C-system parameters was observed for C. carinata. We hypothesize that Sr/Ca ratios may serve as reliable proxy for the C-system for selected benthic foraminifera species.

How to cite: Mojtahid, M., Depuydt, P., Mouret, A., Rihani, F., Le Houedec, S., Fiorini, S., Chollet, S., Massol, F., Dohou, F., Filipsson, H. L., Boer, W., Reichart, G.-J., Quinchard, S., La, C., and Barras, C.: Decoupling the impact of different carbonate system parameters from controlled growth experiments with deep-sea benthic foraminifera, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6254, https://doi.org/10.5194/egusphere-egu22-6254, 2022.

It is commonly thought that recent progress of ocean warming effect on ocean ecosystems. Especially on calcifying organisms, it is concerned negatively such as coral blanching. Larger benthic foraminifers (LBFs) are one of important calcifying organisms in coral reef area, their carbonate productivity is the third highest rate in there. Therefore, it is important to elucidate the relationship between seawater temperature and the response of LBFs for estimating future ocean environment particularly in coral reef area. It has been reported that LBFs shell growth would decline when they growth higher temperature, while the physical characteristics of their shell growth remain unknown since their small and complex structures make it difficult to quantify shell growth in three dimensions. In this study, to determine how their shell volume would be affected by growth temperature, we cultured two species of LBFs which calcifying systems are different (porcelaneous LBF Sorites orbiculus and hyaline LBF Calcarina gaudichaudii) under six different temperature situations (19°C−29°C). After three months culturing, their shells were scanned by micro X-ray computed tomography (MicroCT). Here we found that　their shell volume growths were optimal at 24.4 to 24.6°C (S. orbiculus) and at 26.2 to 26.4°C (C. gaudichaudii), and declining at lower and higher temperatures than optimum temperatures. On the other hand, the intensity of the response to water temperature varies in different species. If the shell of S. orbiculus would be grown in temperature that is ±3°C different from the optimum temperature, the shell volume would be reduced by about 15%. Meanwhile, the shell of C. gaudichaudii would be showed only 7% decreasing at the same degree of temperature change. C. gaudichaudii lives at relatively shallower site than S. orbiculus with larger diurnal variation in water temperature, this difference of water temperature tolerance may have influenced their abundance. In any case, these findings demonstrate that LBF growth is already suppressed in summer and might be exacerbated in the future by ocean warming.

How to cite: Kinoshita, S., Kuroyanagi, A., Nishi, H., Sasaki, O., Fujita, K., Suzuki, A., and Kawahata, H.: Decrease in shell volume of large benthic foraminifers with progressing ocean warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6988, https://doi.org/10.5194/egusphere-egu22-6988, 2022.

Larger benthic foraminifera (LBF) are important carbonate producers in tropical and subtropical settings and play a large role in the carbon cycle. They suffer from bleaching (the expulsion/loss of the photosymbiotic microalgae) under increased sea surface temperature due to climate change. For artificial bleaching experiments, we used the diatom-bearing foraminiferan Amphistegina lobifera, because of its robustness in the laboratory for symbiosis investigations, and also the more sensitive Sorites orbiculus which hosts endosymbiotic dinoflagellates. In order to induce bleaching, the LBF were exposed to menthol at non-lethal concentrations. Additionally, DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) was applied as a photosynthetic inhibitor. After the 6 week experiment, foraminifera were >95% bleached, visible with the flourescence microscope. Survival rate of protists was high, as pseudopodial movement was still visible. The foraminifer in this bleached state was able to move and extend its pseudopodial network. The next step will be to test symbiont-uptake of those bleached foraminifera, and measure survival time and ecophysiological features of re-infected foraminifera.

How to cite: Schmidt, C., Stuhr, M., Raposo, D., Pochon, X., and Davy, S.: Menthol-induced bleaching as a tool to rear aposymbiotic foraminifera for symbiosis investigations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12500, https://doi.org/10.5194/egusphere-egu22-12500, 2022.

Benthic foraminifera (marine protists) with a calcareous shell (test) show a variety of feeding strategies including detrivory, herbivory, bacterivory, carnivory or mixotrophic adaptations. However, little is known about the feeding habits of agglutinated foraminifera, which build there tests from sedimentparticles, embedded in organic cement secreted by the foraminifer. Liebusella goesi is a benthic foraminifer with an agglutinated test, which requires stable hydrographic conditions with low seasonal variation. In general, information on the biology or ecology of this species is very limited. Furthermore, there are no data available on foraminiferal metabolic rates and their feeding ecology  (energy consumption in calories/time, food consumption rates) of such foraminifera by now.

In this study, we compared the respiration rates of L. goesi at in situ conditions incubated in sterile seawater with or without 1.5 mM labelled glucose (33 atom% ¹³C/¹²C) as a potential food source. Additionally, we estimated the individual metabolic rates of L. goesi specimens from their rate of glucose uptake over time.

Liebusella goesi individuals were collected in August 2021 with the R/V Oscar von Sydow at the deepest spot of the Swedish Gullmar Fjord (Alsbäck deep, 120m), by sampling the surface layer of sediments recovered from multiple box corer hauls. Subsequently, specimens from the 5000 µm - 125 µm sediment fraction were picked under a stereo microscope, in the laboratory at the Sven Lovén Centre in Kristineberg. Seventy specimens were pooled in six replicates per treatment and incubated within glass vials (1.5 mL) filled with either plain sterile seawater or with seawater amended with ¹³C-glucose, and sealed airtight. Finally, simultaneous non-invasive oxygen measurements were carried out over the course of 45 h. Foraminifera incubated with ¹³C-glucose were prepared for elemental analysis and isotope ratio mass spectrometry to evaluate the amount of ¹³C-glucose intake during the experimental period.

The respiration rates of L. goesi were in the range of previously observed rates of other foraminifera. Liebusella goesi actively feeded on dissolved organic carbon in the form of glucose and a significant increase of the respiratory activity of the specimens incubated with the ¹³C-glucose was observed. Metabolic rates of L. goesi will be presented in comparison with those of other protists based on data synthesis from other available sources.

The results of this experiment enhance the knowledge about the metabolism of agglutinated foraminifera. However, further experimentation with other species and eventually further variation of incubation factors will be needed, to get a more comprehensive picture of the feeding strategies and metabolic adaptations of agglutinated foraminifera.

How to cite: Wukovits, J., Nagy, M., Wanek, W., and Heinz, P.: Respiration rates and glucose intake by the agglutinated foraminifer Liebusella goesi from the Gullmar Fjord (Sweden), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9903, https://doi.org/10.5194/egusphere-egu22-9903, 2022.

An in vitro experiment was designed to describe how benthic foraminifera (as witness of the benthic ecosystem) reacts to “one-time high volume” vs “frequent low volume” sediment discharge, as it may occur in coastal benthic environments regularly or occasionally buried during (e.g.) river flood massive deposits, or glacier melting events in polar regions. The influence of these events on the ecology of benthic ecosystems is often neglected and the resilience of benthic foraminiferal communities is poorly known. During a 53-day long experiment in microcosm, the NE Atlantic mudflat foraminifera community, mainly represented by Ammonia T6 and Haynesina germanica species, was confronted to two kinds of sedimentary disturbance: 1) one-time high volume (OHV) deposit, i.e. about 3 cm thick sediment is added in one time at the beginning of the experiment, and 2) frequent low volume (FLV) deposits, i.e. about 0.5 cm added each week for 4 weeks. The geochemical environment (e.g. O₂ penetration in the sediment, salinity, temperature and nutrient content in the supernatant water) was monitored to follow its steady-state before and during the experiment. In the two studied cases, the foraminifera react to the disturbance by immediately moving upward to the surface within 1 day after the deposit. In the OHV treatment, a species vertical distribution in relation to the surface, comparable to the vertical distribution before the disturbance (i.e. a resilient state), is established at most 1 week after the deposit, and no effects are visible on the foraminiferal diversity after 1 month experiment (without any other sediment input). In the FLV treatment, the resilient state is already reached 1 day after a low thickness burial. This suggests that foraminifera can migrate rapidly to their preferential life position under the new sediment-water interface. However, after 4 recurrent burring events the density of H. germanica drastically decreases, changing in this way the foraminiferal community structure. The results of this microcosm experiment suggest that the entire foraminiferal community can migrate upward quickly enough to keep pace with at least 3 cm of abrupt burial but needs several days to reach a resilient state. Furthermore, frequent sediment deposition may affect foraminiferal biodiversity more than a massive erratic event.

How to cite: Corentin, G., Maria Pia, N., Hélène, H., Damien, L. M., Antonio, P., Sophie, S., and Aurélia, M.: Short-term response of benthic foraminifera to fine sediment depositional events simulated in microcosm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4770, https://doi.org/10.5194/egusphere-egu22-4770, 2022.

Squids are an evolutionary-biological success model since the Palaeozoic. The presence of cartilage enables them to a high-speed predatory lifestyle. Although coleoid and vertebrate cartilage are histological very similar, there is no need for in vivo mineralisation in squids. Contrary, its mineralisation in dead specimens under laboratory conditions was investigated several times, but until now taphonomic studies on coleoid cartilage are rare. We present an experimental setting in which we investigate the decay and possible mineralisation processes of coleoid cartilage under semi-natural conditions, using a substrate from the eastern Black Sea, which was collected during the Mare Nigrum Expedition 226. Elemental analysis of the sediment with X-ray fluorescence (XRF) revealed hints for palaeoenvironmental similarities to the deposits of the Late Triassic Polzberg Konservat-Lagerstätte near Lunz am See (Lower Austria, Northern Calcareous Alps), which provides deep insights to the morphology and ecology of the fossil belemnitid Phragmoteuthis bisinuata, including the preservation of soft tissues such as cranial cartilage. Mineralogical composition of the recent sediment was analysed by X-ray diffractometry (XRD) and clay mineral analysis. In a test series, full specimens of the coleoid Loligo vulgaris were buried in the sediment samples for two months. After exhumation of the “fossilised” squid, decay processes will be documented with a strong focus on cephalic cartilage. Possible mineralisation can be determined by the use of XRD and Fourier-Transformation-Infrared-Spectroscopy (FTIR). Stained histological thin sections of Sepia officinalis cranial cartilage before and after the experiment, as well as Magnetic Resonance Tomography (MRI) of two cephalopod specimens (Octopus vulgaris and Loligo vulgaris) and the corresponding reconstructions constitute the dataset for cephalic cartilage morphology and its comparisons to the semi-fossilized cartilages. The fossilisation process will be tested under different environments, while changes in temperature, oxygen saturation and pH-values will be monitored. Associated morphological changes will be quantified with Micro-Computertomography (Micro-CT) and the methods above mentioned.

The obtained data on the decay and preservation in microenvironments of the coleoid carcasses and possible onset of cartilage mineralisation will increase the knowledge on the individual factors that are involved in the fossilisation processes, which lead to exceptional preservation in Konservat-Lagerstätten.

How to cite: Lukeneder, P., Heinz, P., Gier, S., Lukeneder, A., Ottner, F., Pojar, I., Hiden, T. E., Ritschl, H., Zuschin, M., Reishofer, G., Tintner-Olifiers, J., and Sihorsch, P.: Experimental taphonomy and in-vitro mineralisation of coleoid cranial cartilage at semi-natural conditions., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7270, https://doi.org/10.5194/egusphere-egu22-7270, 2022.

Beach wrack, defined as material washed ashore by wind, waves and tides, is a natural phenomenon observed at all coasts worldwide. Often seen as a nuisance and being removed at recreational beaches, it is an important component for dune vegetation succession and habitat for beach faunal components both being negatively impacted by beach management practices. In order to balance the conflicting interests of tourism and nature protection, sound data about amounts, seasonality and composition of beach wrack washed ashore as well as residence time and decomposition kinetics are required, but not available yet for microtidal Seas as the Baltic.

The decay of beach wrack at the beach and under controlled and dry conditions was investigated in the past several times. In this work, the decay of beach wrack, and i.e. seagrass of the genus Zostera marina was documented under natural conditions. Therefore, litterbags of fine mesh were sewed and filled with a defined amount of freshly detached seagrass from the local shore. Altogether six experiments were carried out: first two experiments starting in summer or winter, respectively, with constant wet conditions in appx. 1 m water depth. The remaining four experiments were conducted throughout the four seasons. Here, the litterbags were put into water, removed onto land, and vice versa for a total time period of six weeks. The experiments were run in the shallow water at the island of Poel completely submerged and, for a comparison with changing conditions between water and land, at the beach of Warnemünde. Additionally, the experiments were split between light and dark conditions by the use of different mesh colors.

Data about degradation rate through loss of biomass have been retrieved, as well as abiotic parameters influencing the rate of decomposition. For additional insights into the decay of seagrass each sampling time the biofilm was removed, DNA extracted and analyzes of the microbial biofilm are at an initial stage. This work will give valuable information on the degrading community, the influence of seasons, temperature, light availability and the continued change when beach wrack is washed ashore and retrieved back by the sea for many times through all decomposition stages.

How to cite: Schätzle, P.-K. and Schubert, H.: Evaluating beach wrack decay through the seasons under wet (underwater) and changing (wet/dry) conditions at the Baltic Sea coast, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7567, https://doi.org/10.5194/egusphere-egu22-7567, 2022.

A considerable growth of industrial facilities has been taking place along coastal environments over the past century. Some of these facilities have major economical and national importance, yet their operation can introduce a wide range of potentially harmful chemicals, such as heavy metals (HM), that might impact local ecosystems and human health. Efforts to monitor the presence of HM at low concentrations before damaging the ecosystem are contingent for protecting and conserving these coastal environments.   

Many recent studies have shown the applicability of benthic foraminiferal shell chemistry for monitoring HM in coastal environments. Foraminiferal shells grow by sequential addition of chambers, thereby yielding a chronological record of HM concentrations in ambient seawater. This study introduces a new concept of defining a HM baseline assessment levels (BAL) in coastal seawater environments using foraminiferal shells. The BAL provide an absolute reference for documenting the temporal variation in HM that can be used to quantify the magnitude and duration following pollution events.

We demonstrate the potential of this approach by examining a pristine site in a nature reserve along the Mediterranean coast of Israel. Our previous investigation of this site in 2013-14 using foraminiferal single chamber LA-ICPMS created a large dataset that consisted of HM measurements in the last few chambers of two species Lachlanella and P. calcariformata. This database was used to establish the BAL metals/Ca ratios of Zn, Cu and Pb, three HM associated with anthropogenic sources.

The BAL of each metal was defined as the 5th lower percentile value from the LA-ICPMS dataset of each species. To encompass the natural variability of non-contaminant natural sources in the BAL, 2 STDEV (in RSD%) of the observed variation of the alkaline earth metal Sr/Ca ratios were added. The potential biological variations between specimens to the resulting ratios based on laboratory culturing experiments of the two species.

In February 2021, a significant oil spill event affected the entire Mediterranean coast of Israel, and included a considerable out wash of tar onto the shore. The event provided a unique opportunity to test the applicability of foraminiferal BAL by revisiting the previously studied site. Our strategy was to compare whole shell ICP-MS measurements of the two species collected shortly after the event and six months later, and compare them with the established BAL values. Our results revealed a significant increase (2-20 folds) in Zn/Ca, Cu/Ca, Pb/Ca ratios between 2013-14 and 2021. Among these, the increase in Pb/Ca is the most substantial and observed in both species. This implies a possible linkage between the oil spill event and the substantially elevated metals/Ca ratios measured by the foraminifera in 2021. Our study also demonstrates that bulk ICP-MS analyses will most likely yield similar ratios as those of average values of single chamber LA analyses of shells from the same location and period. This observation confirms that once BAL values are established, the analysis of bulk shell ICP-MS is effective for monitoring HM contamination of coastal environments. 

How to cite: Hoober, L., Titelboim, D., Abramovich, S., Herut, B., Teutsch, N., and Torfstein, A.: Establishing the baseline assessment levels for monitoring coastal heavy metals in seawater using benthic foraminiferal shells, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5204, https://doi.org/10.5194/egusphere-egu22-5204, 2022.

Foraminifera are highly abundant marine unicellular eukaryotes. They are known for their important ecological role in most marine ecosystems, their major contribution to the carbon cycle, and their remarkable physiological plasticity. Many foraminiferal species have mixotrophic metabolism that is often based on partnerships with diverse algae, or in some cases, on harvesting diatom chloroplasts, known as kleptoplasty. To date, kleptoplasty was shown only in rotaliid lineages. Here, we report the first discovery of a diatom kleptoplasty in the Hauerina diversa, a tropical shallow-water miliolid that is an unexpected candidate for this life strategy. To elucidate this adaptation, we collected H. diversa specimens from the southeastern Mediterranean coast and visualized many intact chloroplasts in clustered structures within the foraminiferal cytoplasm using transmission electron microscopy. Preliminary genetic analyses confirmed that the harvested chloroplasts originated from diatoms. Primary production estimates using isotopically labeled NaH¹⁴CO₃ as a carbon source suggest photosynthetic activity of the ‘stolen’ chloroplasts inside the host cell. This activity was found to be about two orders lower compared to the diatom-bearing species Amphistegina lobifera. We finally provide the first molecular phylogeny of H. diversa and its evolutionary relationship to ancient alveolind foraminifera. We thus demonstrate the first case of kleptoplasty in the ancient group of alveolind-miliolids, expanding the evolutionary range of kleptoplasty in foraminifera

How to cite: Pinko, D., Abramovich, S., Rahav, E., Natasha, B., Rubin Blum, M., Holzmann, M., and Abdu, U.: Chloroplast harvesting by a miliolid expands the evolutionary range of kleptoplasty in foraminifera, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5024, https://doi.org/10.5194/egusphere-egu22-5024, 2022.

Shallow-water banks of foraminiferal propagules (tiny juveniles <63 µm) harbor a hidden assemblage composition that has altered our understanding of traditional distribution patterns. Propagules can be transported well beyond their environmental limits and remain dormant until local conditions become suitable. Therefore, the composition of propagule assemblages is expected to differ from “adult” assemblages. This offers various opportunities for a better understanding of foraminiferal reactions to environmental changes and also of the variability of living foraminiferal populations throughout the year.

To date, propagule assemblages have only been analyzed “passively” through growth experiments with propagule banks under laboratory conditions. Here, we apply for the first time a combination of a multi-week cultivation experiment and eDNA metabarcoding of the different size fractions.

Sediment samples were taken from a shallow lagoon in Corfu (Greece) and sieved over 63 µm to separate the propagule bank from the coarser fraction. The in-situ material of the sampling site was used as a baseline for the subsequent experiment (T0). The finer fraction (<63 µm) was set up in a culture experiment for 15 weeks under stable conditions (22°C, 38 psu, constant aeration). The cultures were repeatedly harvested for grown foraminifera (>63 µm) every 5 weeks (T1–T3). At the same intervals, samples were taken and re-sieved over 63 µm for eDNA metabarcoding of both size fractions.

The morphology-based count data of the foraminiferal specimens revealed significantly different assemblage compositions after each harvest (T0–T3). The differences between the in-situ (T0) and the experimental samples (T1–T3) were most distinct, indicating a specific composition of the propagule bank. The differences between in-situ and experimental assemblages as well as the shifting assemblage compositions over time were mirrored by the metabarcoding data from the respective intervals. Our results highlight the potential for metabarcoding to complement and expand insights gained from morphology-based approaches in foraminiferal studies.

How to cite: Weinmann, A. E., Morard, R., Hassenrück, C., Goldstein, S. T., Li, Q., Raposo, D., Triantaphyllou, M. V., and Langer, M. R.: Assessing assemblages from foraminiferal propagule banks: A combined approach of culture experiments and eDNA metabarcoding, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2315, https://doi.org/10.5194/egusphere-egu22-2315, 2022.

The transcriptomic signature of cold and heat stress in benthic foraminifera - Implications for range expansions of marine calcifiers

Global warming permits range expansions of tropical marine species into mid-latitude habitats, where they are, however, faced with cold winter temperatures. Therefore, tolerance to cold temperatures may be the key adaptation controlling zonal range expansion in tropical marine species. Here we investigated the molecular and physiological response to cold and heat stress in a tropical symbiont-bearing foraminifera that has successfully invaded the Eastern Mediterranean. Our physiological measurements indicate thermal tolerance of the diatom symbionts but a decrease of growth for the foraminifera host under both cold and warm stress. The combined (“holobiont”) transcriptome revealed an asymmetric response in short-term gene expression under cold versus warm stress. Cold stress induced major reorganization of metabolic processes, including regulation of genes involved in photosynthesis. Analyses limited to genes that are inferred to belong to the symbionts confirm that the observed pattern is due to changes in the regulation of photosynthesis-related genes and not due to changes in abundance of the symbionts. In contrast to cold stress, far fewer genes change expression under heat stress and those that do are primarily related to movement and cytoskeleton. This implies that under cold stress, cellular resources are allocated to the maintenance of photosynthesis, and the key to zonal range shifts of tropical species could be the cold tolerance of the symbiosis.

How to cite: Abdu, U., Titelboim, D., Morard, R., Kucera, M., Ashckenazi-Polivoda, S., Almogi-Labin, A., Herut, B., Manda, S., Abramovich, S., and Gold, D.: The transcriptomic signature of cold and heat stress in benthic foraminifera - Implications for range expansions of marine calcifiers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1699, https://doi.org/10.5194/egusphere-egu22-1699, 2022.

Jullienella foetida is probably the largest agglutinated foraminifer in modern oceans and can reach a length of up to ~14 cm. Because of its large size, the species was initially considered to be a bryozoan, but later correctly described as a single-chambered (monothalamous) foraminifer with a large, flat or slightly undulating plate-like test, leaf-like, or fan-like in overall shape and with the chamber interior subdivided by longitudinal partitions. It occupies a restricted geographical range around part of the NW African margin where it is found in eutrophic settings with a preference for energetic environments.

We have applied a suite of non-destructive methods, namely light microscopy, SEM, X-ray and high-resolution micro-computed tomography (micro-CT) to 1) explore its external and internal test characteristics and 2) to provide a first-order estimate of its possible contribution to sea floor biomass. High-resolution SEM images show the test wall to comprises a smooth, outer veneer of small mineral grains that overlies the much thicker inner layer, which has a porous structure and is composed of grains measuring several hundreds of microns in size.  X-ray images of the test reveal an elaborate system of radial partitions that subdivides the test interior into channels that may serve to direct the flow of the cytoplasm, and perhaps increase its surface to volume ratio.  Micro-CT scans suggest that much of the test interior is filled with cytoplasm with a biomass comparable to that of slightly larger xenophyophores. This remarkable species appears to play an important, perhaps keystone, role in benthic ecosystems where it is abundant, providing the only common hard substrate on which sessile organisms can settle.

How to cite: Langer, M. R., Weinmann, A. E., Makled, W., Koenen, J., and Gooday, A. J.: Jullienella foetida Schlumberger, the largest shallow-water agglutinated foraminifer in modern oceans, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3818, https://doi.org/10.5194/egusphere-egu22-3818, 2022.

In this study, we explore the use of Species Distribution Models (SDM) to infer spatial distribution of four species of benthic foraminifera around the globe. We modelled the distributions of Peneroplis planatus, P. pertusus, P. arietinus and Coscinospira hemprichii against a large collection of ecologically meaningful environmental variables (EMEV) variables in the Arabian Gulf. To identify combinations of effective predictor EMEV, we compiled several models and narrowed down to a subset based on set of predictive performance metrics. Mean iron concentration, diffusion attenuation, and dissolved oxygen were identified as important variables influencing the distribution of these species. The modelling task is essentially composed of two parts (1) Initial modelling of the actual known distributions of species in a well-defined basin and subsequent validation. (2) Spatial extrapolation over a global extent. Our model successfully predicted current habitat suitability for the four species within Arabian Gulf basin (AUROC = 92%).  It also identified areas along the western coastline as highly suitable habitats (Habitat Suitability Index > 0.8). Further, it reliably identified areas with known distributions of the four species (AUROC = 89%) around the world. Here we demonstrate how a SDM model can be a useful tool in capturing complex habitat features for benthic organisms and reduce sampling and accessibility concerns.

How to cite: Abduljamiu, A., Frontalini, F., Argadestya, I., Kaminski, M., and Muller, P.: Predicting spatial distribution of benthic foraminifera using Species distribution models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9467, https://doi.org/10.5194/egusphere-egu22-9467, 2022.

Benthic foraminiferal assemblages were analysed to determine their seasonal variation and evaluate the effects of environmental factors on their density, species composition and distribution, in the semi-enclosed Thermaikos Gulf, in the NW part of the Aegean Sea. Three major rivers, two minor ones and several ephemeral streams flow into the shallow Thermaikos basin, discharging annually tonnes of sediment, forming a submarine delta on the west part of the gulf and causing the constant occurrence of dissolved solids in the water column. During the high precipitation period (January-May), the fresh water intrusion extends to the major part of the gulf (surface salinities <25), while during the whole year more saline waters from the northern Aegean flow towards the northeast, entering the gulf.

Changes in the foraminiferal abundance and composition was explored during a twelve-month monitoring, compared to a multi-parameter environmental dataset (temperature, salinity, pH and nutrients), metal content and organic carbon. Sampling of the top 2cm of the surface sediment was carried out on a monthly basis (January-December 2016) at one station (S1), and at 5 stations (S1-S5) during winter (February), spring (April), summer (July) and autumn (October), located in Thessaloniki Bay (inner part of the Thermaikos Gulf). During late spring-summer (April to August), foraminiferal densities and relative percentages of the living specimens displayed the highest values, while high diversities (Shannon-Wiener index) were observed during winter. The different samples investigated seasonally present a variability, with respect to both abiotic parameters and the foraminiferal assemblage. The main part of the gulf (muddy bottom - max depth 23 m) is dominated mainly by Bulimina spp., Bolivina spp., Uvigerina spp. and various species of agglutinated foraminifera, such as Textularia bocki, Eggereloides scaber, and Reophax spp. Samples from the western part of the gulf (sandy bottom - max depth 3 m) were characterized by a more diversified assemblage also including miliolids and a variety of small, epiphytic rotaliid taxa.

The exceptional environmental conditions that prevail in the environments of the inner Thermaikos Gulf, are reflected in foraminiferal composition, making it an ideal laboratory for the study of the microfauna in response to a combination of stressful parameters in a natural physiochemically complex environment.

How to cite: Koukousioura, O., Georgiou, S., Dimiza, M., Avramidis, P., and Triantaphyllou, M.: Seasonal benthic foraminifera response to the complex physicochemical conditions of the semi-enclosed Thermaikos Gulf (NW Aegean Sea), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7087, https://doi.org/10.5194/egusphere-egu22-7087, 2022.

Benthic foraminifers are one of major biota at marine environments. We have long been worked deep sea benthic foraminiferal communities at the Western Pacific since 1990^th.  We analyzed more than ten localities of the western Pacific deep-sea, in particular to hadal depths. Hadal foraminiferal community consists of monothalamous soft-shelled forms, agglutinated forms, porcelaneous forms, hyaline forms and large xenophyophores.  In the shallower deep-sea such as abyssal depths, there are many environmental factors that are limiting distribution of species.  They are temperature, salinity, hydraulic pressures, oxygen concentrations and others.  Benthic foraminifers are so sensitively adapted to these environmental factors, benthic foraminifers are used as proxy organisms.  How about populations of hadal depth?

We compare populations between Challenger deep (10,899m) and Horizon deep (10,811m) of the western Pacific hadal trenches, where differences of the depth show less than 100m each other. Foraminiferal population at the Horizon Deep shows much higher concentrations of agglutinated forms. How can we explain populational differences between two deeps? What kind of factors show differences in hadal environments?  Sea water environments are mostly the same in hadal depths.

I propose sediment characters that give hidden diversities of bottom environments at hadal trenches.  There are two types of subduction tectonics at hadal trenches, both Mariana-type and Chilean-type.  Mariana-type is characterized by sedimentary rocks that are accreted  when oceanic plate subducted.  Mariana-type trenches are characterized by big earthquakes and tsunamis.  In contrast, Chilean-type is characterized by mantle peridotite and related rocks such as serpentinite.  There is few earthquakes at Chilean-type subduction area.  The differences of foraminiferal faunal composition between Marianas and Tonga Trenches should be related to the sediment characters that are reflecting trench geology.

How to cite: Kitazato, H.: What kind of factors do give diversities of benthic foraminiferal fauna at hadal depths ?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3320, https://doi.org/10.5194/egusphere-egu22-3320, 2022.