A hidden treasure: Ecological implications from benthic foraminiferal propagule banks in coastal environments of Corfu (Ionian Sea)
Palaeontology
Final Report Abstract
The project “A hidden treasure: Ecological implications from benthic foraminiferal propagule banks in coastal environments of Corfu (Ionian Sea)” covered several aspects of the ecology and diversity of shallow-water foraminifera. A total of 200 benthic species were identified that showed specific distribution patterns along the island: assemblages from the rocky shores of the north and the sandy bays of the south showed the most striking differences. Water depth and vegetation cover contributed highly to the different faunal compositions. Most sediment samples contained specimens of Amphistegina lobifera, which is classified as an invasive alien species. Whenever A. lobifera exceeded 20% of the relative abundances in a sample, it had a significant negative effect on diversity. In particular, small miliolid foraminifera and attached or partially attached epiphytes showed reductions in abundances as they occupy the same microhabitats. However, for the moment this was only observed in a few samples. Nevertheless, with ongoing ocean warming and a continuing proliferation of A. lobifera, further assemblage changes in the shallow-water communities can be expected. Several independent culture experiments on foraminiferal propagules (small juveniles) from lagoon sites in Corfu offered new insights into the structure and composition of local propagule banks as well as assemblage reactions to different environmental variables: The experiments showed that the propagule assemblages varied between seasons (spring and fall) and that sampling time appears to be important for interpretation. Propagule banks from different lagoons were also composed differently, even though environmental conditions were comparable. Contrary to expectations, the use of different substrate types during the experiments had no significant effect on the resulting assemblages. Overall, there seemed to be a more dominant influence from the higher amount of organic material in fine sediments. Cultivation experiments of propagule banks under different pH-values revealed significant differences between higher (7.8) and lower pH conditions (7.2). Higher treatments were dominated by porcelaneous specimens, while lower treatments showed much higher abundances in agglutinated specimens. Propagules grown under lower pH and subsequently under higher pH were again strongly dominated by porcelaneous specimens. Interestingly, mortality was rather low even under low pH conditions and some porcelaneous specimens were able to survive with broken or partially diluted shells. This suggests some recovery potential of shallow-water communities. Cultivation experiments of propagules under different temperatures showed differences between the settings, which corroborates previous studies. Assemblages were able to grow under temperatures of 29–36°C, but in lower numbers and with a lower survival rate than in 22°C. When material from both settings was re-cultivated under lower temperatures (22°C and 26°C), the assemblages still exhibited significant differences according to the first treatment (29–36°C and 22°C). This suggests that shallow-water assemblages are able to sustain episodes of very high temperatures, but could be lastingly influenced by these conditions. High numbers of allochthonous (non-local) foraminifera grew in all experiments. As these species suggest a “hidden” diversity within the propagule banks, sub-samples of long-term cultivation experiments were analyzed with morphological and molecular methods (metabarcoding). Both approaches revealed comparable patterns in the resulting assemblages, mostly influenced by sampling season (spring or fall) and cultivation time (5, 10, or 15 weeks). With the metabarcoding, it was possible for the first time to compare the fine fraction (<63 µm) and the grown fraction (> 63 µm), which revealed significant differences that also sustained over the course of the experiments. This gives insights into the mechanisms behind quick assemblage reactions of foraminifera to environmental changes.
Publications
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(2018): Is timing everything? The effects of site, seasonality and substrate on foraminiferal assemblages grown from propagule banks. – In: Aze T., Woodhouse A. & Mair A. (Eds): TMS Annual Conference 2018 “Microfossil Insights into Greenhouse Worlds” (November 14–15 2018, Leeds, UK). Abstracts with Programs
Weinmann A.E., Goldstein S.T., Triantaphyllou M.V. & Langer M.R.
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(2018): New insights from propagule experiments in a shallow-water lagoon in Corfu (Greece, Ionian Sea). – FORAMS 2018 – International Symposium on Foraminifera “Foraminifera in a Changing World” (June 17–22 2018, Edinburgh, UK). Abstracts: 681
Weinmann A.E., Goldstein S.T., Triantaphyllou M.V. & Langer M.R.
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(2018): What could have been – Implications from laboratory experiments on foraminiferal assemblages for environmental reconstructions. – In: Froitzheim N., Grevel K.-D., Hoffmann G., Luguet A., Martin T. & Strack R. (Eds): GeoBonn 2018 “Living Earth” (September 2–6 2018, Bonn, Germany). Abstracts: 268
Weinmann A.E., Langer M.R., Goldstein S.T. & Triantaphyllou M.V.
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(2019): Ecology and community structure of modern intertidal foraminifera from Corfu Island (Greece): Insights from propagule experiments. – GSA Annual Meeting 2019 (September 22–25 2019, Phoenix, AZ, USA). Abstracts with Programs 51/5: 270-10
Weinmann A.E., Goldstein S.T., Triantaphyllou M.V. & Langer M.R.
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(2019): Effects of sampling site, season, and substrate on foraminiferal assemblages grown from propagule banks from lagoon sediments of Corfu Island (Greece, Ionian Sea). – PLoS One 14: e0219015
Weinmann A.E., Goldstein S.T., Triantaphyllou M.V. & Langer M.R.
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(2020): Compositional shifts in shallow-water foraminiferal assemblages in response to pH variations: Insights from a culture experiment with propagules. – GSA Annual Meeting 2020 (October 26–30 2020, online). Abstracts with Programs 52/6: 177-12
Weinmann A.E., Goldstein S.T., Langer M.R. & Triantaphyllou M.V.
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(2021): Community responses of intertidal foraminifera to pH variations: a culture experiment with propagules. – Aquatic Ecology 55: 309–325
Weinmann A.E., Goldstein S.T., Triantaphyllou M.V. & Langer M.R.
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(2021): The propagule method as a tool to study assemblage dynamics in benthic foraminifera: An example with pH variations. – EGU General Assembly 2021 (April 19–30 2021, online). EGUsphere: EGU21–7192
Weinmann A.E., Goldstein S.T., Triantaphyllou M.V. & Langer M.R.
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(2021): The recent distribution of benthic shallow-water foraminifera in Corfu Island (Greece, Ionian Sea) – A biodiversity hotspot between the eastern and western Mediterranean. – In: Stumpf S., Türtscher J., Pfaff C., Jambura P.L. & Kriwet J. (Eds): 92nd Annual Meeting of the Paläontologische Gesellschaft (September 27–30 2021, online). Berichte der Geologischen Bundesanstalt 142: 100
Weinmann A.E., Triantaphyllou M.V. & Langer M.R.
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(2022): Assessing assemblages from foraminiferal propagule banks: A combined approach of culture experiments and eDNA metabarcoding. – EGU General Assembly 2022 (May 23–27 2022, Vienna, Austria). EGUsphere: EGU22–2315
Weinmann A.E., Morard R., Hassenrück C., Goldstein S.T., Li Q., Raposo D., Triantaphyllou M.V. & Langer M.R.
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(2022): Cenozoic mass occurrences of Larger Benthic Foraminifera in the Mediterranean region: What can we learn from the current range expansion of Amphistegina lobifera? – In: Rantitsch G. & Raith J.G. (Eds): PANGEO 2022 (September 10–13 2022, Leoben, Austria). Berichte der Geologischen Bundesanstalt 143: 199
Weinmann A.E., Koukousioura O., Triantaphyllou M.V. & Langer M.R.
