A hidden treasure: Ecological implications from benthic foraminiferal propagule banks in coastal environments of Corfu (Ionian Sea)

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Benthic foraminifera have become increasingly important as bioindicators, especially in shallow-water and coastal environments. Due to their ubiquity, high abundances, and short generation times, they are able to react quickly to various environmental changes. Changes in assemblage compositions as well as the presence or absence of indicator taxa are frequently used in biomonitoring or ecological change studies. In the last few years, a new approach has been developed to complement conventional field and laboratory studies on foraminiferal ecology: The Propagule Method. This experimental approach targets propagule banks – assemblages of tiny foraminiferal juveniles that occur in the fine fraction of the sediment. Propagules can be easily dispersed and are able to settle outside of their natural distribution ranges. Isolating the propagule bank and exposing it to different environmental conditions in the laboratory allows the evaluation of possible faunal reactions to the environmental variations in question. By targeting the growth of juvenile specimens under specific conditions, it becomes possible to better understand and evaluate the potential of the propagule bank as a species pool.The aim of this research project is to study assemblage reactions of foraminiferal propagule banks from Corfu (Greece) to changes in oceanic variables that will become increasingly important in coming decades: temperature extremes and decreasing pH values. The Mediterranean Sea is particularly impacted by these environmental changes. Ongoing ocean warming will lead to seasonal temperature peaks in the summer months that will create particularly stressful conditions for shallow-water faunas and floras. Additionally, ocean acidification and the subsequent drop in pH poses a threat to calcifying organisms – including foraminifera. With the application of the Propagule Method, the project will target assemblage reactions to extreme conditions that might occur in the coming decades. At the same time, the potential of the propagule bank to provide recovery mechanisms of impacted assemblages will be analyzed. Subsequently, the remarkable capacity of the propagule bank as a species pool will be evaluated. In this context, the experimental Propagule Method will, for the first time, be complemented by genetic analyses (barcoding and metabarcoding).