Comparison between living and death shallow benthic assemblages between areas with different exposure to seawater temperatures in the eastern Mediterranean Sea.

Abstract

In the Mediterranean Sea's Levantine Basin, a region vulnerable to rising temperatures and biological invasions, the effects of climate change and the invasion of thermo-tolerant alien species threaten native organisms. This research project evaluates taxonomic diversity and composition variations between two thermally distinct regions within Cyprus, Cape Greco and Akrotiri. While in Cape Greco the sea temperature has risen, in Akrotiri the temperatures remain unaffected due to an upwelling phenomenon observed during the summer season in the area. The analysis was conducted by comparing living and death assemblages, encompassing not only different geographical locations but also distinct ecological habitats, rocky substrate and Posidonia meadow. The examination of death assemblages provides insights into the recent ecological history and helps quantify changes and losses; information highly valuable considering the lack of a speciation database in the region. The hypothesis is that the warmer Cape Greco exhibits reduced species richness and an increased number of non-native mollusks compared to Akrotiri, indicating an impacted area. Additionally, it is expected that Posidonia meadow faces higher rarified richness than rocky substrate, mainly due to photosynthesis that causes oxygen-super saturation which increases the thermotolerance of the species. In contrast with the expectations, the results show a pristine condition in both areas with alien species having a minor impact on the native benthic mollusks. However, Akrotiri maintains nearly triple the rarified richness compared to Cape Greco, suggesting an optimal refugia. Posidonia meadow has indeed greater rarified richness than the rocky substrate. This research aims to shed light on the biodiversity patterns and ecological relationships in the Mediterranean ecoregion, contributing to our understanding of the impacts of climate change and biological invasions on marine ecosystems.