Macroalgal dynamics shape epiphytic foraminiferal assemblages in the eastern Mediterranean rocky reef

Epiphytism of macroalgae by benthic foraminifera is a common commensal association in rocky intertidal and subtidal reefs. This interaction may be directly and indirectly influenced by climate change and bioinvasions. We investigated this association on rocky reefs of the Eastern Mediterranean Sea, a recognized hotspot of biological invasions and rapid warming, with the aim of establishing a recent baseline of epiphytic foraminiferal dynamics for future monitoring. Epiphytic benthic foraminifera (EBF) attached to macroalgal hosts representing diverse species were collected across seasons and along a very shallow-to-intermediate depth gradient at several rocky reef sites between 2013 and 2017. Macroalgae from all surveyed reefs hosted diverse EBF assemblages composed of both native and alien species. Assemblages were largely dominated by the invasive, endosymbiont-bearing larger benthic foraminifer Amphistegina lobifera, together with native taxa including Pararotalia calcariformata, Textularia agglutinans, and Tretomphalus bulloides. The alien miliolids Sigmamiliolinella australis and Borelis schlumbergeri were recorded alive for the first time in this region, although the latter occurred at low abundances. Algal type and complexity, site, depth, season, and year significantly structured EBF assemblages, whereas no significant differences were detected between sites located inside and outside a marine protected area (MPA). The richest EBF communities occurred on Halopteris scoparia and Laurenciella marilzae, while Dictyota dichotoma and Liagora ceranoides supported the lowest diversity. Spring and summer exhibited the highest richness of larger benthic foraminifera. This study provides a dynamic baseline for epiphytic benthic foraminiferal communities associated with Levantine macroalgae, highlighting increasing invasion dominance and potential responses to ongoing warming.