Foraminifers associated with macroalgae on a wave-cut platform off Abu Qir coastal area, Egypt

Since their earliest history, benthic foraminifers have diversified to inhabit a vast array of habitats, from semi-terrestrial to the deep-sea floor. Epiphytic foraminifers developed morphologies that have allowed them to inhabit macroalgal fronds and thalli. This study examined the presence of benthic foraminiferal species living on algal species inhabiting rocky coastal environments in the southeastern Mediterranean Sea. Fronds of six algal taxa found abundantly on a carbonate wave-cut platform off the east coast of Alexandria were collected and the associated foraminifers living on each frond were identified. Twenty foraminiferal species were recorded, with seven epiphytic species (Asterigerinata mamilla, Elphidium aculeatum, Elphidium crispum, Peneroplis pertusus, Peneroplis planatus, Rosalina bradyi, and Rosalina macropora) comprising > 80% of the assemblage. Nearly 70% of the foraminiferal specimens were found on two algal species, Caulerpa racemosa and Ellisolandia elongata. Two Indo-Pacific foraminiferal species found in the samples (Amphistegina lobifera and Amphisorus hemprichii), in addition to Caulerpa racemosa, are considered invasive species in the Mediterranean. The widespread occurrence of the opportunistic invasive Caulerpa spp., which apparently provides suitable habitat for many epiphytic foraminifers, may partially compensate for the predicted decline in coralline-algal habitat under the effect of ocean acidification.