Foraminiferal assemblages from the Abu Qir coastal area (Alexandria, Egypt): Wave-cut platform versus shallow-bay sediments

Abstract

Benthic foraminifers living in euphotic coastal and shelf environments commonly occur in association with macrophytes (macroalgae and seagrasses), and many lineages have evolved morphologic adaptations to thrive in such habitats. Species that did not occur in the Mediterranean Sea prior to recent centuries, commonly known as “introduced” or “alien” species, are now widespread, and some are so abundant that they are altering coastal habitats. With accelerating climatic change and warming of Mediterranean surface waters, recognizing how invasive algal and foraminiferal species are affecting sedimentation and microenvironments has become increasingly urgent. This project examined 18 sets of sediment samples collected in the Abu Qir coastal area east of Alexandria for comparison with a previous assessment of live assemblages within the macroalgae. Overall, 68 foraminiferal species were identified, of which sixteen species were categorized as epiphytic. The hyaline epiphytic Elphidium crispum was the most common species found in sediments from the platform, while the porcelaneous free-living Quinqueloculina auberiana dominated sediments from the small bay. Eleven introduced foraminiferal species were recorded, one of which, Amphistegina lobifera, was commonly found, especially in the platform sediment samples. Taxa recorded live (stained) in platform sediments were predominantly (>10% each) Peneroplis, Amphistegina and Elphidium, while bay sediments were dominated by Quinqueloculina, followed in order by Elphidium, Amphistegina and Peneroplis. The assemblage differences from previously reported live assemblages associated with macralgae, compared with live and dead assemblages in sediments, appear to reflect hydrodynamic influence of sediment sorting and resistence of larger taxa to physical degradation.