Foraminifera associated with macroalgae on tropical coastal sandstone reefs

While they are extremely abundant and ecologically important, the epiphytic foraminifera of tropical reefs are still poorly known. The present study describes the foraminiferal assemblages associated with macroalgae on tropical reefs of the Brazilian coast. Samples of four species of macroalgae, two foliose (Padina antillarum and Ulva lactuca) and two corticated (Palisada perforata and Gelidiella acerosa), were collected from intertidal sandstone reefs at Pina, Enseada dos Corais, and Toquinho (Northeastern Brazil). Overall, only 13.3% of the 708,754 foraminifera specimens were alive, belonging to 37 species, with dominance of Rosalina anglica. Most tests were hyaline-perforate and conical in shape, and most species were permanently or temporarily sessile. The majority of living foraminifera were attached to the surface of Palisada and Gelidiella, and no attached specimens were found in either Padina or Ulva. The species richness and abundance of the living foraminifera varied significantly among the macroalgae, occurring the high values in P. perforata. The assemblages varied significantly between the two species of corticated macroalgae, and between the corticated and foliose species, but not between the two foliose algae. Some of the specimens of Glabratella and Rosalina were reproducing, and had juveniles attached to the parental test. This is the first study to focus on the ecological interactions of the epiphytic foraminifera of the tropical southern Atlantic Ocean, and its results indicate that the characteristics of the epiphytic assemblages can be used as a proxy for the understanding of the structure and function of microbenthic communities on tropical reefs.