Diatom accumulations on a tropical meso-tidal beach: Environmental drivers on phytoplankton biomass

Abstract

Diatom accumulations are important phenomena that occur on many sandy beaches worldwide, but little is known about their seasonal occurrence and environmental drivers at lower latitudes. The results revealed that the diatom Anaulus cf. australis and Asterionellopsis tropicalis were accumulated on a tropical beach near the Equator (3°41′S; northeastern Brazil). The highest frequency of diatom accumulation (81%) occurred during the rainy season, when wind intensity was weak and waves had lower heights. The main environmental driver that control occurrence of the patches on this oligotrophic sandy beach is a rainfall that is associated with the availability of nutrients. Tides are a physical driver that affect the phytoplankton biomass at the surf zone, large tidal ranges were related to dispersal and biomass reduction of the diatom accumulations. In addition, there was an association between swell and patches, this kind of wave appear be an important physical driver, however this mechanism is not fully understood. These findings provide novel insights into the environmental drivers and general knowledge of diatom accumulations worldwide.