Seasonal Dynamics of Benthic Foraminiferal Biocoenosis in the Tropical Saquarema Lagoonal System (Brazil)

This study investigates and compares the seasonal variations during winter and summer of living benthic foraminiferal assemblages in the Saquarema Lagoon System (SLS) located in a tropical coastal region of SE Brazil. The physicochemical parameters in the SLS presented strong differences between both seasons; however, they remained quite homogeneous in winter and exhibited great oscillations in summer. In the study area, 29 and 19 living foraminiferal species were identified in summer and winter, respectively. Ammonia tepida was the dominant species in both seasons followed by Ammonia parkinsoniana and Cribroelphidium excavatum. The detrended correspondence analysis showed that in the SLS: the calcareous species, such as Adelosina carinatastriata, Bulimina patagonica, and Miliolinella antartica were mostly influenced by high dissolved oxygen contents and low temperature, whereas the agglutinated foraminiferal species were indicators of the most confined lagoonal areas, under the lowest pH and salinity values. The results of this work evidence that the seasonal variation in the SLS might play a more important role in the benthic foraminiferal assemblages' distribution than the anthropogenic impacts and shows the importance of seasonal studies for coastal biomonitoring programs.