The spatiotemporal responses of phytoplankton to environmental variables in 7 coastal lagoons of Kızılırmak Delta (Samsun, Türkiye)

Coastal lagoons are unique ecosystems in terms of their phytoplankton community structure, due to their unstable environment in terms of biological, chemical, and physical conditions as a result of flooding and seasonality. Seasonal and spatial variations in phytoplankton are controlled by various biotic and abiotic factors. In this study, temporal and spatial changes in the phytoplankton biovolume, species richness, diversity, and Reynolds functional groups (FGs) with the effect of different environmental variables were investigated seasonally in 2020 and 2021 for seven coastal lagoons of Kızılırmak Delta (Samsun, Türkiye). Phytoplankton biovolume and species richness were lower in more saline lagoons. Moreover, their species composition was significantly different compared to lagoons with lower salinity. Phytoplankton biovolume, species richness, and diversity were generally recorded lower in spring periods. During the studied periods, 14 FGs ( C, D, J, Lo, M, MP, P , S1, S2, S N , W1, W2, X1 , and X2 ) were prominent in the total biovolume. Three FGs ( C, P , and S N ) were only found as dominant in Karaboğaz, Gıcı, and Cernek lagoons, and their distributions were affected by pH, nitrate–nitrogen, and low light availability (high Z mix / Z eu ). Due to the seasonality and hydrology, environmental parameters and dominant FGs were generally segregated into flooding (spring), drying (summer), and transition (fall) periods.