The influence of hydrodynamics on the spatial and temporal variation of phytoplankton pigments in a large, sub-tropical coastal lake (Brazil)

Abstract

This study evaluated the spatial and temporal distribution of phytoplankton pigments in Itapeva Lake and its relationship with hydrodynamic aspects. Regarding spatial distribution, a decreasing N®S gradient was generally observed for the pigments, except in summer. This inversion observed during the summer was influenced by the predominant fetch (N-E). The horizontal heterogeneity was proved (ANOVA) for all seasons of the year, except spring. Spatially in spring, the vertical variance was much more significant (p<0.05) than the horizontal one. The sampling shifts presented a permanent degree of variability among the seasons of the year, showing the existence of a diurnal cycle in the concentration of chlorophyll a. This behavior was related to the fetch, mainly from the NE and SW quadrants, disturbing the system because it is a shallow lake. This confirmed the influence of the Itapeva Lake's hydrodynamic regime on the spatial-temporal distribution of the phytoplankton pigments.