The effects of inter-annual fluctuations in precipitation, lake surface area, and wind speed on phytoplankton structure in three shallow Mediterranean lakes (Sakarya, Turkey)

Abstract

Phytoplankton biomass, diversity, functional groups (FGs), and environmental parameters in three shallow lakes were evaluated to show the inter-annual fluctuations in precipitation, lake surface area, and wind speed which might affect the community structure and distribution of phytoplankton. Three lakes (Taskisigi, Little Akgol, and Poyrazlar) in Sakarya province (Turkey) were sampled taking into account two periods (Period A and Period B). Monthly (PRE)-daily (dPRE) total precipitation, lake surface area, and monthly (WD)-daily (dWD) average wind speed values were obtained higher in Period B. Moreover, in Period B, probably due to increased runoff, high total phosphorus values were recorded which slightly triggers the increase in biomass. Besides, higher WD and dWD values have also caused biomass increase due to the reinforcement of nutrients to the water column from the sediment in this period. It is thought that the increase in the species richness and diversity values in Period B is related to the unstable environmental conditions as well as their relationship with water temperature, total phosphorus, orthophosphate, specific conductance, soluble silica, and pH. During the studied periods, 16 phytoplankton functional groups (FGs) were prominent in the total biomass; however, FGs F, N, X1, X2, Lo, and T were abundant during Period A, while Y, E, W1, and H1 were important components of phytoplankton during Period B. Light availability was low in both periods; therefore, FGs that prefer or are tolerant to low light conditions were dominant in the lakes. However, elevated light availability in some months of Period B has selected coda W1 and H1. Higher nutrient levels in Period B have also determined the distribution of the FGs, and FGs that prefer or are tolerant to high nutrient conditions were prominent in this period.