The response of phytoplankton assemblages to environmental parameters in the Azad Dam Lake in the west of Iran

Seasonal variations of phytoplankton abundance, species composition, and their interaction with environmental parameters were investigated in the Azad Dam Lake, in the West of Iran during 2015–2016. Sampling was conducted seasonally at five stations in the lake. Multivariate statistical analyses were carried out to define the abiotic variables influencing phytoplankton community composition. A total of 51 taxa of phytoplankton belonging to six phyla were identified. Bacillariophyta (diatoms) were most diverse with 22 taxa, comprised more than 90% of the total density. Despite the low Shannon–Wiener index (H ′) diversity (0.10–1.54), pointing out the dominant density of Bacillariophyta resulted in high water quality. Statistical analysis showed seasonal phytoplankton assemblages differences indicating a biogeographical gradient. Distance-based Linear Model (DisTLM) analysis displayed six environmental variables showing significant relationships with the phytoplankton abundance in the resemblance matrix (p < 0.05). Based on Akaike's information criterion (AIC), the combination of total phosphorus (TP), water temperature (WT), Secchi disc depth (SD), total nitrogen (TN), nitrite (NO2−), and dissolved oxygen (DO) by the DisTLM model elucidated 63.1% of the total variability. Since the dam is newly constructed and has not yet been exploited, and the factors caused by human activities that threaten the lake have not yet spread much, findings of the present study suggest Azad Dam Lake appears to have been not highly affected by anthropogenic activities up to now.