Seasonal variations in phytoplankton composition and biomass in a small lowland river-lake system (Melen River, Turkey)

A series of studies were carried out to determine the succession and phytoplankton community of the Melen River in the Western Black Sea region of Turkey. The study was conducted at 6 stations at monthly intervals between May 2003 and April 2004. It was observed that the abundance and biovolume of phytoplankton were low in winter, though higher values were recorded in late spring and summer. Among the values noted, the spring peak was 534.38 × 105 ind. L^-1 and 7384.8 mm3 L^-1 belonging to Peridinium sp. The most common diatom, Cyclostephanos dubius, was favoured by low discharge at stations 1 and 2 in the early summer (214.29 × 105 ind. L^-1 and 9.84 × 10^5 ind. L^-1), respectively. Chlorophyll-a concentrations were between 0.86 and 64.2 μg L^-1. A total of 135 taxa belonging to Cyanophyta, Bacillariophyta, Chlorophyta, Dinophyta, Euglenophyta, Heterokontophyta, Streptophyta, and Xanthophyta were identified. The total biomass of the stations 1 and 2 was mainly characterised by Dinophyta and at other stations by Bacillariophyta. Five major genera (Peridinium, Ceratium, Phacus, Cyclostephanos, and Melosira) accounted for over 70% of the total phytoplankton abundance. Phytoplankton abundance was significant and positively correlated with Chl-a and temperature (r = 0.57 and r = 0.78, respectively P 0.05). Species richness and diversity indices increased gradually throughout the course of the river.