Total and size fractionated phytoplankton biomass off Karatas, north-eastern Mediterranean coast of Turkey

Abstract The biomass of phytoplankton in terms of chlorophyll a was investigated in an Mediterranean coastal area, off Karatas. Data were obtained during four cruises conducted in July 2003, November 2003, February and May 2004. In addition to total chlorophyll a determination, chlorophyll a was fractionated into size classes as: <20 µm and >20 µm fractions. Inorganic nutrients were also determined. Total chlorophyll a values ranged from 0.10 to 7.43 µg l-1. The conributions of the <20 µm and >20 µm fractions to the total chlorophyll a were similar. The proportion of <20 µm fraction to total chlorophyll a ranged between 9% and 96%. On the other hand, the lowest proportion of >20 fraction to total chlorophyll a was 4 %, and the highest one was 91 %. Despite the dominancy of small sizes in the oligotrophic seas such as Mediterranean, the biomass of small size fraction was not higher than large size in the present study.