Seasonal variations of phytoplankton species in the Kapidağ peninsula

This study aims to detect the phytoplankton species in the Kapıdağ Peninsula and the ecologic variables affecting their distribution. To this end, phytoplankton samples collected from three pre-determined stations between April 2011 and January 2012 were analyzed and a total of 42 taxa, being 21 of Dinophyceae class (50%), 19 of Bacillariophyceae class (45%) and 2 of Dictyochophyceae class (5%) were identified. Of these species, Achnanthes longipes and Tripos falcatus species identified are the new records for the Sea of Marmara while Pseliodinium fusus (= Gyrodinium falcatum) species are the second record for the sea. The maximum number of species belonged to Tripos and the highest number of representatives in terms of abundance belonged to Prorocentrum micans (20200 h/L) species. In January 2012 sample which represents the winter period in terms of abundance, only one peak was observed and P. micans species played a role in this increase. According to the correlation results, nitrite+ nitrate (p˂ 0.05) and silicate (p˂ 0.01) increased when chlorophyll-a and abudance number decreased. A negative correlation was found between salinity and dissolved oxygen, the number of species (p˂ 0.01) and chlorophyll-a values (p˂ 0.05) while a positive correlation was found between salinity and nitrite+ nitrate (p˂ 0.01) and silicate (p˂ 0.05). The parallel increase between depth, salinity, and nutrients reveals that Mediterranean water is effective on the bottom layer of the seafloor, nutrients accumulate on this layer due to the limited phytoplankton activity and these nutrients are consumed on the upper layer mostly due to phytoplankton activity. Variety index results obtained from the stations were found low with a value below 2 and Bray-Curtis similarity index results showed approximately 60% similarity between the stations. Considering the overall findings, it was observed that the brackish-characterized Black Sea waters were effective in the detection of phytoplankton composition and abundance in upper layer waters of the Sea of Marmara.