Spatio-temporal distribution of picophytoplankton (Pico-eukaryotes, Synechococcus and Prochlorococcus) abundance in the northeastern mediterranean

© 2020 Parlar Scientific Publications. All rights reserved.Primary productivity mostly relies on marine cyanobacteria in the oligotrophic north-eastern Mediterranean (NEM). However, wide shelf basin is fed by nutrient-rich rivers (namely Goksu, Lamas, Seyhan, Ceyhan, Asi) leading to apparent increase in algal production at coastal regions. In the present study, variation of picophytoplankton (pico-eukaryotes, Synechococcus and Prochlorococcus) abundance of at different trophic levels of NEM were investigated. Sample collection was carried out at 50 different stations including Mersin Bay, Goksu River discharge area and oligotrophic offshore waters during October 2017, February, April and July 2018. Minimum and maximum abundance of picoeukaryotes, Synechococcus and Prochlorococcus were found as 1-lxlO4, 103 - 3.3xl04 and SxlO1 - 7.3xl04 cell/ml, respectively. Eukaryotic picoplankton are observed mainly in Goksu River discharge area and could not compete with marine cyanobacteria in offshore waters. Annual average ofpico-eukaryotes abundance was decreased by 1.4 folds from inshore to offshore; while, annual average of Synechococcus abundance was increased by 1.2 folds. Prochlorococcus abundance did not vary from inshore to offshore but decreased by 4 folds from river discharge area to offshore area. Synechococcus and Prochlorococcus have displayed similar abundance profiles with peak levels near the Deep Chlorophyll Maximum (DCM) in October and July. Results showed that Synechococcus was the most abundant regardless of location or season. Even though Synechococcus abundance was found to be higher than Prochlorococcus abundance, a significant increase in the contribution of Prochlorococcus to the total picophytoplankton was observed in July