标题：SPATIO-TEMPORAL DISTRIBUTION OF PICOPHYTOPLANKTON (PICO-EUKARYOTES, SYNECH OCOCCUS AND PROCH LOROCOCCUS) ABUNDANCE IN THE NORTHEASTERN MEDITERRANEAN
摘要：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 Gftksu, Lamas, Seyhan, Ceyhan, Asi) leading to apparent increase in algal production at coastal regions. In the present study, variation of picophytoplaiikton (pico-cukary-otes, 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, G6ksu River discharge area and oligotrophic offshore waters during October 2017, Febniary. April and July 2018. Minimum and maximum abundance of pico-eukaryotes, Synechococcus and Prochlorococcus were found as 1-lxlO4,103 - 3.3xl04 and 8x10* -7.3x104 ccll/ml, respectively. Eukaryotic picoplank-ton are observed mainly in G6ksu River discharge area and could not compete with marine cyanobacteria in offshore waters. Annual average ofpico-eukar-yotes abundance was decreased by 1.4 folds from inshore to offshore; while, annual average of Synechococcus abundance was increased by 1.2 folds. Pro-chlorococcus 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 S)u-echococcus 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.
