Göksu nehri etki alanında fitoplankton yamaları (Kuzeydoğu Akdeniz)

Seasonal phytoplankton samplings were made onboard R/V Bilim-2 of the Institute of Marine Sciences of Middle East Technical University around the Göksu river estuary to reveal a possible patchy distribution of phytoplankton due to presence of contrasting water masses with varying trophicity. To achieve this, biological, physical and chemical parameters were collected from 51 stations representing nutrient-rich Göksu river estuary, productive coastal, mesotrophic shelf and oligotrophic offshore waters. Over the year, the total number of 246 phytoplankton species belonging to Bacillariophyceae (79), Pyrrophyceae (146), Prymnesiophyceae (16), Cryptophyceae, Chrysophycea, Euglenophycea, Ebriophyceae and Chlorophyceae (with single species each) were identified. The community was found most diverse during spring followed by winter, summer and autumn. Based on seasonal surface mean cell abundances, summer population abundances (2.3 x 105 cells/l) were exceeded much the winter (1.2 x 105 cells/l), spring (1.1 x 105 cells/l) and lastly autumn (2.6 x 104 cells/l) population densities. Diatoms were observed dominant over dinoflagellates and remaining other groups in all seasons. The population has always found most species diverse and abundant in shallow coastal areas fed by nutrient-rich Göksu River and Lamas creek waters. Taşucu Bay surface waters have retained maximal population densities in all seasons due to direct freshwater inputs from the nearby Göksu River. Based on the Spearman Rank Correlation analysis, highly significant positive correlation between surface phytoplankton abundance and ambient temperature (r = 0.675, P < 0.01) and negative correlation with surface salinity (r = -0.398, P < 0.01) whereas almost no correlation with any of nutrient species were observed in autumn. In contrast, highly significant positive correlations were only present with nutrients (nitrate, nitrite, silicate) in winter. Despite a highly significant negative correlation with salinity (r = -0.806, P < 0.01), highly significant positive correlations with phosphate, nitrate, nitrite were observed in spring. Lastly, in summer, a highly significant negative correlation between phytoplankton abundance and salinity & temperature and a significant positive relationship with phosphate (r = 0.283, P < 0.01) were observed. Similar to Pielous' index values, Shannon diversity index values were found maximal during spring followed in decreasing order by autumn, winter and summer. Multivariate analyses have shown the formation of several distinct phytoplankton assemblages in each season. The number of patches observed in autumn (10) and in winter (8) have exceeded greatly those observed in spring (2) and summer (3). Despite the very complex affinities observed within various minor patches observed in autumn and winter, surface flora has split into two major, namely coastal - offshore, and east - west subpopulations in spring and summer.