Impact of nutrient load coming from Göksu River on the northeastern Mediterranean

Abstract

Even though North-Eastern Mediterranean (NE Med) is classified as oligotrophic, inshore areas are highly eutrophic due to the discharge of silicate and nitrate-rich surface waters. Aim of this study was to investigate the nutrient load coming from the Göksu River and to estimate its impact on the river domain using satellite images. Monthly, average nitrite (NO2), nitrate (NO3), ammonium (NH4) and phosphate (PO4) load found to be varying between 0.07-31.2 ton/month, 15-1226 ton/month, 0.5-539 ton/month, 1-267 ton/month, respectively. Satellite images showed that surface chlorophyll– a (chl-a) in the river downstream had an increase in both winter and spring seasons as a result of intense precipitation; while, primary production at the offshore regions was mainly impacted by winter mixing and summer stratification. The highest chl-a concentration was observed at the river impacted zone and decreased by more than two folds at the offshore regions. Increased NO3 load observed during winter and spring leads to phytoplankton blooms in the river downstream. The high P content of Göksu River surface waters has increased the productivity at all seasons. As a consequence, correlation analysis showed significant relationship between surface chl-a concentration and PO4-NO3 load.