VARIABILITY IN PHYTOPLANKTON PIGMENT COMPOSITION IN MERSIN BAY

Abstract

Phytoplankton pigment composition and associated biochemical (chlorophyll a, nitrate+nitrite, ammonia, phosphate, silicate) and physical (temperature, salinity) parameters were studied seasonally in the river-fed eutrophic coastal and oligotrophic offshore waters of the Mersin Bay located on NE Mediterranean. Total chlorophyll a concentrations varied seasonally between 0.023 - 7.73 µg/l in the river fed coastal zone (salinity: 36.54-39.68), exhibiting less seasonality in the offshore station (0.01 – 0.91 µg/l). Seven different phytoplankton taxa (namely diatoms, cyanobacteria, prymnesiophytes, dinoflagellates, chlorophytes, chrysophytes, prochlorophytes), determined by High Performance Liquid Chromatography (HPLC), were consistently present in the coastal waters during 2008-2011. The predominant diatom and coccolithophorid taxa in the river-fed coastal waters were replaced by prokaryotic picoplankters (cyanobacteria & prochlorophytes) and prymnesiophytes in the offshore. Contribution of prokaryotic picoplankton and eukaryotic nanoflagellates to total chlorophyll (% 23 to 47 and % 28 to 43, respectively) increased by about 50% from the coastal to the offshore station. Contribution of large cells to total chlorophyll decreased from 49% to 10% towards offshore. Prochlorophytes were observed as the dominant group in relatively colder and darker deep waters. 

Keywords

• Pigments,HPLC,phytoplankton,nutrients,northeastern Mediterranean

References

1. Yucel, N. (2008). Phytoplankton pigment distribution in the Cilician basin (northeastern Mediterranean). MSc Thesis, Institute of Marine Science, Middle East Technical University, Mersin, Turkey, 175 pp, unpublished.