Vol. 11, No. 21, 98-107, 2012

Abstract
Variations in salinity and nitrogen concentration in the aquatic environment are among the observed effects of global climate change. They affect the structure of phytoplankton communities and the physiological state of algae and cyanobacteria. Results of laboratory studies of these effects are presented. A combination of Nonlinear Laser Fluorimetry (NLF) and Fluorescence Induction and Relaxation (FIRe) fluorimetry is used to evaluate the photophysical parameters of photosystem II and Chlorophyll a in native samples of the diatom algae Thalassiosira weissflogii, the zooxanthellae Symbiodium sp. CCMP 2467, and the cyanobacteria Synechococcus sp. CCMP 1379, grown under different salinity (40, 18, and 5 psu) and nitrogen concentration (normal, ×0.5, ×2).

Cyanobacteria are shown to be most resistant to these variations, while zooxanthellae are the most sensitive species. This suggests that an effect of global climate change on the phytoplankton community might be the transformation of its structure towards an increasing role of cyanobacteria. Another alarming outlook is the negative impact of climate change on the physiological state of corals, which live in symbiotic relationship with zooxanthellae. This suggests that the reasons for the degradation of coral reefs are not entirely anthropogenic. It is suggested that coral reef monitoring of variations in the photophysical characteristics of zooxanthellae might be one of the most effective ways for detecting the influence of global climate change on marine biota in early stages. It is advisable to monitor coral reefs in the oceanic areas with lowest anthropogenic impact as “background stations” for climate change monitoring.