Microbial response to seasonal changes in a Mediterranean lagoon (Cape Peloro, Messina)

Research conducted in recent years in different Sicilian transitional areas (Leonardi et al., 2009; Caruso et al., 2010; Zaccone et al., 2014) has highlighted the close link between the trophic quality of the suspended particles and the efficiency of microbial metabolism in organic matter turnover; climatic change has been found to cause variations in prokaryotic metabolism more than in cell abundance. Due to its location near the city of Messina, the Capo Peloro lagoon, constituted by two brackish lakes (Faro and Ganzirri), suffers the negative effects of human activity, rainwater and run-off from surrounding areas. From 2006 to 2009, the effects of seasonal changes on microbial parameters in this brackish ecosystem were examined. The abundances of prokaryotes and vibrios as well as the rates of enzymatic hydrolysis of proteins by leucine aminopeptidase (LAP), polysaccharides by ß-glucosidase (GLU) and organic phosphates by alkaline phosphatase (AP), heterotrophic prokaryotic production (HPP), respiration (R), were studied. Physical and chemical parameters (temperature -T, salinity, nutrients) and particulate organic carbon and nitrogen (POC, PN) were also measured, and the influence of these factors on prokaryotic abundances and activities was analyzed. Our study showed that T was an important variable which affects variations in prokaryotic metabolism. Positive correlations between T (13.3- 29.6°C) and HPP, LAP, AP, POC, PN were observed in Ganzirri Lake, suggesting the use of microbial activities as potential indicators of the prokaryotic response to climate changes in temperate lagoon areas.