engleski

Estimation of Freshwater Influx Along Eastern Adriatic Coast as a Possible Source of Stress for Marine Organisms

Seawater salinity changes and thermal stress have been considered to be among the most important determinants (and possible stressors) of organism distribution in the rocky intertidal zone. Due to the changes in physical characteristics of water, the marine environment can be stressful to its inhabitants. Some of them, including the mussels, can be used as tracers of environmental conditions and pollution. The aim of present study was to determine the freshwater influx and evaluate the mussel Mytilus galloprovincialis shells as indicators of natural environmental conditions by comparing δ13C of shell carbonate layers with seawater salinity and temperature values measured over the period 1998-2007 on different locations included in the Croatian National Biomonitoring Programme “Project Adriatic”. Our results show that the salinity was relatively constant in the open sea, with typical values in the northern and southern Adriatic of 37.65 ± 0.40 and 38.37 ± 0.19 psu respectively (derived from average monthly values in the 1998-2007 period). It varied in intertidal zones, estuaries, close to under-sea freshwater springs and during rainy days in closed lagoons. At the same time, seawater temperatures showed some intra-seasonal differences (due to freshwater influence) in addition to strong seasonal variation. Salinity and temperature variations at investigated sites from Limski kanal to Dubrovnik (northern to southern Adriatic coast) showed freshwater influx which was also reflected in lower 13C values of mussel M. galloprovincialis shell carbonates. Based on the measured variables of seawater temperature, salinity and 13C, three groups of locations in the investigated area (25 locations) can be assigned: strong to medium freshwater influence (9 locations), minor freshwater influence (6 locations) and those of the marine environment (10 locations). Our results confirmed that mussel M. galloprovincialis sensitively responded to subtle changes in the environmental conditions. Results of the isotopic analyses presented in this study, support the hypothesis that the δ13C in mussel’s shell might be used as an indicator of environmental salinity stress. Therefore such investigations might represent an additional tool for waste water management and environmental protection.

salinity ; temperature ; stable carbon isotopes ; shell ; Mytilus galloprovincialis ; biomonitoring

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