engleski

Influence of condition index and hydroghraphic parameters on the concentration of metals in soft tissue of oysters (Ostrea edulis L.) from Mali Ston Bay, Eastern Adriatic, Croatia

Samples of oysters (Ostrea edulis L.) were collected monthly during 2005 at the location near the island Otok života in the Mali Ston Bay, Eastern Adriatic, Croatia. Condition index of the oyster samples was determined, and the concentration of cadmium, lead and mercury was measeured by the AAS method in the lyophilized soft tissue. At the location average monthly values were measured for temperature, dissolved oxygen, salinity and pH. The data analysis showed specific influences of basic hidrographic parameters and condition index on the concentration of metals in the soft tissue of oysters throughout the year. Time series analysis for each particular metal showed a positive trend according to the Anderson test. At the same time, temporal distribution of lead and mercury was statistically similar, while cadmium showed significant variations in relation to the first two. Matrix developed to document similarities and differences beetwen condition index and metal concentrations showed negative correlation for all three investigated metals. The concentration of metals were lower in the late winter and early spring, when the condition index of oysters showed the highest values. Similarity Bray-Curtis testing also showed existence of two distinct periods regarding metal concentrations and condition indeks relation: February – May and June-January. During the period of the lowest temperatures the highest concentration of metals was recorded. As for the influence of other hydrographic parameters the most significant finding was a high negative correlation beetwen dissolved oxigen and cadmium. Values of metal concentration expressed on the wet weight basis (calculated by multiplying concentration on the dry weight basis with conversion factor) have not exceeded maximum permited levels according to Croatian and EU regulations.

oyster; Ostrea edulis; condition index; hydroghraphic parameters; soft tissue metal concentration

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