| Research Abstract |
We investigated ecosystem health in coastal areas by analysis of behavior and respiration metabolites in bivalve. Our studies suggested that above methods are useful for evaluation of ecosystem health in coastal areas.
[Pen shell, Atrina pectinata japonica] We examined the effect of repeated hypoxia on up and down movement behavior and energy metabolism of pen shell(Atrina pectinata japonica). Pen shells were sampled from the area mass motality was occurred, and those adductor muscles were sampled and frozen with liquid nitrogen. Concentrations of products of energy metabolism, namely lactate, pyruvate, malate, fumarate and succinate in the adductor muscles were measured. As results, the concentrations of malate were decreased and succinate were increased , which accorded with the results of hypoxia exposure test. In another experiments, pen shells were placed in plastic chamber filled with the ca. 2 L of sediment collected from Ariake Sea, Japan. Pen shell were exposed to repeated hypo
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xia(DO<0.5 mg/L; 6 hours at one day; for 7 day). Before and after the exposure of hypoxia, height of shell at top form bottom was measured. At the end of the experiment, adductor muscles were sampled and frozen with liquid nitrogen. As a result, move up behavior was observed under anaerobic condition, and shell sinking behavior under aerobic conditions. However, movements of shell at anaerobic and aerobic conditions were decreased at the 6th and 7th day of exposure. Also concentrations of malate in adductor muscle were decreased(p<0.05).
[Manila clam, Ruditapes philippinarum] Since the late 1990s, natural and cultured populations of marine bivalves have been experiencing mass mortalities caused by a novel toxic dinoflagellate species, Heterocapsa circularisquama, in western Japan. Such recurrent outbreaks are associated with important economic loss and serious social problems. To predict such blooms, the shell valve movements of the Manila clam, Ruditapes philippinarum, have been studied in the presence of the toxic dinoflagellate using a valve movement monitor. In the presence of H. circularisquama, a significant increase in the amplitude and frequency of valve adductions, starting from as low as 5 cells ml^<-1>, and a decrease in the amplitude of valve opening(AVO)and duration of valve opening(DVO)starting from 500 cells ml^<-1> were observed. After transfer to clean seawater, clams resume a normal valve adduction activity. The Manila clam is highly sensitive to the bivalve-killer H. circularisquama and hence could be used as an early biological warning species against lethal H. circularisquama outbreaks. Less
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