乳山牡蛎养殖海域水质状况季节分析与评价

ANALYSIS AND EVALUATION OF SEASONAL VARIATION OF WATER QUALITY IN THE OYSTER CULTIVATION REGIONS OF RUSHAN

基于2010年5月至2011年4月12个航次的调查数据,利用化学参数法以及综合指数法(营养水平指数(E)和营养状态质量指数(NQI)),评价了乳山太平洋牡蛎(Crassostrea gigas)周年养殖区和秋季暂养育肥区的水质状况和营养状况。结果显示,2个养殖区总磷、总氮、无机磷、无机氮的含量变动范围分别为2.01～7.00μmol.L-1,11.38～75.45μmol.L-1,0.002～0.035mg.L-1,0.03～0.54mg.L-1;两地COD和叶绿素a的含量变动范围分别为1.03～3.41mg.L-1和0.68～42.17μg.L-1,季节差异较大。化学参数法的评价结果表明,乳山牡蛎养殖区春季水质状况最优,冬夏季次之,秋季稍差。由于养殖区内潮流畅通但水深较浅,水中的磷含量易受再悬浮颗粒的影响,E和NQI的评价结果并不吻合。牡蛎养殖对于养殖区叶绿素a的抑制作用较为明显,对氮、磷含量直接效用不显著,但长期养殖可能会造成氮、磷在海区底质中的积累,再悬浮的沉积物颗粒可能会增加水体中的氮磷含量。

Rushan, located in Shandong province, is famous for Pacific oyster（Crassostrea gigas）culture. Based on monthly survey of two culture areas in Rushan from May 2010 to April 2011, the con- centration of nitrogen, phosphorus, chemical oxygen demand （COD） and chlorophyll-a （Chl-a） was determined and the water quality was assessed by eutrophication assessment indices （E） and nutritional quality indices （NQI）, respectively. Results showed that the concentration of total nitrogen （TN）, total phosphorus （TP）, dissolved inorganic nitrogen （DIN）, dissolved inorganic phosphorus （DIP）, COD and Chl-a was at the range of 2.01~7.00 μmol/L, 11.38-75.45 μmol/L, 0. 002-0. 035 mg/L, 0.03-0.54 mg/L, 1.03-3.41 mg/L and 0.68-42.17μg/L, respectively. Basis on these data, E values of the two regions showed that all spring and summer months were below 1, which indicated that water quality was in a benign condition. Nevertheless, almost year-round NQI values were higher than 4, demonstrating that the annual water quality was in eutrophic state. The inconsistence might result from the effect of phosphorus-rich sediment particulate matters that resuspended to water column under the perturbations from tide and wind. The significantly different content of Chl-a showed clearly that biomass of was inhibited by oyster cultivation. Despite no direct influence on the nitrogen and phos- phorus concentration, the environmental factors could be changed by cultivated oysters after the accumulating sediments through their filtration were recycled back into upper water column.