底栖线虫和桡足类丰度比与环境的关系分析

Study on Relativity between Benthic Nematode to Copepod Ratio of Abundance and Environmental Factors

为了了解海洋底栖线虫和桡足类丰度比值(N/C)与环境污染评价的应用性,于2006年7月至2007年10月间分四个季节在天津海域用箱式取样器采集底泥,研究了N/C值与水体和沉积物环境因素的关系;并分析了17项水体环境因子和15项沉积物环境因子与N/C比值的相关性.结果表明,该比值在研究海域内差异较大,变化范围为4.00～620.00;并且其波动范围随季节而变.春季的波动范围最宽,为11.50～343.25,而夏季的则变化幅度最小,为7.35～43.52.总体上,无论沉积物表层还是总量的N/C比值超过70的情况较少;更多的比值集中在30以内.相关性分析表明,水深、水温、盐度、硝酸盐、亚硝酸盐、总碱度、溶解氧、溶解氮和叶绿素a等环境因子与N/C比值有显著相关性.该比值不但和沉积环境有关,而且可以反映水体环境的状况,在环境监测和评价中有着较好的应用前景.取样的深度将影响N/C值与环境因素间的关系,表层2 cm深度和10 cm深度的比值在夏季显著不同(P=0.012),在研究中应该给与重视.参照已往阈值,此研究的N/C比值反映出了海域环境的污染情况,污染程度从近岸到远岸有逐渐减轻的趋势.此外,对N/C值应用于污染评价时存在的问题也作了简要分析和研究展望.

Free-living nematode and copepod are the most dominant taxa of meiofauna in many marine sediment environments, and their abundance ratio is often used as an indicator of various degree of pollution. In order to examine the application of the Nematode to Copepod ratio （N/C） in marine environmental monitoring and quality assessment, the meiofaunal survey including four seasonal cruises was carried out in Tianjin coastal area from July, 2006 to Octo- ber, 2007. Four core subsamples were taken from a 0. 05 m2 box sediment corer with Perspex tubes （2.4 cm inner diameter） to a depth of 10 cm. After sampling and processing, the N/C ratios of the surface layer （0-2 cm depth） and the total layer （0-10 cm depth） were calculated, respectively. A total of seventeen environmental factors in water and fifteen factors in sediment were also chosen to analyze the relativity. The results showed that the N/C ratios varied greatly from 4.00 to 620.00 in this survey area, and its fluctuationrange changed with season. The fluctuation range in spring cruise was the greatest from 11.50 to 343.25, and in summer cruise was the least from 7.35 to 43.52. In general, most of the N/C ratios, which included both the surface and total layer, were less than 30 and the ratio frequencies exceeding 70 were less. The relativity between the N/C ratio and the environmental factors was studied with the help of SPSS 13.0 software. Nine of those environmental factors presented significant relativity with the N/C ratios. They were water depth, water temperature, salinity, nitrate, nitrite, total alkalinity, dissolved oxygen, dissolved nitrogen, and chlorophyll a in sediment, respective- ly. Therefore, although the nematode and copepod lived in the sediment, the N/C value not only was related to the sediment factors, but also could reflect the conditions of water environ- ment. Thus the N/C ratio would have a good potential in environmental monitoring and assessment. In summer, for example, the N/C ratios between the surface layer and the total layer had significant difference （P=0. 012）. The results reflected the pollution levels in some extent according to the former threshold of N/C ratio. The pollution level decreased gradually from the alongshore area to offshore area.