海水鱼类网箱养殖水域沉积物有机质的来源甄别

利用稳定碳氮同位素示踪技术,对南沙港网箱养殖水域沉积物中有机质的来源进行了分析研究。结果表明,网箱养殖区(距离网箱边缘100 m范围内)及对照区(距离网箱边缘大于500 m)沉积物的δ13C值分别为(-17.72±1.2)‰和(-12.73±0.38)‰,δ15N分别为(6.44±0.2)‰和(5.61±0.2)‰。网箱养殖区沉积物的有机质来源主要为残饵和鱼类粪便,比例分别占47.70%和27.71%。随着与养殖网箱距离的增加,网箱养殖源有机质(残饵和鱼类粪便之和)的比例降低,变化趋势符合指数方程y=97.167e-0.007 4x(R2=0.848 1),在潮流驱动的沉积物再悬浮及野生鱼类的扰动影响下,网箱养殖源有机质的水平位移可达400 m。鱼类网箱养殖的养殖废物是南沙港水域沉积物有机污染的主要来源。

Identification of aquaculture-derived organic matter in the sediment associated with coastal fish farming

We used stable carbon and nitrogen isotope analysis to identify the proportion of aquaculture-derived organic matter in the sediment in and around a coastal fish farm in China.The mean δ13C values were(-17.72 ± 1.2)‰ and(-12.73 ± 0.38)‰ in the regions around the fish farm(within 100 m from the edge of cages) and the control area(500 m from the edge of cages),respectively.The mean δ15N values were(6.44 ± 0.2)‰ and(5.61 ± 0.2)‰,respectively,for the same areas.The sediment near the fish farm contained a high proportion of waste feed and fish feces(47.70% and 27.71%,respectively).As the distance from the cages increased,the amount of aqua-culture-derived organic matter decreased exponentially(y=97.167e-0.0074x,R2=0.848 1).The spatial extent of waste dispersal extended to an area up to 400 m due to bioturbation by wild or escaped fish and resuspension events.The waste organic matter generated by fish cage aquaculture is the primary source of organic pollution in the sediment of Nansha bay.