桑沟湾长牡蛎生物沉积物对环境底质影响的同位素证据

摘要

Shellfish has significant biodeposition which can accelerate the transport of particulate matter from sea water to seabed. In Sanggou Bay, long-line cultured oyster works in this way by its biodeposits including faeces and pseudofaeces. In the purpose of quantitative study of sediment impacts on the biodeposits from long-line cultured Crassostrea gigas in Sungo Bay, we set up 8 sites (5 of oyster cultural area, 3 as control sites) to sample. Sediments from each site, biodeposits and suspended particulate matters from SG 2 and SG 6 were sampled for stable isotope analysis. The results showed that δ13C and δ15N values of sediments were δ13C‰ –22.82 to –21.62, 15N‰ 4.73 to 6.21, respectively. In suspended particular matter of SG 2 site, biodeposits contributed about 9.95%, and sediments from control site and SG 2 were 54.19% and 35.86%, respectively. Results of this study showed that in typical site, stable isotope method could be effective in organic matter resource analyses. Biodeposits from oyster contributed 4.06% to 28.64% in the sediments of each area, with an average value of 13.96% ± 8.62 %, suggesting that the aquaculture activities of oyster had certain effect on the sediments of Sungo Bay.%贝类通过生物沉积作用加速了养殖海区水体中的颗粒物质向海底的输送.在桑沟湾中筏式养殖的长牡蛎(Crassostrea gigas), 将大量的有机物以生物沉积物(真粪和假粪)的形式排向养殖区海底.为完成对桑沟湾筏式养殖长牡蛎生物沉积物对环境底质影响的量化研究, 作者通过在桑沟湾内不同的海区设置采样点(5 个养殖区, 3 个对照点), 对采样点 SG 2 与 SG 6 两个点的长牡蛎生物性沉积物与海区悬浮颗粒物进行了稳定同位测定及有机物来源分析.实验结果表明: 选取的采样点沉积物稳定碳氮同位素丰度集中于 δ13C–22.82‰~–21.62‰, δ15N 4.73‰~6.21‰.在 SG 2 点的悬浮颗粒物中, 长牡蛎生物性沉积物贡献有机物占 9.95%, 对照区沉积物与 SG 2 区沉积物贡献分别为 54.19%和 35.86%.在典型的采样点, 稳定同位素法能较准确地量化出各有机物来源的贡献比例.以 SG C 点为对照, 其余 7 个采样点长牡蛎生物性沉积物有机物贡献在 4.06%~28.64%, 平均贡献率为 13.96 %± 8.62 %, 牡蛎养殖已经对桑沟湾底质造成了一定的影响.