广东流沙湾海草分布现状及其与不同养殖生境的关系

2016和2017年对广东流沙湾海草床进行现场调查,获得了海水、海草、浮游生物、底栖动物和大型底栖海藻的数据资料。结果表明流沙湾卵叶喜盐草(halophila ovalis)平均生物量为3.74 g/m^2,总面积为26.9 hm^2,呈斑块状分布。利用水质参数进行主成分分析,对各主成分得分进行聚类,将调查区域划分为渔排和捕鱼网影响区(Ⅰ区)、贝类养殖区(Ⅱ区)和非养殖区(Ⅲ区)3种生境类型,主成分综合得分表明Ⅰ区污染最严重。比较Ⅰ区和Ⅱ区两种不同养殖方式下的生境类型,Ⅰ区的海草生物量、底栖动物生物量、浮游植物丰度、溶解氧、活性磷酸盐和盐度低于Ⅱ区,大型底栖海藻生物量、氨氮、无机氮、N/P比值和COD高于Ⅱ区。流沙湾海草床的分布面积和生物量较2002年出现了严重退化,网箱渔排和捕鱼网的生产方式、小个体贝类的大量繁殖以及低盐度的近岸河流输入降低了海草生物量。海草生物量与其他指标的关系体现了贝类养殖对海草的生存有积极作用,较强的水体自净能力有利于海草的生长。本文还从提高公共意识、加强自然保护区管理和实施常态监测三个方面提出了流沙湾海草的保护建议。

Distribution status of seagrass and its relationship with different habitat types in Liusha bay of Guangdong province

Field investigation was carried out in 2016 and 2017, indexes including seawater, sediment, seagrass, plankton, zoobenthos and benthic macroalgae was obtained from Liusha bay of Guangdong Province.The results showed that average biomass and total distribution area of Halophila ovalis were 3.74 g/m2 and 26.9 hm2 with patches distribution pattern.Three habitat types were divided by principal component-cluster analysis of seawater parameters, they were "influence area of fish raft and fishing net" (Area Ⅰ), "shellfish farming area" (Area Ⅱ) and "non-cultured area" (Area Ⅲ).Comprehensive scores of principal component showed that Area Ⅰ was most polluted.Comparison between Area Ⅰ and Area Ⅱ showed that biomass of seagrass and zoobenthos, concentration of dissolved oxygen and active phosphate, phytoplankton abundance, salinity in Area Ⅰ were lower than that in Area Ⅱ, biomass of benthic macroalgae, N/P ratio, concentration of ammonia nitrogen, inorganic nitrogen and COD in Area Ⅰ were higher than that in Area Ⅱ.Total distribution area and biomass of seagrass bed in Liusha bay seriously degraded in 2017 when compared with that in 2002.Due to the production mode of fish raft and fishing net, mass multiplication of small shellfishes and low-salinity water derived from river input, seagrass biomass decreased.The relationship between seagrass biomass and other indexes reflected that shellfish culture played a positive role in seagrass survival and strong self-purifying ability of water was beneficial to seagrass growth.Also, this paper put forward the suggestions of protecting seagrass including promoting public consciousness, strengthening natural reserve management and implementating normal monitoring.