围隔海域水质评价及底栖曲浒苔对水质修复能力评估研究

The evaluation of water quality in enclosed mariculture bay and assessment of bioremediation abilities of Ulva flexuosa

摘要:

于2015年1—12月对杭州湾北部沿岸碧海金沙围隔海域水环境质量进行每月一次的跟踪监测，进行围隔海域水质分析评价，通过调查底栖浒苔群落的种类组成及其生物量，评估其对围隔海域水质的修复能力。根据富营养化状态指数（E）表明，2015年该围隔海域1—9月份属于高富营养化状态，10—12月份属于富营养化状态，其中溶解无机氮（DIN）全年平均为（0.91±0.11）mg/L，属劣Ⅳ类海水水质标准；溶解无机磷（DIP）全年平均为（0.031±0.005）mg/L，属Ⅲ类海水水质标准；根据有机污染指数（A）显示，2015年该围隔海域2—7月份开始受到有机污染，8月、9月和12月属于轻度有机污染，10月和11月属于中度有机污染。底栖浒苔类的优势种为曲浒苔（Ulva flexuosa），占底栖藻场总生物量的97.3%。2015年3月至12月碧海金沙围隔海域底栖曲浒苔全年总生物量净增长量为1 497.3 t，实验测得曲浒苔组织内总氮（TN）和总磷（TP）平均含量分别为3.50%±0.02%和0.13%±0.01%（干重），全年吸收水体中氮和磷量分别为（4 354.90±46.78）kg和（161.75±1.74）kg。分析表明，碧海金沙围隔海域天然曲浒苔种群通过同化养殖水体中氮磷，具备一定的水质修复能力，但尚未平衡由水产养殖活动造成的营养负荷。因此，在近岸海水养殖海域，除需进行底栖海藻场的构建外，还需要调整养殖结构，如增加大型海藻栽培以建立多营养层次的综合养殖模式（IMTA），实现近岸海水养殖产业的可持续发展。

Abstract:

Based on investigation data obtained from January to December in the enclosed Fengxian bay throughout 2015, water quality and eutrophication conditions were evaluated on the basis of organic pollution index (A) and eutrophication index (E) and the species composition, biomass as well as bioremediation abilities of benthic algae community were analyzed. The results of water quality indicate that this mariculture area has been in serious eutrophication state. Dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) complied with the Grade inferior Ⅳ and Ⅲ, respectively. The annual average values of A and E were 1.88 ±0.21 and 29.95±1.18, respectively. The results also show that the dominant species of green algae is Ulva flexuosa, accounting for 97.3%. From March to December in 2015, the biomass of U. flexuosa increased by 1497.3 tons. The average N and P contents of algae were 3.50% ± 0.02% and 0.13%±0.01% and (4354.90±46.78)kg of N and (161.75±1.74)kg of P could be removed by this seaweed. The population of U. flexuosa has certain bioremediation abilities by assimilating nutrients generated by human aquaculture activities. However, the biomass of U. flexuosa stocked on hand could not completely remove all excess nutrients. Establishing an integrated multi-trophic level system co-cultured with macroalgae showed high bioextraction efficiencies on nutrients and could balance the nutrient produced by marine aquatic animal farming in the enclosed bay.