徐轶肖^1,2, 陶晓娉¹, 刘成辉³, 韦光领¹, 何喜林¹, 姚秋翠¹, 陈武荣¹, 李斌³
1.南宁师范大学 北部湾环境演变与资源利用教育部重点实验室, 广西 南宁 530001;2.广西大学 广西南海珊瑚礁研究重点实验室, 广西 南宁 530004;3.广西科学院 广西红树林研究中心, 广西 北海 536000

摘要:
近年北部湾藻华灾害频发，为了解与藻华暴发密切相关的营养盐及水质状况，2020年8月作者对北部湾北海半岛铁山港、营盘、涠洲岛、斜阳岛及涠洲岛西部远岸海域共21个站位采集表层海水，分析营养盐含量和结构特征，并利用富营养化指数和有机污染指数对该海域水质进行等级划分与评价。结果表明：北海半岛海域DIN、PO₄-P和SiO₃-Si均值分别为0.210、0.021和0.270 mg/L。其中，铁山港营养盐由港内至港外呈递减趋势，营盘海域由近岸至远岸，DIN和SiO₃-Si含量先递减再增加，PO₄-P则表现为递增，涠洲岛海域及远岸各站位营养盐分布无明显特征。北海半岛海域N/P、Si/N和Si/P均值分别为11.8、1.7和14.6，显示47.6%海域为潜在N限制，而潜在P限制和Si限制海域均为9.5%；叶绿素a仅与COD显著相关，相关系数为0.475。调查海域富营养化指数均值1.82，以铁山港港内富营养化程度最高，由港内严重富营养至港外贫营养递减，营盘近岸7号站位中度富营养，其余76.2%调查站位仍处于贫营养水平；有机污染指数均值1.85，良好和较好水质共占38.1%，其余61.9%水质受到不同程度有机污染，亦以铁山港水质污染最为严重，重度污染仅在该海域发现。可见，北海半岛夏季表层海水以潜在N限制为主，铁山港和营盘近岸富营养化和有机污染较严重，其余站位基本良好，影响表层水体叶绿素a含量的主要因素是有机质，可能与海域微生物强烈降解作用相关。本研究可为北部湾海洋环境保护和赤潮研究提供基础环境数据。
关键词:营养盐水质评价北海北部湾
DOI：10.11759/hykx20210112001
分类号:P76
基金项目:国家自然科学基金项目（41976155）；广西自然科学基金项目（2020GXNSFDA297001）；广西南海珊瑚礁研究重点实验室开放基金项目（GXLSCRSCS2019002）

Nutrients and water quality in the Beihai Peninsula of Guangxi during summers
XU Yi-xiao^1,2, TAO Xiao-ping¹, LIU Cheng-hui³, WEI Guang-ling¹, HE Xi-lin¹, YAO Qiu-cui¹, CHEN Wu-rong¹, LI Bin³
1.Key Laboratory of Environment Change and Resources Use in Beibu Gulf, Ministry of Education, Nanning Normal University, Nanning 530001, China;2.Guangxi Laboratory on the Study of Coral Reefs in the South China Sea, Guangxi University, Nanning 530004, China;3.Guangxi Mangrove Research Center, Guangxi Academy of Sciences, Beihai 536000, China
Abstract:
In this study, nutrients and water quality conditions closely related to algal blooms, a recent frequent occurrence in the Beibu Gulf, are investigated. Nutrients and water quality from surface seawater collected in August 2020 from 21 stations across Tieshan Bay, Yingpan, Weizhou Island, Xieyang Island, and the far west coast of Weizhou Island in the Beihai Peninsula of Beibu Gulf were analyzed. The eutrophication and organic pollution indexes were used for evaluating the nutrients and water quality. An average dissolved inorganic nitrogen (DIN) content of 0.210 mg/L, an average PO₄-P content of 0.021 mg/L, and an average SiO₃-Si content of 0.270 mg/L in the Beihai Peninsula were calculated. Results showed that the nutrients were decreasing in the Tieshan Bay from inside to outside, nutrients of DIN and SiO₃-Si in Yingpan first decreased and then increased, and there was an increasing trend in PO₄-P from inshore to offshore. However, no nutrient distribution pattern was observed near the Weizhou Island and at other offshore stations. Average values of 11.8 for N/P, 1.7 for Si/N, and 14.6 for Si/P in the Beihai Peninsula were calculated, exhibiting 47.6% of the sea areas with potential N limitation, and potential P and Si limitations of 9.5%, each. Chlorophyll-a was only significantly correlated with chemical oxygen demand, with a correlation coefficient of 0.475. The average eutrophication index was found to be 1.82 in the Beihai Peninsula, with Tieshan Bay having the most serious eutrophication, from severe eutrophication inside the port to oligotrophic status outside the port of Tieshan Bay. There was moderate eutrophication in Station 7 located at Yingpan inshore; in contrast, oligotrophic status was shown by 76.2% of the Beihai Peninsula. The average organic pollution index was calculated to be 1.85 for the Beihai Peninsula, with good water quality (38.1%) and organic pollution (61.9%) to some extent. Heavy water pollution, the most serious one, was found only in Tieshan Bay. Generally, there is potential N limitation in the main surface water of the Beihai Peninsula during summers, and eutrophication and organic pollution in Tieshan Bay and Yingpan are much worse than those in the other stations. Chlorophyll-a content is affected majorly by organic matter in surface water, which may be related to the strong degradation of marine microorganisms. This study will provide basic data for marine environmental protection and harmful algal blooms management in the Beibu Gulf region.
Key words:nutrientswater qualityassessmentBeihaiBeibu Gulf





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