The temporal and spatial distributions of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved silicate (DSi), and their long-term changes were investigated in Bohai Bay (BHB) in spring, summer, and autumn (2013-2014). The high DIN values were consistently distributed in the western inshore waters, mainly determined by terrestrial factors, e.g., riverine input, while DIP and DSi were mostly distributed in the southern coastal waters, the central BHB, or near the sea port Caofeidian in northern BHB, largely related to non-terrestrial factors, e.g., sediment release. Based on the nutrient distribution, BHB could be partitioned into western and eastern parts, with -15 m depth as the separation. The long-term variations of nutrients since 2000 showed an increase in DIN and decreases in DIP and DSi. Relatively slow changes in DIN and DIP and a rapid decrease in DSi were exhibited in summer, which was associated with precipitation and sediment release.Copyright © 2019 Elsevier Ltd. All rights reserved.

As China's only continental sea, the Bohai Sea is a relatively closed environment and is vulnerable to natural changes and human activities. In this paper, the long‐term variations in nutrients in the Bohai Sea and the potential influencing factors were analyzed based on historical summer and winter data from 1978 to 2016. The results showed that the concentrations of dissolved inorganic nitrogen (DIN) in the Bohai Sea continuously increased from 1990 and rapidly increased after 2002, the phosphate (PO4‐P) concentration exhibited a decreasing trend, and the silicate (SiO3‐Si) concentration decreased from 1978 to 1987 and increased from 1987 to 2008. The nutrient concentrations were lower in summer than in winter, and the bottom concentrations were higher than the surface concentrations in summer, whereas the vertical differences were insignificant in winter. The dominant factor determining the long‐term variations in DIN were atmospheric deposition and nonpoint sources due to various human activities; the primary factors affecting PO4‐P were riverine inputs and nonpoint sources related to natural changes and human activities; the primary factors afftecting SiO3‐Si were riverine inputs. The N/P ratio followed the DIN variation, the Si/P ratio followed the SiO3‐Si variation, and the Si/N ratio decreased. The nutrient ratios were lower at the bottom than at the surface and were lower in winter than in summer. The nutrient limitation changed from nitrogen limitation to phosphorus and silicon limitations. The long‐term nutrient variations in the Bohai Sea have potential ecological impacts on the local red tide features.

根据2002年4月25日～5月2日的调查数据，分析了东海近海海域营养盐(NO3--N，PO4^3-P，SiO3^2-Si，NH4-N等)的分布特征，并初步探讨了营养盐分布与赤潮发生的关系．结果表明，调查海区营养盐浓度较高，与国家一类海水水质相比，无机氮和无机磷的超标率分别为46％和60％，长江口及杭州湾附近海域富营养化程度比较严重．调查海域由于受沿岸长江等河流输入的影响。营养盐浓度自近岸向外海快速递减，等值线几乎与海岸线平行．根据调查结束后赤潮发生的特点和区域，表明营养盐浓度的增加，尤其是DIN和PO4^3-P的增加，与赤潮的发生有一定关系。但本次赤潮并不是发生在营养盐浓度最高的海区，因此，富营养化并不是诱发本次赤潮发生的唯一环境因素．

We provide a global assessment, with detailed multi-scale data, of the ecological and toxicological effects generated by inorganic nitrogen pollution in aquatic ecosystems. Our synthesis of the published scientific literature shows three major environmental problems: (1) it can increase the concentration of hydrogen ions in freshwater ecosystems without much acid-neutralizing capacity, resulting in acidification of those systems; (2) it can stimulate or enhance the development, maintenance and proliferation of primary producers, resulting in eutrophication of aquatic ecosystems; (3) it can reach toxic levels that impair the ability of aquatic animals to survive, grow and reproduce. Inorganic nitrogen pollution of ground and surface waters can also induce adverse effects on human health and economy. Because reductions in SO2 emissions have reduced the atmospheric deposition of H2SO4 across large portions of North America and Europe, while emissions of NOx have gone unchecked, HNO3 is now playing an increasing role in the acidification of freshwater ecosystems. This acidification process has caused several adverse effects on primary and secondary producers, with significant biotic impoverishments, particularly concerning invertebrates and fishes, in many atmospherically acidified lakes and streams. The cultural eutrophication of freshwater, estuarine, and coastal marine ecosystems can cause ecological and toxicological effects that are either directly or indirectly related to the proliferation of primary producers. Extensive kills of both invertebrates and fishes are probably the most dramatic manifestation of hypoxia (or anoxia) in eutrophic and hypereutrophic aquatic ecosystems with low water turnover rates. The decline in dissolved oxygen concentrations can also promote the formation of reduced compounds, such as hydrogen sulphide, resulting in higher adverse (toxic) effects on aquatic animals. Additionally, the occurrence of toxic algae can significantly contribute to the extensive kills of aquatic animals. Cyanobacteria, dinoflagellates and diatoms appear to be major responsible that may be stimulated by inorganic nitrogen pollution. Among the different inorganic nitrogenous compounds (NH4+, NH3, NO2-, HNO2NO3-) that aquatic animals can take up directly from the ambient water, unionized ammonia is the most toxic, while ammonium and nitrate ions are the least toxic. In general, seawater animals seem to be more tolerant to the toxicity of inorganic nitrogenous compounds than freshwater animals, probably because of the ameliorating effect of water salinity (sodium, chloride, calcium and other ions) on the tolerance of aquatic animals. Ingested nitrites and nitrates from polluted drinking waters can induce methemoglobinemia in humans, particularly in young infants, by blocking the oxygen-carrying capacity of hemoglobin. Ingested nitrites and nitrates also have a potential role in developing cancers of the digestive tract through their contribution to the formation of nitrosamines. In addition, some scientific evidences suggest that ingested nitrites and nitrates might result in mutagenicity, teratogenicity and birth defects, contribute to the risks of non-Hodgkin's lymphoma and bladder and ovarian cancers, play a role in the etiology of insulin-dependent diabetes mellitus and in the development of thyroid hypertrophy, or cause spontaneous abortions and respiratory tract infections. Indirect health hazards can occur as a consequence of algal toxins, causing nausea, vomiting, diarrhoea, pneumonia, gastroenteritis, hepatoenteritis, muscular cramps, and several poisoning syndromes (paralytic shellfish poisoning, neurotoxic shellfish poisoning, amnesic shellfish poisoning). Other indirect health hazards can also come from the potential relationship between inorganic nitrogen pollution and human infectious diseases (malaria, cholera). Human sickness and death, extensive kills of aquatic animals, and other negative effects, can have elevated costs on human economy, with the recreation and tourism industry suffering the most important economic impacts, at least locally. It is concluded that levels of total nitrogen lower than 0.5-1.0 mg TN/L could prevent aquatic ecosystems (excluding those ecosystems with naturally high N levels) from developing acidification and eutrophication, at least by inorganic nitrogen pollution. Those relatively low TN levels could also protect aquatic animals against the toxicity of inorganic nitrogenous compounds since, in the absence of eutrophication, surface waters usually present relatively high concentrations of dissolved oxygen, most inorganic reactive nitrogen being in the form of nitrate. Additionally, human health and economy would be safer from the adverse effects of inorganic nitrogen pollution.

为给海水贝类健康养殖提供依据，本文总结了近年国内外的报道，从氮、磷、重金属、石油类、有机氯农药等海洋污染物对贝类及其环境影响及进行了归纳综述，发现由于特殊的取食方式，贝类体内的污染物含量较其它生物要高，此外，同种污染物在不同种类贝类体内的积累也存在显著差异。因此，贝类养殖区的选择要比其他养殖区的选择更加谨慎，另外，也可以针对不同养殖海域的具体情况因地制宜的选择不同的养殖种类。

于2017—2019年的5月至11月对烟台养马岛贝类养殖区进行水质监测，分析了该贝类养殖区近三年来的营养盐含量变化，并对该海域的有机污染状况进行评价，探讨其营养盐的潜在富营养化水平。结果表明，调查期间养马岛贝类养殖海域的溶解氧、化学需氧量、无机氮和活性磷酸盐均符合国家一类海水水质标准；该海域为氮限制的贫营养化水平；有机污染指数评价分析显示该海域水质状况以良好和较好为主；硝酸盐与铵盐呈显著的正相关；水温分别与溶解氧、亚硝酸盐呈显著负相关。总体而言，养马岛贝类养殖区符合国家养殖区水质标准，营养盐含量基本正常，适合贝类养殖。