河流营养物质输入及结构变化对河口富营养化潜力的影响

河口是连接陆地-海洋的一个关键区域,具有重要的生态系统服务价值。然而,随着经济快速发展,河口接纳了越来越多来自于流域等地的营养物质,导致河口生态系统的富营养化潜力大大增加。本研究利用沿海富营养化潜力指数(index of coastal eutrophication potential,ICEP)量化河流输入对九龙江河口所产生的影响,特别是对富营养化指标的年度和季节性变化动态进行了分析。结果表明,九龙江河口区溶解性无机氮(DIN)和溶解性无机磷(DIP)浓度年均值均呈波动性增长,自1980s以来九龙江河口营养负荷发生了较显著变化,1980s—2006年期间DIN通量平均值为3.967×10³ t/a,而2006—2020年期间增加到2.924×10⁴ t/a,增长了637.14%,其中最高值达8.279×10⁴ t/a。两个时期DIP通量平均值分别为1.131×10²和2.282×10² t/a,增长了101.87%,其中最高值达6.128×10² t/a...

Assessment of impacts of river nutrient input and structural changes on estuarine eutrophication potential

Estuary is a key area of the land-ocean interaction zone with important ecosystem services. It had received more and more nutrients from watersheds and other sources due to rapid economic development, leading to a significant increase in eutrophication potential. In this study, the Index of Coastal Eutrophication Potential (ICEP) was used to quantify the impacts of riverine inputs in the Jiulong River Estuary, particularly focusing on analyzing the annual and seasonal dynamics of ICEPs. The results showed that the annual average dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) concentrations remarkably increased with large fluctuation. Nutrient loads in the Jiulong River Estuary had significantly altered since the 1980s, with a mean DIN flux of 3.967×10³ t/a during 1981-2006 and 2.924×10⁴ t/a during 2006-2020, respectively. The DIN fluxes during 2006-2020 increased 637.14% compared to the previous period (1981-2006), with a peak flux of 8.279×10⁴ t/a. The annual mean DIP fluxes in the same two periods were 1.131×10² t/a and 2.282×10² t/a, respectively, with an increasing rate of 101.87% and the highest flux of 6.128×10² t/a. The riverine nutrient fluxes and their structure in the estuary were significantly altered. After 2006, the N-ICEPs became positive for 90% of the years, while the P-ICEPs were negative throughout all years. Seasonal variation showed the ICEPs were low in Winter, but high in Summer. The chlorophyll-a concentrations were significantly correlated with both N-ICEPs and P-ICEPs. However, diatom abundance was negatively correlated with both N-ICEPs and P-ICEPs. The contribution of the P-ICEPs to chlorophyll-a concentrations was higher than that of the N-ICEPs in the estuary, suggesting primary productivity of the estuary was generally phosphorus-limited, but with dual limitation by P and Si in both summer and autumn. Therefore, seasonal variation is essentially taken into account when dealing with the eutrophication problem. Since ICEP directly reflects changes in stoichiometric ratios of N, P, Si and ecological consequence, it is a powerful management tool in estuaries for future sustainable development goals.