【作者】 李瑞环；

【导师】 刘素美；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2010， 硕士

【摘要】 近岸海域通常具有较高的初级生产力,以及多样和复杂的生态结构,因此,近岸海域营养盐的生物地球化学循环已成为海洋生态学等的重要研究内容。本研究于2006年12月、2007年8月、2008年7-8月和2009年3-4月对我国海南东部热带近岸海域不同水体(河流、河口、渴湖和近岸等)中营养盐及相关参数进行调查,旨在研究海南东部近海地区不同水体中营养盐浓度、分布特征及其季节和区域变化,探讨海南东部近岸营养盐的结构及其影响因子。主要研究结果如下：1、文昌/文教河营养盐浓度的季节变化很大。除2008年夏季文教河外,其他航次两条河中的DIN浓度均处于全球平均浓度与污水浓度水平之间；文昌/文教河中DIP浓度相对较低,属于清洁水体。由于氮肥的使用、污水排放,2007年NH4-N在DIN中的比例达到37-44%。冬、夏季DOP为TDP的主要组成成分,春季时无机磷则成为TDP的主要组成部分；文昌/文教河中DON/TDN的值分别为23%、55%。硅酸盐含量低于一般热带河流中的浓度,明显低于同一区域的万泉河中的含量。文昌/文教河口受潮汐作用影响明显,且有明显的季节变化。2006年冬季硝酸盐仅受海水稀释作用影响,呈现保守变化；2009年存在再生现象；2007年、2008年夏季存在反硝化,被大量消耗。说明河口区存在有机质的分解使无机氮得到再生以及氮的反硝化过程。因悬浮颗粒物含量大,河口区磷酸盐有吸附/解吸现象发生,以及有机质的分解而再生。2、万泉河中DIN含量高于一般未受污染的热带河流中浓度,低于受人类活动影响大的长江、珠江等,并低于文昌/文教河中含量。磷酸盐处于原始水体与干净水体间浓度。硅酸盐含量不仅高于全球河流中平均浓度,也明显高于热带河流中平均浓度。不同季节万泉河口硝酸盐成为DIN的主要组成成分。NO3-N、SiO3-Si在河口区跟盐度有负相关关系,呈保守分布；亚硝酸盐、铵盐变化复杂,表现出非保守的变化；由于颗粒物的吸附/解吸作用,磷酸盐在河口区有浓度相对恒定,且在2007年夏季低盐度区(<2.5PSU)出现再生。在河流及河口中,P成为浮游植物生长的潜在限制因子。3、于2008年8月、2009年4月对小海、老爷海进行多次调查,结果表明：小海潟湖内整体盐度低,且夏季高于春季。春季硝酸盐含量高于夏季,其他各项营养盐则为春季低于夏季。夏、春季DON分别占TDN的79%、36%；DOP/TDP分别为49%、47%,但夏季DOP含量约是春季的2.6倍。存在由春季潜在P限制到夏季N限制的转变。老爷海渴湖口门处受潮汐作用影响明显,营养盐含量低。潟湖中无机态营养盐及有机质含量高,无机磷、有机氮成为总溶解态氮、磷的主要组成部分。’渴湖内不存在营养盐限制。4、东部近岸海区陆源输入对沿岸浅水区影响比较大,深水区受陆源输入影响不如沿岸明显,营养盐含量由沿岸至远海逐渐降低。浓度由表至底逐渐升高,有明显的层化现象。不同季节中P都成为浮游植物生长的限制因子。5、于2008年8月25日至9月6日对南海北部进行了调查。结果表明：南海北部海区上层营养盐贫乏。营养盐浓度由表到底递增,有明显的层化现象。南海北部表层水体中氮磷营养盐通常低于浮游植物的生长阈值,此次调查时为P限制。6、根据营养盐收支模型计算可知,文昌/文教河口NO2-N、NH4-N、DSi、DON、DOP主要来源于河流输入,N03-N主要来源于地下水输入,为NO3-N、DOP的汇,NO2-N、NH4-N、DSi、DIP的源。万泉河口成为NO3-N、DIP、DSi和DOP的汇,NO2-N、NH4-N及DON的源。小海渴湖是除DON外其他各项营养盐的汇。老爷海渴湖是NO3-N、NH4-N、DIP、DOP的汇,DSi、DON的源。文昌/文教河、小海和老爷海对沿岸水体的影响不如万泉河产生的影响大。更多还原

【Abstract】 The coastal ecosystems usually have high primary productivity, diverse and complex community, therefore, nutrient biogeochemical cycles have become the cone theme in ocean science. Four cruises were carried out along coastal ecosystems of Eastern Hainan(such as rivers, estuaries, lagoons and near-shore waters) to understand the level, distribution and seasonal variations of nutrients, in order to examine biogeochemical processes that influence nutrients composition. Some important conclusions are drawn as follows.1. Nutrient levels in the tropical Wenchang/Wenjiao rivers show wide range of seasonal variations. DIN concentrations in these two rivers are generally at the levels between the average global conditions to polluted waters except that Wenjiao river one cruise in 2008 are at clean waters levels. Ammonium contribution to DIN concentration is relatively up to 37-44% in the August 2007 cruise related to the the application of inorganic N fertilizer and wastewater discharge. DIP concentrations in the rivers are at the levels between pristine level and clean waters level compared to the global river data. So DIN/DIP ratios show wide range of variation(60-413). DON was the major part of TDN in winter and summer, DIP was the main part of TDP in spring. DON accounted for 23% of TDN in the Wenchang river and 55% in the Wenjiao river. Dissolved silicate levels in Wenchang and Wenjiao rivers are lower than average levels of tropical rivers, it’s lower than the level of Wanquan river.Wenchang/Wenjiao river estuaries significantly affected by tidal action and had obvious seasonal variation. Nitrate behaved conservatively subjected to a simple estuarine dilution in the winter 2006; underwent regeneration in the spring 2009; has denitrification in both summer 2007 and 2008. This indicated that dissolved inorganic and organic nitrogen regenerated from degradation of organic matter and denitrification processes existed in the estuary in the summer. Phosphorus behaved desorption/adsorption from suspended particles along the salinity or degradation of organic matter in the estuary. Dissolved silicate behaved conservatively in the winter 2006 and spring 2009.Nutrients showed obvious tidal effect with low values at flood tide in Gaolong bay.2. DIN concentrations in the Wanquan river were higher than tropical river that were not polluted in the world, such as Amion and Zaire rivers, but lower than temperate rivers which significantly affected by human activities, such as Changjiang, Huanghe and Pearl rivers. DIP concentration in the river is at the levels between pristine level and clean waters level compared to the global river data. Dissolved silicate level in the Wanquan river is not only higher than average global conditions, but also at higher to general levels in tropical systems.NO3-N/DIN is the main part of DIN. Nitrate and dissolved silicate had a negative correlation with salinity in the estuary, indicating largely subjecting to a simple estuarine dilution, while nitrite and ammonium were non-conservative; phosphate undergo desorption/adsorption from onto suspended particles along the salinity gradient and/or degradation of organic matter in the estuary and has regeneration in 2007 when salanity below 2.5. In addition, phosphorus maybe the potential limit element for phytoplankton growth with high N/P concentration ratio (averagely, more than 61).3. Nutrient concentrations in surface waters of the Xiaohai and Laoyehai lagoon were determined during surveys in both August 2008 and April 2009. The results showed that:the overall salinity of the Xiaohai lagoon is low, and summer higher than spring. The concentrations of nutrients were higher in summer than spring except nitrate. DON accounted for 79% and 36% of TDN in summer and winter, respectively; DOP concentrations represented-49% of TDP in summer and 47% in spring, but the concentrations of DOP increased by 2.3 fold in summer 2008 than in spring 2009. Nutrient ratios showed obvious seasonal variation, indicating that limiting nutrients were nitrogen in summer and phosphorus might be the potential limiting element for phytoplankton growth in spring.The salinity in the inner bay of Laoyehai lagoon is lower than the mouth of the lagoon, and the average salinity was higher than that that in Xiaohai lagoon. Nutrient concentrations showed an obvious tidal effect with low values in the mouth of the lagoon.4. Nutrients level are low in eastern coastal of Hainan. Shallow coastal waters were significantly affected by terrestrial input, but deep water was not obvious. Nutrient concentrations increased from surface to bottom waters. Phosphorus was the limiting factor for phytoplankton.5. One cruise was carried out in the northern South China Sea(SCS). The result showed that oligotrophy is a significant characteristic in upper water column of the northern SCS. The concentration increased with obvious stratification from surface to bottom. According to nutrient concentrations, the limiting nutrient for phytoplankton growth was phosphotus in this region.6. Nutrient budgets demonstrate that in Wenchang/Wenjiao estuary, riverine input is a major source of NO2-N, NH4-N, DSi, DON, DOP, while groundwater discharge is the major source of NO3-N, and the estuary is the sink of NO3-N、DOP, source of NO2-N, NH4-N, DSi and DIP. Wanquan estuary behaves as a sink of NO3-N, DIP, DSi and DOP, source of NO2-N, NH4-N and DON. Xiaohai lagoon is a sink of all nutrients except for DON. Laiyehao lagoon behaves as a sink of NH4-N, DIP and DOP, source of DSi and DON. Wanquan river estuary transports more nutrients to coastal waters than Wenchang/Wenjiao estuary, Xiaohai lagoon and Laoyehai lagoon.更多还原