湖光岩玛珥湖水体中营养盐的时空分布特征及其影响因素

湖光岩玛珥湖是世界上最大的玛珥湖，它几乎是封闭的，受外界的干扰小.目前有关玛珥湖的研究主要集中在古气候及生态环境研究方面，而有关玛珥湖营养盐在一年中的生物地球化学循环的研究较少，因此研究湖光岩玛珥湖营养盐的生物地球化学过程具有重要意义.于2015年10月-2016年9月对湖光岩玛珥湖全水柱的营养盐及其他相关参数进行逐月调查，分析营养盐的结构特征、垂直分布特征和时间变化情况，并讨论营养盐时空变化的影响因素.结果表明，湖光岩玛珥湖水中的无机氮（DIN）以铵态氮（NH₄⁺-N）为主（>60%），其次是硝态氧（NO₃^--N），亚硝态氮（NO₂^--N）所占比利最低.湖光岩玛珥湖水中的硅酸盐（SiO₃^2--Si）浓度较高，水体浮游植物生长受磷限制.冬季风期间，水体垂直混合较均匀，导致营养盐的垂直分布比较均匀；夏季风期间，水体层化，营养盐浓度在浅层水体较低，在深层水体较高.湖光岩玛珥湖表层水中的NO₃^--N、NH₄⁺-N和SiO₃^2--Si具有明显的时间变化规律：NO₃^--N浓度从10月-次年3月升高，从3-9月降低；NH₄⁺-N浓度从10月-次年5月降低；SiO₃^2--Si浓度从11月-次年5月降低，从5-9月持续升高.营养盐浓度的时间变化受有机质的矿化分解、水体的季节性混合、浮游植物的吸收、降雨的输入等多种因素的综合影响.

Spatial and temporal distributions of nutrients and their influencing factors in the Huguangyan Maar Lake

The Huguangyan Maar Lake is the biggest maar lake in the world. It is nearly closed and less disturbed by the surroundings. Existing work is mainly on its palaeoclimatological and the ecology environment research. The research on nutrients and their biogeochemical cycling in maar lakes is rare. Therefore, it has great significance to conduct such research in the Huguangyan Maar Lake. Nutrients and related parameters were investigated monthly in the water column of the Huguangyan Maar Lake from October 2015 to September 2016, in order to analyze the compositions, vertical distributions and temporal variations of nutrients and their influencing factors. The results showed that ammonium nitrogen (NH₄⁺-N) was the predominant speciation of dissolved inorganic nitrogen (>60%) in the water of the Huguangyan Maar Lake, followed by nitrate nitrogen (NO₃^--N), and nitrite nitrogen (NO₂^--N) was the lowest speciation. The concentrations of silicate (SiO₃^2--Si) were relatively high, while phosphorus was the limiting nutrient for phytoplankton growth in the Huguangyan Maar Lake. During the winter monsoon, the concentrations of nutrients were vertically stable due to the enhanced vertical mixing. While during the summer monsoon, the water column stratified and nutrients in shallow water were generally low and deep water higher. Monthly variations of NO₃^--N, NH₄⁺-N and SiO₃^2--Si showed obvious variation patterns. Concentrations of NO₃^--N increased from October to March but decreased from March to September; concentrations of NH₄⁺-N decreased from October to May; and concentrations of SiO₃^2--Si decreased from November to May and increased from May to September. Their temporal variations were influenced by combined factors of organic matter decomposition, seasonal water-column mixing, phytoplankton absorption, rain-induced inputs and so on.