Characteristics of primary productivity of Lake Poyang in wet and dry seasons and the correlations with environmental factors using the Vertically Generalized Production Model

Abstract

于2014年1月(枯水期)、7月(丰水期)对鄱阳湖湖水进行采集,测定相应的理化参数、叶绿素a浓度和光合有效辐射,结合初级生产力垂向归纳模型估算浮游植物初级生产力,分析湖区初级生产力特征及与环境因子的相关性.结果表明,鄱阳湖枯水期浮游植物初级生产力波动范围为83.50~355.43 mg C/(m³·d),平均值为193.33 mg C/(m³·d),初级生产力空间分布特征主要受水体类型的影响,枯水期初级生产力与氮、磷营养盐浓度呈负相关,其中与铵态氮浓度呈显著负相关,枯水期不会出现营养盐限制现象;丰水期浮游植物初级生产力波动范围为113.80~1134.06 mg C/(m³·d),平均值为412.12 mg C/(m³·d),初级生产力空间分布主要受河流注入的影响,丰水期浮游植物初级生产力与总磷及悬浮物浓度呈显著正相关,由于悬浮物对浮游植物生长的促进作用大于抑制作用,鄱阳湖丰水期会出现磷营养盐的限制;鄱阳湖整体平均流速约为0.28 m/s,易于浮游植物的生长,南鄱阳湖平均流速约为0.21 m/s,而北鄱阳湖平均流速约为0.35 m/s,所以南鄱阳湖比北鄱阳湖更容易发生水体富营养化并暴发水华.;The water samples from Lake Poyang were collected in January(dry season) and July(wet season) of 2014 in order to measure the corresponding physical factors, chlorophyll-a concentration and photosynthetically active radiation. Vertically Generalized Production Model was used to estimate the primary productivity of phytoplankton, characteristics and relationship with the lake environmental factors. Results show that the range of phytoplankton's primary productivity in Lake Poyang is fluctuated between 83.50 and 355.43 mg C/(m³·d), and the average is 193.33 mg C/(m³·d) during the dry season. The spatial distribution of primary productivity is mainly affected by different types of water quality in dry season. The primary productivity is negatively correlated with nutrients, of which NH₄⁺-N was highly significant due to the absences of nutrient limitation. In wet season the range of primary productivity of phytoplankton is between 113.80 and 1134.06 mg C/(m³·d), and the average is 412.12 mg C/(m³·d), which was affected by the river flow inputs. Primary productivity was significantly positively correlated with the total phosphorus and suspended solids concentrations. Because the positive effect caused by suspended solids was greater than the negative effect on phytoplankton, these effects caused that the restricted phosphorus nutrients occur frequently. The overall average velocity is about 0.28 m/s in the Lake Poyang which is beneficial to the growth of phytoplankton. However, the average speed in the south is approximately 0.21 m/s, while it is approximately 0.35 m/s in the north. Therefore, eutrophication, or even algal bloom are more often occurred in the southern Lake Poyang.