水体光照强度的变化对浮游甲壳动物群落结构的影响

近年来，我国淡水湖泊富营养化现象日益严重，藻类大量生长导致水体光照强度减弱，水生植物严重衰退。为了解水体光照强度减弱对生活在沿岸带草丛中的浮游甲壳动物分布情况的影响，本研究于2015年5月至2015年11月在水族箱中通过移植苦草并覆盖不同层黑色遮阳布来建立4个光照梯度（L1- L4），其透光率分别是40.5%、17.1%、7.1%和2.8%，来模拟自然条件下沿岸带浮游甲壳动物群落对低光压力的响应，分析了水体理化指标、苦草和浮游甲壳动物群落结构变化。结果表明：（1）从不同的光照处理来看，浮游甲壳动物生物量随光照强度减弱而减少，其平均值分别是1.27 mg/L、0.99 mg/L、0.95 mg/L和0.45 mg/L，丰度和多样性也随光照强度减弱逐渐降低；（2）与其他3个处理组相比，L4组中除了锯缘真剑水蚤相对生物量百分比从5%升高到25%，其他种类都有所下降，其中晶莹仙达溞从50%降至9%；（3）浮游甲壳动物的平均生物量在秋季（1.28 mg/L）大于夏季（0.54 mg/L），而夏季（83.79 ind./L）平均丰度大于秋季（53.59 ind./L）。统计分析表明浮游甲壳动物群落结构变化与光照强度和苦草生长引起的水体理化的变化显著正相关，主要是溶解氧和pH值。

The effects of light intensity on the crustacean zooplankton community

In recent years, eutrophication induces low light and seriously reduced submersed vegetation in shallow lakes. To examine the effects of declining light intensity on the crustacean zooplankton community, a medium-scale experiment was carried out from May 2015 to November 2015. Four light intensity regimes were set through covering aquarias by black nylon nets. The light regimes were 40.5% (L1), 17.1% (L2), 7.1% (L3), and 2.8% (L4) of the air light intensities respectively. The water physicochemical characters, crustacean zooplankton communities and Vallisneria natans biomass were analyzed. The results showed that: (1) The biomass of crustacean zooplankton decreased with the decreasing light intensity and the biomass were 1.27 mg/L, 0.99 mg/L, 0.95 mg/L and 0.45 mg/L from L1 to L4 respectively. Moreover, the abundance and species diversity decreased with the decreasing light. (2) Compared with other light treatments, the relative biomass of Eucylops serrulatus in L4 increased from 5% to 25%. However, the relative biomass of other species reduced, especially for Sida crystalline, which reduced from 50% to 9%. (3) Crustacean zooplankton had higher biomass in autumn (1.28 mg/L) than that in summer (0.54 mg/L), while higher abundance in summer (83.79 ind./L) than that in autumn (53.59 ind./L). In addition, the crustacean zooplankton community was positively correlated with light intensity, V. natans biomass, dissolved oxygen and pH.