光照和营养盐对浮游动物和浮游植物生物量及其营养联系的影响

Light and Nutrients as Determinants of Zooplankton and Phytoplankton Biomass and Their Impacts on Pelagic Trophic Linkage

水生态系统中物质(营养盐)和能量(光照)输入的不平衡能影响浮游动物和浮游植物的生长,但两者的交互作用在浮游生物现存量的预测中还较少涉及。通过对湖北省内14个水体进行春采样,研究了光照和营养盐的交互作用对浮游动植物生物量预测能力的影响,并探讨了两者对浮游动植物间营养联系的影响,以期为湖泊生态系统的监测和管理提供理论依据。研究结果显示:浮游植物和浮游动物生物量均与营养盐不存在显著相关性;ρ_(Chl a)与漫射衰减系数(K_d)(r=0.526,P=0.036)和光照×营养盐(r=0.57~0.70,P<0.05)均呈显著正相关;浮游甲壳动物的生物量随着K_d增加而显著减少(r=-0.544,P=0.029)。浮游动物、植物生物量之比(ρ_Z/ρ_P)随着K_d(r=-0.651,P=0.006)和营养状态指数(TSI)(R^2=0.64,P<0.001)的增加而显著下降,表明两者之间的营养联系在低光照、高营养盐的环境下变弱。逐步线性回归分析显示:浮游甲壳动物生物量能够单独被K_d更好地预测(R^2=0.30,P=0.029);光照和总溶解性氮的交互作用提高了多元线性回归模型对ρ_(Chl a)(R^2=0.47,P=0.003)和ρ_Z/ρ_P(R^2=0.45,P=0.004)的预测。

Light and nutrients can affect zooplankton and phytoplankton development through the imbalanced inputs of material and energy, but their interaction effects in the prediction of plankton biomass are rarely examined. We sampled 14 water bodies in spring in Hubei Province to explore how phytoplankton and zooplankton biomass and their trophic linkage could be predicted based on light and nutrients as well as on their interaction effects. The results showed that no significant correlation between plankton biomass and dissolved nutrients was found. ρChl a was positively correlated with light attenuation coefficient （Kd） （r=0.526, P=0.036） and the interaction effects of Kd×nutrients （r=0.57~0.70, P〈0.05）. Only a negative correlation was found between zooplankton biomass and Kd （r=-0.544, P=0.029）. The ratio of zooplankton to phytoplankton biomass （ρZ/ρP） decreased significantly with increasing Kd （r=-0.651, P=0.006） and trophic state index （R^2=0.64, P〈0.001）, indicating that the pelagic trophic linkage was weakened under low-light and high-nutrient conditions. Stepwise linear regressions showed that Kd alone was a good predictor of zooplankton biomass （R^2=0.30, P=0.029）, and Kd in conjunction with total dissolved nitrogen could better predict phytoplankton biomass （R^2=0.47, P=0.003） and the ρZ/ρP ratio （R^2=0.45, P=0.004）.