三峡大宁河水体光学特征及其对藻类生物量的影响

基于2012-04-27—2013-01-19大宁河不同水文期的监测数据,确定大宁河水体光学特性的季节变化特征,并探究其对藻类生物量的影响. 结果表明:①不同水文期大宁河的D_eu(真光层深度)差异显著(P＜0.01),最高值出现在高水位运行期,为(5.22±2.70)～(8.71±5.20)m；最低值出现在汛限期,为(3.22±0.08)～(3.81±0.14)m. ②回归分析结果表明,ρ(SS)能较好地反演真光层深度的时空变化规律,而ρ(Chla)的解释度不高,仅用ρ(SS)即可有效地反推真光层深度. ③利用局部多项式回归拟合大宁河E_t(总能量密度)和浮游生物量的回归模型,结果表明,在100t≤300时,藻类生物量随着E_t的增加而增大；E_t>300时则出现“光抑制”现象,藻类生物量随着E_t的增加而减少,基本符合藻类生物量随光辐射强度而改变的响应机制. 

Optical Characteristics of Daning River in the Three Gorges Reservoir and its Impact on Algae Biomass

Using monitoring data from the Daning River in different seasons from April 2012to January 2013, the factors influencing optical properties (euphotic depth and light attenuation) were analyzed, and its impacts on algae biomass in typical tributaries of river-style reservoirs were revealed. The operational period of the Three Gorges Reservoir was classified into four stages according to the water level:stage Ⅰ (pre-November-April), stage Ⅱ (May-July), stage Ⅲ (July-September) and stage Ⅳ (September-November). The results indicate that the Daning River has a comparatively high spatial heterogeneity in the euphotic depths (D_eu)(ANOVA,P<0.01). The mean values of euphotic depth in stage Ⅰ were significantly greater than those in stage Ⅲ and Ⅳ, This indicates that the concentration of suspended substance (SS) was the most important factor impacting optical properties, followed by transparency and chlorophyll-a (chla). The results of regression analysis showed that the SS influence on the D_eu was significant, and there was no significant correlation between the D_eu and the transparency and chla. Locally weighted regression analysis was performed to illuminate the relationship between index of feasible energy for phytoplankton (E_t) and algae biomass. The resule indicated that in a certain range (100t≤300), an increasing of algae biomass was associated with increasing E_t, while an decreasing of algae biomass was associated with increasing E_t when exceeding a threshold value (E_t>300).