| As an indispensable organic component of a healthy lake ecosystem, littoral zone has numerous ecological functions such as trapping and purifying pollutants, enhancing littoral biodiversity, providing wildlife habitats, controlling sedimentation and erosion and so on, which is the key area of wetlands’ecological restoration as well.Littoral water quality is affected by near-shore hydrodynamic conditions, shoreline morphology and deposition processes, vegetation characteristics and microhabitats.To study the relationship between littoral water quality and microhabitat factors, we compared the main water quality indicators in different microhabitats in an ecological restoration area (embankment returning to lake) in the north of Gonghu Bay, Tai Lake. We used CleverChem200, an automatic water quality analyzer to measure the concentrations of the major water quality indicators.The differences under different microhabitats were tested through one-way ANOVA, every microhabitat factor’s correlation with water quality was analyzed and every microhabitat factor’s explanatory power on water quality was calculated based on redundancy analysis. The results showed that:1.The differences of pH and dissolved oxygen among each microhabitat were not significant in both summer and winter, though dissolved oxygen in summer water was significantly lower than in winter.The difference of vegetation coverage among each water depth was relatively more evident in summer and winter,while coverage in deep water was highest in winter and the difference of vegetation coverage among each water depth varied due to the types of shorelines.2.The major water quality indicators in summer were higher than those in winter, and the heterogeneities among different forms of shorelines and different water depths were more evident. With the change of water depth, concentrations of the major water quality indicators under the three shorelines in summer existed contrary trend to winter, while under the straight shoreline, the variation tendencies of total phosphorus (TP), ammonia nitrogen (NH4+-N) and chemical oxygen demand (COD)’s concentrations with water depth were relatively consistent.3. The concentrations of total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH4+-N) and nitrate nitrogen (NO3--N) in winter littoral zone were relatively lower where the vegetation coverage was higher,while the the concentration of chemical oxygen demand (COD) was higher comparatively. And in summer,the situation was converse to some extent. The concentrations of total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH4+-N) and nitrate nitrogen (NO3--N) in winter were relatively higher under the concave shoreline, and the concentration of chemical oxygen demand (COD) was comparatively higher under the convex and straight shorelines, while in summer, the concentration of chemical oxygen demand (COD) was relatively higher under the concave shoreline, and the concentrations of total phosphorus (TP) and ammonia nitrogen (NH4+-N) were comparatively higher under the convex shoreline. And whether in summer or winter, the water major nutrient salts’ concentrations were generally higher in riffle area, relatively lower in shallow water and deep water.4.Redundancy analysis showed that shoreline morphology was the most significant microenvironmental factor that affected the main water quality indicators in winter, followed by vegetation coverage and water depth in turn; while in summer, water depth was the most significant microenvironmental factor that affected the major water quality indicators, followed by shoreline morphology and vegetation coverage. In general, the major water quality indicators changed differently among different shorelines along the water depth gradient, also the heterogeneities among different shorelines existed.In summary, building relatively tortuous shorelines can help to the increase the heterogeneity of water quality indicators, thereby enhance the diversity of littoral habitat. |
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