Study On Biological Diversity In Different Habitat Type Lakes And Ecological Classification Of Lakes

Being a worldwide environmental problem,eutrophication has been paid more and more attention in past three decades.China has a very large geographical span,so there are significant differences between lake ecosystems and habitats in different regions.Accordingly there are also different problems in and different needs for environmental protection between these water bodies.Today’s lake scientists and national environmental management departments face a huge challenge on how to take appropriate procedures to protect the lake ecosystems.In order to better protect the lake ecosystem,classify nutrient ecological zones,and serve for construction of ecological civilization,it is highly important to establish the lake ecosystem classification system.In this paper,the following aspects are studied in this paper:1.Community structure and biodiversity of phytoplankton and their relationships with trophic state were investigated in different type lakes.Univariate and multivariate analysis showed that density,biomass,diversity and characteristic species differed significantly among the three type lakes.The diversity indices showed significant negative correlations with trophic state index and no significant correlation with dry weight ratio of macrophytes to phytoplankton.Canonical Correspondence Analysis(CCA)illuminated that temperature,dissolved oxygen and chemical oxygen demand could be the main forces structuring the phytoplankton community.2.Community structure and biodiversity of macro zoobenthos and their relationships with trophic state were investigated in different type lakes.Univariate and multivariate analysis showed that density,biomass,diversity and characteristic species differed significantly among the three type lakes.The group of macrophyte-dominated lakes had the highest density.There were significant positive correlations among Shannon-Wiener,Margalet Pielou and Gleason diversity indices.The trophic state and aquatic vegetation were the key factor to determine the distribution and biodiversity of macrozoobenthos.3.An uniform indicator,the equivalent chlorophyll a content of phytoplankton and macrophytes,was developed to assess the potential trophic state in some shallow lakes of Jiangsu province,China.This approach permits an approximation of the potential impact of macrophytes on the trophic state in shallow lakes.No significant correlation appeared between the EC-a and TSI in the three lake groups,which implied that the conventional criteria to classify the trophic state emphasised conditions in the water and ignored the nutrient salts,plant biomass and production associated with macrophytes in the lake ecosystem.Our results showed that the large biomass of macrophytes is another eutrophication and indicated that EC-a could be a marker to determine and predict possible scenarios of the trophic state in shallow lakes considering the potential inpact of macrophytes.4.Gleason richness index can be used to calculate fish abundance of the lake in different regions.Because of the positive correation between the fish richness and richness of other lake species such as phytoplankton and benthic animals,fish abundance can be used to quantitatively characterize the species diversity of the lake ecosystem in different regions,and study the differences of structure in different lake ecosystems.5.Rmax values of TP to Chl-a can reflect the energy flow rate in the lake ecosystems and the differences in their function.While the ecosystem species richness index,represented by fish richness index of Df,can characterize the structure and complexity of the lake ecosystem.Therefore,the energy flow rate(Rmax values of TP to Chl-a)and ecosystem species richness index(fish richness index represented by Df)were used as primary indicators in the lake ecosystem classification system,to reflect the differences of structure and function between different lake ecosystems.Since the primary producers and the depth of the lake is another two important factor affecting the structure and function of lake ecosystems,therefore,at the ecosystem level classification based on the depth of the lake(average depth,H)and the type of primary producers(dry weight ratio of macrophytes to phytoplankton,B)were used as secondary indicators in the lake ecosystem classification system,to characterize the differences in primary productivity and nutrient cycling characteristics between different lake ecosystems.The conclusions could provide important theoretical foundations for the establishment of the different lake ecoregions as well as the formulation of nutrients criteria and standards by the central and local governments.