Effect Of Dissolved Organic Carbon On The Growth Of Phytoplankton

In the past 20 years,people began to pay attention to the transboundary flow of matter and energy between adjacent ecosystems,especially the impact of terrestrial organic carbon on aquatic ecosystems.With the intensification of lake eutrophication,the migration and transformation of N and the coupling relationship with C have became research hotspots.Dissolved organic carbon(DOC)was an important component of dissolved organic matter(DOM)in lakes.It was divided into endogenous DOC and exogenous DOC.Endogenous DOC was mainly derived from phytoplankton,and exogenous DOC was mainly derived from watershed terrestrial plants.Exogenous DOC could have both positive and negative effects on phytoplankton.This study investigated the relationship between dissolved organic carbon,nutrient and phytoplankton(Chl a)content in summer and winter seasons in 13 shallow lakes in Wuhan,and the addition of exogenous dissolved organic carbon to phytoplankton and grass/algae in indoor research.The results were as follows:(1)The biomass of phytoplankton in lake water had a significant negative correlation with C/N and C/P of water.(2)0.5 g/L glucose could inhibit the growth of Microcystis aeruginosa,whether the initial concentration of Microcystis aeruginosa was 100 or 20 mg/m~3.But the former was more inhibited.While the initial concentration of Chlorella vulgaris is 100mg/m~3,glucose inhibited the growth of chlorella at medium and low nutrient levels,and has no significant effect on chlorella at high nutrient levels.(3)With the addition of 125 mg C/L sucrose or straw,the Chl a in phytoplankton-dominated group increased,and the Chl a in the macrophyte-dominated group did not change significantly.(4)Straw powder leaching solution can subsidize the primary consumers in the macrophyte-dominated group.Mixing model results showed that straw powder leaching solution constituted a large fraction of basal production sources for the invertebrate(Radix,Bellamya,zooplankton).The proportional contribution of straw powder leaching solution to invertebrate varied from 10%-45%.