The Contribution Of Terrestrial Organic Carbon To Zooplankton In Eutrophic Water

Most of the terrestrial organic carbon comes from higher plants on land,which is considered to be a poor food source.The food value of terrestrial organic carbon can be improved through heterotrophic microbes,which exists in all types of freshwater.Studies show that terrestrial organic carbon affects zooplankton only during phytoplankton deficiency.In this experiment,fresh corn stover was used to represent terrestrial organic carbon,and NaH₁₃CO₃?98at.%13C?was used for isotopic labeling of corn stover to prepare ¹³C-enriched terrestrial organic carbon,and added it to the phytoplankton abundant in eutrophic freshwater.By analyzing changes in water quality,species and quantity of phytoplankton and zooplankton,and changes in bacterial abundance,combined with stable isotope technology and fatty acid analysis,this experiment study the contribution of terrestrial organic carbon to zooplankton when phytoplankton is abundant.The main results are as follows:1.When terrestrial organic carbon enters the freshwater,pH and DO concentration are reduced,while CO₂ concentration and K_d are increased;2.The concentration of total phosphorus,abundance of phytoplankton,bacterial and protozoan increased after terrestrial organic carbon entered freshwater,the abundance of rotifers,Chydorus sphaericus and Alona sp.decreased,and the abundance of Mesocyclops thermocyclopoides increased;3.The dependence of bacteria on phytoplankton decreased,and the food structure of Chydorus sphaericus and Mesocyclops thermocyclopoides were changed.According to the stable isotope mixture model,the contribution of terrestrial organic carbon to Chydorus sphaericus and Mesocyclops thermocyclopoides were 32%±12%and 14%±1%,respectively.Therefore,when terrestrial organic carbon enters the freshwater and phytoplankton are abundant,terrestrial organic carbon can be transferred to zooplankton,in which bacteria and protozoa play an important role.