Zooplankton Community Structures Of Shallow Lakes In Southern China: Effect Of Fish And Biomanipulation

As a main contributor of secondary productivity, zooplankton played animportant role in lake ecosystem. Zooplankton act as intermediate link in materialcycling and energy flow, and play a connecting role in the freshwater food web whichconnect phytoplankton and higher trophic level. This paper studied the influence offish, allochthonous carbon, aquatic macrophyte and other factors on zooplanktoncommunity structure.In order to evaluate the influence of the fish on zooplankton community, thechanges in species composition, abundance of zooplankton before and afterfilter-feeding omnivorous fish stocking was studied in this paper. The results showedthat, after the fish stocking, there was a rapidly decrease in abundance of Cladocera(Diaphanosoma dubium and Moina micrura) and Copepoda (Thermocyclopsmongolicusand and Tropodiaptomus australis). The density of Rotifera increased oneweek after stocking, and then high density was maintained. The dominant species ofrotifers were also changed, Brachionus dominating in the first two weeks andTrichocereidae pusilla, Polyarthra trigla and Anuraeopsis fissa dominating the rest ofthe study period. Our study demonstrated that filter-feeding omnivorous fish canimpose a significant impact on zooplankton community, and large-sized zooplanktonsuffered a high negative effect leading to the dominance of small-sized individualsand species in zooplankton community.The influence of ecological restoration on zooplankton community structure wasanalyzed by monitoring the zooplankton community structure in restored (fishregulate and submerged vegetation reestablish) and unrestored lake areas in Huizhouwest Lake. The results showed that, Copepoda was the main crustacean both inunrestored part(Ping Lake） and restored area while Cladocera only accounted forextremely low proportion. Copepoda was mainly consisted of nauplius andcopepodids in Ping Lake while only nauplius dominated in restored areasYuanmiaoguan lake and South Lake. Compared the abundance and biomass ofcopepod adult, it was found that Ping Lake was dominated by cyclops while the two restored lake areas were dominated by calanoids. The species richness, abundance,biomass and biodiversity of crustacean plankton were all higher in restored lake areasthan in unrestored lake areas. The study indicated that ecological restoration couldincrease the abundance, biomass and biodiversity of crustacean plankton effectively.The contribution of allochthonous carbon (terrestrial plant detritus) tozooplankton was studied by experiments. The result showed that the adding ofterrestrial plant detritus changed the value of carbon stable isotope of zooplanktonwhich indicates that zooplankton have the ability to use terrigenous organic carbon(allochthonous carbon). At the same time, the contribution of allochthonous carbon tothe carbon source of zooplankton increased with the quantity of terrestrial plantdetritus added.