Response Of Interaction Between Two Species Of Microalgae And Two Species Of Rotifer To Climate Changes: A Experimental Ecology Study

No matter whether climate change caused by human activities, the consequencesof climate change have been revealed. Ocean is the biggest buffer system and carbonsink in the earth, but it also under the threat of climate change. Elevated CO₂concentration and temperature as well as enhanced UV-B radiation are threateningmarine ecosystem. Marine phytoplankton and zooplankton are considered asimportant components of marine ecosystem, and the interaction between them plays akey role in material cycle and energy transportation as well as the structure andfunction of marine ecosystem. Therefore the investigation on the interaction betweenphytoplankton and zooplankton under the background of global climate change couldreveal the results of climate change affects marine plankton, and provide data toilluminate the process and mechanism on which the climate change affects marineecosystem. In the present study, bloom-forming microalgae （Heterosigma akashiwoand Prorocentrum donghaiense） and marine rotifer （Brachionus plicatilis andBrachionus urceus） were chose as study object, and temperature, CO₂concentrationand UV-B radiation as typical climatic factors, the study on the interaction betweenbloom-forming and marine rotifer under climate change condition was conducted.The results show that:1. The feeding of rotifer on bloom-forming microalgae under climate changeconditions（1） The rates of both ingestion and filtration have obvious differentes for B.plicatilis on H. akashiwo and P. donghaiense compared with the control groupswhich increased first and then decreased with elevated temperatures and CO₂concentration, and the similar result was obtained for B. urceus. （2） Both the filtration and the ingestion rates gradually decreased with theenhancement of UV-B, and there are significant differences between treated andcontrol groups.2. Effects of bloom-forming microalgae on population growth of rotifer underclimate change conditions（1） The maximum environmental capacity（K） was intensively inhibited by H.akashiwo for two species rotifer when the environmental temperature was set as24,26and28℃. The adverse effect increased for B. plicatilis, but did not rise for B.urceus with the elvated concentrations of algae. P. donghaiense suppressed thepopulation growth of both rotifers and the negative influence turned more serious asthe temperature rose.（2） The population growth of B. plicatilis and B. urceus was seriously repressedby H. akashiwo and the value of K decreased when the CO₂level was set at0mL min^-1and mL min^-1, which seemed to be more severe as the concentration of CO₂elevated. But,there are no bad impacts when the CO₂level changed to300mL min^-1.For P. donghaiense, the suppression exsited among all treated groups on the growth oftwo species.（3） The population growth of B. plicatilis and B. urceus was seriously repressedby H. akashiwo and the value of K decreased when the UV-B radiation dose was set at0kJ·m^-2and0.8kJ·m^-2, which seemed to be more severe as the dose of UV-Belevated for some treated groups.3. Effects of bloom-forming microalgae on interspecific competition betweenrotifer under climate change conditions（1） Two species harmful alga affected the competition between B. plicatilis and B.urceus as the temperature rose. The competition seemed to gradually shift from B.urceus winning to unstable balance in favor of B. plicatilis by a combination ofelevated temperature with H. akashiwo. The elevated temperature and P. donghaiensechanged the competition result from B. urceus winning to stable co-exist.（2） Two species harmful alga affected the competition between B. plicatilis and B.urceus as the CO₂level rose. The competition seemed to gradually shift from B. urceus winning to unstable balance in favor of B. plicatilis by a combination ofelevated CO₂level with H. akashiwo. The elevated CO₂level and P. donghaiensechanged the competition result, separatly. However, the combination had no impact oncompetition.（3） Two species harmful alga affected the competition between B. plicatilis and B.urceus as the dose of UV-B radiation rose. The competition seemed to gradually shiftfrom B. urceus winning to unstable balance in favor of B. plicatilis by UV-B radiation,but a combination of elevated UV-B radiation with H. akashiwo did not at work. Theelevated UV-B radiation and P. donghaiense contributed to change the competitionresult from B. urceus winning to stable co-exist.4. Effects of bloom-forming microalgae on development of rotifer under climatechange conditions（1） B. plicatilis and B. urceus suffered the adverse impact from the bloom-formingmicroalgae as the temperature rose. There were no differeces between treated andcontrol groups only considering the temperature, and then the addition of H. akashiwoposed the obvious effect occur to the development of the rotifers. The role of P.donghaiense played more importantly in the developmental effect than the elevatedtemperature, however the temperature could help a lot.（2） B. plicatilis and B. urceus suffered the adverse impact from the bloom-formingmicroalgae as the CO₂concentration rose. The elevated CO₂concentration andbloom-forming microalgae affected the development as two stress factors（3） The rotifer suffered the adverse impact from the bloom-forming microalgae asthe dose of UV-B radiation was set at0kJ·m^-2and0.8kJ·m^-2, and there was nosignificant differense in1.6kJ·m^-2treated group. The elevated dose of UV-B radiationand bloom-forming microalgae affected the development as two stress factorsThe results showed that H. akashiwo and P. donghaiense has influence on thefeeding, population growth and development of B. plicatilis and B. urceus underclimate changes, which suggested that the climate changes altered the interationbetween bloom-forming microalgae...