| Over the past century, climate warming became the most severe environment problem around the world. It is predicted to have great impacts on the Earth’s ecosystems with other climate change events. It caused effect on ecosystem structure and function and the consequences for ecosystem services. A lot of domestic and foreign researches focus on climate warming. At present, our studies mainly focused on paleoclimate evolution and the effects of climate change on terrestrial ecosystems, however, researches about the impacts of climate warming on lake ecosystems is lacking. Although there is a lot about these studies abroad, but much of focus on temperate area, only a few pay attention to the tropical and subtropical regions. In order to disentangle the effects of warming on crustacean zooplankton community characteristics in subtropical lake ecosystems at contrasting nutrient levels, we performed an outdoor in situ mesocosm experiment with two temperature regimes and two nutrient levels in 2013, to simulate the projected future scenario for two subtropical different nutrient level lakes(the high nutrient level lake and the low nutrient level lake). Furthermore, climate warming and eutrophication will still co-exist for a long time in our country in the future. As a result, we performed a mesocosm experiment with four treatments(the control, warming, nutrient addition, warming+nutrient addition) in 2014, simulating the projected future scenario for a subtropical shallow lake in Yangtze River region, to address potential interactive effects of warming and eutrophication on crustacean zooplankton recruitment and community dynamics in spring. The results are as follows:(1) The responses of crustacean zooplankton towards warming in shallows lakes with contrasting trophic states indicated that warming may change the community of zooplankton and lead to the heat tolerant and plant-associated taxa dominated in the heating treatments. Warming also changed the size class of community and increased the proportion of medium-sized individuals companied with the decrease of large and smallindividuals. Except delaying the peak time of Copepod in high nutrient mesocosms, warming did not make other peak time advance or delay in both heated mesocosms, due to the initial temperature was well above 15 ℃ in the ambient treatments, allowing for fast production and growth in all scenarios for crustacean zooplankton. The mean abundance and biomass of cladoceran decreased in the high nutrient treatments and increased in the low nutrient treatments significantly when elevated the temperature. It was resulted from the changes of nutrient load by warming, which leading to the changes of phytoplankton. In the high nutrient treatments, warming decreased the concentrations of nutrient and biomass of phytoplankton, which was opposite in the low nutrient treatments.(2) An outdoor mesocosms was performed to study the co-effects of warming and eutrophication on crustacean zooplankton recruitment and spring community dynamics. The results showed that both elevated temperature and added nutrition may have considerable effects on spring recruitment and pelagic establishment. Warming mainly changed the spring phenology and advanced the beginning time of recruitment and the occurrence in the water column for both the copepods and cladocerans, while also advanced the peak time of copepods. Warming significantly increased the average abundance and the relative proportion of Cladoceran in water column. Nutrient addition changed the abundance of crustacean zooplankton through the change of phytoplankton by bottom-up mechanism. Nutrient addition had little effect on spring phenology, it only inhibit the recruitment and community establishment in water column of Cladoceran. Because of the difference in life history, the cladocerans will benefit more from elevated temperature than copepods do, which is likely to change the dominance pattern of zooplankton communities in spring in a future climate-change scenario. |
PDF Full Text Request