Akademik Veri Yönetim Sistemi
Shallow Lakes, Natal, Brezilya, 01 Mart 2021, ss.1-20, (Özet Bildiri)
While global climate change has major impacts on freshwater ecosystems, a mechanistic understanding of these effects on food web dynamics is poorly understood. A key effect of climate change is increased allochthonous dissolved organic carbon (DOC) input to aquatic environments, which serves as an energy source for heterotrophic plankton and altering plankton dynamics. We aimed to link pattern and process in a plankton ecosystem by comparing the bottom up effects of DOC (i.e., Humin Feed and local source) to the top-down effects of zooplankton with contrasting grazing selectivity (Daphnia vs. calanoid copepods) on phytoplankton biomass and composition in a series of laboratory and in-situ mesocosm grazing assays. We expected that both DOC and zooplankton would reduce phytoplankton biomass; stronger herbivory by Daphnia compared to copepods; and stronger grazing on larger sized phytoplankton. The laboratory experiment revealed that total phytoplankton biomass was reduced by DOC, and that smaller cells were reduced more than larger ones. The grazers reduced total phytoplankton biomass, though effects varied such that zooplankton increased the biomass of smaller phytoplankton while they reduced the biomass of larger phytoplankton. Moreover, copepods had a stronger effect on phytoplankton biomass compared than Daphnia, but only in the treatments with DOC. The mesocosm experiments; however, showed that both DOC sources increased total phytoplankton and species-specific biomass, except Chlorophyta spp. that decreased with presence of Humin Feed. Overall, the results highlight the role of zooplankton grazing traits not only for regulating top-down effects but also for the bottom up effects of DOC.