The effects of CO2 on sestonic stoichiometry and community structure of crustacean zooplankton in a eutrophic lake: Increased competitive ability of Bosmina

Abstract

To explore the effects of CO2 concentration on the sestonic stoichiometric values and the community structure of crustacean zooplankton in a eutrophic lake, in situ microcosm experiments were conducted at the Lake Taihu Ecosystem Station in spring and summer of 2012. The experimental treatments were three concentrations of CO2, 270, 380 and 750 ppm, which represented preindustrial and present levels and the level predicted for the end of this century, respectively. The elevated atmospheric CO2 concentration increased the sestonic C:P ratio, particularly in the spring when the C:P ratio was two-fold greater at the high level of CO2 than at the low level of CO2. As a result, the contribution of Bosmina to total crustacean zooplankton abundance increased, most likely because of the low phosphorus content and high adaptability to foods with large elemental ratio variation. The other dominant crustacean zooplankton genera, including Daphnia, Ceriodaphnia, Diaphanosoma and Sinocalanus, had no response to the change in pCO2 during the microcosm experiments. The shift in crustacean zooplankton community structure between two seasons was primarily due to the transition of the phytoplankton community.