The effect of elevated CO2 on autotrophic picoplankton abundance and production in a eutrophic lake (Lake Taihu, China)

Abstract

The effects of elevated CO2 concentrations on the community structure and primary production of the autotrophic picoplankton of a eutrophic lake were studied in Lake Taihu, China. We conducted in situ experiments with three CO2 concentrations (270, 380 and 750ppm) over four seasons during 2012 and 2013. Our results showed that phycocyanin-rich picocyanobacteria were dominant in winter and that photosynthetic picoeukaryotes were prevalent during the other three seasons. CO2 elevation could significantly increase the abundance of photosynthetic picoeukaryotes in all seasons except winter, but did not have any influence on picocyanobacterial abundance. CO2 enrichment caused an increase in the primary production of the picoplankton community in most seasons, and significant differences were observed among the treatments in summer and winter. In addition, the contribution of picoplankton to total primary production significantly increased under higher CO2 concentrations in winter. The increase in the abundance of photosynthetic picoeukaryotes and the primary production of picoplankton under high CO2 concentrations may reduce the transfer of matter and energy to higher trophic levels and increase the importance of the microbial food web.