Horizontal distribution of pelagic crustacean zooplankton biomass and body size in contrasting habitat types in Lake Poyang, China.

To evaluate the possible effects of habitat type on crustacean plankton (hereafter zooplankton) biomass and body size, a 5-year study (2011 to 2015) was conducted during wet seasons in three habitats in Lake Poyang, China. The lacustrine habitat with the most stable hydrologic regime had the highest zooplankton biomass coinciding with the highest phytoplankton biomass. The riverine habitat with the lowest Secchi depth overall had the largest zooplankton body size, but high zooplankton biomass only in high water level years. The seasonally inundated floodplain habitats had the lowest zooplankton biomass and the smallest individual body size, coinciding with the lowest phytoplankton biomass and the highest predation pressure, the latter indicated by a low zooplankton: phytoplankton biomass ratio (ZB:PB). Multiple linear regression analyses indicated that pelagic zooplankton assemblages were primarily influenced by phytoplankton biomass in lacustrine habitat, by advection and turbidity in riverine regions, and by predation pressure in seasonally inundated floodplain region. We conclude that the importance of bottom-up and top-down effects on zooplankton biomass and body size varied with habitat type in Lake Poyang.