Zooplankton rhapsody: Unexpected response in community following increased fish predation

摘要

The impact of increased fish density on the crustacean zooplankton was studied in a small,forest lake. Interestingly and contrary to our hypothesis, increased fish density resulted inan increase in biomass of large-sized cladocerans, but a decrease in biomass of smaller anddominant cladoceran species. Thus, the effect of increased planktivory of fish was likelytempered by compensatory dynamics of zooplankton, wherein abundance of some speciesincreased to compensate for population decreases by other species. This change in the relativespecies composition of zooplankton was seen as the increased diversity in crustaceanzooplankton community. We conclude that instead of simple “top-down” or “bottom-up”regulation of zooplankton, the diverse array of connections among species is more likelyto cause community dynamic fluctuations in zooplankton. Moreover, behavioural changese.g. habitat change of fish may also have a pronounced effect on the response of zooplanktoncommunity on fishing.