There are a lot of factors that influence the composition and abundance of zooplankton communities which are namely physical, chemical and biological. Factors recognised mostly are temperature, pH, and availability of food, these act simultaneously causing it to interact to different degrees resulting the structure of zooplanktons to be in a variety.
Temperature controls the reproductive rate, population size and metabolism of the species (Edmondson, 1965) while in tropical regions, precipitation and wind are the physical factors which are significant in affecting the composition of zooplanktons (Matsumara-Tundinsi & Noguiera, 1996). Predation by fish may affect its structure as well in accordance with the fish feeding mode: selective feeders, differential capture of organisms, tendency to eliminate large species which are replaced by less vulnerable forms (Brooks & Dodson, 1965). The diversity of species may be lesser sometimes but single species may be superior over other groups in terms of its abundance, and this has a relation to hydrography, physico-chemical factors and availability of phytoplankton. Temparature and pH are both positively connected to species diversity while conductivity and salinity are negatively related. Quality and quantity of food, interference competition, predation and ecological conditions influence plankton communites which will lead in favoring species over others that is why reservoirs mostly found in Brazil is being dominated by a species of zooplanktons called Rotifers.
Based from a study conducted by (Lirio et al, ) Copepods, which is another group of zooplankton, became dominant in Laguna de Bay on which it can be differentiated to the data gathered by (Sampaio et al, 2002) wherein Rotifers normally outweigh tropical waters. Species diversity is smaller during hot season and higher during cold season which will come up an accurate evidence that changes in water temperature would really play a significant role when it comes to the richness of some copepods (Duggan et al, 2001)