Influence of the chlorophyll-a gradient on the community structure of plankton microcrustaceans (Cladocera and Copepoda) in a Neotropical reservoir

Abstract

Fish farming in net cages is considered as an alternative to food production in response to elevated population growth, and zooplankton is an important resource to the development of this economic activity. We (i) compared microcrustacean composition in eutrophic and oligotrophic habitats under net tank infl uence, (ii) investigated changes in species distributions in these habitats, and (iii) indicated which chlorophyll-a concentrations presented thresholds that alter community structure. We expected different responses of species to changes in chlorophyll-a concentration due to net cage management, as chlorophyll-a represents an estimate of food availability.Microcrustacean samplings and chlorophyll-a estimation were made upstream, downstream and close to the net cages, during 120 days, in the Rosana Reservoir (Brazil). Species composition differed signifi cantly (p<0.05) among habitats where in the eutrophic environment was found the largest number of species. However, only in the eutrophic habitats did frequency of occurrence and relative abundance of some species change with chlorophyll-a variation. Thus, net cage management infl uenced species distribution only in the most productive habitat. These responses can affect ecosystem processes related to trophic dynamics as secondary productivity and nutrient cycling.

Effects of cage fish (Oreochromis niloticus L. 1758) farming on the water quality in selected bays of the Bukavu basin, Lake Kivu, Democratic Republic of the Congo

“…Tibúrcio et al (2021) who found the same results in in the Rosana Reservoir (Brazil). However, the authors stated further that chlorophyll-a represents an estimate of food availability in the ecosystem(Tibúrcio et al 2021). Therefore, the high concentration of Chl a could be, according toPergent et al.…”