Estruturação taxonômica e funcional da comunidade zooplanctônica e a ocorrência do Ceratium furcoides, um dinoflagelado invasor, em uma lagoa costeira subtropical dominada por cianobacterias

Abstract

The zooplankton community was studied in a subtropical coastal lagoon used for public supply and which has in its history, the limitation of nutrients and the dominance of cyanobacteria. The aim of the present study was to analyze the taxonomic composition and functional diversity of zooplankton, observing its spatial and temporal changes in Lagoa do Peri (Florianópolis-Santa Catarina), a coastal lagoon in the Brazilian South-Atlantic region. For that, monthly samplings of zooplankton and environmental variables were carried out in four regions of the lagoon, between January 2017 and December 2018. The zooplankton community was characterized by high density of rotifers, small cladocerans and copepods. Rotifers were responsible for more than 60% of the relative abundance of zooplankton in all sampling months. The total richness of the zooplankton community corresponded to 47 taxa with rotifers being the most abundant in all sampling points and periods. Both, spatial and temporal heterogeneity were evaluated. The presence and historical dominance of filamentous cyanobacteria in the Peri lagoon appear to be the main regulatory factors for zooplankton, exerting a bottom-up effect and favoring the dominance of rotifers. On the other hand, wind speed and water temperature influenced zooplankton diversity, being positively related to increased species richness and functional diversity. Functional richness (FRic) and functional uniformity (FEve) indicated that functional diversity of zooplankton in Lagoa do Peri is low, ranging from 0.1 to 0.5. Also, there was greater functional diversity in summer than in the winter. The functional divergence (FDiv) varied between 0.5 and 0.9, with the highest values recorded in the summer. The greater FDiv in summer indicates that despite the dominance of cyanobacteria, there is probably a greater range of available resources that allow the co-occurrence of zooplankton species with different niches. In addition, higher temperatures favor the reproduction of different species. Thus, groups of species that are less abundant in the plankton (scraper cladocerans and filter feeder copepods) may coexist with those usually predominant (rotifers and raptorial copepods). The seasonal focus revealed substitutions of functional traits or the loss of these attributes providing an indication of functional homogenization. These findings are subsidies to improve the analyses of the zooplankton community in environmental studies, so that can contribute to no loss of information and damage to communities and the ecosystem.