Summer micro- and mesozooplankton from the largest reef system of the South Atlantic Ocean (Abrolhos, Brazil): Responses to coast proximity

Abstract

Zooplankton samples were collected in summer and in three distinct Neotropical areas (the coastal reef arc, the outer reef arc and the Abrolhos Archipelago). Two stations in each sampling area were established (a reef station and an outer station) to sampling zooplanktonic assemblage with two different mesh sizes (64- and 200-μm plankton nets). Approximately 110 taxa were identified, and the assemblages from the two nets were significantly different. Zooplankton abundances were three orders of magnitude higher in the 64-μm net samples with an average abundance of 217,000 ± 93,418 ind m−3 (64-μm net) and 189 ± 122 ind m−3 (200-μm net). A permutational multivariate analysis of variance (PERMANOVA) of the zooplankton community structure revealed significant differences between all three regions and showed a heterogeneous distribution of these animals, even though no significant differences were observed in terms of abundance for both net catches (two-way ANOVA, P > 0,05). SIMPER analyses showed that most highly abundant taxa occurred in all sampling areas. Though, some other taxa were clearly identified as characteristic of a particular area by their relative frequency, rather than relative abundance. It is hypothesized that variations in suspended particle concentration play an important role in the observed differences in community composition. Our results suggest that the pelagic components of these reef zooplankton assemblages may be as important as demersal zooplankters to benthic-pelagic coupling. Because the much higher abundance of the microzooplankton assemblages compared to the mesozooplankton is a common feature of reef communities, the studies that use only coarse nets miss assessing the contribution of a large and important portion of the reef zooplankton assemblage and therefore misinterpret the community as a whole.