Temporal variation and spatial factors affecting zooplankton communities in freshwater rock pools

Abstract

Most ecological studies have focused on one snapshot in a single location and the same taxonomic group. However, relatively few studies have explored different taxonomic groups over multiple periods, particularly in ephemeral Neotropical ecosystems. This study investigates the seasonal dynamics of zooplankton communities and their responses to environmental variables in temporary pools in the Seasonally Dry Forest Ecosystem, Pernambuco, Brazil. We examined the seasonal fluctuations in species abundance, diversity, and evenness of Cladocera, Copepoda, and Rotifera in five temporary rock pools. Although these pools are meters apart, they vary considerably in size and drought sensitivity, leading to distinct seasonal dynamics mediated by water availability. We asked (i) how do species abundance, diversity, and evenness vary seasonally? (ii) Do these seasonal shifts differ between Cladocera, Copepoda, and Rotifera? And (iii) How do water environmental variables and spatial distance of pools influence zooplankton species composition? We hypothesized that Cladocera and Copepoda are positively affected by the rainy season, but Rotifera is mostly common in the dry season. Our findings underscore seasonality as the primary driver influencing the abundance and composition of zooplankton communities. We observed higher abundance of Cladocera and Rotifera during the post-rainy season, but Copepoda was dominant in the rainy season, leading to a strong seasonal variation in species evenness. These differences among groups highlight the importance of considering biological differences when understanding the ecological drivers of temporary freshwater ecosystems.