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Metacommunity theory assumes that communities are not only affected by local processes but also interact with each other through dispersal. It is generally assumed that zooplankton can quickly recolonise water bodies after droughts, via both dormant egg banks and dispersal of resting eggs. Hitherto, few studies have evaluated the relative importance of resting egg bank recruitment and airborne dispersal in the re-establishment of zooplankton communities. As zooplankton communities of temporary ponds are frequently confronted by dry phases and have the potential to build up large resting egg banks, we expected the contribution of such resting egg bank to be more important than airborne dispersal for community re-establishment after drought. We also expected that the relative importance of airborne dispersal would be higher for rotifers than for microcrustaceans, as the former group has key traits (e.g. smaller body sizes, shorter generation times and higher reproductive potential) that are thought to enhance the dispersal to and colonisation of vacant habitat. We performed an enclosure experiment in the vicinity of seven temporary ponds, simulating the colonisation by zooplankton exclusively via the resting egg bank, exclusively via airborne dispersal and via both pathways simultaneously. The enclosures were sampled five times during a period of 53 days. Our results show that zooplankton organisms were able to rapidly colonise the experimental enclosures, either through their resting egg bank or by airborne dispersal of resting eggs. However, microcrustaceans tended to rely more on recolonisation from the resting egg banks than rotifers, at least for the spatial and temporal scales considered in our study.

The changes in species composition between habitat patches (beta diversity) are likely related to a number of factors, including environmental heterogeneity, connectivity, disturbance and productivity. Here, we used data from aquatic environments in five Brazilian regions over two years and two seasons (rainy and dry seasons or high and low water level periods in floodplain lakes) in each year to test hypotheses underlying zooplankton beta diversity variation. The regions present different levels of hydrological connectivity, where three regions present lakes that are permanent and connected with the main river, while the water bodies of the other two regions consist of permanent lakes and temporary ponds, with no hydrological connections between them. We tested for relationships between zooplankton beta diversity and environmental heterogeneity, spatial extent, hydrological connectivity, seasonality, disturbance and productivity. Negative relationships were detected between zooplankton beta diversity and both hydrological connectivity and disturbance (periodic dry-outs). Hydrological connectivity is likely to affect beta diversity by facilitating dispersal between habitats. In addition, the harsh environmental filter imposed by disturbance selected for only a small portion of the species from the regional pool that were able to cope with periodic dry-outs (e.g., those with a high production of resting eggs). In summary, this study suggests that faunal exchange and disturbance play important roles in structuring local zooplankton communities.

Human activities are exposing freshwater ecosystems to a wide range of stressors, whose direct and indirect effects can be alleviated or exacerbated through interactive effects with dynamic environmental drivers. This study used long-term data from two Neotropical lacustrine freshwater systems (Batata Lake, an Amazonian floodplain lake and Imboassica lagoon, an Atlantic coastal lagoon) subjected to different kinds of environmental fluctuations (i.e., flood pulse and sandbar opening) and anthropogenic impacts (i.e., siltation and eutrophication). Our objective was to determine whether the effects of human perturbations are contingent on modifications of important biotic and abiotic characteristics through environmental variability. For both ecosystems, environmental variability consistently interacted with anthropogenic perturbations to alter most of the variables analyzed, such as nutrient dynamics, chlorophyll- a concentration, zooplankton and benthic invertebrate species richness, and temporal community stability, which indicates that interactive effects between environmental variability and anthropogenic perturbations may impact a myriad of ecosystem properties. Furthermore, the nature of these interactive effects was highly dependent on the variable considered and on the ecosystem analyzed. For example, at Imboassica lagoon, sandbar openings interacted synergistically with trophic state to increase the phosphorus concentration in the water column. At Batata Lake, flooding generally alleviated the negative effects of siltation on species richness by both diluting inorganic suspended material concentration and by promoting local recruitment from the regional species pool. Such results indicate that our ability to understand and predict the outcome of anthropogenic impacts on inland aquatic systems can be hampered if we consider human stressors as “static” phenomena disconnected from dynamic interactions with major local environmental drivers.