A presença de peixes anuais influencia o banco de propágulos dormentes de invertebrados aquáticos em áreas úmidas intermitentes?

Abstract

Wetlands play an important role due to its ecosystem services. The dry soils from intermittent wetlands accumulate a variety of dormant structures that adopt survival strategies against adverse environmental conditions. These strategies ensure the survival of the dormant propagule bank at the beginning of the hydrological cycle, allowing this bank to act as food source for late colonizers, which support the establishment of important trophic relationships, such as predation. The effects of predation are diverse and may both diminish or elevate the diversity of the local zooplankton community. Thus, the general objective of this work was to evaluate the influence of the presence of annual predatory fish over the structure and emergence of the dormant propagule bank of aquatic invertebrates in intermittent wetlands. Therefore, it was selected 8 wetlands from the surroundings of the Lagoa do Peixe National Park, four of them with the presence of annual fishes. The dry sediment of each wetland was sieved and homogenized in order to perform two different procedures. In the first one, a sub-sample of each wetland was floated and, in the second step, a sub-sample was incubated and parameters as photoperiod, temperature and oxygen were controlled for 36 days. The results reject the two hypotheses of this work, in other words, the density of dormant stages was similar between the areas (U = 10, df = 1, p = 0.564) and there was no variation in body size of aquatic invertebrates in areas under predation pressure from annual fish (x2 = 0.555, df = 3). The species richness (F1.6 = 0.040, p = 0.849), abundance (F1.6 = 0.692, p = 0.437) and composition (r2 = 0.069, p = 0.827) was similar among wetlands. However, there was difference in the temporal increase of abundance among taxa, as well as certain species are more related to certain areas. These results should be interpreted taking into account that the eclosion of efipial eggs in controlled experiment conditions eliminates others relevant factors that occurs in natural environments, such as abiotic factors related to luminosity, temperature and salinity, as well as several biotic interactions. Then, the study with dormant propagule banks offers information about the aquatic invertebrate community, but there is still a lack of effort in order to increase the understanding of their responses to different environmental conditions.