Abundance, composition and spatial variation in the egg bank of a tropical zooplankton community

Resting eggs have important ecological roles in zooplankton communities, but characterizations of egg banks in tropical systems remain scarce. Here, we describe the abundance, composition and spatial variation in the egg bank of a tropical zooplankton community in a shallow aquatic system (Imboassica lagoon, Brazil). Due to sporadic disturbances by sandbar openings at this system, we hypothesized that the abundance and species richness close to the sandbar is lower when compared to other sites. Sediment samples were collected at four sampling stations, and the egg bank was analyzed using ex situ hatching experiments. Hatchlings from 21 rotifer and five cladoceran species were identified considering all sampling stations. The number of hatchlings at the sampling stations ranged from 14.2 (+/- 3.8 SE) to 192.8 (+/- 37.1), whereas species richness ranged from 3.6 (+/- 0.7) to 12.2 (+/- 0.5) in 100 g of wet sediment. Abundance and species richness were similar at three of the sampling stations, suggesting low spatial variations in the egg bank of shallow systems. Significantly lower values for abundance and species richness were found close to the sandbar when compared to the other sampling stations, probably as a result of local and recurrent disturbances due to artificial sandbar openings. The presence of an egg bank is a possible mechanism for facilitating the reestablishment of active populations after disturbances by sandbar openings and consequent increases in salinity at Imboassica lagoon.