Meroplankton spatial structure and variability on Abrolhos Bank and adjacent areas, with emphasis on brachyuran larvae

• Meroplanktonic larvae were abundant throughout the Abrolhos Bank and shelf area.
• Meroplankton and brachyuran assemblages differed between shallow and deep areas.
• The brachyuran larval assemblage had a fairly homogeneous distribution over the bank.
• The reef ecosystem was likely the major larval source to the pelagic environment.
• Oceanic and tidal currents associated to larval behavior control larval distribution.

The spatial distribution of meroplanktonic stages of benthic invertebrates was investigated on the Abrolhos Bank and adjacent shelf and oceanic areas during winter. Meroplanktonic larvae occurred at all stations, with higher total density in shallow sites, the same being observed for eight out of 14 taxonomic groups identified, including brachyurans. Brachyuran larvae were analyzed in detail, leading to a list of 61 taxa for the area, 24 of which accounted for half of the total brachyuran larval density. No estuarine species of brachyuran larvae was recorded in the surveyed area, suggesting that continental input from nearby river estuaries is negligible on the shelf ecosystem. Larvae of coastal species, such as Acantholobulus schmitti, Hexapanopeus spp. and Pinnixa sayana dominated at certain innermost stations and were not found on the outer shelf, suggesting the existence of larval retention mechanisms within the reef system. The occurrence of a single cluster of shallow stations in ordination analysis, associated with high densities of early developmental stages throughout the Abrolhos Bank, indicates a relatively homogeneous distribution of larval assemblages over the bank and the existence of a certain degree of connectivity among spatially separated populations, by means of larval dispersion.