Large-scale spatial variability of decapod and stomatopod larvae along the South Brazil Shelf

- Our sampling area covers 13º of latitudinal gradient and up to 400 km offshore.
- Large-scale maps of abundance of decapod larval groups are presented.
- Correlations between larval abundance and abiotic factors were tested.
- The oceanographic environment influencing larval composition is discussed.
- Spatial distributions of larvae are compared to parental habitats.

The spatial distribution of a spring/summer community of combined decapod and stomatopod larvae along the southwestern Atlantic shelf, and its possible linkages with hydrographical processes and with parental habitats were investigated. Vertical plankton hauls were performed between 21 °S and 34 °S, at 107 stations, distributed along 2000 km of coastline and up to 400 km offshore, during late spring 2010 and early summer 2011. Salinity and temperature were obtained with a CTD/rosette system, which provided seawater for chlorophyll and nutrient concentrations. A coupling between chlorophyll concentration and abundance of early larvae of benthic species was observed, suggesting that the larval release could be synchronized with phytoplankton maxima. Our findings indicated that the composition and abundance of larvae are strongly influenced by distance from the coast, freshwater sources and water mass distribution. Assemblages of larvae were observed in the most relevant environmental scenarios: (1) coastal environments, dominated by intertidal, shallow water or coastal species; (2) offshore environments, with predominance of holopelagic and deepwater species; and (3) southern continental runoff, mainly represented by benthic neritic crabs and shrimps. In addition, the large-scale distribution of larvae revealed a relationship with the adult's distribution, shown mainly by the occurrence of larvae transported from the estuaries in the inner shelf and by larvae of the deepwater fauna found mainly along the outer shelf.