Sinkhole-like structures as bioproductivity hotspots in the Abrolhos Bank

• The sinkhole-like reef structures described for the Abrolhos Bank aggregate biomass.
• Higher nutrient content, microbial abundance and activity are found in the structures.
• Higher fish abundance suggests sinkhole-like structures as productivity hotspots.
• This system should be managed and represented in the regional marine protected areas.

We performed a biological survey in the novel system of sinkhole-like structures (“buracas”) of the Abrolhos Bank, Brazil. We found dissimilar benthic assemblages and higher nutrient concentration, microbial abundance (and activity) and fish abundance inside the buracas than in the surrounding rhodolith beds. Our results support the view that these cup-shaped structures trap and accumulate organic matter, functioning as productivity hotspots in the mid and outer shelf of the central portion of the Abrolhos Bank shelf, where they aggregate biomass of commercially important fishes. This distinctive system is being increasingly pressured by commercial fisheries and needs urgent management measures such as fishing effort control and representation in the network of Marine Protected Areas (MPAS).