Whale bone communities in the deep Southwest Atlantic Ocean

Abstract

Whale falls are considered important habitats contributing to biodiversity, evolutionary novelty and connectivity of deep-sea environments. The organic input of a whale carcass increases the community standing stock and changes the species composition in comparison with the surrounding benthic infauna. However, endofauna living inside the bone matrix seems to contribute to the overall whale-fall biodiversity. Benthic infauna is distributed in bathymetric ranges, but the contribution of endofauna from whale bones in different depth regions is still not accessed. We investigated endofauna composition of whale vertebrae of a humpback whale (Megaptera novaeangliae) in two distinct depths, bathyal (1500 m, stations SP1500 and ES1500) and abyssal (3300 m, stations SP3300, RJ3300 and ES3300), deployed in the SW Atlantic Ocean. Even though each bone represented the same energetic input, a higher density of endofauna was found at 1500 m while diversity was higher at 3300 m. The whale-fall endofaunal assemblages were distinct according to the depth zones. SP3300 site was distinct from bones placed at 1500 m depth, while the assemblages at RJ3300 and ES3300 sites consisted of a mixture between both depths. This pattern seems to be related to the water currents of the region, once SP3300 was under influence of the Antarctic Bottom Water (AABW), while SP1500 and ES1500 were dominated by the North Atlantic Deep Water (NADW).