Seabed pockmarks associated with deepwater corals off SE Brazilian continental slope, Santos Basin

Several factors bear evidence of chemosynthetic ecosystem occurrence in the Brazilian coast; these motivated our investigation to sample three pockmarks located on the continental slope off SE Brazil (26degreesS and 46degreesW) at similar to700 in depth. The crater-like features were similar to I kin in diameter and 100 in in depth, and were identified with an echo-sounder (EK-500). They were sampled along two transects using a rectangular dredge. Our main objective was to identify possible evidence of a seep-related community. The surrounding sediments of the pockmarks seem to be filled with coral rubble harboring a rich fauna of metazoans including epilithic and chasmolithic organisms. A total of 9565 organisms were sampled. The most abundant group was the Ophiuroidea, followed by Cirripedia and Polychaeta. A number of new occurrences and new species were registered. The polychaete worm Amelinna was the first record for the Atlantic Ocean, which has been found in reducing habitats such as wood islands. The echo-sounder records also showed the presence of big deepwater coral mounds associated with the edge of the pockmarks. These features are similar to20 in in height and from 180 to 360 in wide. Records of demersal fishes were also registered right above coral mounds. The presence of deepwater coral mounds at the edge of pockmarks may be related to the flow of the cold, oxygen-rich Antarctic Intermediate Water over the bottom, or else may benefit from the fertilization of the water by the microseepage of hydrocarbons from the sediment. We suggest a more thorough survey in order to map and recognize these environments. Furthermore, our findings may shed some light on new research perspectives concerning the ecology, biogeography and evolution of reducing habitats off the Brazilian coast. (C) 2004 Elsevier B.V. All rights reserved.