Study of benthic fauna asociated to volcanic structures of Bransfield Strait central basin

In English:

During GEBRAP 96 Survey, 9 trawls from 647 to 1592 meters in depth were carried
out on underwater volcanic structures located at the central basin of
Bransfield Strait. Its objective was to collect lithological samples and
associated benthic fauna, supposedly exposed to hydrotermalism.

A rocky dredge of 0.80 x 0.30 (hotizontal and vertical opening), with 10 mm of
mesh size and leather protection, was basically used. Samples were sieved and
separated into 35 faunistic groups whose numerical abundance and biomass were
quantificated on board.

At neither of four sampled volcanic structures, invertebrates with hydrothermal
characteristics were found, being Hexactinellida, Polychaeta (Errantia y
Sedentaria), Ophiuroidea y Ascidiacea more frequent taxa.

Mainly numerical abundance corresponded to Polychaeta Sedentaria (56%) and
Ophiuroidea (14%), and highest biomass (we weight) to Porifera (38%),
Ophiuroidea (16.5%) and Polychaeta Sedentaria (10%).

Benthic communities were basically constituted by deposit-feeding fauna,
Polychaeta Sedentaria (Maldanidae) and Ophiuroidea as correspond to deep areas
related to mud or mixed sediments, subjects to high sedimentation rate. The
presence of suspension-feeders, Porifera, Bryozoa, Polychaeta Sedentaria
(Serpulidae), Brachiopoda, and Crinoidea, was in relation to coarse sedimentary
deposits (gravels to blocks), at more slope zones, exposed to current, mainly
in volcanic structure.

En Espanol:

Durante la campana GEBRAP 96 se realizan 9 arrastres entre 647 m y 1592 m de
profundidad sobre los edificios volcanicos submarinos existentes en la cuenca
central del estrecho de Bransfield, con el objetivo de obtener muestras
litologicas y de la fauna bentonica asociada, presumiblemente sometida a
hidrotermalismo.

Se utilizo basicamente una draga de roca de 0.80 x 0.30 m (abertura horizontal
y vertical) con red de 10 mm de malla y proteccion de cuero. Las muestras se
tamizaron y separaron en 35 grupos faunisticos, cuyas abundancias numericas y
ponderales fueron cuantificadas a bordo.

En ninguna de las cuatro estructuras volcanicas muestreadas se han encontrado
invertebrados de caracteristicas hidrotermales, siendo Hexactinellida,
Polychaeta (Errantia y Sedentaria), Ophiuroidea y Ascidiacea los taxones mas
frecuentes. La mayor abundancia en numero correspondio a Polychaeta Sedentaria
(56%) y Ophiuroidea (14%) y en biomasa (peso fresco) a Porifera (38%),
Ophiuroidea (16.5%) y Polychaeta Sedentaria (10%).

Las comunidades bentonicas estuvieron constituidas basýcamente por fauna
detritivora, Polychaeta Sedentaria (Maldanidae) y Ophiuroidea, como corresponde
a ýreas profundas asociadas a depositos fangosos y mixtos, sujetos a elevadas
tasas de sedimentacion. La presencia de suspensivoros, Porifera, ryozoa,
Polychaeta Sedentaria (Serpulidae), Brachiopoda, y Crinoidea, estuvo
relacionado con la presencia de depositos sedimentarios groseros (graves a
bloques), en zonas de mayor pendiente, sometidas a corrientes.