ABSTRACT
Gorgonians are important components of coastal ecosystems, as they provide niches, natural compounds with medical applications and are used as bioindicators. Species composition and assemblage structure of gorgonians (Anthozoa: Octocorallia) were studied along a bathymetric profile in the Southern Mexican Pacific coast. Species composition was based on specimens collected within a depth range of 0-70m in 15 sites. The relative abundance of species was determined in six sites at four depths (5, 10, 20 and 25m) using three 10m2 transects at each depth level. Twenty-seven species of gorgonians belonging to six genera and three families were registered. The species composition varied with depth: 11 species were distributed between 0-25m depth, while 17 species were found between 40-70m depth interval. The shallow zone is characterized by a relatively large abundance of gorgonians, dominated by colonies of Leptogorgia cuspidata and L. ena. In contrast, the deepest zone was characterized by relatively low abundance of gorgonians, dominated by L. alba, the only species observed in both depth intervals. The similarity analysis showed differences in the composition and abundance of species by depth and site, suggesting that the main factor in determining the assemblage structure is depth. Results of this study suggest that the highest richness of gorgonian species in the study area may be located at depths of 40-70m, whereas the highest abundances are found between 5 and 10m depth. This study represents a contribution to the poorly known eastern Pacific gorgonian biota.
La composición de especies y estructura de la comunidad de gorgonáceos se determinó a lo largo de un perfil batimétrico en la costa suroeste del Pacífico Mexicano. La composición de especies se realizó a través de una revisión y recolecta de especímenes entre 0 y 70m de profundidad en 15 sitios de muestreo. La caracterización de la estructura de la comunidad se realizó en seis sitios, en los cuales se colocaron tres transectos de 10m² cada uno a 5, 10, 20 y 25m de profundidad. Se encontraron 27 especies de gorgonáceos pertenecientes a seis géneros y tres familias; aunque seis especies requieren ser confirmadas. La mayor riqueza de especies se registró entre 40 y 70m. La estructura de la comunidad entre 5 y 25m de profundidad mostró la existencia de dos zonas con la misma composición de especies pero con diferente abundancia relativa: una somera entre 5 y 10m de profundidad, caracterizada por una mayor abundancia de gorgonáceos y dominado por colonias de Leptogorgia cuspidata y Leptogorgia ena y una zona profunda entre 20 y 25m de profundidad, caracterizada por una baja abundancia de gorgonáceos y dominada por colonias de Leptogorgia alba.
Subject(s)
Animals , Anthozoa/classification , Ecosystem , Biodiversity , Mexico , Population DensityABSTRACT
Polychaetes inhabiting deep-sea soft bottoms from the southeastern Gulf of California were collected during four oceanographic cruises during 2000 and 2001. Sampling of benthic organisms was performed with a benthic sledge to collect epifauna and a Karling dredge for epifauna and infauna, in a depth range from 732 to 2 250 m. A list of the polychaetes that were collected and their distribution are presented here. A total of 73 species (distributed among 33 families) were identified. Moreover, 11 species were identified only to genus level and 20 species only to family level. With the exception of Ancistrosyllis hartmanae and Melinnampharete eoa, all identified species have been previously reported in soft bottoms of the Gulf of California or in adjacent areas. Additional previously unreported information is provided herein regarding depth ranges, geographical distribution, morphology and tubes inhabited by the organisms. The morphology of the ampharetids Amage sp. and Samytha sp. does not coincide with that of other species in these genera reported for the Gulf of California, which suggests that they are probably undescribed species.
Se recolectaron anélidos poliquetos de fondos profundos del SE del golfo de California durante cuatro campañas oceanográficas entre 2000 y 2001. El muestreo de organismos bentónicos se llevó a cabo mediante una draga de arrastre bentónica para recolectar epifauna y una draga tipo Karling para epifauna y endofauna, en un intervalo de profundidad de 732 a 2 250 m. Se presenta un listado de poliquetos con su distribución dentro del área de estudio. En total se identificaron 73 especies (distribuidas en 33 familias). Además, 11 especies fueron identificadas a nivel genérico y 20 a nivel de familia. Con excepción de Ancistrosyllis hartmanae y Melinnampharete eoa, todas las especies habían sido registradas en fondos blandos del golfo de California o zonas adyacentes. Se proporciona nueva información sobre los intervalos de profundidad, la distribución geográfica, la morfología y la descripción de tubos donde los organismos fueron encontrados. Las características morfológicas de Amage sp. y Samytha sp. no coinciden con las especies de estos géneros registradas en el golfo de California, lo que sugiere que podría tratarse de especies no descritas.