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ON THE PELAGIC COPEPOD COMMUNITY OF THE CENTRAL MEXICAN TROPICAL PACIFIC (AUTUMN, 1990)

2000; Brill; Volume: 73; Issue: 6 Linguagem: Inglês

10.1163/156854000504778

1568-5403

Suárez-Morales, Franco-Gordo, Saucedo-Lozano,

Ocean Acidification Effects and Responses

[Zooplankton samples were collected during autumn (September, 1990) off the coasts of the Mexican state of Jalisco, northwestern Mexico, in the eastern tropical Pacific. Taxonomic analysis of the pelagic Copepoda yielded 44 species, Subeucalanus subcrassus, Temora discaudata, Undinula vulgaris, Euchaeta marina, Centropages furcatus, and Candacia catula being the overall dominant forms. Together they represented almost 75% of total copepod numbers. The influence of the North Equatorial Current, related to tropical conditions, is clear in the local community structure. Shannon-Wiener diversity was homogeneously high (over 3.2 bits/ind.) in most samples. Highest densities were recorded in the neritic zone. Overall copepod density values suggest a moderate to high productivity in the surveyed area. Station clustering showed a neritic and an oceanic facies, their limits roughly determined by the outer border of the narrow shelf. However, the coast-ocean gradient is moderate, with abundant neritic-oceanic forms, and oceanic representatives over the continental shelf. These effects may result from across-shelf mixing of neritic and oceanic water due to (1) the effect of inshore-wards wind-driven advective processes, and (2) the narrowness of the continental shelf. It is suggested that these processes favour a degree of homogeneity of the copepod community along this and other parts of the Mexican tropical Pacific. Durante el otono (septiembre de 1990) se recolectaron muestras de zooplancton en la costa del estado de Jalisco, en el Pacifico Tropical Oriental. El analisis taxonomico de los copepodos pelagicos produjo 44 especies. Las formas dominantes fueron Subeucalanus subcrassus, Temora discaudata, Undinula vulgaris, Euchaeta marina, Centropages furcatus y Candacia catula, las cuales representaron aproximadamente el 75% de los copepodos recolectados. La influencia de la corriente Nor-Ecuatorial, esta relacionada con las condiciones tropicales y es clara su influencia en la estructura de la comunidad local. La diversidad de Shannon-Wiener se considero alta (H′ = 3.2). Las maximas densidades fueron registradas en las zonas neriticas. En general, las densidades de copepodos indican una productividad moderada a alta en el area estudiada. El patron de agrupamiento de estaciones identifica un facie neritica y una oceanica; aparecen limitadas aproximadamente por el borde exterior de la estrecha plataforma continental. Sin embargo, el gradiente costero-oceanico es moderado, con abundantes formas neritico-oceanicas y oceanicas sobre la plataforma continental. Estos efectos resultan de la mezcla de agua neritica y oceanica sobre la plataforma debido a (1) procesos de adveccion inducidos por viento hacia la costa, y (2) a la estrechez de la plataforma continental. Se sugiere que ambos efectos podrian favorecer la homogeneidad de la comunidad de copepodos a largo de esta y otras zonas del Pacifico tropical mexicano., Zooplankton samples were collected during autumn (September, 1990) off the coasts of the Mexican state of Jalisco, northwestern Mexico, in the eastern tropical Pacific. Taxonomic analysis of the pelagic Copepoda yielded 44 species, Subeucalanus subcrassus, Temora discaudata, Undinula vulgaris, Euchaeta marina, Centropages furcatus, and Candacia catula being the overall dominant forms. Together they represented almost 75% of total copepod numbers. The influence of the North Equatorial Current, related to tropical conditions, is clear in the local community structure. Shannon-Wiener diversity was homogeneously high (over 3.2 bits/ind.) in most samples. Highest densities were recorded in the neritic zone. Overall copepod density values suggest a moderate to high productivity in the surveyed area. Station clustering showed a neritic and an oceanic facies, their limits roughly determined by the outer border of the narrow shelf. However, the coast-ocean gradient is moderate, with abundant neritic-oceanic forms, and oceanic representatives over the continental shelf. These effects may result from across-shelf mixing of neritic and oceanic water due to (1) the effect of inshore-wards wind-driven advective processes, and (2) the narrowness of the continental shelf. It is suggested that these processes favour a degree of homogeneity of the copepod community along this and other parts of the Mexican tropical Pacific. Durante el otono (septiembre de 1990) se recolectaron muestras de zooplancton en la costa del estado de Jalisco, en el Pacifico Tropical Oriental. El analisis taxonomico de los copepodos pelagicos produjo 44 especies. Las formas dominantes fueron Subeucalanus subcrassus, Temora discaudata, Undinula vulgaris, Euchaeta marina, Centropages furcatus y Candacia catula, las cuales representaron aproximadamente el 75% de los copepodos recolectados. La influencia de la corriente Nor-Ecuatorial, esta relacionada con las condiciones tropicales y es clara su influencia en la estructura de la comunidad local. La diversidad de Shannon-Wiener se considero alta (H′ = 3.2). Las maximas densidades fueron registradas en las zonas neriticas. En general, las densidades de copepodos indican una productividad moderada a alta en el area estudiada. El patron de agrupamiento de estaciones identifica un facie neritica y una oceanica; aparecen limitadas aproximadamente por el borde exterior de la estrecha plataforma continental. Sin embargo, el gradiente costero-oceanico es moderado, con abundantes formas neritico-oceanicas y oceanicas sobre la plataforma continental. Estos efectos resultan de la mezcla de agua neritica y oceanica sobre la plataforma debido a (1) procesos de adveccion inducidos por viento hacia la costa, y (2) a la estrechez de la plataforma continental. Se sugiere que ambos efectos podrian favorecer la homogeneidad de la comunidad de copepodos a largo de esta y otras zonas del Pacifico tropical mexicano.]