Volumen 44 - Número 2: 477-488 | 2009
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Vertical distribution of zooplankton biomass and ichthyoplankton density during an annual cycle on the continental shelf of the southern Gulf of Mexico |
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María de la Luz Espinosa-Fuentes1*, César Flores-Coto1, Laura Sanvicente-Añorve1 and Faustino Zavala-García1 |
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Seasonal zooplankton biomass (ZB) and ichthyoplankton density (ID) in the water column on the continental shelf of the southern Gulf of Mexico were analyzed to determine their vertical distribution patterns and assess if there is a relationship between both components. Five depth levels were sampled: 0-6, 6-12, 12-18, 45-55 and 95-105 m. The vertical distribution patterns of ZB and ID were similar for all sampling seasons, with the greatest concentration of organisms in the upper levels and the lowest at deeper levels. These results suggest that the water column in the study area may be divided into a surface layer (0-18 m) and a deep layer (45-100 m), and seasonal differences may be attributed to mixing processes. The difference between the surface and the deep layers occurs because, in general, the upper layer is the most productive sector of the water column. The relationship between ZB and ID in the water column was positive and significant (ANCOVA, P < 0.05) throughout the sampling seasons for most depths, probably because the production cycle is continuous in the southern Gulf of Mexico, as is common in tropical and subtropical areas, and it maintains the availability of food, and consequently the predator-prey relationships. The relationship between the ZB and the ID in the water column is mainly affected by the seasonal variations in the continental water discharges and the mixing processes. |
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Key words: Continental water discharges, mixing layer, stratification, zooplankton-ichthyoplankton relationship |
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1Laboratorio de Zooplancton, Instituto de Ciencias del Mar y Limnología,Universidad Nacional Autónoma de México. A. P. 70-305, 04510 México, D. F. México