Response of benthic polychaetes to environmental variability and El Niño conditions at Petacalco Bay (Guerrero, Mexico)
J.A. RodrÃguez-Valencia
Abstract
Se analizaron las fluctuaciones en temperatura, salinidad y oxÃgeno disuelto en las capas superficial (0â??7 m) e inferior (7â??23 m) de la columna de agua de BahÃa Petacalco (Guerrero, México), y sus efectos sobre los poliquetos bentónicos, en diferentes fechas de 1992â??1994. Los muestreos de 1992 permitieron capturar la fase terminal del evento El Niño 1992, seguido de la descarga de agua dulce del sistema de enfriamiento de una central termoeléctrica (2100 MW) en la superficie de la bahÃa. Durante El Niño 1992 el agua de la bahÃa estuvo significativamente más caliente, salina y oxigenada que entre 1993â??1994. Al retirarse las condiciones El Niño, se incrementó la estratificación en la columna de agua y los niveles de oxÃgeno disuelto y salinidad se redujeron notoriamente. Después de El Niño, los poliquetos se recuperaron de niveles mÃnimos de abundancia y número de especies, a pesar de las descargas de la termoeléctrica que se mantuvieron sobre la superficie de la columna de agua. Afloramientos de agua profunda a través del cañón submarino Petacalco durante la primavera pudieron haber tenido un efecto positivo.
Fluctuations of temperature, salinity, and dissolved oxygen in the superficial (0â??7 m) and lower (7â??23 m) layers of the water column in Petacalco Bay (Guerrero, Mexico) and their effects on benthic polychaetes were analyzed on different dates between 1992 and 1994. Samplings undertaken during 1992 allowed the detection of the terminal phase of the 1992 El Niño event, followed by the discharge of warm freshwater from a power plant (2100 MW) over the surface of the bay. During the 1992 El Niño, the water was significantly warmer, more saline, and contained more oxygen than during 1993â??1994. Stratification of the water column increased after the dissipation of El Niño conditions, and dissolved oxygen and salinity levels decreased noticeably. Polychaete abundances and the number of species were lowest during the El Niño period and increased afterwards. These changes occurred despite the operation of the power plant, since its discharges remained on the surface of the bay. Emersions of deep water through the Petacalco submarine canyon in spring may also have had a positive effect.
Fluctuations of temperature, salinity, and dissolved oxygen in the superficial (0â??7 m) and lower (7â??23 m) layers of the water column in Petacalco Bay (Guerrero, Mexico) and their effects on benthic polychaetes were analyzed on different dates between 1992 and 1994. Samplings undertaken during 1992 allowed the detection of the terminal phase of the 1992 El Niño event, followed by the discharge of warm freshwater from a power plant (2100 MW) over the surface of the bay. During the 1992 El Niño, the water was significantly warmer, more saline, and contained more oxygen than during 1993â??1994. Stratification of the water column increased after the dissipation of El Niño conditions, and dissolved oxygen and salinity levels decreased noticeably. Polychaete abundances and the number of species were lowest during the El Niño period and increased afterwards. These changes occurred despite the operation of the power plant, since its discharges remained on the surface of the bay. Emersions of deep water through the Petacalco submarine canyon in spring may also have had a positive effect.
Full Text: PDF