Distribution and abundance of zooplankton of the lagoon system Chacahua- La Pastoria, Oaxaca, Mexico

Abstract

THE ZOOPLANKTON COMMUNITY OF THE LAGOON SYSTEM CHACAHUA-LA PASTORÍA WAS STUDIED BEFORE THE OPENING OF THE SANDY BAR OF CHACAHUA BY THE SECRETARÍA DE MARINA. A TOTAL OF 26 GROUPS OF ZOOPLANKTON WERE IDENTIFIED AT THE LAGOON COMPLEX CHACAHUA-LA PASTORIA MADE DURING FIVE SAMPLINGS IN MAY, OCTOBER AND DECEMBER, 1996 AND FEBRUARY AND JUNE, 1997. IN LA PASTORIA WERE RECORDED 25 GROUPS AND 19 IN CHACAHUA. FROM 26 GROUPS RECORDED, 18 WERE COMMON IN BOTH LAGOONS. BRAQUIURID LARVAE WERE THE MOST ABUNDANT GROUP, AND REPRESENT 35.7% OF TOTAL ZOOPLANKTON, FOLLOWED BY FISH LARVAE AND EGGS WITH 22.74 AND 15.26%, RESPECTIVELY. THE MAXIMUM MEAN VALUES OF ABUNDANCE WERE OBSERVED IN THE DRY PERIOD IN THE ADJACENT ZONES TO THE CHANNEL OF INTERCOMMUNICATION OF BOTH LAGOONS, AS WELL AS IN THE NEIGHBORHOOD OF THE COMMUNICATION CHANNEL WITH THE SEA. IN CHACAHUA THE HIGHEST VALUES WERE OBSERVED IN JUNE, 1997 AND IN LA PASTORÍA IN DECEMBER, 1996. IN GENERAL THE GROUP RICHNESS WAS GREATER IN LA PASTORÍA LAGOON. ZOOPLANKTIC COMMUNITY COMPOSITION WAS CONDITIONED FOR THE SALINITY AND WATER INTERCHANGE RATE BETWEEN THE SEA AND THE LAGOON.