VARIACIONES NICTEMERALES EN LA COMUNIDAD DE ZOOPLANCTON DE LA BAHIA DE SANTA MARTA, MAR CARIBE COLOMBIANO

Abstract

Day-night and between-day variation in surficial zooplankton composition and its relationship to environmental parameters were analyzed in the Santa Marta Bay, Colombian Caribbean, by Principal Components Analysis. Sampling was carried out every four hours in three different days between August and October 1989. The greatest variation in abundance (first principal component) was due to an increase over the mean in most groups at nightfall and during night hours. This variation was inversely and significantly correlated with incident light intensity, and was interpreted as consequence of the vertical migration out of the surface zone. On the other hand, the second and third principal components showed differences amog days for groups and within groups; those that existed in the first sampling day with respect to the other two were highlighted by the second component,, and were negatively correlated with temperature and positively correlated with disolved nitrates. These results were interpreted as a consequence of movements of water masses with different physical-chemical characteristics and zooplankton composition over the sampling site. However, a case of close association between these parameters and the changes in migrating movements could not be ruled out.