Spatial and temporal variations in Caribbean zooplankton near Puerto Rico

Spatial and temporal patterns of abundance were examined in selected zooplankton categories sampled from oceanic surface waters (upper 100 m) south of Puerto Rico during 1980. In general, variations in abundances: (i) did not increase with spatial scales ranging from a few to −150 km; and (ii) were not correlated with geostrophic current patterns, These results imply a lack of zooplankton pattern characteristic of these spatial scales, hence that corresponding physical processes do not affect zooplankcton abundances in this region. Significantly higher abundances of zooplankton occurred during July in conjunction with peak chlorophyll a concentrations, the initial seasonal decline in surface salinities and an eastward geostrophic flow. These observations are consistent with the hypothesis that upwelling at the edge of large low salinity lenses underlies increased abundances of plankton. Because these variations in salinities result from the annual pattern of rainfall in low latitude zones of the Western Hemisphere, we conclude that the temporal pattern of zooplankton abundance represents true seasonality and is associated with large scale, regional processes occurring throughout the Eastern Caribbean.