Zooplankton distribution during opposite tidal directions in the Chelem lagoon complex, Yucatan, Mexico

Zooplankton was surveyed in a tropical lagoon system of the northern coast of the Yucatan Peninsula in high tide, December (1998) and low tide, March 1999 (northerlies season). Zooplankton biomass was measured, zooplankters w ere counted, and copepods were identified and quantified. Despite the fact that both months were influenced by winds from the North, they showed a dif ferent salinity gradient which developed a particular structure of the zoop lankton community. Biomass tended to be accumulated in certain areas appare ntly because of the high residence time of water in Chelem, the forcing eff ect of the northerlies, and of the tidal current. Biomass values suggest a relatively high secondary production when compared with other systems of th e Yucatan Peninsula. The distribution of the copepods Acartia lilljeborgii and A. tonsa is related to saline conditions and tidal flow. The overall fa unistic and hydrologic data suggest that even during a single climatic seas on, the zooplankton community shows strong changes due to mesoscale hydrolo gical processes.