Seasonal Responses of Phyloplankton Productivity to Water-Quality Variations in a Coastal Karst Ecosystem of the Yucatan Peninsula

Dzilam Lagoon (DL) is a shallow, semienclosed, coastal ecosystem located on the north coast of the Yucatan Peninsula. With 9.4 km3 surface area, this system is influenced by groundwater (GD) supply and inorganic nutrients drained from the nearby mangrove. DL is highly preserved and provides a unique site to address the seasonal responses of phytoplankton production to environmental variability in a karstic and pristine scenario. Twelve monthly sampling trips were undertaken during Sep. 1998–Aug. 1999 to record in situ physicochemical parameters and collect water for inorganic nutrients, chlorophyll a (Chl a), and phytoplankton production at seven stations plus one GD. Highest Chl a concentrations were determined at the innermost points of the lagoon, whereas primary production peaked at brackish zones. The average net primary production in DL (80 g C m-3 yr-1) is lower than that reported for other coastal lagoons of the Yucatan Peninsula. Differences in the physical setting and disturbance extent between DL and those ecosystems are discussed as the context underlying their distinct production levels