Seasonal patterns of phytoplankton productivity, zooplankton abundance and hydrological conditions in Laguna Joyuda, Puerto Rico
Jorge R. García, José M. López

This study examined temporal variations of zooplankton, jellyplankton and phytoplankton standing crops and productivity within the context of environmental changes in Laguna Joyuda, a shallow tropical lagoon in Puerto Rico. The plankton community of the lagoon displayed marked seasonal patterns which appear to be regulated by biological interactions and climatological factors. Phytoplankton productivity rates (range: 0.262 - 0.992 g C m-3 day-1). chlorophyll-a concentrations (range: 4.1 - 24.1 mg m-3), and abundance of scyphomedusae (range: 0 - 143 individuals 10-3 m-3) were higher during the period between May and October (warmtwet season). Conversely. non-gelatinous zooplankton abundance (range: 16,427 - 122,717 individuals m-3) was higher during the period between November and April (coolldry season). Taxonomically, the non-gelatinous zooplankton community was dominated by developmental stages and adults of the calanoid copepod Acartia tonsa Dana, chaetognath worms, and meroplanktonic populations of decapod and polychaete larvae. The seasonal pattern of phytoplankton standing crops and productivity appeared to be mostly controlled by the combined effects of nutrient inputs from rainfall runoff and zooplankton grazing. A significant negative correlation between phytoplankton productivity and non-gelatinous zooplankton abundance was found. Correlative evidence also suggests that scyphomedusae (Phyllorhiza punctata von Lendenfeld) had a significant predatory impact upon non-gelatinous zooplankton, and thereby, played an important ecological role in the plankton dynamics of Laguna Joyuda.

Keywords: phytoplankton, zooplankton, scyphomedusae, hydrology, coastal lagoons.
Contents of this volume Sci. Mar. 53(2-3) : 625-631 Back PDF
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