Phytoplankton size structure, distribution, and primary production as the basis for trophic analysis of Caribbean ecosystems

An oceanographic survey was conducted in Caribbean waters in April and May 2006 to assess the marine ecosystem in the context of a trophic analysis of the foodweb. Analyses of pigment and absorption data revealed that the phytoplankton community was dominated by pico- and nanophytoplankton, particularly at the deep chlorophyll maximum. Based on cluster analysis of remotely sensed data, three dynamic provinces were defined for the region. A 5-year time-series of sea surface temperature and chlorophyll concentration provided information on the annual cycle of these properties. To implement the computation of primary production on a synoptic scale, parameters characterizing the biomass profiles and photosynthesis-irradiance relationships were assigned using four protocols: two regional approaches, a regression with surface chlorophyll, and the nearest-neighbour method (NNM), which has the advantage of assigning parameters on a pixel-by-pixel basis. Monthly images of primary production were computed over an annual cycle using MODIS chlorophyll a concentration. The NNM and the use of dynamic provinces emerged as the methods of choice for parameter assignment. Finally, a new approach from remotely sensed data was developed to estimate production-to-carbon ratios, a key input to Ecopath models. The results contribute to ecotrophic analysis of the Lesser Antilles Pelagic Ecosystem project.