Comparative productivity and biomass yields of the Guinea Current LME

• We report for the first time results from Continuous Plankton Recorder survey in the GCLME.
• Diatoms and zooplankton <2 mm dominate the plankton yield.
• Zooplankton exhibit similar community structure during minor and major upwelling seasons.
• Phytoplankton distribution regulates zooplankton distribution all year round except major upwelling.
• Sea surface temperature during major upwelling accounted for 65% of variability in zooplankton distribution.

Plankton production patterns in the Guinea Current Large Marine Ecosystem (GCLME) were investigated using data obtained from Continuous Plankton Recorder (CPR) tows carried out in the GLCME, from December 1995 to November 1999. Four CPR routes were established between Cote d'Ivoire and Cameroon as part of the pilot phase of the GCLME project, funded by the Global Environment Facility. Phytoplankton and zooplankton yields were greatest during the major upwelling compared to the other identifiable hydrographic seasons. The phytoplankton was dominated by diatoms whereas smaller zooplankton (<2 mm) occurred in greatest abundance. Analyses of ten years sea surface temperature (SST) data from 1990 to 2000 revealed two thermal regimes; a warmer phase followed by a colder phase that commenced in 1997. Annual phytoplankton and zooplankton yields in 1997 were relatively higher than the other years of the CPR sampling. Analyses of zooplankton community structure, in terms of species occurrence and relative abundances, was found to be similar during the minor and major upwelling. The zooplankton taxa contributing to dissimilarity in community structure were Chaetognath (<2 mm), Oithona spp., Oncaea spp, copepod nauplii, echinoderm larvae, Para-Pseudocalanus, Temora spp., Eucalanus spp., and Clausocalanus spp. Spatial and seasonal variation in phytoplankton communities did not follow any pattern. It was observed from a multiple regression analysis that phytoplankton distribution alone accounted for a significant proportion of the variation in zooplankton distribution in all hydrographic seasons except the major upwelling, during which period sea surface temperature contributed over 60% of the observed variation. This investigation using CPR is the first of its kind in the GCLME and thus provides a baseline information to guide future studies.