Modelling the influence of abiotic and biotic factors on plankton distribution in the Bay of Biscay, during three consecutive years (2004–06)

Three surveys were carried out in the Bay of Biscay during the springs of 2004, 2005 and 2006. Hydrographic, nano-microplankton (diatoms, ciliates and unidentified particles) and mesozooplankton biomass data were collected at mesoscale spatial resolution. Generalized additive models (GAMs) based on a combination of hydrographic, geographic and biological terms were used to understand the factors affecting distribution. The final models accounted for 66% of the variability in the biomass distribution of unidentified particles, 60% for diatoms, 44% for mesozooplankton and 23% for ciliates. The contribution of hydro-geographical terms was greater than the information described by the biological variables. Geographical location (latitude and longitude) was the main explanatory factor for all of the plankton groups identified, revealing that the presence of mesoscale fronts related to geographical structures is more relevant than the hydrographic variables per se, to describe plankton distribution.