Influence of the Hydrodynamics on the Phytoplankton-Biomass Variability in Bahía de los Ángeles, Baja California: Results from a Numerical Physical-Biological Coupled Ocean Model

Bahía de los Ángeles is a bay located at the western coast of the Gulf of California, west of Midriff Islands, connected to Canal de Ballenas. This bay is home to important species of different trophic levels and some of them form aggregations in particular areas within the bay; this is the case of the whale shark (Rhincodon typus) which stays in the bay from June to November for feeding. Nevertheless, the processes involved in these aggregations, specifically the ones that affect the lowest trophic levels, are still poorly understood. Therefore, herein we analyze the role of the water circulation on the formation of the high phytoplankton-biomass areas within the bay. To achieve this task, a high-resolution three-dimensional hydrodynamic numerical model, coupled to a Nutrients-Phytoplankton-Zooplankton-Detritus (NPZD) trophic model, was implemented for a multiyear simulation (2013-2017). Preliminary results show areas with intense currents associated with low phytoplankton-biomass, whilst areas with weak currents are associated with high phytoplankton-biomass; this shows that longer residence times of the water favor the phytoplankton growth. This circulation pattern within the bay is mostly influenced by upwelling waters induced by the regional winds. Thus, this numerical-modeling study will contribute to the knowledge of the physical-biological process within such an ecologically important bay.