Phytoplankton Ecology During a Spring-Neap Tidal Cycle in the Southern Tidal Front of San Jorge Gulf, Patagonia

XIMENA FLORES MELO; IRENE SCHLOSS; GUSTAVO FERREYRA

OCEANOGRAPHY

OCEANOGRAPHY SOC

Año: 2018

1042-8275

Tidal fronts are interfaces that separate stratified from mixed waters. Thestratified surface zone of a front has lower inorganic nutrient concentrations than themixed side, and thus, phytoplankton assemblages are expected to differ from one sideof the front to the other. Here, we characterize the physics, nutrient dynamics, and biology of the southern front in San Jorge Gulf (SJG), Argentina, during a spring-neap tidalcycle. Baroclinic instabilities influence the shape and position of the front and presumably play an important role in the horizontal transport across the front. The highestphytoplankton biomass concentrations were found in the waters of the stratified sideof the front during neap tide, with picophytoplankton, cyanobacteria, and nanophytoplankton being the main contributors to the total autotrophic biomass. Bacteria contribute the most to heterotrophic biomass. In contrast, during spring tide, the carboncontribution of microphytoplankton was higher than during neap tide. In the mixedside, cells photoacclimate to optimum light conditions, suggesting that cells near thesurface, which are probably photoinhibited, and cells below the euphotic zone, whichare light-limited, are quickly advected by turbulent vertical motions to depths withoptimal irradiance conditions.