Browning, nutrient inputs, and fast vertical mixing from simulated extreme rainfall and wind stress alter estuarine phytoplankton productivity

HELBLING, E. WALTER; BANASZAK, ANASTAZIA T.; VALIÑAS, MACARENA S.; VIZZO, JUAN I.; VILLAFAÑE, VIRGINIA E.; CABRERIZO, MARCO J.

NEW PHYTOLOGIST

WILEY-BLACKWELL PUBLISHING, INC

Año: 2023

0028-646X

Browning and nutrient inputs from extreme rainfall, together with increased vertical mixingdue to strong winds, are more frequent in coastal ecosystems; however, their interactive effectson phytoplankton are poorly understood. We conducted experiments to quantify how browning, together with different mixing speeds (fluctuating radiation), and a nutrient pulse alterprimary productivity and photosynthetic efficiency in estuarine phytoplankton communities. Phytoplankton communities (grazers excluded) were exposed simultaneously to these drivers, and key photosynthetic targets were quantified: oxygen production, electron transportrates (ETRs), and carbon fixation immediately following collection and after a 2-d acclimation/adaptation period. Increasing mixing speeds in a turbid water column (e.g. browning) significantly decreasedETRs and carbon fixation in the short term. Acclimation/adaptation to this condition for 2 dresulted in an increase in nanoplanktonic diatoms and a community that was photosynthetically more efficient; however, this did not revert the decreasing trend in carbon fixation withincreased mixing speed. The observed interactive effects (resulting from extreme rainfall and strong winds) mayhave profound implications in the trophodynamics of highly productive system such as theSouthwest Atlantic Ocean due to changes in the size structure of the community and reducedproductivity