Role of marine macroalgae in the pH regulation in an eutrophic Argentinean coastal area

BECHERUCCI MARIA EUGENIA; MARTINETTO PAULINA; FANJUL, EUGENIA; IRIBARNE, OSCAR; NARVARTE, MAITE; PEREYRA PATRICIO

Otro; OA week 2021; 2021

Nutrient input drives macroalgal blooms and increases in photosynthetic activity in coastal ecosystems. An intense macroalgal photosynthetic activity can increase the surrounding pH and counteract the acidification that often follows an eutrophication process. This hypothesis was tested with field sampling and experiments in a macrotidal (up to 9 m in amplitude) coastal system within a semi-desert region with contrasting eutrophic conditions and Ulva lactuca blooms in the northern Argentinean Patagonia (San Antonio Bay). The results indicate that daily pH variability during low tide could be controlled by the photosynthetic activity of Ulva lactuca under eutrophic conditions. At seasonal scale, the pH variations were related to environmental features, particularly seawater temperature. Both environmental (i.e. high solar radiation, negligible freshwater inputs and large tidal action) and anthropogenic nutrient inputs into the studied area promote the Ulva lactuca blooms, which in turn increases the surrounding pH in well oxygenated seawater through the intense photosynthetic activity.