Interactive effects of ultraviolet radiation, nutrients and temperature on oxygen production, respiration and PSII responses of marine phytoplankton of the Patagonian coast

CABRERIZO, M.; CARRILLO, P.; VILLAFAÑE, V. E.; HELBLING, E.W

Sevilla

Congreso; Adapting to global change in the Mediterranean hotspot Conference; 2013

Multiple stressors related to global change [drought, enhancements of ultraviolet radiation (UVR, 280-400 nm) and sea-surface temperatures, releases of atmospheric aerosols, etc.] are causing numerous alterations in the structure and functioning on aquatic ecosystems. Changes in UVR, nutrients inputs and temperature are three important stressors affecting aquatic phytoplankton communities. Our objective was to quantify the responses of these organisms under a global change scenario in a mid-term scale (weeks). We carried out experiments during the period April-June, 2013 with natural communities collected from the Patagonian coast, in which we manipulated radiation quality [i.e., with UVR (PAB) versus without it (only PAR (P)], nutrient concentrations [enriched (f/2) versus ambient conditions] and temperature [in situ versus + 3ºC]. The interactive effects of these variables were evaluated by determination of oxygen production, respiration, effective photochemical quantum yield (Y), taxonomic composition and Chlorophyll-a (chl-a). We further obtained oxygen production and respiration rates, inhibition (k), recovery (r) and the relationship k to r as an estimation of damage-repair processes. There were important changes in taxonomic composition coupled with an increase in [chl-a] from mid-autumn to mid-winter. Together with this, we observed under the PAB, enriched nutrients and increased temperature a higher decrease in oxygen-production (54.11 versus 23.67 µM O2 h-1), while respiration was higher at in situ temperature (6.30 versus 3.32 µM O2 h-1). These effects were reflected in a larger inhibition of Y under the same conditions. However, temperature did not exert an effect on recovery. All together, our results suggest that phytoplankton communities from Patagonia will be more damaged under global change conditions.