Photochemical activity of PSII of tropical phytoplankton communities of Southern Brazil exposed to solar radiation and nutrient addition

VILLAFAÑE, VIRGINIA E.; ERZINGER, G. S.; STRAUCH, S. M.; E WALTER HELBLING

JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 vol. 459 p. 199 - 207

0022-0981

We carried out short- and mid-term incubations to assess the combined impact of solar ultraviolet radiation (UVR, 280?400nm) andnutrient additionon tropical phytoplankton communities fromBabitongaBay, Southern Brazil. Sampleswere collectedat a station~10kminward fromthemouth i.e., Inlet, and incubated inmicrocosms under solar radiation at the surface of the water, with or without UVR, and under two nutrient conditions (ambient and with addition of macronutrients). Nutrient addition had the largest impact on specific growth rates, almost doubling the growth of algae as compared to ambient conditions. UVR-induced inhibition of the ef-fective photochemical quantum yield (Y) at the initial conditionswas higher at ambient nutrient conditions than in samples with nutrient addition, demonstrating the antagonistic effect among the two factors. Inhibition (k)and recovery (r) rates of Y at the beginning of the experiment suggest a high sensitivity of this community, but they were reduced after 4 days of exposure in the microcosms, hinting for the presence of acclimation mecha-nisms. Also, differences in taxonomic composition, with increasing dominance of diatoms in nutrient-enriched cultures, as compared to the initial time and in ambient nutrient conditions (with higher proportion offlagellates) may account for the observed variability in responses along the time as well as within treatments.