Impact of Solar Ultraviolet Radiation on Marine Phytoplankton of Patagonia, Argentina ¶

• Published in: Photochemistry and Photobiology
• Main Authors: Helbling, E. Walter, Barbieri, Elena S., Marcoval, M. Alejandra, Gonçalves, Rodrigo J., Villafañe, Virginia E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2005
• Subjects: Antarc*; Antarctic
• Online Access: http://dx.doi.org/10.1111/j.1751-1097.2005.tb01447.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1751-1097.2005.tb01447.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1751-1097.2005.tb01447.x

ABSTRACT Patagonia area is located in close proximity to the Antarctic ozone “hole” and thus receives enhanced ultraviolet B (UV‐B) radiation (280–315 nm) in addition to the normal levels of ultraviolet A (UV‐A; 315–400 nm) and photosynthetically available radiation (PAR; 400‐700 nm). In marine ecosystems of Patagonia, normal ultraviolet radiation (UVR) levels affect phytoplankton assemblages during the three phases of the annual succession: (1) prebloom season (late summer‐fall), (2) bloom season (winter‐early spring) and (3) postbloom season (late spring‐summer). Small‐size cells characterize the pre‐and postbloom communities, which have a relatively high photosynthetic inhibition because of high UVR levels during those seasons. During the bloom, characterized by micro‐plankton diatoms, photosynthetic inhibition is low because of the low UVR levels reaching the earth's surface during winter; this community, however, is more sensitive to UV‐B when inhibition is normalized by irradiance ( i.e. biological weighting functions). In situ studies have shown that UVR significantly affects not only photosynthesis but also the DNA molecule, but these negative effects are rapidly reduced in the water column because of the differential attenuation of solar radiation. UVR also affects photosynthesis versus irradiance (P vs E) parameters of some natural phytoplankton assemblages ( i.e. during the pre‐ but not during the postbloom season). However, there is a significant temporal variability of P vs E parameters, which are influenced by the nutrient status of cells and taxonomic composition; taxonomic composition is in turn associated with the stratification conditions ( e.g. wind speed and duration). In Patagonia, wind speed is one of the most important variables that conditions the development of the winter bloom by regulating the depth of the upper mixed layer (UML) and hence the mean irradiance received by cells. Studies on the interactive effects of UVR and mixing show that responses of phytoplankton vary according to ...