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Halac S.R.,Estacion de Fotobiologia Playa Union EFPU | Halac S.R.,Instituto Nacional Del Agua INA | Villafane V.E.,Estacion de Fotobiologia Playa Union EFPU | Villafane V.E.,CONICET | And 4 more authors.
Journal of Photochemistry and Photobiology B: Biology | Year: 2014

We carried out experiments using long-term (5-7 days) exposure of marine phytoplankton species to solar radiation, in order to assess the joint effects of ultraviolet radiation (UVR) and temperature on the photochemical responses and photoprotective mechanisms. In the experiments, carried out at Atlantic coast of Patagonia (4318.7′S; 652.5′W) in spring-summer 2011, we used three species as model organisms: the dinoflagellate Prorocentrum micans, the chlorophyte Dunaliella salina and the haptophyte Isochrysis galbana. They were exposed under: (1) two radiation quality treatments (by using different filters): P (PAR, >400 nm) and PAB (PAR + UV-A + UV-B, >280 nm); (2) two radiation intensities (100% and 50%) and (3) two experimental temperatures: 18 C and 23 C during summer and 15 C and 20 C in spring experiments, simulating a 5 C increase under a scenario of climate change. In addition, short-term (4 h) artificial radiation exposure experiments were implemented to study vertical migration of cells pre- and non-acclimated to solar radiation. We observed species-specific responses: P. micans displayed a better photochemical performance and a lower inhibition induced by UVR than D. salina and I. galbana. In accordance, P. micans was the only species that showed a synthesis of UV-absorbing compounds (UVACs) during the experiment. On the other hand, non-photochemical quenching (NPQ) was activated in D. salina at noon throughout the exposure, while I. galbana did not show a regular NPQ pattern. This mechanism was almost absent in P. micans. Regarding vertical migration, I. galbana showed the most pronounced displacement to deepest layers since the first two hours of exposure in pre- and non-acclimated cells, while only non-acclimated D. salina cells moved to depth at the end of the experiment. Finally, temperature partially counteracted solar radiation inhibition in D. salina and I. galbana, whereas no effect was observed upon P. micans. In particular, significant UVR and temperature interactive effects were found in I. galbana, the most UVR sensitive species. The joint effects on UVR and temperature, and the species-specific photoprotective responses will affect the trophodynamics and production of aquatic ecosystems in a way that is difficult to predict; however the specificity of the responses suggests that not all phytoplankton would be equally benefited by temperature increases therefore affecting the balance and interaction among species in the water column. © 2014 Elsevier B.V. All rights reserved.

Hernandez Moresino R.D.,Estacion de Fotobiologia Playa Union EFPU | Hernandez Moresino R.D.,CONICET | Goncalves R.J.,Estacion de Fotobiologia Playa Union EFPU | Goncalves R.J.,CONICET | And 2 more authors.
Journal of Plankton Research | Year: 2014

First larval stage (Zoea I) of the crab Cyrtograpsus altimanus can obtain photoprotective compounds (PPCs) from their mother (indirect acquisition) and also via feeding on PPC-producers such as phytoplankton (direct acquisition). The bioaccumulation of PPC resulted in higher survival of larvae exposed to ultraviolet radiation (UVR), when comparing larvae with high and low content of PPC. Thus, both ways of acquiring PPC may contribute to maximize survival of Zoea I when they are exposed to natural UVR. © 2014 The Author 2014.

Goncalves R.J.,Estacion de Fotobiologia Playa Union EFPU | Goncalves R.J.,University of Guelph | Hernandez Moresino R.D.,Estacion de Fotobiologia Playa Union EFPU | Hernandez Moresino R.D.,University of Guelph | And 2 more authors.
Latin American Journal of Aquatic Research | Year: 2014

Many marine species spend part of their development in upper layers of the water column, where they may be exposed to solar ultraviolet radiation (UVR). For many of these species, light is one of the key environmental clues which triggers behaviorally-mediated adjustments in vertical distribution. We incubated planktonic larvae of the crab Cyrtograpsus altimanus in column-like aquaria to study their responses with/without UVR (under a solar simulator) and with/without a potential prey (the dinoflagellate Alexandrium tamarense). Their vertical distribution was recorded and used to evaluate the combined effects of UVR and the presence of the dinoflagellate on larval behavior. When UVR was absent, most larvae showed a tendency to swim upwards and to aggregate near the surface, regardless of the dinoflagellate presence. However, UVR inhibited this tendency and induced a repellent effect, which resulted in a more homogeneous vertical distribution of larvae. A. tamarense did not affect the vertical distribution of larvae. These results suggest that UVR-triggered, quick adjustments in vertical distribution might be an important strategy for C. altimanus larvae to cope with high solar radiation, which typically occur during the hatching season. © 2014, Escuela de Ciencias del Mar. All rights reserved.

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