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Van De Poll W.H.,University of Groningen | Van De Poll W.H.,Netherlands Institute for Sea Research | Lagunas M.,Estacion de Fotobiologia Playa Union | Lagunas M.,University of Victoria | And 3 more authors.
Marine Ecology Progress Series | Year: 2011

Sensitivity to photoinhibition from near-surface irradiance was determined in coastal phytoplankton from Potter Cove (King George Island, Antarctica) in relation to hydrographic conditions shaped by summertime meltwater influx. Slow (indicative for PSII damage) and fast (indicative for xanthophyll cycle activity) relaxing non-photochemical chlorophyll fluorescence quenching (NPQ) was measured during recovery from excess photosynthetically active radiation (PAR) and PAR + ultraviolet radiation (UVR) for 3 stations differentially affected by sediment influx. Additionally, assemblages were incubated outside to study xanthophyll cycle activity during PAR and PAR+UVR exposure. For comparison, NPQ and xanthophyll cycle activity were determined for high (125 μmol photons -2 s-1) and low (20 μmol photons m -2 s-1) light acclimated Chaetoceros brevis (Bacillariophyceae) and Phaeocystis antarctica (Haptophyceae) cultures. Pigment analysis (CHEMTAX) revealed diatom dominance (average 74%) at all locations, with haptophytes being of minor importance (average 13%). All stations were stratified by a vertical density gradient, whereas sediment influx was significantly higher at the innermost station. Taxonomic composition, NPQ characteristics, and photoprotective pigment ratios were not different among stations. At the chlorophyll maximum, phytoplankton showed high light acclimation at all locations, and fast relaxing NPQ dominated after excess PAR and PAR+UVR. Samples from below the chlorophyll maximum were enriched in haptophytes, showed lower photoprotective pigment ratios, reduced capacity for NPQ, and increased contribution of slow relaxing NPQ. The photoprotective capacity of high and low light acclimated C. brevis and P. antarctica differed significantly. P. antarctica induced less NPQ and there was a stronger slow relaxing NPQ component than in the diatom, particularly after low light acclimation. Although total NPQ decreased and slow relaxing NPQ increased after UVR in field samples, NPQ and the xanthophyll cycle de-epoxidation state of cultures were not affected by UVR. A higher photoprotective capacity of diatoms over haptophytes may explain their dominance in stratified meltwater-affected coastal Antarctic waters. © Inter-Research 2011. Source


Hader D.-P.,Friedrich - Alexander - University, Erlangen - Nuremberg | Williamson C.E.,Miami University Ohio | Wangberg S.-A .,Gothenburg University | Rautio M.,University of Quebec at Chicoutimi | And 5 more authors.
Photochemical and Photobiological Sciences | Year: 2015

Interactions between climate change and UV radiation are having strong effects on aquatic ecosystems due to feedback between temperature, UV radiation, and greenhouse gas concentration. Higher air temperatures and incoming solar radiation are increasing the surface water temperatures of lakes and oceans, with many large lakes warming at twice the rate of regional air temperatures. Warmer oceans are changing habitats and the species composition of many marine ecosystems. For some, such as corals, the temperatures may become too high. Temperature differences between surface and deep waters are becoming greater. This increase in thermal stratification makes the surface layers shallower and leads to stronger barriers to upward mixing of nutrients necessary for photosynthesis. This also results in exposure to higher levels of UV radiation of surface-dwelling organisms. In polar and alpine regions decreases in the duration and amount of snow and ice cover on lakes and oceans are also increasing exposure to UV radiation. In contrast, in lakes and coastal oceans the concentration and colour of UV-absorbing dissolved organic matter (DOM) from terrestrial ecosystems is increasing with greater runoff from higher precipitation and more frequent extreme storms. DOM thus creates a refuge from UV radiation that can enable UV-sensitive species to become established. At the same time, decreased UV radiation in such surface waters reduces the capacity of solar UV radiation to inactivate viruses and other pathogens and parasites, and increases the difficulty and price of purifying drinking water for municipal supplies. Solar UV radiation breaks down the DOM, making it more available for microbial processing, resulting in the release of greenhouse gases into the atmosphere. In addition to screening solar irradiance, DOM, when sunlit in surface water, can lead to the formation of reactive oxygen species (ROS). Increases in carbon dioxide are in turn acidifying the oceans and inhibiting the ability of many marine organisms to form UV-absorbing exoskeletons. Many aquatic organisms use adaptive strategies to mitigate the effects of solar UV-B radiation (280-315 nm), including vertical migration, crust formation, synthesis of UV-absorbing substances, and enzymatic and non-enzymatic quenching of ROS. Whether or not genetic adaptation to changes in the abiotic factors plays a role in mitigating stress and damage has not been determined. This assessment addresses how our knowledge of the interactive effects of UV radiation and climate change factors on aquatic ecosystems has advanced in the past four years. © The Royal Society of Chemistry and Owner Societies 2015. Source


Salgado-Salazar C.,Cell Biology and Immunogenetics Unit | Salgado-Salazar C.,University of Antioquia | Jones L.R.,Estacion de Fotobiologia Playa Union | Jones L.R.,University of Buenos Aires | And 3 more authors.
Cladistics | Year: 2010

Paracoccidioides brasiliensis is the aetiological agent of paracoccidioidomycosis, the most important systemic mycosis in Latin America. In order to study the diversity of P. brasiliensis mitochondrial genes, to evaluate previous taxonomic proposals, and to explore the hypothesis that the previously described "divergent isolate" B30 (also called Pb01) could represent a new P. brasiliensis species, we undertook a molecular phylogenetic analysis based on five mitochondrial markers. Mitochondrial sequences of 59 P. brasiliensis isolates obtained from clinical and environmental samples, and the orthologous genes from outgroup species, are reported and analysed using parsimony and Bayesian methods. The combined data set comprised 2364 characters, of which 426 were informative. One of the studied strains presented a 376-nt insertion at the apocytochrome b (cob) gene. The corresponding sequence had a high similarity (79%) with an intron found in the Neurospora crassa cob gene. Interestingly, this intron is absent in the previously published sequence of the P. brasiliensis mitochondrial genome. Our trees were moderately congruent with the previous P. brasiliensis taxonomic proposals. Furthermore, we identified a new monophyletic group of strains within P. brasiliensis. Nevertheless, the phylogenetic species recognition (PSR) analyses described here suggested that these groups of strains could represent geographical variants rather than different Paracoccidioides cryptic species. In addition, and as previously proposed by other authors, these analyses supported the existence of a new specie of Paracoccidioides, which includes the previously described, divergent isolate B30/Pb01. This is the first report providing evidence, independent of nuclear markers, for the split of this important human pathogen into two species. We support the formal description of the B30/Pb01 as new specie. ©The Willi Hennig Society 2010. © The Willi Hennig Society 2010. Source


Villafane V.E.,Estacion de Fotobiologia Playa Union | Villafane V.E.,CONICET | Banaszak A.T.,National Autonomous University of Mexico | Guendulain-Garcia S.D.,National Autonomous University of Mexico | And 5 more authors.
Limnology and Oceanography | Year: 2013

The effects of temperature and ultraviolet radiation (UVR; 280-400 nm) on seasonal succession in phytoplankton assemblages of Patagonia (Argentina) were studied in the context of global change. Samples collected during pre-bloom, bloom onset, bloom, and spring were exposed to in situ and increased (+4°C) temperatures and solar radiation with and without UVR. Daily cycles of effective photochemical quantum yield exhibited a pattern of high values in the morning, decreasing towards noon, and increasing in the afternoon. The decrease in yields towards noon as the season progressed increased from 30% in the pre-bloom to 80% in the spring; in the latter there were significant differences between radiation treatments under both temperature conditions. The highest inhibition rates were during the bloom, whereas the highest recovery rates were during the spring. Inhibition rates were generally higher in treatments exposed to UVR in comparison to photosynthetically active radiation-only treatments and some stages of the succession exhibited an additional temperature effect. Increasing temperatures had little effect on pre-bloom communities but helped to counteract the magnitude of the yield decrease during the bloom onset. However, during the bloom and in the spring, temperature and UVR acted synergistically, increasing the overall photochemical inhibition. Feedback mechanisms of increased temperatures causing a shallower mixing depth will expose phytoplankton to higher radiation, which will have a negative effect on the bloom and on spring assemblages. Due to the differential effects of solar UVR and increased temperature on phytoplankton, future studies should consider the repercussions on higher trophic levels. © 2013, by the Association for the Sciences of Limnology and Oceanography, Inc. Source


Halac S.R.,Estacion de Fotobiologia Playa Union | Halac S.R.,Instituto Nacional del Agua | Guendulain-Garcia S.D.,National Autonomous University of Mexico | Villafane V.E.,Estacion de Fotobiologia Playa Union | And 4 more authors.
Journal of Experimental Marine Biology and Ecology | Year: 2013

The aim of this study was to evaluate the effects of UVR on growth and taxonomic composition of tropical plankton communities in a scenario of increased temperature and ultraviolet radiation. Water samples were collected from a reef lagoon in the Mexican Caribbean (20.5° N, 86.5° W) during July 2010 and grown for 16. days in microcosms under two natural radiation treatments: a) PAB (PAR + UV-A + UV-B, 280-700. nm) and, b) P, (PAR, 400-700. nm) and two temperature conditions: a) ambient (28 °C), and, b) increased (ambient + 3 °C). A differential factorial response of the studied variables among the main taxonomic groups and more frequent species was found. The biomass of dinoflagellates and colorless plankton was negatively affected by UVR while the increased temperature had negative effects on diatom biomass and cell abundance. During the experimental period there were changes in the contribution of each taxonomic group. At ambient temperature there was a shift from a flagellate- to a diatom-dominated community; whereas at increased temperature diatoms co-dominated with flagellates. UVR exposure decreased the contribution of naked dinoflagellates (> 20 μm) and cryptophytes. On the other hand, the most frequent diatom, Cylindrotheca closterium was negatively affected at increased temperature, while small chlorophytes (< 10 μm), which were one of the dominant groups of flagellates, contributed significantly to the biomass at increased temperature at the end of the experiment. Synergistic effects of UVR and temperature were only detected at the species level in large diatoms (> 20 μm; e.g. Leptocylindrus sp. and Amphora sp.) and in cryptophytes (> 10 μm). Our results suggest that planktonic assemblages from the Mexican Caribbean are generally well-adapted to the high UVR fluxes and temperature with some species being positively influenced by increased temperature. However there are exceptions with some species being negatively affected by UVR, increased temperature or the combination of both factors. Therefore, our results indicate that under the high radiation conditions of tropical oceans, changes in community structure in terms of taxonomic composition and size distribution would occur in a scenario of global climate change. © 2013 Elsevier B.V. Source

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