Estacion de Fotobiologia Playa Union

Rawson, Argentina

Estacion de Fotobiologia Playa Union

Rawson, Argentina
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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.

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.

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.

Halac S.R.,Estacion de Fotobiologia Playa Union | Halac S.R.,Instituto Nacional del Agua | Villafane V.E.,Estacion de Fotobiologia Playa Union | Villafane V.E.,CONICET | And 2 more authors.
Journal of Photochemistry and Photobiology B: Biology | Year: 2010

The aim of this study was to assess the combined effects of temperature and UVR on the photosynthesis performance of two diatoms - Chaetoceros gracilis and Thalassiosira weissflogii. In particular, we evaluated the role of UVR in inducing photoinhibition and the potential mitigation of this negative effect by an increase in temperature. Cultures were pre-acclimated at two temperatures - 18 °C and 23 °C - and exposed to different radiation treatments - UVR. +. PAR (280-700 nm); UV-A. +. PAR (315-700 nm) and PAR only (400-700 nm) under two temperatures: 18 °C (local surface summer water temperature) and 23 °C (simulating a potential increase estimated by the year 2100). Exposure to natural solar radiation resulted in UVR-induced photoinhibition that was significantly higher in T. weissflogii than in C. gracilis. Both species benefited from the higher temperature (23 °C) resulting in a lower photoinhibition as compared to samples exposed at 18 °C. Inter-specific differences were determined in regard to the heat dissipation processes (NPQ) which were higher at high temperatures, and much more evident in C. gracilis than in T. weissflogii. The analyses of inhibition and recovery rates under different irradiances indicate that the balance between negative (inhibition) and positive (repair-dissipation) effects shifted towards a more positive balance with increasing temperature. Our results highlight for a beneficial effect of temperature on photosynthesis performance during exposure to UVR, although important inter-specific differences are found, probably due to differences in cell size as well as in their distribution within the oceanic realm (i.e., coastal versus oceanic species). © 2010 Elsevier B.V.

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.

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.

Hader D.-P.,Neue Str. 9 | Villafane V.E.,Estacion de Fotobiologia Playa Union | Villafane V.E.,CONICET | Helbling E.W.,Estacion de Fotobiologia Playa Union | Helbling E.W.,CONICET
Photochemical and Photobiological Sciences | Year: 2014

The productivity of aquatic primary producers depends on a number of biotic and abiotic factors, such as pH, CO2 concentration, temperature, nutrient availability, solar UV and PAR irradiances, mixing frequency as well as herbivore pressure and the presence of viruses, among others. The effects of these factors, within a climate change context, may be additive, synergistic or antagonistic. Since some of them, e.g. solar radiation and temperature, vary along a latitudinal gradient, this perspective about the effects of global climate change on primary producers will consider ecosystems individually, separated into polar (Arctic and Antarctic), temperate and tropical waters. As coastal waters are characterized by lower light penetration and higher DOM and nutrient concentrations, they are considered in a separate section. Freshwater systems are also governed by different conditions and therefore also treated in their own section. Overall, we show that although there are general common trends of changes in variables associated with global change (e.g. the impact of UVR on photosynthesis tends to decrease with increasing temperature and nutrient input), the responses of aquatic primary producers have great variability in the different ecosystems across latitudes. This is mainly due to direct or indirect effects associated with physico-chemical changes that occur within water bodies. Therefore we stress the need for regional predictions on the responses of primary producers to climate change as it is not warranted to extrapolate from one system to another. This journal is © the Partner Organisations 2014.

Giordanino M.V.F.,Estacion de Fotobiologia Playa Union | Giordanino M.V.F.,CONICET | Strauch S.M.,Estacion de Fotobiologia Playa Union | Villafane V.E.,Estacion de Fotobiologia Playa Union | And 3 more authors.
Journal of Photochemistry and Photobiology B: Biology | Year: 2011

During the late austral spring of 2009 we carried out experiments (4 days of duration) with four cyanobacteria species, Anabaena sp., Nostoc sp., Arthrospira platensis and Microcystis sp., to assess the combined effects of temperature and solar radiation on photosynthesis performance and morphology. Two experimental temperatures (18°C and 23°C, simulating a 5°C increase under a scenario of climate change) and three radiation treatments (by using different filters/materials) were implemented: (i) P (PAR, 400-700 nm), (ii) PA (PAR + UV-A, 320-700 nm) and, (iii) PAB (PAR + UV-A + UV-B, 280-700 nm). In general, samples under the P treatment had less decrease/higher recovery rates of effective photochemical quantum yield (Y) than those receiving UV-A or UV-A + UV-B. The effects of increased temperature were species-specific: At the end of the experiments, it was seen that increased temperature benefited photosynthetic performance of Anabaena sp. and Nostoc sp. but not of Microcystis sp. and A. platensis. Higher temperature was also associated to an increase in the chain area of Anabaena sp., and to bigger trichomes in A. platensis; however, no morphological effects were observed in Microcystis sp. In addition, in Nostoc sp. the increase in temperature counteracted the UVR impact on the reduction of the chain area. How these effects and mechanisms will affect the trophodynamics and production of aquatic ecosystems is still uncertain, but the specificity of the responses suggests that not all cyanobacteria would be equally benefited by temperature increases therefore affecting the balance and interaction among species in the water column. © 2011 Elsevier B.V. All rights reserved.

Walter Helbling E.,Estacion de Fotobiologia Playa Union | Walter Helbling E.,CONICET | Perez D.E.,Estacion de Fotobiologia Playa Union | Medina C.D.,Estacion de Fotobiologia Playa Union | And 3 more authors.
Limnology and Oceanography | Year: 2010

The aim of this study was to determine the effects of the tidal dynamics and physical forcing on phytoplankton distribution and photosynthesis dynamics in the Chubut River estuary, Argentina. Physical, chemical, and biological variables measured at the surface and at the bottom of the water column (variable between 0.5-m and 6-m depth) were made every 30-45 d during tidal cycles (13 h of duration) from June 2007 to November 2008 (11 tidal cycles). There was a remarkable consistency among different tidal cycles throughout the year, with strong stratification during the flood and almost complete mixing during the period high tide-ebb-low tide. Strong stratification during the flood resulted in significant inhibition of photosynthesis of mostly nanoplankton cells at the surface, while microplankton sank out of this upper layer and, thus, were less inhibited. Mixing conditions during the ebb, together with relatively high concentration of dissolved organic matter and particulate material, resulted in partial protection for phytoplankton against solar radiation stress and, therefore, relatively high maximum electron transport rate values were determined under this condition. However, the lowest photoinhibition and higher maximum rate of production (Pmax) values occurred at depth during stratified conditions, probably due to relatively low solar radiation in this condition. Tidal dynamics together with physical forcing are key factors that condition the distribution, dynamics, and photoinhibition of phytoplankton in the Chubut River estuary. © 2010, by the American Society of Limnology and Oceanography, Inc.

Manrique J.M.,Estacion de Fotobiologia Playa Union | Calvo A.Y.,Estacion de Fotobiologia Playa Union | Jones L.R.,Estacion de Fotobiologia Playa Union
Virus Genes | Year: 2012

A phylogenetic analysis of new Ostreococcus virus (OV) sequences from the Patagonian Coast, Argentina, and homologous sequences from public databases was performed. This analysis showed that the Patagonian sequences represented a divergent viral clade and that the rest of OV sequences analyzed here were clustered into six additional phylogenetic groups. Analyses of 18S gene libraries supported a close relationship of the Patagonian Ostreococcus host with clade A sequences described elsewhere, corroborating previous studies indicating that clade A strains are ubiquitous. Besides the Patagonian OV sequences, several phylogenetic groupings were linked to particular geographic locations, suggesting a role for allopatric cladogenesis in viral diversification. However, and in agreement with previous observations, other viral lineages included sequences with diverse geographic origins. These findings, together with analyses of ancestral trait trajectories performed here, are consistent with an evolutionary dynamics in which geographical isolation has a role in OV diversification but can be followed by rapid dispersion to remote places. © Springer Science+Business Media, LLC 2012.

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