Quantifying the response of phytoplankton photosynthesis
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Aquatic Sciences Meeting (Aquatic Sciences: Global And Regional Perspectives - North Meets South), 22-27 February 2015, Granada, Spain.
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In the Baltic Sea, climate change has caused shifts in the phytoplankton spring bloom communities with co-occurrence of diatoms and dinoflagellates. Such changes likely affect the composition and function of associated bacterioplankton,... more
In the Baltic Sea, climate change has caused shifts in the phytoplankton spring bloom communities with co-occurrence of diatoms and dinoflagellates. Such changes likely affect the composition and function of associated bacterioplankton, key members of the carbon cycling, although the actual effects are unknown. To understand how changes in phytoplankton impact on bacterioplankton composition and function, we analysed bacterioplankton communities and their production during different phases of the spring bloom in four consecutive years across the Baltic Sea, and related them to environmental variables. Phytoplankton communities varied largely in composition, modifying the taxonomic structure and richness of the associated bacterioplankton assemblages. In presence of certain diatoms (Achnanthes taeniata, Skeletonema costatum and Chaetoceros spp.), bacterial production and diversity were high and with more relative abundance of Flavobacteriia, Gammaproteobacteria and Betaproteobacteria...
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Research Interests: Geology and Oceanography
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The differential sensitivity of five chlorophyll c-containing marine microalgae to different components of solar radiation, e.g. photosynthetic active radiation (PAR), ultraviolet-A (UV-A) and ultraviolet-B (UV-B), was investigated in an... more
The differential sensitivity of five chlorophyll c-containing marine microalgae to different components of solar radiation, e.g. photosynthetic active radiation (PAR), ultraviolet-A (UV-A) and ultraviolet-B (UV-B), was investigated in an exclusion experiment involving exposure to PAR, PAR+UV-A and PAR+UV-A+UV-B (P-, PA- and PAB-treatment, respectively) for 20 min and subsequent recovery for up to 24 h in dim light. The decrease in the variable to maximal chlorophyll fluorescence ratio (F v /F m ) was used as indicator of photoinhibition. Changes in photosynthetic oxygen production, cell densities and pigment contents were also ascertained. The ratio Fv/Fm decreased in all the algae after exposure, but differences were found between the algae and the treatments. In relation to the inhibition extent, Chaetoceros sp. was the least affected alga in each treatment, while Phaeodactylum tricornutum was the most sensitive. Data of F v /F m during recovery fitted well to a sigmoid exponentia...
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Here it is reported the first detection of DV-chl a together with the usual chl a in the marine dinoflagellate Alexandrium ostenfeldii from the Baltic Sea. Growth response and photosynthetic parameters were examined at two irradiances (80... more
Here it is reported the first detection of DV-chl a together with the usual chl a in the marine dinoflagellate Alexandrium ostenfeldii from the Baltic Sea. Growth response and photosynthetic parameters were examined at two irradiances (80 and 240 μmol photons ·m(-2 ·) s(-1) ) and temperatures (15° and 19 °C) in a divinylic strain (AOTV-OS20) vs a monovinylic one (AOTV-OS16), using in vivo chl a fluorescence kinetics of PSII to characterize photosynthetic parameters by pulse amplitude modulated fluorescence, (14) C assimilation rates and toxin analyses. The divinylic isolate exhibited slower growth and stronger sensitivity to high irradiance than normal chl a strain. DV-chl a: chl a ratios decreased along time (from 11.3 to <0.5 after 10 months) and to restore them subcloning and selection of strains with highest DV-chl a content was required. A mutation and/or epigenetic changes in the expression of divinyl reductase gene/s in A. ostenfeldii may explain this altered pigment compo...
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The cyanobacterium Prochlorococcus is the smallest and most abundant photosynthetic organism on Earth [1]. Being a main global primary producer and ubiquist in the tropical and subtropical regions of the world’s oceans [2], it constitutes... more
The cyanobacterium Prochlorococcus is the smallest and most abundant photosynthetic organism on Earth [1]. Being a main global primary producer and ubiquist in the tropical and subtropical regions of the world’s oceans [2], it constitutes a good sentinel species for evaluating the effect of environmental stressors on oceanic photosynthesis. We developed a sensitive method to monitor the expression of two genes responsible of photosynthesis in Prochlorococcus , rbc L (RuBisCO) and psb A (D1 protein), using rnp B as reference gene [3,4]. We applied the method to samples from 63 stations of the Malaspina circumnavigation cruise (December 2010 - July 2011), sampled at three depths. In addition, natural communities of nano-and picoplankton were experimentally exposed to organic pollutant mixtures. Expression of Prochlorococcus rbcL and psbA genes correlated with several physical variables and other biological measurements, and were sensitive to low levels of organic pollutant mixtures. W...
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On December 1999 an interdisciplinary survey was carried out in the Gerlache Strait. The survey was focussed towards the interdisciplinary sampling (hydrography and distribution/structure of the planktonic community) of the Strait. One... more
On December 1999 an interdisciplinary survey was carried out in the Gerlache Strait. The survey was focussed towards the interdisciplinary sampling (hydrography and distribution/structure of the planktonic community) of the Strait. One along Strait and several cross Strait transects were carried out with high spatial resolution (mean dis- tance between stations of 5 nm). The distribution of hydrographic properties along
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ABSTRACT The light-induced de-epoxidation of xanthophylls is an important photoprotective mechanism in plants and algae. Exposure to ultraviolet radiation (UVR, 280–400 nm) can change the extent of xanthophyll de-epoxidation, but... more
ABSTRACT The light-induced de-epoxidation of xanthophylls is an important photoprotective mechanism in plants and algae. Exposure to ultraviolet radiation (UVR, 280–400 nm) can change the extent of xanthophyll de-epoxidation, but different types of responses have been reported. The de-epoxidation of violaxanthin (V) to zeaxanthin (Z), via the intermediate antheraxanthin, during exposure to UVR and photosynthetically active radiation (PAR, 400–700 nm) was studied in the marine picoplankter Nannochloropsis gaditana (Eustigmatophyceae) Lubián. Exposures used a filtered xenon lamp, which gives PAR and UVR similar to natural proportions. Exposure to UVR plus PAR increased de-epoxidation compared with under PAR alone. In addition, de-epoxidation increased with the irradiance and with the inclusion of shorter wavelengths in the spectrum. The spectral dependence of light-induced de-epoxidation under UVR and PAR exposure was well described by a model of epoxidation state (EPS) employing a biological weighting function (BWF). This model fit measured EPS in eight spectral treatments using Schott long pass filters, with six intensities for each filter, with a R2 = 0.90. The model predicts that 56% of violaxanthin is de-epoxidated, of which UVR can induce as much as 24%. The BWF for EPS was similar in shape to the BWF for UVR inhibition of photosynthetic carbon assimilation in N. gaditana but with about 22-fold lower effectiveness. These results demonstrate a connection between the presence of de-epoxidated Z and the inhibition under UVR exposures in N. gaditana. Nevertheless, they also indicate that de-epoxidation is insufficient to prevent UVR inhibition in this species.
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... JULIO AFONSO-CARRILLO* AND CRISTINA SOBRINOt ... 5); Punta Hidalgo (J. Reyes &amp;amp;amp;amp; M Sanson, 1 April 1992, TFC Phyc 9909); El Medano (J. Reyes &amp;amp;amp;amp; M. Sanson, 29 October 1 99 1 ,TFC Phyc 77 1 0, 77 1 1... more
... JULIO AFONSO-CARRILLO* AND CRISTINA SOBRINOt ... 5); Punta Hidalgo (J. Reyes &amp;amp;amp;amp; M Sanson, 1 April 1992, TFC Phyc 9909); El Medano (J. Reyes &amp;amp;amp;amp; M. Sanson, 29 October 1 99 1 ,TFC Phyc 77 1 0, 77 1 1 ; M. Gonн zalez, 28 April 1 997, TFC Phyc 1 04 1 7) ; Pena Marfa (Me ...
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It is well known that UV radiation can cause deleterious effects to the physiological performance, growth and species assemblages of marine primary producers. In this review we describe the range of interactions observed between these... more
It is well known that UV radiation can cause deleterious effects to the physiological performance, growth and species assemblages of marine primary producers. In this review we describe the range of interactions observed between these impacts of ultraviolet radiation (UVR, 280-400 nm) with other environmental factors such as the availability of photosynthetically active radiation (PAR), nutrient status and levels of dissolved CO2, all of which can, in turn, be influenced by global climate change. Thus, increases in CO2 levels can affect the sensitivity of some species to UV-B radiation (UV-B), while others show no such impact on UV-B susceptibility. Both nitrogen- and phosphorus-limitation can have direct interactive effects on the susceptibility of algal cells and communities to UVR, though such effects are somewhat variable. Nutrient depletion can also potentially lead to a dominance of smaller celled species, which may be less able to screen out and are thus likely to be more susceptible to UVR-induced damage. The variability of responses to such interactions can lead to alterations in the species composition of algal assemblages.
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ABSTRACT The relationship of photosynthesis (14C incorporation) to ultraviolet (UVR) and photosynthetically active radiation (PAR) was measured over the course of the late-spring to early-summer phytoplankton bloom in the Ross Sea Polynya... more
ABSTRACT The relationship of photosynthesis (14C incorporation) to ultraviolet (UVR) and photosynthetically active radiation (PAR) was measured over the course of the late-spring to early-summer phytoplankton bloom in the Ross Sea Polynya (Southern Ocean). Experiments were conducted in November 2005 to determine PAR-only photosynthesis-irradiance (P-E) curves, biological weighting functions (BWFs) using a new version of the “photoinhibitron” laboratory spectral incubator, and variation in photosynthesis under high vs. low solar UVR treatments in on-deck incubations. These observations were incorporated into a new spectral model of photosynthetic response to UVR + PAR with time-dependent repair rates. The distinguishing feature of this model is that repair scales with inhibition up to a maximum absolute repair rate (rmax). Once repair is limited at the maximum rate, additional exposure has a more severe inhibitory effect on photosynthesis, consistent with measured exposure response curves. Parameters for the BWFRmax/P-E model were determined for 10 sampling locations ranging from mixed diatom and Phaeocystis antarctica assemblages at the beginning of the bloom to assemblages dominated by P. antarctica at the peak of the bloom. The model explained 86-97% of the measured spectral variation with BWFs severalfold higher (more inhibitory) than those previously measured in the Weddell-Scotia Confluence and coastal waters near the Antarctic Peninsula. Predicted relative productivity (ratio of modeled photosynthesis under high vs. low UVR) was close to observed relative productivity, but absolute photosynthetic rates were higher in the on-deck incubations than in the photoinhibitron.