Publications by authors named "Angela Wulff"

19 Publications

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A reflection on four impactful Ambio papers: The biotic perspective : This article belongs to Ambio's 50th Anniversary Collection. Theme: Climate change impacts.

Ambio 2021 Mar 1. Epub 2021 Mar 1.

Department of Biological and Environmental Sciences, University of Gothenburg, Carl Skottsbergs gata 22B, 413 19, Gothenburg, Sweden.

Climate change represents one of the most pressing societal and scientific challenges of our time. While much of the current research on climate change focuses on future prediction, some of the strongest signals of warming can already be seen in Arctic and alpine areas, where temperatures are rising faster than the global average, and in the oceans, where the combination of rising temperatures and acidification due to increased CO concentrations has had catastrophic consequences for sensitive marine organisms inhabiting coral reefs. The scientific papers highlighted as part of this anniversary issue represent some of the most impactful advances in our understanding of the consequences of anthropogenic climate change. Here, we reflect on the legacy of these papers from the biotic perspective.
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http://dx.doi.org/10.1007/s13280-020-01442-5DOI Listing
March 2021

At the frontier of climate change: Red alert from the European Alps, the Arctic and coral reefs : This article belongs to Ambio's 50th Anniversary Collection. Theme: Climate change impacts.

Authors:
Angela Wulff

Ambio 2021 Mar 1. Epub 2021 Mar 1.

Department of Biological & Environmental Sciences, Box 461, 405 30, Gothenburg, Sweden.

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http://dx.doi.org/10.1007/s13280-021-01514-0DOI Listing
March 2021

Cultivation and Photophysiological Characteristics of Desmids in Moderately Saline Aquaculture Wastewater.

J Phycol 2021 Feb 17. Epub 2021 Feb 17.

Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, SE40530, Göteborg, Sweden.

Although desmids typically inhabit freshwater environments characterized by low amounts of nutrients and low salinity, several desmid species have been recorded in eutrophic waters, indicating their adaptation to elevated pollution and conductivity. This study aimed to determine whether desmids could be used for remediation of moderately saline aquaculture wastewater (AWW) from a fish farm situated in the southeast of Sweden. Fourteen desmid strains isolated from different climates (tropical to polar) and trophic conditions (oligotrophic to eutrophic) were cultivated in diluted AWW and we estimated their growth rates, biomass, nutrient removal efficiency, chlorophyll fluorescence parameters and cellular C, N and P quotas. Despite being grown at moderate salinity, unfavourable N:P ratio, and relatively low light/temperature regime the eutrophic strains, Cosmarium humile, Cosmarium laeve and a meso-oligotrophic species Cosmarium impressulum, completely absorbed nitrate and phosphate from AWW media after 7 d, indicating their potential for remediation of fish effluents in colder climates. These species, along with the typical eutrophic species, Cosmarium meneghinii and Staurastrum chaetoceras, had biomass in the range 0.45-1.19 g · L while maximum growth rates ranged from 0.36 to 0.51 · d , similar to published rates for several fast-growing green microalgae cultivated in various AWW types. Tropical desmids had distinctly high values of saturating irradiance (I  > 1,000 µmol photons · m  · s ), and, along with eutrophic desmids, had high potential electron transport (rETR  > 155 rel. units). Hence, the desmids studied demonstrated inherent photophysiological responses corresponding to their climate and trophic origin under the suboptimal growth conditions.
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http://dx.doi.org/10.1111/jpy.13150DOI Listing
February 2021

Glacial melt disturbance shifts community metabolism of an Antarctic seafloor ecosystem from net autotrophy to heterotrophy.

Commun Biol 2021 Jan 29;4(1):148. Epub 2021 Jan 29.

Marine Biology Research Group, Ghent University, Ghent, Belgium.

Climate change-induced glacial melt affects benthic ecosystems along the West Antarctic Peninsula, but current understanding of the effects on benthic primary production and respiration is limited. Here we demonstrate with a series of in situ community metabolism measurements that climate-related glacial melt disturbance shifts benthic communities from net autotrophy to heterotrophy. With little glacial melt disturbance (during cold El Niño spring 2015), clear waters enabled high benthic microalgal production, resulting in net autotrophic benthic communities. In contrast, water column turbidity caused by increased glacial melt run-off (summer 2015 and warm La Niña spring 2016) limited benthic microalgal production and turned the benthic communities net heterotrophic. Ongoing accelerations in glacial melt and run-off may steer shallow Antarctic seafloor ecosystems towards net heterotrophy, altering the metabolic balance of benthic communities and potentially impacting the carbon balance and food webs at the Antarctic seafloor.
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http://dx.doi.org/10.1038/s42003-021-01673-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7846736PMC
January 2021

Future HAB science: Directions and challenges in a changing climate.

Harmful Algae 2020 01 30;91:101632. Epub 2019 Sep 30.

Environment and Fisheries Sciences Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd. E., Seattle, WA 98112, USA.

There is increasing concern that accelerating environmental change attributed to human-induced warming of the planet may substantially alter the patterns, distribution and intensity of Harmful Algal Blooms (HABs). Changes in temperature, ocean acidification, precipitation, nutrient stress or availability, and the physical structure of the water column all influence the productivity, composition, and global range of phytoplankton assemblages, but large uncertainty remains about how integration of these climate drivers might shape future HABs. Presented here are the collective deliberations from a symposium on HABs and climate change where the research challenges to understanding potential linkages between HABs and climate were considered, along with new research directions to better define these linkages. In addition to the likely effects of physical (temperature, salinity, stratification, light, changing storm intensity), chemical (nutrients, ocean acidification), and biological (grazer) drivers on microalgae (senso lato), symposium participants explored more broadly the subjects of cyanobacterial HABs, benthic HABs, HAB effects on fisheries, HAB modelling challenges, and the contributions that molecular approaches can bring to HAB studies. There was consensus that alongside traditional research, HAB scientists must set new courses of research and practices to deliver the conceptual and quantitative advances required to forecast future HAB trends. These different practices encompass laboratory and field studies, long-term observational programs, retrospectives, as well as the study of socioeconomic drivers and linkages with aquaculture and fisheries. In anticipation of growing HAB problems, research on potential mitigation strategies should be a priority. It is recommended that a substantial portion of HAB research among laboratories be directed collectively at a small sub-set of HAB species and questions in order to fast-track advances in our understanding. Climate-driven changes in coastal oceanographic and ecological systems are becoming substantial, in some cases exacerbated by localized human activities. That, combined with the slow pace of decreasing global carbon emissions, signals the urgency for HAB scientists to accelerate efforts across disciplines to provide society with the necessary insights regarding future HAB trends.
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http://dx.doi.org/10.1016/j.hal.2019.101632DOI Listing
January 2020

Fatty acids as chemotaxonomic and ecophysiological traits in green microalgae (desmids, Zygnematophyceae, Streptophyta): A discriminant analysis approach.

Phytochemistry 2020 Feb 19;170:112200. Epub 2019 Nov 19.

Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, SE40530, Göteborg, Sweden.

Desmids (Zygnematophyceae) are a group of poorly studied green microalgae. The aim of the present study was to identify fatty acids (FAs) that could be used as biomarkers in desmids in general, and to determine FAs as traits within different ecophysiological desmid groups. FA profiles of 29 desmid strains were determined and analysed with respect to their geographic origin, trophic preference and age of cultivation. It appeared that merely FAs present in relatively large proportions such as palmitic, linoleic, α-linolenic and hexadecatrienoic acids could be used as biomarkers for reliable categorization of this microalgal group. Linear discriminant analysis applied to three a priori defined groups of desmids, revealed clear strain-specific characteristics regarding FA distribution, influenced by climate and trophic conditions at the source sites as well as by the age of culture and growth phase. Accordingly, when considering FAs for the determination of lower taxonomic ranks we recommend using the term "trait" instead of "biomarker", as the latter designates unchangeable "fingerprint" of a specific taxon. Furthermore, despite that desmids were regarded as microalgae having stable genomes, long-term cultivation appeared to cause modifications in FA metabolic pathways, evident as a larger proportion of stearidonic acid in desmid strains cultivated over extensive time periods (>35 years).
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http://dx.doi.org/10.1016/j.phytochem.2019.112200DOI Listing
February 2020

Effects of scrubber washwater discharge on microplankton in the Baltic Sea.

Mar Pollut Bull 2019 Aug 3;145:316-324. Epub 2019 Jun 3.

Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, SE 405 30 Gothenburg, Sweden.

In 2020, the global cap of maximum allowable sulphur content in marine fuel will be reduced from the current 3.5% to 0.5%. Another way to reduce the sulphur emissions is to install a seawater scrubber that cleans exhausts but instead release acidic water containing nutrients and contaminants back to the marine environment. In the current study, scrubber washwater was tested on a Baltic Sea microplankton community. A significant increase in chlorophyll a, particulate organic phosphorus (POP), carbon (POC) and nitrogen (PON) were observed when the community was exposed to 10% scrubber washwater for 13 days as compared to the control. A laboratory experiment with the filamentous cyanobacteria Nodularia spumigena and the chain-forming diatom Melosira cf. arctica showed negative responses in photosynthetic activity (EC10 = 8.6% for N. spumigena) and increased primary productivity (EC10 = 5.5% for M. cf. arctica), implying species-specific responses to scrubber washwater discharge.
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http://dx.doi.org/10.1016/j.marpolbul.2019.05.023DOI Listing
August 2019

Microalgal photophysiology and macronutrient distribution in summer sea ice in the Amundsen and Ross Seas, Antarctica.

PLoS One 2018 10;13(4):e0195587. Epub 2018 Apr 10.

Department of Marine Sciences, University of Gothenburg, Göteborg, Sweden.

Our study addresses how environmental variables, such as macronutrients concentrations, snow cover, carbonate chemistry and salinity affect the photophysiology and biomass of Antarctic sea-ice algae. We have measured vertical profiles of inorganic macronutrients (phosphate, nitrite + nitrate and silicic acid) in summer sea ice and photophysiology of ice algal assemblages in the poorly studied Amundsen and Ross Seas sectors of the Southern Ocean. Brine-scaled bacterial abundance, chl a and macronutrient concentrations were often high in the ice and positively correlated with each other. Analysis of photosystem II rapid light curves showed that microalgal cells in samples with high phosphate and nitrite + nitrate concentrations had reduced maximum relative electron transport rate and photosynthetic efficiency. We also observed strong couplings of PSII parameters to snow depth, ice thickness and brine salinity, which highlights a wide range of photoacclimation in Antarctic pack-ice algae. It is likely that the pack ice was in a post-bloom situation during the late sea-ice season, with low photosynthetic efficiency and a high degree of nutrient accumulation occurring in the ice. In order to predict how key biogeochemical processes are affected by future changes in sea ice cover, such as in situ photosynthesis and nutrient cycling, we need to understand how physicochemical properties of sea ice affect the microbial community. Our results support existing hypothesis about sea-ice algal photophysiology, and provide additional observations on high nutrient concentrations in sea ice that could influence the planktonic communities as the ice is retreating.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0195587PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5892929PMC
July 2018

Diatom frustules protect DNA from ultraviolet light.

Sci Rep 2018 03 23;8(1):5138. Epub 2018 Mar 23.

Biomolecular and organic electronics, Department of Physics, Chemistry and Biology, Linköping University, 581 83, Linköping, Sweden.

The evolutionary causes for generation of nano and microstructured silica by photosynthetic algae are not yet deciphered. Diatoms are single photosynthetic algal cells populating the oceans and waters around the globe. They generate a considerable fraction (20-30%) of all oxygen from photosynthesis, and 45% of total primary production of organic material in the sea. There are more than 100,000 species of diatoms, classified by the shape of the glass cage in which they live, and which they build during algal growth. These glass structures have accumulated for the last 100 million of years, and left rich deposits of nano/microstructured silicon oxide in the form of diatomaceous earth around the globe. Here we show that reflection of ultraviolet light by nanostructured silica can protect the deoxyribonucleic acid (DNA) in the algal cells, and that this may be an evolutionary cause for the formation of glass cages.
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http://dx.doi.org/10.1038/s41598-018-21810-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5865130PMC
March 2018

Ocean acidification and desalination: climate-driven change in a Baltic Sea summer microplanktonic community.

Mar Biol 2018 9;165(4):63. Epub 2018 Mar 9.

2Department of Marine Sciences, University of Gothenburg, Box 461, 405 30 Göteborg, Sweden.

Helcom scenario modelling suggests that the Baltic Sea, one of the largest brackish-water bodies in the world, could expect increased precipitation (decreased salinity) and increased concentration of atmospheric CO over the next 100 years. These changes are expected to affect the microplanktonic food web, and thereby nutrient and carbon cycling, in a complex and possibly synergistic manner. In the Baltic Proper, the extensive summer blooms dominated by the filamentous cyanobacteria sp., spp. and the toxic contribute up to 30% of the yearly new nitrogen and carbon exported to the sediment. In a 12 days outdoor microcosm experiment, we tested the combined effects of decreased salinity (from 6 to 3) and elevated CO concentrations (380 and 960 µatm) on a natural summer microplanktonic community, focusing on diazotrophic filamentous cyanobacteria. Elevated CO had no significant effects on the natural microplanktonic community except for higher biovolume of spp. and lower biomass of heterotrophic bacteria. At the end of the experimental period, heterotrophic bacterial abundance was correlated to the biovolume of Lower salinity significantly affected cyanobacteria together with biovolumes of dinoflagellates, diatoms, ciliates and heterotrophic bacteria, with higher biovolume of spp. and lower biovolume of , dinoflagellates, diatoms, ciliates and heterotrophic bacteria in reduced salinity. Although the salinity effects on diatoms were apparent, they could not clearly be separated from the influence of inorganic nutrients. We found a clear diurnal cycle in photosynthetic activity and pH, but without significant treatment effects. The same diurnal pattern was also observed in situ (CO, pH). Thus, considering the Baltic Proper, we do not expect any dramatic effects of increased CO in combination with decreased salinity on the microplanktonic food web. However, long-term effects of the experimental treatments need to be further studied, and indirect effects of the lower salinity treatments could not be ruled out. Our study adds one piece to the complicated puzzle to reveal the combined effects of increased CO and reduced salinity levels on the Baltic microplanktonic community.
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http://dx.doi.org/10.1007/s00227-018-3321-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5843668PMC
March 2018

Harmful algal blooms and climate change: Learning from the past and present to forecast the future.

Harmful Algae 2015 Nov 22;49:68-93. Epub 2015 Sep 22.

Romberg Tiburon Center for Environmental Studies, San Francisco State University, 3152 Paradise Drive, Tiburon, CA 94920-1205, USA.

Climate change pressures will influence marine planktonic systems globally, and it is conceivable that harmful algal blooms may increase in frequency and severity. These pressures will be manifest as alterations in temperature, stratification, light, ocean acidification, precipitation-induced nutrient inputs, and grazing, but absence of fundamental knowledge of the mechanisms driving harmful algal blooms frustrates most hope of forecasting their future prevalence. Summarized here is the consensus of a recent workshop held to address what currently is known and not known about the environmental conditions that favor initiation and maintenance of harmful algal blooms. There is expectation that harmful algal bloom (HAB) geographical domains should expand in some cases, as will seasonal windows of opportunity for harmful algal blooms at higher latitudes. Nonetheless there is only basic information to speculate upon which regions or habitats HAB species may be the most resilient or susceptible. Moreover, current research strategies are not well suited to inform these fundamental linkages. There is a critical absence of tenable hypotheses for how climate pressures mechanistically affect HAB species, and the lack of uniform experimental protocols limits the quantitative cross-investigation comparisons essential to advancement. A HAB "best practices" manual would help foster more uniform research strategies and protocols, and selection of a small target list of model HAB species or isolates for study would greatly promote the accumulation of knowledge. Despite the need to focus on keystone species, more studies need to address strain variability within species, their responses under multifactorial conditions, and the retrospective analyses of long-term plankton and cyst core data; research topics that are departures from the norm. Examples of some fundamental unknowns include how larger and more frequent extreme weather events may break down natural biogeographic barriers, how stratification may enhance or diminish HAB events, how trace nutrients (metals, vitamins) influence cell toxicity, and how grazing pressures may leverage, or mitigate HAB development. There is an absence of high quality time-series data in most regions currently experiencing HAB outbreaks, and little if any data from regions expected to develop HAB events in the future. A subset of observer sites is recommended to help develop stronger linkages among global, national, and regional climate change and HAB observation programs, providing fundamental datasets for investigating global changes in the prevalence of harmful algal blooms. Forecasting changes in HAB patterns over the next few decades will depend critically upon considering harmful algal blooms within the competitive context of plankton communities, and linking these insights to ecosystem, oceanographic and climate models. From a broader perspective, the nexus of HAB science and the social sciences of harmful algal blooms is inadequate and prevents quantitative assessment of impacts of future HAB changes on human well-being. These and other fundamental changes in HAB research will be necessary if HAB science is to obtain compelling evidence that climate change has caused alterations in HAB distributions, prevalence or character, and to develop the theoretical, experimental, and empirical evidence explaining the mechanisms underpinning these ecological shifts.
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http://dx.doi.org/10.1016/j.hal.2015.07.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4800334PMC
November 2015

Long-term acclimation to elevated pCO2 alters carbon metabolism and reduces growth in the Antarctic diatom Nitzschia lecointei.

Proc Biol Sci 2015 Sep;282(1815)

Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden.

Increasing atmospheric CO2 levels are driving changes in the seawater carbonate system, resulting in higher pCO2 and reduced pH (ocean acidification). Many studies on marine organisms have focused on short-term physiological responses to increased pCO2, and few on slow-growing polar organisms with a relative low adaptation potential. In order to recognize the consequences of climate change in biological systems, acclimation and adaptation to new environments are crucial to address. In this study, physiological responses to long-term acclimation (194 days, approx. 60 asexual generations) of three pCO2 levels (280, 390 and 960 µatm) were investigated in the psychrophilic sea ice diatom Nitzschia lecointei. After 147 days, a small reduction in growth was detected at 960 µatm pCO2. Previous short-term experiments have failed to detect altered growth in N. lecointei at high pCO2, which illustrates the importance of experimental duration in studies of climate change. In addition, carbon metabolism was significantly affected by the long-term treatments, resulting in higher cellular release of dissolved organic carbon (DOC). In turn, the release of labile organic carbon stimulated bacterial productivity in this system. We conclude that long-term acclimation to ocean acidification is important for N. lecointei and that carbon overconsumption and DOC exudation may increase in a high-CO2 world.
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http://dx.doi.org/10.1098/rspb.2015.1513DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4614754PMC
September 2015

Physicochemical control of bacterial and protist community composition and diversity in Antarctic sea ice.

Environ Microbiol 2015 Oct 7;17(10):3869-81. Epub 2015 May 7.

Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, SE-40530, Sweden.

Due to climate change, sea ice experiences changes in terms of extent and physical properties. In order to understand how sea ice microbial communities are affected by changes in physicochemical properties of the ice, we used 454-sequencing of 16S and 18S rRNA genes to examine environmental control of microbial diversity and composition in Antarctic sea ice. We observed a high diversity and richness of bacteria, which were strongly negatively correlated with temperature and positively with brine salinity. We suggest that bacterial diversity in sea ice is mainly controlled by physicochemical properties of the ice, such as temperature and salinity, and that sea ice bacterial communities are sensitive to seasonal and environmental changes. For the first time in Antarctic interior sea ice, we observed a strong eukaryotic dominance of the dinoflagellate phylotype SL163A10, comprising 63% of the total sequences. This phylotype is known to be kleptoplastic and could be a significant primary producer in sea ice. We conclude that mixotrophic flagellates may play a greater role in the sea ice microbial ecosystem than previously believed, and not only during the polar night but also during summer when potential food sources are abundant.
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http://dx.doi.org/10.1111/1462-2920.12865DOI Listing
October 2015

Inheritance of mitochondrial DNA in the Pennate diatom Haslea ostrearia (Naviculaceae) during auxosporulation suggests a uniparental transmission.

Protist 2013 May 7;164(3):340-51. Epub 2013 Mar 7.

MMS EA 2160, Faculté des Sciences et des Techniques, Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France.

We present the first study examining mtDNA transmission in diatoms, using sexual progeny of the pennate species Haslea ostrearia (Naviculaceae). A fragment of the cytochrome oxidase subunit I gene (cox1) with 7 nucleic substitutions between parental clones was used as a parental tracer in 16 F1 clones obtained from two pairs of mating crosses. Each cross involved a parental clone isolated from France (Bay of Bourgneuf) and Sweden (Kattegat Bay). We determined that all progeny possessed only one cox1 parental haplotype. These results suggest that the mitochondrial DNA transmission in H. ostrearia is uniparental. Implications and new topics of investigation are discussed.
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http://dx.doi.org/10.1016/j.protis.2013.01.001DOI Listing
May 2013

UVR defense mechanisms in eurytopic and invasive Gracilaria vermiculophylla (Gracilariales, Rhodophyta).

Physiol Plant 2012 Oct 24;146(2):205-16. Epub 2012 Apr 24.

Department of Marine Ecology, Marine Botany, University of Gothenburg, Göteborg, Sweden.

The invasive success of Gracilaria vermiculophylla has been attributed to its wide tolerance range to different abiotic factors, but its response to ultraviolet radiation (UVR) is yet to be investigated. In the laboratory, carpospores and vegetative thalli of an Atlantic population were exposed to different radiation treatments consisting of high PAR (photosynthetically active radiation) only (P), PAR+UV-A (PA) and PAR+UV-A+UV-B (PAB). Photosynthesis of carpospores was photoinhibited under different radiation treatments but photosystem II (PSII) function was restored after 12 h under dim white light. Growth of vegetative thalli was significantly higher under radiation supplemented with UVR. Decrease in chlorophyll a (Chl a) under daily continuous 16-h exposure to 300 µmol photons m(-2) s(-1) of PAR suggests preventive accumulation of excited chlorophyll molecules within the antennae to minimize the generation of dangerous reactive oxygen species. Moreover, an increase in total carotenoids and xanthophyll cycle pigments (i.e. violaxanthin, antheraxanthin and zeaxanthin) further suggests effective photoprotection under UVR. The presence of the ketocarotenoid β-cryptoxanthin also indicates protection against UVR and oxidative stress. The initial concentration of total mycosporine-like amino acids (MAAs) in freshly-released spores increased approximately four times after 8-h laboratory radiation treatments. On the other hand, initial specific MAAs in vegetative thalli changed in composition after 7-day exposure to laboratory radiation conditions without affecting the total concentration. The above responses suggest that G. vermiculophylla have multiple UVR defense mechanisms to cope with the dynamic variation in light quantity and quality encountered in its habitat. Beside being eurytopic, the UVR photoprotective mechanisms likely contribute to the current invasive success of the species in shallow lagoons and estuaries exposed to high solar radiation.
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http://dx.doi.org/10.1111/j.1399-3054.2012.01615.xDOI Listing
October 2012

Interspecific resource competition-combined effects of radiation and nutrient limitation on two diazotrophic filamentous cyanobacteria.

Microb Ecol 2012 May 6;63(4):736-50. Epub 2011 Nov 6.

Department of Marine Ecology, Marine Botany, University of Gothenburg, Göteborg, Sweden.

The cyanobacterial blooms in the Baltic Sea are dominated by diazotrophic cyanobacteria, the potentially toxic species Aphanizomenon sp. and the toxic species Nodularia spumigena. The seasonal succession with peaks of Aphanizomenon sp., followed by peaks of N. spumigena, has been explained by the species-specific niches of the two species. In a three-factorial outdoor experiment, we tested if nutrient and radiation conditions may impact physiological and biochemical responses of N. spumigena and Aphanizomenon sp. in the presence or absence of the other species. The two nutrient treatments were f/2 medium without NO (3) (-) (-N) and f/2 medium without PO (4) (3-) (-P), and the two ambient radiation treatments were photosynthetic active radiation >395 nm (PAR) and PAR + UV-A + UV-B >295 nm. The study showed that Aphanizomenon sp. was not negatively affected by the presence of N. spumigena and that N. spumigena was better adapted to both N and P limitation in interaction with ultraviolet radiation (UVR, 280-400 nm). In the Baltic Sea, these physical conditions are likely to prevail in the surface water during summer. Interestingly, the specific growth rate of N. spumigena was stimulated by the presence of Aphanizomenon sp. We suggest that the seasonal succession, with peaks of Aphanizomenon sp. followed by peaks of N. spumigena, is a result from species-specific preferences of environmental conditions and/or stimulation by Aphanizomenon sp. rather than an allelopathic effect of N. spumigena. The results from our study, together with a predicted stronger stratification due to effects of climate change in the Baltic Sea with increased temperature and increased precipitation and increased UV-B due to ozone losses, reflect a scenario with a continuing future dominance of the toxic N. spumigena.
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http://dx.doi.org/10.1007/s00248-011-9964-yDOI Listing
May 2012

SENSITIVITY OF ANTARCTIC UROSPORA PENICILLIFORMIS (ULOTRICHALES, CHLOROPHYTA) TO ULTRAVIOLET RADIATION IS LIFE-STAGE DEPENDENT(1).

J Phycol 2009 Jun 1;45(3):600-9. Epub 2009 Jun 1.

Institute for Polar Ecology, Wischhofstraße 1-3, Bldg. 12, D-24148 Kiel, GermanyCONICET, Instituto Antártico Argentino, Cerrito 1248 (C1010AAZ), CA de Buenos Aires, ArgentinaSection Functional Ecology, Department Seaweed Biology, Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, D-27570 Bremerhaven, GermanyBiozentrum Klein Flottbek, University of Hamburg, Ohnhorst-Str. 18, D-22609 Hamburg, GermanyInstituto Antártico Argentino, Cerrito 1248 (C1010AAZ), CA de Buenos Aires, ArgentinaDepartment of Marine Ecology, Marine Botany, Gothenburg University, Box 461, SE 40530 Gothenburg, Sweden.

The sensitivity of different life stages of the eulittoral green alga Urospora penicilliformis (Roth) Aresch. to ultraviolet radiation (UVR) was examined in the laboratory. Gametophytic filaments and propagules (zoospores and gametes) released from filaments were separately exposed to different fluence of radiation treatments consisting of PAR (P = 400-700 nm), PAR + ultraviolet A (UVA) (PA, UVA = 320-400 nm), and PAR + UVA + ultraviolet B (UVB) (PAB, UVB = 280-320 nm). Photophysiological indices (ETRmax , Ek , and α) derived from rapid light curves were measured in controls, while photosynthetic efficiency and amount of DNA lesions in terms of cyclobutane pyrimidine dimers (CPDs) were measured after exposure to radiation treatments and after recovery in low PAR; pigments of propagules were quantified after exposure treatment only. The photosynthetic conversion efficiency (α) and photosynthetic capacity (rETRmax ) were higher in gametophytes compared with the propagules. The propagules were slightly more sensitive to UVB-induced DNA damage; however, both life stages of the eulittoral inhabiting turf alga were not severely affected by the negative impacts of UVR. Exposure to a maximum of 8 h UVR caused mild effects on the photochemical efficiency of PSII and induced minimal DNA lesions in both the gametophytes and propagules. Pigment concentrations were not significantly different between PAR-exposed and PAR + UVR-exposed propagules. Our data showed that U. penicilliformis from the Antarctic is rather insensitive to the applied UVR. This amphi-equatorial species possesses different protective mechanisms that can cope with high UVR in cold-temperate waters of both hemispheres and in polar regions under conditions of increasing UVR as a consequence of further reduction of stratospheric ozone.
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http://dx.doi.org/10.1111/j.1529-8817.2009.00691.xDOI Listing
June 2009

Photosynthetic response of Nodularia spumigena to UV and photosynthetically active radiation depends on nutrient (N and P) availability.

FEMS Microbiol Ecol 2008 Nov 25;66(2):230-42. Epub 2008 Aug 25.

Department of Marine Ecology, Marine Botany, Gothenburg University, Gothenburg, Sweden.

Biomass of N. spumigena is distributed within the dynamic photic zone that changes in both light quantity and quality. This study was designed to determine whether nutrient status can mitigate the negative impacts of experimental radiation treatments on the photosynthetic performance of N. spumigena. Cyanobacterial suspensions were exposed to radiation consisting of photosynthetically active radiation (PAR=400-700 nm), PAR+UV-A (=PA, 320-700 nm), and PAR+UV-A+UV-B (=PAB, 280-700 nm) under different nutrient media either replete with external dissolved nitrate (N) and orthophosphate (P; designated as +N/+P), replete with P only (-N/+P), or replete with N only (+N/-P). Under low PAR (75 micromol photons m(-2) s(-1)), nutrient status had no significant effect on the photosynthetic performance of N. spumigena in terms of rETRmax, alpha, and E(k). Nodularia spumigena was able to acclimate to high PAR (300 micromol photons m(-2) s(-1)), with a corresponding increase in rETRmax and E(k). The photosynthetic performance of N. spumigena cultured with supplemental nitrogen was more susceptible to experimental PAR irradiance. Under UVR, P-enrichment in the absence of additional external N (-N/+P) induced lower photoinhibition of photosynthesis compared with +N/-P cultures. However, the induction of NPQ may have provided PSII protection under P-deplete and PAR+UVR conditions. Because N. spumigena are able to fix nitrogen, access to available P can render them less susceptible to photoinhibition, effectively promoting blooms. Under a P-deficient condition, N. spumigena were more susceptible to radiation but were capable of photosynthetic recovery immediately after removal of radiation stress. In the presence of an internal P pool in the Baltic Sea, which may be seasonally available to the diazotrophic cyanobacteria, summer blooms of the resilient N. spumigena will persist.
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http://dx.doi.org/10.1111/j.1574-6941.2008.00572.xDOI Listing
November 2008

Interaction effects of ambient UV radiation and nutrient limitation on the toxic cyanobacterium Nodularia spumigena.

Microb Ecol 2009 May 15;57(4):675-86. Epub 2008 Aug 15.

Department of Marine Ecology, Marine Botany, University of Gothenburg, P.O. Box 461, SE 405 30, Göteborg, Sweden.

Nodularia spumigena is one of the dominating species during the extensive cyanobacterial blooms in the Baltic Sea. The blooms coincide with strong light, stable stratification, low ratios of dissolved inorganic nitrogen, and dissolved inorganic phosphorus. The ability of nitrogen fixation, a high tolerance to phosphorus starvation, and different photo-protective strategies (production of mycosporine-like amino acids, MAAs) may give N. spumigena a competitive advantage over other phytoplankton during the blooms. To elucidate the interactive effects of ambient UV radiation and nutrient limitation on the performance of N. spumigena, an outdoor experiment was designed. Two radiation treatments photosynthetic active radiation (PAR) and PAR +UV-A + UV-B (PAB) and three nutrient treatments were established: nutrient replete (NP), nitrogen limited (-N), and phosphorus limited (-P). Variables measured were specific growth rate, heterocyst frequency, cell volume, cell concentrations of MAAs, photosynthetic pigments, particulate carbon (POC), particulate nitrogen (PON), and particulate phosphorus (POP). Ratios of particulate organic matter were calculated: POC/PON, POC/POP, and PON/POP. There was no interactive effect between radiation and nutrient limitation on the specific growth rate of N. spumigena, but there was an overall effect of phosphorus limitation on the variables measured. Interaction effects were observed for some variables; cell size (larger cells in -P PAB compared to other treatments) and the carotenoid canthaxanthin (highest concentration in -N PAR). In addition, significantly less POC and PON (mol cell(-1)) were found in -P PAR compared to -P PAB, and the opposite radiation effect was observed in -N. Our study shows that despite interactive effects on some of the variables studied, N. spumigena tolerate high ambient UVR also under nutrient limiting conditions and maintain positive growth rate even under severe phosphorus limitation.
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http://dx.doi.org/10.1007/s00248-008-9427-2DOI Listing
May 2009