Photoreactivation in two freshwater ciliates: differential responses to variations in UV-B flux and temperature

Sanders, Robert W.; Macaluso, Amy L.; Sardina, Thomas J.; Mitchell, David L.

doi:10.3354/ame040283

Cited by 34 publications

(61 citation statements)

References 49 publications

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“…Only the activity of the antioxidant enzyme catalase has been shown not to be thermally sensitive in response to UVR exposure in L. peronii tadpoles [72]. However, the DNA repair mechanisms of enzymatic photoreactivation (EPR) and nucleotide excision repair (NER) have been shown to increase with increasing temperature in ciliates [115], freshwater crustaceans [116], marine macroalgae [117], tobacco cells [118] and echinoid embryos [119], however, Connelly et al [120] found the opposite to be true in Daphnia. The photoprotective mechanism of ROS reduction by enzymatic antioxidant activity has also been found to be thermally sensitive in summer-caught mosquito fish Gambusia holbrooki exposed to UVR [39].…”

Section: Uvr and Abiotic Factors Temperaturementioning

confidence: 99%

Drivers of amphibian declines: effects of ultraviolet radiation and interactions with other environmental factors

Alton

Franklin

2017

Clim Chang Responses

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As a consequence of anthropogenic environmental change, the world is facing a possible sixth mass extinction event. The severity of this biodiversity crisis is exemplified by the rapid collapse of hundreds of amphibian populations around the world. Amphibian declines are associated with a range of factors including habitat loss/ modification, human utilisation, exotic/invasive species, environmental acidification and contamination, infectious disease, climate change, and increased ultraviolet-B radiation (UVBR) due to stratospheric ozone depletion. However, it is recognised that these factors rarely act in isolation and that amphibian declines are likely to be the result of complex interactions between multiple anthropogenic and natural factors. Here we present a synthesis of the effects of ultraviolet radiation (UVR) in isolation and in combination with a range of naturally occurring abiotic (temperature, aquatic pH, and aquatic hypoxia) and biotic (infectious disease, conspecific density, and predation) factors on amphibians. We highlight that examining the effects of UVR in the absence of other ecologically relevant environmental factors can greatly oversimplify and underestimate the effects of UVR on amphibians. We propose that the pathways that give rise to interactive effects between multiple environmental factors are likely to be mediated by the behavioural and physiological responses of amphibians to each of the factors in isolation. A sound understanding of these pathways can therefore be gained from the continued use of multi-factorial experimental studies in both the laboratory and the field. Such an understanding will provide the foundation for a strong theoretical framework that will allow researchers to predict the combinations of abiotic and biotic conditions that are likely to influence the persistence of amphibian populations under future environmental change.

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Section: Uvr and Abiotic Factors Temperaturementioning

confidence: 99%

Drivers of amphibian declines: effects of ultraviolet radiation and interactions with other environmental factors

Alton

Franklin

2017

Clim Chang Responses

View full text Add to dashboard Cite

show abstract

“…This implies little role for NER in Paraphysomonas, and a dominant role of PER, which is consistent with observations of some other heterotrophic protists, including the ciliates Paramecium tetraurelia and Glaucoma sp. (26,31). P. tetraurelia had greater clonal longevity if it received PRR when exposed to UV-B, while populations of Glaucoma sp.…”

Section: Discussionmentioning

confidence: 99%

“…However, PER is not ubiquitous in heterotrophic protists and can vary even within the same genus. One strain of the ciliate Cyclidium was found to have very little tolerance of UV-B, whether PRR was present during UV-B exposure or not (26), while another clone did not accumulate any measurable DNA damage when exposed to UV-B with PRR (33). NER is a metabolically costly and relatively slow DNA repair mechanism compared to PER (30,35), and it may be that the rapid population growth of protists selects for PER over NER.…”

Section: Discussionmentioning

confidence: 99%

“…P. tetraurelia had greater clonal longevity if it received PRR when exposed to UV-B, while populations of Glaucoma sp. accumulated lethal amounts of DNA damage in the absence of PRR but had fewer CPDs and grew in the presence of PRR (26,31). However, PER is not ubiquitous in heterotrophic protists and can vary even within the same genus.…”

Section: Discussionmentioning

confidence: 99%

“…Although PER is widespread taxonomically (16), its importance relative to dark repair is highly variable for different organisms. PER has been shown to be a particularly important mechanism of DNA repair in several species of amphibians (2), zooplankton (7,12,14), protists (26,31), and bacteria (22). Zenoff et al (39) found several strains of aquatic bacteria with various degrees of reliance on PER and no obvious use of NER, although Cytophaga sp.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Direct Effects of UV-B Radiation on the Freshwater Heterotrophic NanoflagellateParaphysomonassp

Macaluso

Mitchell

Sanders

2009

Appl Environ Microbiol

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The formation of DNA photoproducts in organisms exposed to ambient levels of UV-B radiation can lead to death and/or reduced population growth in aquatic systems. Dependence on photoenzymatic repair to reverse DNA damage caused by UV-B radiation is demonstrated for Paraphysomonas sp., a member of a widely distributed genus of heterotrophic nanoflagellates. At 20°C, Paraphysomonas sp. was exposed to a range of UV-B intensities encountered in natural systems. Populations of the flagellate survived and grew in a dose-dependent manner, but only when simultaneously exposed to photorepair radiation (PRR). In contrast, flagellates exposed to UV-B at 15°C suffered 100% mortality except at the lowest UV-B level (with PRR) tested, which suggested a photorepair temperature optimum above 15°C. After acute UV-B exposures, DNA damage (measured as the formation of pyrimidine dimers) was reduced only in organisms that underwent subsequent exposure to PRR. Populations kept in the dark after UV-B exposure maintained the initial levels of pyrimidine dimers. These results are the first to demonstrate the reliance of a heterotrophic flagellate on photoenzymatic DNA repair for survival from UV-B exposure.

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Ultraviolet Insights: Attempting to Resolve Enigmatic Patterns in Pelagic Freshwaters – The Historical Context and a View to the Future

Williamson

Rose

2009

International Review of Hydrobiology

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While great advances have been made in our understanding of pelagic freshwater communities and ecosystems in recent years, several unexplained patterns continue to evade our understanding. While no single factor can explain these enigmatic patterns, recent increases in our understanding of the ecology of ultraviolet radiation (UV) are consistent with UV playing an important role. Here we present a brief overview of why UV has historically received so little attention in pelagic freshwater ecosystems, review some of the important aspects of the ecology of UV that are important to these enigmatic patterns, and discuss how this new understanding of the ecology of UV may provide some insights into these previously unexplained patterns. IntroductionGreat advances have been made in our understanding of the structure and function of pelagic freshwater communities and ecosystems in recent years. Yet there are several compelling patterns in these systems that remain enigmatic. For example, Why are laboratory experiments that manipulate pH not adequate to explain the response • of many aquatic organisms to anthropogenic acidification of inland waters? Why is it that zooplankton continue to exhibit vertical migration in lakes where there are • no visual predators to induce their migration? Why are some contaminants so much more toxic when exposure occurs in the sunlight? • Why do decreases in water transparency lead to decreases in species diversity in African • cichlids? Recent advances in our understanding of the ecology of ultraviolet radiation (UV) in freshwaters suggest that UV plays a key role in explaining some portion of these enigmatic observations. UV may also play an important role in understanding the causes and consequences of some more recently observed patterns and trends in freshwaters. For example, Freshwater lakes undergo seasonal increases in transparency to visible light known as a • clear-water phase. Recent studies indicate that these clear-water phases are also observed in the UV wavelengths, but are they driven by the same ecological forces? What are the implications of these DOC trends for the role of UV in freshwaters, and can these changes in UV be used as a metric of environmental change at local and global scales? Here we briefly explore the historical development of the study of the ecology of UV in pelagic freshwaters and examine the potential importance of UV in explaining both these past enigmatic patterns as well as recent trends of environmental change. While no single factor is likely to explain these enigmatic patterns and trends, we argue that UV is a much more potent force in pelagic ecosystems than is currently recognized. We begin here by discussing the variability in UV transparency among and within lakes and outline the historical context of the study of UV in freshwaters. We then briefly discuss some of the important aspects of the ecology of UV before addressing how UV can help us to understand the questions outlined above. We conclude with some brief thoughts on how stud...

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Photoreactivation in two freshwater ciliates: differential responses to variations in UV-B flux and temperature

Cited by 34 publications

References 49 publications

Drivers of amphibian declines: effects of ultraviolet radiation and interactions with other environmental factors

Drivers of amphibian declines: effects of ultraviolet radiation and interactions with other environmental factors

Direct Effects of UV-B Radiation on the Freshwater Heterotrophic NanoflagellateParaphysomonassp

Ultraviolet Insights: Attempting to Resolve Enigmatic Patterns in Pelagic Freshwaters – The Historical Context and a View to the Future

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