Effects of solar ultraviolet radiation on epilithic metabolism, and nutrient and community composition in a clear-water boreal lake

2001 ◽  
Vol 58 (10) ◽  
pp. 2059-2070 ◽  
Author(s):  
Elise Marie Watkins ◽  
David W Schindler ◽  
Michael A Turner ◽  
David Findlay
Keyword(s):  
Ultraviolet Radiation ◽  
Stratospheric Ozone ◽  
Solar Spectrum ◽  
Taxonomic Composition ◽  
Experimental Lakes Area ◽  
Solar Ultraviolet Radiation ◽  
Northwestern Ontario ◽  
Boreal Lake ◽  
Algal Metabolism ◽  
Carbon And Nitrogen Content

Stratospheric ozone depletion, climate change, and acidification will increase the exposure of aquatic eco systems to ultraviolet radiation (UVR; 280–400 nm). The objective of this study was to determine the ecological effects of ambient UVR exposure on epilithon (algal communities attached to rocky substrata) relative to an artificially reduced UVR environment. UVR exposure was altered in the littoral zone of a boreal lake by selectively filtering segments of the solar spectrum with large acrylic sheets. This 130-day study took place at the Experimental Lakes Area, northwestern Ontario, in 1998. Epilithon were monitored for changes in productivity, biomass, pigment, and nutrient and taxonomic composition. The absence of UVR increased epilithic photosynthetic rates 37–46% above epilithon exposed to ambient UVR, increased cellular carbon and nitrogen content, and consequently lowered C:P. UVR effects on algal metabolism were dependent on seasonal trends. Epilithic respiration rates and chlorophyll a concentrations were not significantly different among treatments. A reduction in UV induced taxonomic shifts in epilithon, with diatoms increasingly favoured under low UV conditions. Species richness and diversity were not affected. Overall, the results of this study, considered together with previous research, suggest that the epilithic community is sensitive to changes in the UVR environment of aquatic ecosystems.

scholarly journals Episode of unusual high solar ultraviolet radiation in central Europe due to dynamical reduced stratospheric ozone in May 2005

2005 ◽  
Vol 5 (5) ◽  
pp. 10409-10420 ◽  
Author(s):  
C. Stick ◽  
K. Krüger ◽  
N. H. Schade ◽  
H. Sandmann ◽  
A. Macke
Keyword(s):  
Ultraviolet Radiation ◽  
Uv Radiation ◽  
Stratospheric Ozone ◽  
Solar Ultraviolet Radiation ◽  
Solar Uv ◽  
Resultant Increase ◽  
The Tropics ◽  
Effective Radiation ◽  
Ozone Episodes ◽  
Solar Ultraviolet

Abstract. In late May this year unusual high levels of solar ultraviolet radiation were observed in Europe. In Northern Germany the measured irradiance of erythemally effective radiation exceeded the climatological mean by more than about 20%. An extreme low ozone event for the season coincided with the high solar elevation angles during late spring leading to the highest value of erythemal UV-radiation ever observed at this location in May. This ''ozone mini-hole'' was caused by an elevation of tropopause height accompanied with a poleward advection of natural low total ozone from the tropics. The resultant increase in UV-radiation is of particular significance for human health. Dynamically induced low ozone episodes that happen around the summer solstice can considerably enhance the solar UV-radiation in the mid latitudes and therefore contribute to the UV-burden of people living in the mid latitudes.

scholarly journals Stratospheric ozone depletion

2006 ◽  
Vol 361 (1469) ◽  
pp. 769-790 ◽  
Author(s):  
F. Sherwood Rowland
Keyword(s):  
Ultraviolet Radiation ◽  
Ozone Depletion ◽  
Biological Activities ◽  
Stratospheric Ozone ◽  
Ozone Layer ◽  
Ultraviolet B ◽  
Montreal Protocol ◽  
Atmospheric Measurements ◽  
Solar Ultraviolet Radiation ◽  
Solar Ultraviolet

Solar ultraviolet radiation creates an ozone layer in the atmosphere which in turn completely absorbs the most energetic fraction of this radiation. This process both warms the air, creating the stratosphere between 15 and 50 km altitude, and protects the biological activities at the Earth's surface from this damaging radiation. In the last half-century, the chemical mechanisms operating within the ozone layer have been shown to include very efficient catalytic chain reactions involving the chemical species HO, HO 2 , NO, NO 2 , Cl and ClO. The NO X and ClO X chains involve the emission at Earth's surface of stable molecules in very low concentration (N 2 O, CCl 2 F 2 , CCl 3 F, etc.) which wander in the atmosphere for as long as a century before absorbing ultraviolet radiation and decomposing to create NO and Cl in the middle of the stratospheric ozone layer. The growing emissions of synthetic chlorofluorocarbon molecules cause a significant diminution in the ozone content of the stratosphere, with the result that more solar ultraviolet-B radiation (290–320 nm wavelength) reaches the surface. This ozone loss occurs in the temperate zone latitudes in all seasons, and especially drastically since the early 1980s in the south polar springtime—the ‘Antarctic ozone hole’. The chemical reactions causing this ozone depletion are primarily based on atomic Cl and ClO, the product of its reaction with ozone. The further manufacture of chlorofluorocarbons has been banned by the 1992 revisions of the 1987 Montreal Protocol of the United Nations. Atmospheric measurements have confirmed that the Protocol has been very successful in reducing further emissions of these molecules. Recovery of the stratosphere to the ozone conditions of the 1950s will occur slowly over the rest of the twenty-first century because of the long lifetime of the precursor molecules.

Rapid Communication / Communication RapideAmbient solar ultraviolet radiation and its effects on phosphorus flux into boreal lake phytoplankton communities

2002 ◽  
Vol 59 (7) ◽  
pp. 1090-1095 ◽  
Author(s):  
Paul C Frost ◽  
Marguerite A Xenopoulos
Keyword(s):  
Ultraviolet Radiation ◽  
P Uptake ◽  
Boreal Lakes ◽  
Particulate Phosphorus ◽  
Experimental Lakes Area ◽  
Solar Ultraviolet Radiation ◽  
Variable Effect ◽  
Phytoplankton Communities ◽  
P Flux ◽  
P Addition

We examined the effects of ultraviolet radiation (UVR) on net phosphorus (P) flux into phytoplankton communities in two boreal lakes at the Experimental Lakes Area (ELA), Canada. We manipulated P available to and irradiance received by phytoplankton during four different three-day incubations of dilution bioassays. Net P flux was estimated by measuring the accumulation of particulate P (that retained on glass fiber filters) over the incubation period. No effects of UVR on net P flux were found at ambient P levels in any of the experiments. At the highest levels of P addition, less particulate phosphorus (PP) accumulated in both the minus-UVB (~15–40%; photosynthetically active radiation (PAR) + UVA) and full-sunlight (~25–45%; PAR + UVA + UVB) exposed phytoplankton compared with those that received PAR only. Neither chlorophyll- nor carbon-specific net P flux was affected by UVR exposure at ambient P levels. However, at the highest levels of P enrichment, chlorophyll-specific net P flux increased in response to UVR in both lakes, whereas carbon-specific net P flux declined in one of the lakes and was unaffected by UV exposure in the second lake. Our results indicate that UVR can affect total PP accumulation in enriched systems, but not at ambient P levels, and that UVR has a weak and variable effect on biomass-specific P uptake in phytoplankton under enriched conditions.

scholarly journals Spring and summer time ozone and solar ultraviolet radiation variations over Cape Point, South Africa

2019 ◽  
Vol 37 (2) ◽  
pp. 129-141 ◽  
Author(s):  
David J. du Preez ◽  
Jelena V. Ajtić ◽  
Hassan Bencherif ◽  
Nelson Bègue ◽  
Jean-Maurice Cadet ◽  
...  
Keyword(s):  
South Africa ◽  
Ultraviolet Radiation ◽  
Uv Radiation ◽  
Stratospheric Ozone ◽  
Solar Ultraviolet Radiation ◽  
Clear Sky ◽  
Solar Uv Radiation ◽  
Solar Uv ◽  
Solar Ultraviolet ◽  
Ozone Levels

Abstract. The correlation between solar ultraviolet radiation (UV) and atmospheric ozone is well understood. Decreased stratospheric ozone levels which led to increased solar UV radiation levels at the surface have been recorded. These increased levels of solar UV radiation have potential negative impacts on public health. This study was done to determine whether the break-up of the Antarctic ozone hole has an impact on stratospheric columnar ozone (SCO) and resulting ambient solar UV-B radiation levels at Cape Point, South Africa, over 2007–2016. We investigated the correlations between UV index, calculated from ground-based solar UV-B radiation measurements and satellite-retrieved column ozone data. The strongest anti-correlation on clear-sky days was found at solar zenith angle 25∘ with exponential fit R2 values of 0.45 and 0.53 for total ozone column and SCO, respectively. An average radiation amplification factor of 0.59 across all SZAs was calculated for clear-sky days. The MIMOSA-CHIM model showed that the polar vortex had a limited effect on ozone levels. Tropical air masses more frequently affect the study site, and this requires further investigation.

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