Changing UV warming

Altered II Changes in N, S. 1 decomposition, H & metals cycling Figure 1. Schematic illustrating factors that influence the effects of solar UVR on aquatic ecosystems. Aquatic biogeochemical cycles are affected by increased UVR caused by stratospheric ozone depletion and its interaction with other co-occurring environmental changes such as global warming and land use change. Changes in precipitation chemistry are caused by UV-induced photoreactions in cloud droplets and changing climate...

Solar radiation as an ecosystem modulator

1.2 Size matters - radiation attenuation in relation to loadings of organic matter 6 1.3 Precipitation matters - importance of frequency and intensity of 7 1.5 Allochthonous vs. autochthonous organic matter - key UV-VIS mediated processes regulate heterotrophic 9 1.5.1 Alterations of enzymatic accessibility by the macromolecules 10 1.5.3 Photolysis of dissolved organic nitrogen and phosphorus 11 1.5.4 Complete photolysis of humic substances to CO and CO2 11 1.5.5 Less direct but important...

Indirect effects

There are several ways by which aquatic organisms may be indirectly influenced by UVR. UVR plays a major role in surface water chemistry that in numerous ways may aifect the aquatic biota. Breakdown or oxidation of complex macro-molecules, notably humus molecules, may both induce availability of organic substratum for microbial heterotrophs 61, Chapter 8 . This may also liberate mineral nutrients such as N and P, and in fact the effects on biogeochemical cycling of key elements like C, N and P...

Direct damage and means of protection lines of defense

The general, direct effects of UVR at the cellular level are rather uniform within the animal kingdom. These include first of all DNA-damage, membrane damage and a range of other cellular injuries that may be caused by intracellular photoproducts. They also include immunosuppression, yet the responses here may be more different across phyla, especially between invertebrates and vertebrates. Finally skin lesion, cancers and eye-damage (cataract) may be common responses in vertebrates. These...

UV vision and photoreception

UV vision has been documented in a variety of terrestrial organisms including insects, birds, amphibians, reptiles, and mammals 53-55 . It is therefore not surprising that many aquatic organisms also perceive light in the UV spectrum. Most UV photoreceptors in aquatic organisms have been described in fish species however, UV photoreceptors have also been reported in bacteria and algae as well as some species of protozoans, annelids, cnidarians, and crustaceans (Table 1). Many UV photoreceptors...

Introduction

There are a variety of reports in the literature concerning UV-induced injuries in aquatic organisms, particularly fish 1,2 . An excellent treatise on the vulnerability of fish and amphibians to UVR was recently published 3 . Laboratory studies with different fish species have shown that the short-wave UV-B portion of the solar spectrum is the most damaging. The most commonly reported harmful effect of solar radiation in fish has been skin damage, which is often referred to as sunburn (Figure...

Rsc

A catalogue record for this book is available from the British Library The Royal Society of Chemistry 2003 All rights reserved Apart from any fair dealing for the purposes of research or private study, or criticism or review as permitted under the terms of the UK Copyright, Designs and Patents Act, 1988, this publication may not be reproduced, stored or transmitted, in any form or by any means, without the prior permission in writing of The Royal Society of Chemistry, or in the case of...

Patterns of DNA damage accumulation and repair in aquatic organisms

9.5.1 Evidence from laboratory studies Much information on DNA damage induction in aquatic organisms is based on incubation experiments under artificial UVR. Unfortunately, the ecological relevance of such studies is restricted, mainly due to the differences in spectra between artifical sources (lamps) and solar radiation. As a result, the effects of UV-B may be overestimated even when weighted UV-B irradiances are realistic. On the other hand, laboratory experiments may provide valuable...

Direct and indirect photochemical reactions

The absorption of photon energy by CDOM can lead to several types of photophysical and photochemical reactions, and we emphasize that light absorption may be the first of many steps that can ultimately lead to the chemical changes we observe in CDOM. Most CDOM photochemistry involves the excitation of humic substances, which have a large degree of double bond character (C C and C 0) that readily absorb sunlight energy. However, beyond direct chemical reaction from absorbing photon energy,...

Experimental and modeling considerations for working with CDOM photochemistry

Miller 32 has provided a concise consideration of issues when designing photochemical experiments using CDOM, and the careful measurements that must be made. Here, we will provide a general design concept for an experimental exposure of CDOM to a polychromatic light source (e.g., solar radiation) and Figure 5. Changes in bog water DOM after exposure to solar radiation. (A) Loss of CDOM absorbance at 320 nm, (B) decrease in molecular weight (indicated by increase in ratio), (C) decrease in DOC...

Herbivory and prdation the complex response of trophic interactions to UVR

In the previous section, the response to UVR of populations at one trophic level (basal species) was considered. The interaction of UVR, however, with more than one trophic level adds substantial complexity to the possible responses, with the potential occurrence of positive and negative feedbacks (Figure 1). Both prey and predator populations might be affected by UVR, and, if so, the net effect will depend on the relative tolerance threshold of the interacting species. Yet, as soon as we...

The nature of light and its absorption in natural waters

The most essential step in photochemistry is the absorption of light by chemical species. All photochemistry is driven by the molecular excitation that occurs from the absorption of light. Light exhibits both wave and particle properties that impart the energy available for chemical and physical reactions. Wave theory can be used to describe the propagation of light through various media, where, if optically different, the light might be refracted and or reflected (e.g., transmission of light...

Methodology to assess UVR effects on photosynthesis

In order to assess UVR effects on photosynthesis, three approaches for exposing algae to UVR are used. These include (1) natural solar radiation, modified by various filters that selectively screen off certain wavebands of radiation (2) natural solar radiation which is supplemented with artificial UVR from lamps, and (3) fully artificial radiation, implying laboratory experiments. UVR experiments at their best require both that the target organisms are exposed to as realistic a light field as...

Screening mechanisms

Screening can eliminate or at least reduce exposure to UVR by absorbing or reflecting damaging wavelengths prior to reaching UVR-sensitive cellular components. Screening may consist of the production of physical barriers such as morphological or structural features that prevent damaging wavelengths from passing or by the production of chemical compounds that absorb UVR. Usually, screening mechanisms, both physical and chemical, serve more than one purpose and thereby decrease the energy...

Behavioral responses to UVR

Behavioral responses to radiation often vary with wavelength. Some Figure 3. Simultaneous images taken at (a) green (490-560 nm) and (b) ultraviolet (350-380 nm) wavelengths. Note the bright background in the UV image that silhouettes fish strongly, even against the reef. Taken from Losey et al. 27. Figure 3. Simultaneous images taken at (a) green (490-560 nm) and (b) ultraviolet (350-380 nm) wavelengths. Note the bright background in the UV image that silhouettes fish strongly, even against...

Interactions between vertical mixing and UVR effects

The previous section showed how mixing processes determine the way UML constituents (molecules or organisms) enter the photoactive zone where they may participate in a UVR-mediated process. Under strong stratification, such transport is very limited, so UVR effects will only involve those constituents already present in the active zone. Such extreme stratification can be episodically important in systems where diurnal thermoclines form, but more typically the UML extends below the photoactive...

Wavelength nm

Spectral diffuse attenuation coefficients (Kd J calculated at 10 nm intervals for Crater Lake Oregon, from downwelling irradiance scans at fixed depths, 12 00-13 00 local time, 20 August 2001 (SZA 31 , clear sky) using a LI-COR LI-1800UW spectral radiometer (8 nm bandwidth single monochromator). Kw X for freshwater estimated by Smith and Baker 18 is also compared to two new estimates computed by subtracting particulate absorption (measured similarly to spectra in Figure 10) from...

Measurements

Measurements of solar UVR started in the first decades of the 20th century with chemical detectors 8 , where the changing of the color of a solution was an indicator of UV-B irradiance. Physical measurements of UVR use photoelectric methods to give quantitative information about the intensity and spectral distribution of UVR. The first extensive data sets originate from the 1960's, from Davos (Switzerland) 9 , but it was not until the 1990's that more of such high quality spectral measurements...

Carbon cycle

Although particulates that are predominantly clay mineral in content are important attenuators of UVR in turbulent streams and rivers, dissolved and particulate organic substances largely control the penetration of UV into most lakes and the sea. Hence, this discussion of the carbon cycle begins with a discussion of the interactions of UV with CDOM, with emphasis on the optical properties of aquatic ecosystems and penetration of solar UVR into the water (see also Chapters 3 and 6). 5.2.1...

Photoprotective mechanisms

Protection of freshwater aquatic organisms from UV-induced injury is dependent on a variety of factors that can function as photoprotective mechanisms. When UVR breaches photoprotective mechanisms in sufficient amount, UV-induced injury will occur. Aquatic organisms vary in their tolerance to UV exposure. There is a likely interplay between the ecological niche occupied by an organism and its UV sensitivity. Throughout an organism's life stages, its habitats and habits will likely complement...

XXX

Examples of phototoxic compounds. Solar radiation can also be harmful to biota via less direct mechanisms specifically by dramatically increasing the toxicity of many natural and anthropogenic organic compounds 16-18 (see Figure 1). In fact, many species of plants and animals have evolved mechanisms that take advantage of photoac-tivated toxicity to defend against predators, foragers, and infectious agents 19 . These defense mechanisms involve production of compounds that, once...

Sulfur cycle

Atmospheric sulfur plays an important role in the radiative balance of the atmosphere 169-174 . Anthropogenic sources are dominant in highly-industrialized regions, such as those in the mid-latitudes of the Northern Hemisphere, and are well defined. Natural sources and sinks of sulfur gases are much less well defined, but have received greater scrutiny in recent years due to their potential involvement in the regulation of climate in remote parts of the ocean. The major source of natural sulfur...

Tevini Salmo

The pathological effects of ultraviolet radiation on the epidermis of teleost fish with reference to the solar radiation effects in higher animals. Proc. R. Soc. Edinb., 81B, 199-210. 2. E.E. Little, D. L. Fabacher (1994). Comparative sensitivity of rainbow trout and two threatened salmonids, Apache trout and Lahontan cutthroat trout, to ultraviolet-B radiation. Archiv. Hydrobiol, 43,217-226. 3. R. Hofer (2000). Vulnerability of fish and amphibians to ultraviolet radiation....

Concluding remarks

It is now evident that UV-B induced CPD accumulation is a general phenomenon in aquatic organisms. Viruses and bacteria are especially vulnerable to UV-B induced DNA damage. The small size of viruses and heterotrophic bacteria obviously favors CPD accumulation. The penetration of UV-B inside these cells is high, due to the lack of pigments, nuclear membranes or efficient UV screening by compounds such as MAAs, or, for viruses, the lack of photoreac-tivation potential. CPD accumulation in...

References

Uye (1997). Photoreactivation of UV-induced damage to embryos of a planktonic copepod. J. Plankton Res., 19, 783-787. 2. J.H.M. Kouwenberg, H.I. Browman, JJ. Cullen, R.F. Davis, J.-F. St-Pierre, J.A. Runge (1999). Biological weighting of ultraviolet (280-400 nm) induced mortality in marine Zooplankton and fish. I. Atlantic cod (Gadus morhua) eggs. Mar. Biol, 134, 269-284. 3. J.H.M. Kouwenberg, H.I.Browman, J.A. Runge, J.J. Cullen, R.F. Davis, J.-F. St-Pierre (1999)....