Causes and Effects of Stratospheric Ozone Reduction An Update (1982) / Chapter Skim
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4 ECOSYSTEMS AND THEIR COMPONENTS
4 ECOSYSTEMS AND THEIR COMPONENTS
Pages 62-74
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From page 62... ...
Thus, although data are available on W-B effects on specific organisms and on W -B effects on life cycle stages of organisms, the relationship between the effects on the individual and the effects on the population is not clear. It appears that the yield of food from domestic animals will not significantly decrease even with the most extreme projections of ozone depletion.
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From page 63... ...
In part, such neglect may be justified because the few available studies indicate that in addition to possessing physiological and biochemical mechanisms to alleviate the effects of radiation impinging on the organism, some animals possess behavioral mechanisms that lessen exposure to presumptively damaging radiation. Marine faunal ecosystems have received some attention.
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From page 64... ...
EFFECTS ON PLANTS Research Difficulties The inherent complexity of simulating a reasonable representation of enhanced W-B regimes under ambient field conditions has confined research almost exclusively to greenhouses and growth chambers. However, the levels of visible radiation and UV-A are considerably lower under these experimental conditions than under ambient field conditions.
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From page 65... ...
Advances in Knowledge NRC (1979a) addressed the applicable research to 1979 and the limitations of existing light sources for simulating increases in UV-B corresponding to those that would be caused by reduced atmospheric ozone concentrations.
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From page 66... ...
Even though W-B apparently induced a synthesis of leaf pigments, the attenuation appeared to be insufficient to protect leaf growth processes and the photosynthetic apparatus completely. Nevertheless, this response would be of significant value in alleviating the potentially deleterious effects of any increase in UV-B at the earth's surface.
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From page 67... ...
In these studies, the apparent dependence of response on the total dose rather than on the dose rate suggests that repair of damage within the photosynthetic apparatus may not involve nucleic acid repair systems, which are dose rate dependent (Caldwell 1982)
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From page 68... ...
In order to predict real-life effects of increases in solar UV, the studies would need to be repeated under ambient conditions where UV-B can be adequately supplemented. Since physiological responses of plants to UV are highly wavelength dependent, an appropriate action spectrum for weighting heterochromatic UV-B becomes necessary for expressing effective dose, determining threshold levels for damage, and developing predictive dose-response relationships.
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From page 69... ...
by nutrient availability, by the nature of turbulent mixing of the waters by wind, and, in shallower regions, by tidal frictional forces along the bottom. - ~ are seasonal and annual variations in species compositions, in larval developmental stages, in predation success, and in the physical transport, turbidity, and pigment-absorptive characteristics of coastal and estuarine waters where major food chain productivity Second, there
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From page 70... ...
There is strong experimental evidence that current levels of W-B in surface waters depress near-surface productivity of organisms at the base of food chains (primary productivity) in marine waters (Calkins and Thordardottir 1980, Lorenzen 1979, Smith et al.
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From page 71... ...
the difficulties of mimicking natural mixing conditions, the visible and W-A photic regimes, and the nutrient and predation conditions of the real world make extrapolation of these data to populations in the natural ecosystem difficult. Prediction of the effects on food chains for which phytoplankton serve as food sources is even more difficult.
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From page 72... ...
RESEARCH RECOMMENDATIONS Prediction of the possible effects of increased solar UV-B on economically important biological organisms, such as specific crop species, and on selected ecosystems is not currently possible for two reasons. First, two major areas ot research that may have potential for improving predictive capability and that were proposed bv NRC (1979a)
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From page 73... ...
The absence of ambient levels of visible light and W-A appears to increase substantially the susceptibility of plants to damage by the W levels tested. Thus economically important crop plants need to be evaluated in a field situation where enhanced levels of W -B approximating those predicted to occur under reduced atmospheric ozone conditions are simulated.
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From page 74... ...
the effects on individuals under controlled conditions where all environmental factors are reproduced and W -B levels are varied, and (2) integration of laboratory doseresponse data into ecosystem studies to establish possible effects among populations or specific food chains.
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