Environmental Engineering Reference
In-Depth Information
high-latitude areas of the Northern and Southern Hemisphere (Kerr and
McElroy 1993, Browman et al. 2000, McKenzie et al. 2003). UV-B effects on
Earth's surface are especially pronounced in the Antarctic and Arctic regions
but are not signifi cant in tropics (Madronich et al. 1998).
The penetration of UV into the water column depends upon the
concentration and composition of dissolved organic matter (DOM) along
with non-living particles (De Mora et al. 2000). Solar radiation is absorbed
only by specifi c portions of DOM. Within DOM, the most important
substances involved in the absorption of biological harmful UV, are humic
substances, which are largely composed of chromophoric dissolved organic
matter (CDOM) (Wetzel 2003). Aquatic environments differ enormously in
their UV attenuation. Coastal areas and shallow continental shelf waters,
including coastal Arctic waters, are characterized by low penetration
of UV due to the very high CDOM concentration. In these waters,
photochemical processes (photodegradation of DOM) may dominate
photobiological processes. In open ocean, the low CDOM concentration
allows higher UV penetration. In this system, photobiological processes
(i.e., effects of UV on DNA), which can occur at signifi cant depth (20 m),
may dominate photochemical processes (photodegradation of CDOM).
Signifi cant penetration of UV is observed in Antarctic waters, particularly
during episodes of thinning of the ozone layer, resulting in enhanced
photochemical/photobiological processes (Tedetti and Sempere 2006).
Variability in system's steady state as changes in turbidity, vertical
mixing, migration rates, and seasonality and location of spawning can
influence substantially the actual UV-damage on fresh and marine
organisms. Several studies have demonstrated that solar UV, mostly UV-B
radiation has a wide range of harmful effects on aquatic ecosystems (Häder
and Worrest 1991, Häder et al. 1998, Kouwenberg et al. 1999a, b, Browman
et al. 2000, Browman 2003, Tedetti and Sempere 2006, Häder et al. 2007). In
aquatic organisms, UV radiation produces several effects as a reduction in
productivity, decrease in reproduction, and development and increase in
DNA mutations and damages (Browman 2003, Häder et al. 1998, 2003, 2007).
Changes of solar UV radiation produce a decrease in biomass productivity
which is transferred through the entire food webs and may also affect
biogeochemical cycling within aquatic systems (Häder et al. 1998, 2003,
2007, Browman 2003).
Direct effects of UV radiation on zooplankton
UV-B radiation has been reported to have negative effects on zooplankton,
inducing mortality, especially in early stages, reducing survival and
fecundity in females, and changing sex ratios (e.g.
,
Karanas et al. 1979,
Chalker-Scott 1995, Scott et al. 1999, Alonso Rodriguez et al. 2000, Browman
et al. 2000, Browman 2003) (Fig. 2). Several studies have also documented
