Environmental Engineering Reference
In-Depth Information
of PUFA content in microalgae by UV-B radiation will be transferred
to herbivorous zooplankton that graze on them, thus decreasing the
availability of this essential fatty acid. As a consequence of the reduction
in the nutritional quality of preys, the productivity and health of aquatic
ecosystem could be signifi cantly affected (Brett and Müller-Navarra 1997,
Browman et al. 2003).
Other indirect effects of UV radiation, particularly UV-B, have been
related to suppression of both systematic and local immune to a variety
of antigens (Salo et al. 1998, Browman et al. 2000, Jokinen et al. 2000). All
these indirect (and/or longer-term) effects of UV-B radiation need to be
further investigated.
Zooplankton responses to UV radiation effects
Several strategies to avoid UV radiation such as increase in resting
eggs production, vertical migration, accumulation of photoprotective
compounds, and photoenzymatic repair have been already reported for
zooplankton in both marine and freshwater systems (McFadyen et al. 2004,
Gonçalves et al. 2010, Hylander and Hansson 2010, Hylander and Jephson
2010, Zengling et al. 2010).
Zooplankton has the ability to migrate vertically and horizontally
to defend against UV radiation (Wold and Norrbin 2004, Hylander and
Hansson 2010, Zengling et al. 2010). For instance, the cladocerans genus
Daphnia, Chydorus and Eurycercus
showed vertical migration in response to
UV radiation (Hylander and Hasson 2010).
Daphnia
showed the strongest
response to UV whereas
Chydorus and Eurycercus
, displayed a weak
response remaining mainly at the bottom during daytime (Hylander and
Hasson 2010). Vertical migration in response to UV radiation has also
been observed on female and nauplii of
C. fi nmarchicus
which migrated
downwards when were exposed to radiation (Wold and Norbbin 2004).
The behavioral response to UV in these species has been attributed to the
amount of photo-protective pigmentation in the organisms (Wold and
Norbbin 2004, Hylander and Hasson 2010).
It is also known that zooplankters can synthesize or accumulate photo-
protective compounds such as melanin, carotenoids and mycosporine-like
amino acids (MAAs), which are associated with UV resistance in copepods
(Hansson et al. 2007, Hansson and Hylander 2009, Hylander and Jephson
2010, Zengling et al. 2010). Melanin is the most important photo-protective
compound found in cladocerans (Hansson et al. 2007). Copepods may not
have the capacity of synthesize these compounds and have to obtain these
photo-protective compounds, carotenoids and MAAs, mainly from their
preys. Since carotenoids and MAAs are more abundant in phytoplankton,
the accumulation levels of these photo-protective compounds in copepods
