Environmental Engineering Reference
In-Depth Information
The effects of UV radiation on early settlement stages
Different stages of macroalgae show different sensitivity to UV radiation
stress (Altamirano et al. 2003, Roleda et al. 2004, Véliz et al. 2006). UV-
susceptibility of DNA damage is highly depending on the developmental
stage of the species. Among the different stages in the life-cycle of seaweeds
the unicellular propagules are clearly the most susceptible stages to UV
radiation. The impact of UV-B on the early life stages of macroalgae is
important in shaping up the structure of the community and zonation
pattern (Bischof et al. 2006). Spores seem to be the most sensitive life history
stage found in
Laminaria digitata
,
Laminaria
saccharina
and
Alaria esculenta
and are strongly affected by increased UV-B radiation, both with respect to
their photosynthesis performance and their susceptibility to DNA damage
(Wiencke et al. 2000). Also juvenile stages of red and green algae showed
a pronounced UV sensitivity (Han et al. 2003).
Swarmers of brown seaweeds use light directed movement (phototaxis)
to assemble at the water surface improving the chances of fi nding a mating
partner; however, that phototactic response is drastically inhibited by
solar UV (Wiencke et al. 2006). Flores-Moya et al. (2002) found that the
response of photomovement in
Scytosiphon lomentaria
and
Petalonia fascia
swarmers was negatively infl uenced by UVR. In the same way, Makarov
and Voskoboinikov (2001) also observed that the zoospores of
Laminaria
saccharina
ceased their movement, release and germination after treatment
with UV-B. As a consequence of the UV-B effects, if the swarmers are the
sexual gametes, fertilization is affected and life history may be blocked to a
certain extent, but if they are zoospores recruitment of new thalli by asexual
reproduction can be diminished (Wiencke et al. 2000, 2004).
Roleda et al. (2004) observed that the DNA damage in carpospores of
Mastocarpus stellatus
and
Chondrus
crispus
was lower compared to zoospores
of three species of
Laminaria
. Also, less genetic damage was observed in
diploid carpospores compared to haploid zoospores (Roleda 2006), as the
last ones are known to be less effi cient in DNA damage repair. In a sexual
organism, during the diploid state, DNA damage can be repaired since
there are two copies of the gene in the cell and one copy is presumed to be
undamaged (Long and Michod 1995). This was observed in Laminariales,
where haploid zoospores were more sensitive to DNA damage compared
to the diploid young sporophytes (Bischof et al. 2006).
The effects of UV radiation at the celular level
UV-B radiation causes clear effects in cellular ultrastructure, especially
in chloroplast and mitochondria of marine macroalgae. In red seaweeds,
