Environmental Engineering Reference
In-Depth Information
relatively new problem to marine organisms (Whitehead et al. 2000, Häder
et al. 2010). In that sense, the recognition of the Antarctic ozone hole, initially
prompted considerable research on the effects of UVR over phytoplankton
communities, owing to their importance in primary production. Subsequent
investigations were extended to the microbial loop and higher trophic
levels.
The role of UVR as an environmental stressor has been demonstrated for
aquatic animals including corals, zooplankton and fi sh (Häder et al. 2007,
2010). A meta-analysis revealed negative effects of ambient UV-B on growth
and survival of a range of aquatic organisms (Bancroft et al. 2007).
Increasing atmospheric CO
2
levels and ocean acidifi cation
Atmospheric levels of carbon dioxide (CO
2
) have steadily increased through
anthropic sources (Forster et al. 2007). This excessive atmospheric CO
2
is
uptaken by the world's oceans to maintain the balance of the carbonate
buffer system (Libes 1992). In this naturally-occurring process, atmospheric
CO
2
readily dissolves into seawater; dissolved CO
2
reacts with water to
produce carbonic acid (H
2
CO
3
). In turn, carbonic acid dissociates into H
+
and bicarbonate (HCO
3
-
) ions. Bicarbonate further dissociates into more H
+
and carbonate (CO
3
=
) ions. However, the recent uptake of CO
2
is too rapid
for the supply of CO
3
=
ions, and therefore, H
+
and bicarbonate levels are
increasing, while carbonate levels are decreasing, with the ultimate result
of an increased acidity of ocean waters at a global scale, a phenomenon
termed as ocean acidifi cation (Orr et al. 2005). Ocean acidifi cation (OA)
is a global threat to marine ecosystems and its long term implications for
the diversity of marine organisms and ecosystem functions are diffi cult to
predict (Doney et al. 2009).
There is some experimental evidence that the severity of the impacts
of OA could be dependent upon factors related to an organism's lifestyle
and activity (e.g., infaunal
vs
. epifaunal, deep
vs
. shallow, and deposit
feeder
vs
. suspension feeder) rather than to its phylogeny (Widdicombe and
Spicer 2008). There is also uncertainty over the extent to which organismal
adaptation or acclimation might mitigate the long term effects of OA.
A recent meta-analysis quantifying the variability of biological
responses of marine organisms to OA, revealed a strong negative effect
on calcifi cation and growth, despite the variability in the sensitivity of
taxonomic groups and developmental stages (Kroeker et al. 2010). However,
differential sensitivities may still have important implications for marine
ecosystems in those cases where individual species play disproportionately
strong roles in structuring communities (Shurin et al. 2002, Borer et al. 2005).
Additionally, differential sensitivities will infl uence species interactions and
