Environmental Engineering Reference
In-Depth Information
could drive unforeseen impacts on marine communities and ecosystems
(Kroeker et al. 2010).
A sound knowledge of organismal biology and physiological
mechanisms can help elucidate the larger ecosystem changes that arise in
response to climate change forcings, such as population collapses or local
extinctions (Pörtner and Knust 2007), disruptions in large-scale animal
migrations (Farrell et al. 2008), changes in phenology (Wiltshire and Manly
2004), and changes in food availability and food web structure (Pörtner
and Knust 2007, Farrell et al. 2008). All organisms live within a range of
optimal body temperatures and climate change will differentially favor
species with wide thermal windows, short generation times, and genotypic
variability among their populations. The specifi c effects of CO
2
, hypoxia,
salinity change, and eutrophication reduce the overall fi tness of organisms,
especially at extreme temperatures, therefore narrowing thermal windows
and biogeographic ranges (Pörtner and Farrell 2008).
Laboratory experiments demonstrated that declining pH can negatively
impact calcifi cation in marine organisms like corals, mollusks, coralline
algae and phytoplankton (Kleypas et al. 1999, Riebesell et al. 2007).
However, results from laboratory experiments can be diffi cult to extrapolate
to ecosystem responses because pH may affect other aspects of a species
biology besides calcifi cation, and also because interspecifi c relationships
can enhance or counteract the effects of environmental impacts (Schindler
et al. 1985, Hall-Spencer et al. 2008). In that sense, modeling approaches
provide a means of linking changes in environmental parameters with
the
in situ
dynamics of complex ecosystems and then predict long-term
impacts on community structure. Using such approach Wootton et al.
(2008) demonstrated that coastal ocean pH is unexpectedly dynamic given
the high buffer capacity of oceans, and revealed strong links between
in
situ
benthic species dynamics and variation in ocean pH, with calcareous
species generally performing more poorly than non-calcareous species in
years with low pH.
In the face of OA, there is considerable interest in understanding how
the loss of species and the alteration of communities will affect ecosystem
function. A study by Kroeker et al. (2011) examined how changes of
multispecies assemblages of marine invertebrates were affected by OA with
respect to community composition and structure, density compensation
among taxa, and aggregate biomass and trophic structure. They found
divergent and compensatory responses of marine invertebrates to OA,
and concluded that these do not offset the effects on aggregate biomass or
trophic structure, suggesting that acidifi cation will likely affect ecosystem
function and the services they provide (Kroeker et al. 2011).
