Environmental Engineering Reference
In-Depth Information
toward smaller cells in planktonic communities (Winder et al. 2009), as well
as through top-down impacts that cascade down from the losses or gains
of ecologically dominant consumers (Schmitz et al. 2000). Alterations in
biogeochemical cycling can occur because of the replacement of functional
groups (e.g., calcifi ers) even if overall productivity and diversity remain
approximately constant.
Climate-driven impacts on keystone and foundation species may be
especially important. Some critical habitat-forming marine benthic species,
such as oysters or corals, appear sensitive to CO
2
and climate change both
directly and through pathogens. As has been previously mentioned, in
oyster populations within Delaware Bay (USA) the protistan parasite
Perkinsus marinus
(which causes the disease Dermo) proliferates at high
water temperatures and high salinities, and epidemics followed extended
periods of warm winter weather; these trends in time are mirrored by
the northward spread of Dermo up the eastern seaboard as temperatures
warmed (Cook et al. 1998). Similarly, corals on the Great Barrier Reef showed
more infections by the emerging disease “
white syndrome
” in warmer than
normal years (Bruno et al. 2003). These processes and others resulting from
altered species composition will likely have important rippling affects
through ecosystems.
In addition, climate change and altered ocean circulation may change
organism dispersal and the transport of nutrient and organic matter that
provide important connectivity across marine ecosystems (Walther et al.
2002). If species dispersal is disrupted by climate-induced thermal blocks
or shifts in currents carrying larvae, both species and community dynamics
will be altered (Parmesan 2006).
As a brief summary it can be commented that the Earth's climate
has changed throughout history, showing different processes, effects and
consequences at different times (Pearson and Dawson 2003). Just in the
last 650,000 years there have been seven cycles of glacial advance and
retreat, with the abrupt end of the last ice age about 7000 years ago marking
the beginning of the modern climate era—and of human civilization
(VijayaVenkataRaman et al. 2012). Most of these climate changes are
attributed to very small variations in Earth's orbit that change the amount
of solar energy our planet receives (Bard and Frank 2006).
The evidence for rapid climate change (IPCC Fourth Assessment
Report) is compelling: sea level rise; global temperature rise; warming
oceans; shrinking ice sheets; declining Arctic sea ice; glacial retreat; ocean
acidifi cation (IPCC 2007a).
