Environmental Engineering Reference
In-Depth Information
probably due to reduction in winter sea-ice extent around the western
Antarctic Peninsula (Atkinson et al. 2004). Krill are dependent on the highly
productive summer phytoplankton blooms in the area east of the Antarctic
Peninsula and south of the Polar Front. Salps, by contrast, which occupy
the extensive lower productivity regions of the Southern Ocean and tolerate
warmer water than krill, have increased in abundance. These changes
have had profound effects within the Southern Ocean food web. Penguins,
albatrosses, seals and whales have wide foraging ranges but are prone to
krill shortage. Thus the wide areal extent of change in krill density—not
just its magnitude—is important (Brander 2010).
Regional changes in distribution and phenology of plankton and
other organisms
There are many examples of distribution changes in marine ecosystems
throughout the world (Beare et al. 2002, Beaugrand et al. 2003). The
planktonic ecosystem is dependent on the properties and movement of
the water. The life cycles of most marine fi sh have a planktonic phase,
which often involves transport over long distances. The potential for rapid
distribution change is therefore inherent, but requires favorable conditions
for survival, particularly if the developing juveniles settle to the bottom
(Altieri 2008).
Survival of fi sh larvae during the planktonic stage is thought to depend
strongly on the availability of suffi cient suitable food (
match-mismatch
hypothesis
) (Frank and Leggett 1982, Stenseth et al. 2002). Therefore, in
addition to effects of changes in production, described in the previous
section, climate induced changes in distribution and phenology of fi sh
larvae and their prey can also affect recruitment and production of fi sh
stocks (Durant et al. 2007, Rijnsdorp et al. 2009).
Spread of pathogens
Pathogens have been implicated in mass mortalities of many aquatic
species, including plants, fi sh, corals, and mammals, but lack of standard
epidemiological data and information on pathogens generally makes
it diffi cult to attribute causes (Harvell et al. 1999). An exception is the
northward spread of two protozoan parasites (
Perkinsus marinus
and
Haplosporidium nelsoni
) from the Gulf of Mexico to Delaware Bay and
further north, where they have caused mass mortalities of Eastern oysters
(
Crassostrea virginica
). Winter temperatures consistently lower than 3ºC
limit the development of the MSX disease caused by
Perkinsus
(Hofmann
et al. 2001), and the poleward spread of this and other pathogens can be
