Environmental Engineering Reference
In-Depth Information
waters and 4ºC increase in the maximum summer temperature) led to a
doubling of growth rates of harmful dinofl agellates.
Impacts on benthic communities
Global climate change projections indicate that coastal systems will be
particularly vulnerable to future shifts (McLean et al. 2001), and that
plankton and benthic communities (among other biotic components) will
likely be affected (Barry et al. 1995, Sagarin et al. 1999, Clark and Frid 2001,
Schiel et al. 2004, Beukema and Dekker 2005, Smith et al. 2006). Benthic
communities in coastal ecosystems are probably most affected by global
change. This, on the one hand, has to do with the reduced mobility of benthic
organisms, but also with the location of coastal benthic environments in
proximity to both terrestrial and marine disturbances. While all these
circumstances make benthic environments more susceptible, it is also true
that these environments are remarkably resilient and recovery of biological
resources can occur rapidly due to recruitment from adjacent unaffected
areas (Thompson et al. 2002). In this section of the chapter, we will discuss a
few studies to illustrate the major global change-related impacts on different
benthic communities and organisms.
Ascophyllum nodosum
is a macroalga that extends its southernmost
distribution range (for the western Atlantic) to Long Island Sound. Even
at its range limit
A. nodosum
represents a major primary producer and
habitat-forming organism (i.e., a key species in ecological terms). In recent
years, it has been observed (Keser et al. 2005) that
Ascophyllum
experiences
thermal stress in the area mentioned above (as evidenced by a rapid decrease
in growth rates at temperatures above 25ºC and complete mortality at
temperatures exceeding 27-28ºC). In view of recent continued warming
of Long Island Sound, it is possible that
Ascophyllum
became locally
extinguished for this region, which in turn is likely to have signifi cant
impacts on the ecosystem (Keser et al. 2005).
Another example from coastal Gulf of Mexico, is the fl uctuation in the
stocks of the eastern oyster,
Crassostrea virginica
, correlated with changes
in freshwater infl ow (Hoffmann and Powell 1998). Suspension feeders
such as mussels, clams and oysters are commercially important species
susceptible to changes in temperature and salinity (Scavia et al. 2002). The
freshwater input to Galveston Bay, regulates the salinity and fl uctuates
between maxima and minima with a ~ 7-10 year periodicity (in turn,
governed by climatic factors such as unusual spring storms). Salinity is
the principal environmental factor that determines the spatial distribution
and productivity of oyster reefs. Therefore, dramatic episodic decreases in
salinity are followed by substantially reduced landings occurring about
once every ~ 7-10 years (Hoffmann and Powell 1998).
