Environmental Engineering Reference
In-Depth Information
negative impacts on individual- and population-level animal health
(Bossart 2011). In turn, such warnings permit better characterization and
management of these impacts that ultimately affect human and animal
health associated with the oceans. The effects of exposures to xenobiotics
in the marine environment have focused on marine mammals for several
reasons (Reddy et al. 2001): 1) they have relatively long life spans that
permit the expression of chronic diseases including cancer, abnormalities in
growth and development, and reproductive failure; 2) are long-term coastal
residents; 3) feed at a high trophic level; 4) and have large blubber stores
that can serve as depots for anthropogenic chemicals and toxins (Bossart
2011, Reif et al. 2008). Because all of these, marine mammals integrate and
refl ect ecological variation across large spatial and long temporal scales,
they are prime sentinels of marine ecosystem change (Moore 2008). As a
high level predator of the marine food chain many marine mammals (such
as odontocetes and pinnipeds) tend to bioaccumulate high concentrations of
anthropogenic contaminants, such as organochlorine contaminants (OCs),
heavy metals and polycyclic aromatic hydrocarbons (PAHs) (Leonzio et
al. 1992, Marcovecchio et al. 1994, Fossi and Marsili 1997, Lailson-Brito et
al. 2008). A large body of evidence links pollutants exposure to a range of
deleterious biological effects (e.g., immune, endocrine system dysfunction,
increased risk of infection, impaired reproduction) in marine mammals (De
Guise 1995, Jepson et al. 2005, Hall et al. 2006). The increased interest in
studying these effects is because they could lead to decline in population
of these mammals.
For the study of global trend of pollutants, we have selected three
marine mammal species: the bottlenose dolphin (
Tursiops truncatus
),
the harbour porpoise (
Phocoena phocoena
), and the franciscana dolphin
(
Pontoporia blainvillei
). These species were chosen because the number of
surveys focused on them covered a comparatively wider geographical
range. The harbor porpoises are found in cold temperate to sub-polar waters
of the Northern Hemisphere and they are usually found in continental shelf
waters (Hammond et al. 2008a). The franciscana dolphins inhabit shallow
coastal waters of tropical and temperate regions of the western South
Atlantic Ocean (Crespo 2002) and they are found only along the east coast
of South America (Brazil, Uruguay, and Argentina) (Reeves et al. 2008).
On the other hand, the Common bottlenose dolphins
Tursiops truncatus
are
distributed worldwide through tropical and temperate inshore, coastal,
shelf, and oceanic waters (Hammond et al. 2008b) and is, by far, the species
for which the most comprehensive data exist pertaining to contaminants
—heavy metals and COs (Figs. 1 and 2). The factor of declining trend (FD,
Borrell and Aguilar 2007) was used to evaluate the global trend of Hg, Cu,
Cd, Zn, PCBs and DDTs.
