Geology Reference
In-Depth Information
Figure 17 Ternary diagram showing the relative amounts of PAHs from different sources
(fossil oil, combustion products and natural biological activity) and distin-
guished on a country basis
(From Tolosa et al., 2004.
31
)
pore waters. Despite the negative effects of seaborne plastic debris, this
material can have positive consequences serving as new habitats for
opportunistic colonisers.
4.5.3 Tributyltin
Tributyltin (TBT) provides an interesting case study of a pollutant in the
marine environment.
33
Because TBT compounds are extremely poison-
ous and exhibit broad-spectrum biocidal properties, they have been
utilised as the active ingredient in marine anti-fouling paint formula-
tions. Its potency and longevity ensures good fuel eciencies for ship
operations and guarantees a long lifetime between repainting. TBT-
based paints have been used on boats of all sizes, from small yachts to
supertankers, ensuring the global dispersion of TBT throughout the
marine environment, from the coastal zone to the open ocean.
Notwithstanding such benefits, the extreme toxicity and environmental
persistence has resulted in a wide range of deleterious biological effects on
non-target organisms. TBT is lethal to some shellfish at concentrations as
low as 0.02 mg TBT-SnL
1
. Lower concentrations result in sub-lethal
effects, such as poor growth rates and reduced recruitment leading to the
decline of shellfisheries. The most obvious manifestations of TBT con-
tamination have been shell deformation in Pacific oysters (Crassostrea
gigas), and the development of imposex (i.e., the imposition of male sex
organs on females) in marine gastropods. The later effect has caused
dramatic population decline of gastropods at locations throughout the
