Environmental Engineering Reference
In-Depth Information
environmental heterogeneity? We have already touched upon Pollution
Induced Community Tolerance and shown that this is as sensitive as conven-
tional monitoring for nematodes and much more sensitive for microbes (see
above). Another alternative approach is to expose organisms to environmental
samples and examine their responses, dealing with environmental heterogen-
eity by exposing the same species to all samples, although this does not directly
give information on what is happening in the field. If environmental samples
are toxic to a widespread organism, it gives cause for concern. With this end in
mind, considerable effort has gone into developing methods of sediment
toxicity testing, using both whole sediments and pore waters (e.g., Matthiessen
et al. 1998 ; Chapman et al. 2002 ; Thomas et al. 2003 ; Borgmann et al. 2005 ;
McCready et al. 2006 ; Shipp & Grant 2006 ). In particular, the development of
sensitive sub-lethal sediment toxicity tests have allowed detection of effects of
contaminant concentrations lower than those that are acutely toxic (Thain et al.
1997 ; Shipp & Grant 2006 ; Allen et al. 2007 ). What is apparent from published
studies using sediment toxicity testing is that toxic sediments may be remark-
ably widespread. Matthiessen et al. ( 1998 ) found acute and chronic toxicity of
sediments from a number of sites in the Tyne estuary. Tests on more than 100
sites in and around Sydney Arbour, Australia, found that nearly a quarter of
sediments showed a marked effect on amphipod reburial and over half showed
a more than 20% reduction of sea urchin egg fertilisation (McCready et al. 2004 ).
This study also reported that more than 80% of sediments were highly toxic to
the Microtox test, but this overestimates toxicity as the authors did not remove
elemental sulphur from solvent extracts of contaminants before testing (and
see also Pardos et al. 1999 ; McCready et al. 2006 ). The performance of sediment
toxicity testing in the Fal and Hayle systems shows that it is of similar sensitiv-
ity to the best available ecological monitoring. Shipp and Grant ( 2006 ) found
that growth rate of the gastropod Hydrobia ulvae in a 28-day test was reduced
when exposed to sediment from all the tributaries of the Fal estuary except
Percuil River.
A conceptually related approach is the use of Scope for Growth (SFG) in
Mytilus edulis as an indicator of environmental quality. Other evidence suggests
that marine organisms and communities can be extremely sensitive to contam-
inants. Widdows et al.( 1995 , 2002 ) collected individuals of the mussel Mytilus
edulis from an uncontaminated site, deployed them at field sites around the UK,
then returned them to the laboratory and measured Scope for Growth by
quantifying feeding and respiration rates. SFG was reduced at many sites in
the southern North Sea and at a number of locations in western Scotland, the
Irish Sea and South West England. At some locations, surplus energy was less
than 25% of that in unstressed animals. Tissue body burdens of PAHs at the end
of the exposure were sufficient to explain between 50 and 80% of the reduction
in SFG. The ecological significance of these results is not known, but if
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