Ecological monitoring and assessment of pollution in rivers - Ecology of Industrial Pollution - page 142

cost-effective manner. Once the influence of temporal and spatial variance has
been quantified relative to sampling variance, sampling strategies can be
designed to reduce that component that is having the largest effect. Uncer-
tainty can be combined with an estimate of monetary cost per sample to derive
a cost-effective precision based on the number of samples required to achieve a
set level of precision, and thus enable comparisons of different techniques
(or sampling strategies). It can be the case that superficially expensive tech-
niques (per sample) are, in fact, more cost-effective than superficially cheaper
ones as overall fewer samples need to be collected (Neale et al. 2006 ) . Such
an approach is vital to compare quick-and-dirty approaches (e.g., the use of
aerial photographs) to more traditional labour intensive techniques (e.g., field
survey).
A further aspect of uncertainty that needs to be addressed is the response of
the water body to programmes of measures. According to the directive, appro-
priate management must be put into place to ensure that all water bodies have
achieved 'good' status by 2015. Such management techniques are likely to be
costly and difficult, and managers will have to be confident that the measures
put into place will not only reduce the level of stress that the water body is
suffering (e.g., resulting in reduced nutrient loading and hence lower concen-
trations in the water), but that the biota will respond to the improved condi-
tions to a sufficient extent that the measured O/E will achieve 'good' status.
Issues of cost-effectiveness will complicate these decisions further. As well as
knowledge of the effectiveness of the management technique in controlling
the pressure, a full understanding of the response of the biota to a reduction in
the pressure and the sensitivity of the assessment model to changes in the
biota, together with any uncertainty associated with each level of response will
be required to achieve informed and defensible decisions. Although the infor-
mation used to develop tools such as RIVPACS are available to inform many
steps in this decision process (e.g., biological response to pressures, uncer-
tainty), for most biological quality elements and pressures this knowledge is
still lacking and, until better estimates of the required values are available,
other approaches such as Bayesian belief networks may have to be used to
achieve the required goals within the available time frame.
Conclusions
Although in recent years the WFD has precipitated an unprecedented drive by
water managers and freshwater biologists to develop a wide range of biomoni-
toring tools (Furse et al. 2006 ), continued effort will be required if society is to
achieve the goal of sustainable use of water resources. The world faces a future
where water resources will come under increasing pressure from climate change
and population growth. Bioassessment techniques will be needed to assess the
impact of newly identified pressures (e.g., pharmaceutical residues), and separate