UK National Marine Monitoring Programme - Second ... - JNCC - Defra

data are assessed against national and international criteria to describe the state of the marine environment.
Biological effects measured on individual organisms and by modification of benthic community structure
indicate the impacts of contaminants. Notably, this is the first UK NMMP report that uses tentative
Background Reference Concentrations (BRCs) and Ecotoxicological Assessment Criteria (EACs) to evaluate
present levels of contamination against pristine conditions. The results must be treated with a great deal of
caution because BRC values do not yet reflect regional differences in geochemistry and EAC values have been
extrapolated from limited datasets.
The results show that:
• Water borne loads (direct and riverine inputs) of measured contaminants to coastal waters have decreased
since 1990;
• Riverine inputs of nitrogen appear to be increasing. However, these nitrogen inputs are strongly correlated
with riverine flow and, since 1997, flows have been significantly above the long-term average. When this
skewed distribution in flow rates is taken into account, there would appear to be no underlying change in
the riverine inputs of nitrogen;
• The highest nitrate concentrations inevitably occur in coastal waters subject to most dilution by nutrient
rich river waters, such as the eastern Irish Sea where the size of the river inputs and restricted circulation
combine to reduce dilution;
• Contaminant concentrations in waters vary in relation to tidal state and changes in discharges.
Concentrations are generally low and not toxic to sensitive test organisms. Higher concentrations are
recorded where there are known inputs and impacts are measured occasionally on sensitive test organisms
at some sites;
• Historical inputs of contaminants to estuaries still lead to elevated concentrations of mercury, cadmium,
Polychlorinated Biphenyls (PCBs) and PAHs in some estuarine sediments. Concentrations are lower
at coastal sites. Benthic community structure was determined more by environmental factors than
contaminant concentrations. However, localised areas of contaminated sediments in industrialised
estuaries were found to be toxic to test organisms;
• Highest concentrations of contaminants in biota continue to be found in industrialised estuaries and those
adjacent coastal areas with a known history of contaminant input. Biological effects, such as induction
of increased enzyme activity (e.g. EROD), were found in some fish populations from these areas. Imposex
in dogwhelks, induced by exposure to tributyl tin (TBT), remains widespread, but reproduction was only
impaired significantly in the vicinity of harbours and marinas;
• The data collected to date show that the power of the present programme to detect trends is variable
between contaminant and matrix. This information will be used to refine the programme so that, for
example, sampling may be increased at 'key' monitoring stations to maximise returns on sampling effort.
In the light of these results, the following amendments to the programme are proposed:
• The programme will be adapted to fulfil future monitoring requirements arising from changes to the JAMP
programme and the new EC Water Framework Directive;
• The nutrient monitoring programme will be revised to align more closely with the OSPAR criteria;
• Where contaminant concentrations in sediment exceed assessment criteria levels, sediment bioassays will
be used to assess any impact on biota;
• The biological effect of metals and other contaminants on mussels will be assessed through the
measurement of metallothionein and scope for growth;
• The programme will be redesigned to target effort at identified ‘key’ monitoring sites.
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