Report No FR/D0017
Experimental Evaluation of the Effects of Low
of Contaminants on Marine Benthic Communities
- Laboratory experiments have been carried out to evaluate the effects of sediment
contamination on marine and estuarine meiobenthic communities at a range of
environmentally realistic concentrations. These microcosm experiments have more ecological
're alism' and their results are of greater ecological significance than single species
- Low levels of contaminants are known to affect the structure of benthic communities but
field data are difficult to interpret because they are often a response to a cocktail of
contaminants and are also influenced by natural changes in the environment. Using
controlled laboratory experiments it is possible to distinguish the effects of different
contaminants. For various reasons which include their smaller size, meiobenthic
communities can be more easily studied in the laboratory than macrobenthic communities and
are being increasingly used for pollution studies.
- This jointly funded DOE and NRA project interfaces with a two-phase MAFF project
concerning the field response of meiobenthos to anthropogenic disturbance and the
establishment of field survey protocols. The ultimate objective of the two projects is to
provide more sensitive methods for assessing the biological effects of low levels of
pollutants using meiobenthic communities.
- A simple microcosm design and methodology was developed to determine the effects of
experimentally contaminated sediment or natural field sediment from potentially polluted
sites on natural meiobenthic communities. Field collected meiobenthic communities in
natural sediment were mixed with defaunated test sediment in small (0.57 l) bottles. The
meiobenthos and sediment were covered with filtered sea water which was aerated via an
aquarium airstone diffuser. The experiments were maintained in the dark at constant
temperature for a period of two months. The meiobenthos in the different treatments was
then compared to the meiobenthos in control sediments to determine any effects of the
contaminant or the field sediment.
- This microcosm system was used to determine the effects of seven contaminants: Cu, Zn,
Cd, Pb, TBT, arochlor 1254 and permethrin on estuarine intertidal and sublittoral
meiobenthic communities from different sediment types. Each contaminant was dosed at three
levels. The highest dose was near the extreme values found in the UK and was chosen to
elicit a response from the meiobenthos if any was likely to occur in the field. The
meiobenthos were most strongly affected by the Cu, Zn and arochlor 1254; they were
affected by the Pb but not in a dose dependant manner; they were affected by the TBT but
only at the high dose levels (the community in estuarine mud was not affected at all);
they were not affected by the permethrin or Cd treatments. The sensitivity to the
different contaminants and the range of doses differed between the communities tested.
- The system was successfully used as a sediment bioassay to validate results from the
MAFF project survey of the meiobenthos of the Fal estuary.
- The results from this study need to be generalised by conducting similar studies
elsewhere, to see whether repeatable features of community change can be associated with
the effects of specific contaminants. The regulatory authorities should explore the use of
meiobenthic community microcosm experiments as routine bioassays for sediments and to set
stringent environmental quality standards.
Copies of the report are available from FWR, price £25.00, less 20% to FWR Members.