Shellfish as biomonitors of heavy metal contamination : programme design considerations

The use of shellfish as biomonitors of heavy metal contamination in the estuarine and coastal environments is investigated. Ten criteria were developed from a literature review as being fundamental components of a shellfish biomonitoring programme: • establishment of clear concise, relevant and achievable objectives; • allocation of sufficient resources - time, money and expertise; • scientific establishment of the biomonitoring species, principally; the ability to accumulate the contaminants in question in a manner which can be simply correlated with contaminant levels in the ambient environment. • the timing and frequency of monitoring; • selection of representative, accessible and secure sampling sites; • control of possible sources of variability in biomonitor contaminant burdens, notably variation due to season, organism size (age), sex, or sampling position (e.g., tidal height). • adoption of sampling variables and procedures that address the monitoring aims in a standardised, scientifically acceptable manner; • the use of analytical procedures that are standardised and scientifically acceptable; • the implementation of a quality assurance/quality control programme; and • information management - the recording of data and communication of information in a form(s) able to be utilised by its intended audience. The above criteria were used to evaluate one specific monitoring programme; the Christchurch City Council's Avon-Heathcote Estuary Heavy Metal Monitoring Programme (CCCMP). A critical component of this evaluation was the assessment of the suitability of Amphibola crenata as a biomonitor of heavy metal contamination. This species was found to be a poor biomonitor due to its ability to regulate internal metal burdens. The information obtained from the literature review and evaluation of the CCCMP were synthesised to develop a framework for shellfish heavy metal biomonitoring. This framework is intended to guide local authorities in their selection and use of biomonitor species, and also in the planning and development of their shellfish monitoring programmes. Programmes based on this design should be capable of producing monitoring data that is not only scientifically valid, but also reliable and worthy of confidence. Such data will aid resource managers and decision-makers. It is strongly recommended that local authorities look to standardise their use of both shellfish biomonitors and monitoring methodologies to enable inter-regional comparisons and, ultimately, the development of a national picture of the state of our estuarine and coastal environments