Population responses of the pulmonate gastropod, Amphibola crenata, reflect estuarine trace metal contamination

This study assessed the potential of the mud snail Amphibola crenata as a bioindicator of estuarine health. Multiple sites with varying contaminant inputs were identified within a small, shallow estuary (Avon-Heathcote/Ihutai in the South Island of New Zealand). Population structures of field-collected A. crenata were related to measurements of sediment trace metal profiles. Whole-body soft tissue metal concentrations were significantly positively correlated with sediment trace metals for all elements analysed (arsenic, cadmium, copper, nickel, lead and zinc). In terms of population biomarkers, medium-sized mud snails (7.9–17.9 mm shell length) dominated the population size structure at the most contaminated sites. That sites which were more highly enriched in trace metals were distinguishable by application of a simple population structure assessment, suggests that A. crenata has potential value for evaluating estuarine health. However, further investigation of other biotic and abiotic factors that may influence population structure are required.