Sediment quality thresholds: Estimates from hockey stick regression of liver lesion prevalence in English sole (Pleuronectes vetulus)

Comprehensive, integrative assessments of coastal sediment quality are best effected by using large, diverse data sets that include measures of biological dysfunction observed in association with chronic exposure to sediment contaminants. Under the auspices of the National Oceanic and Atmospheric Administration's National Status and Trends Program, the National Benthic Surveillance Project accumulated a database of synoptic sediment contaminant concentrations and indices of biological effects that were measured in indigenous animals collected during field surveys conducted from 1984 to 1994. This compilation of data provided the opportunity to develop a new approach for determining sediment quality criteria to add to the current repertoire of environmental assessment tools. Using a two-segment hockey stick regression, statistically significant chemical thresholds of biological effects were estimated for hepatic lesion prevalences in English sole (Pleuronectes vetulus, formerly Parophrys vetulus) in relation to sediment concentrations of polycyclic aromatic hydrocarbons. These threshold estimates are notably lower than many of those reported for other techniques. Application of this relatively simple dose-response model to subacute, chronic effects that are involved in hepatocarcinogenesis and associated with sediment toxicant content (1) reflects the link between toxicopathic disease progression and conditions observed in benthic fish exposed to contaminants and (2) provides endpoints for assessing sediment quality contaminant concentrations that are not necessarily acutely fatal but may have long-term health implications for populations that are chronically exposed.