Evaluating the techniques for a tiered testing approach to dredged sediment assessment—a study over a metal concentration gradient

Abstract

A sediment quality triad approach was used to evaluate Environment Canada's battery of marine bioassays and the proposed pass/fail criteria along a metals gradient in Belledune Harbour, New Brunswick, Canada. Most assays performed consistently, but certain tests provided less response than expected at the more contaminated stations (amphipod survival and light reduction in photoluminescent bacteria tests passed according to proposed pass/fail criteria). Echinoid fertilization tests were quite sensitive. Bioaccumulation of lead and benthic community structure were related to bulk sediment values (at α = 0.1). Test interpretation criteria appear reasonable, but as the response rate was low in certain tests, further assessment is recommended. With respect to species suitability, only the clam Macoma balthica used in the bioaccumulation test was thought to be less than optimal for routine use on a large scale because of practical handling and cost considerations. Canadian draft Interim Sediment Quality Guidelines, which the Disposal at Sea Program may use for screening purposes in a tiered testing approach, were used in this study as the chemical benchmarks to select test stations on the basis of the relative probability of effects. Guidelines at the threshold effects level (TEL) performed well in the study as levels below which unacceptable biological effects were unlikely to occur. The ratio of simultaneously extractable metals to acid volatile sulfides was also used in addition to the guideline levels to help explain responses (or lack thereof) along the gradient. Each of the chemical approaches was useful in the prediction/explanation of some but not all of the responses seen in the toxicity and/or benthic community results.

A Decision‐Making Framework for Sediment Contamination

“…Thus, if sediment COPC concentrations are below SQGs that predict minimal effects (SQG‐low), then there is likely negligible ecological risk. These observations are corroborated by Porebski et al (1999), for example, who found that such SQG‐low values nearly always represented levels below which unacceptable biological effects were unlikely to occur in sediment. Because SQGs have no role in evaluating human health risks or biomagnification (Wenning and Ingersoll 2002) and there are no such sediment guidelines, initial (conservative) decisions regarding biomagnification potential are simply based on the presence or absence of quantifiable amounts of substances that may biomagnify.…”

Long‐term sediment bioassay of lead toxicity in two generations of the marine amphipod Elasmopus laevis, S.I. Smith, 1873

“…Homogenized control sediment was separated into five aliquots: One 1,200‐g aliquot destined for control; another 1,200‐g aliquot for adjustment to 200 μg/g lead; and three 1,000‐g aliquots to be spiked to 50, 100, and 400 μg/g lead, respectively. This range included the ERM of 218 μg/g and effects‐range low of 47 μg/g for lead reported for other amphipods in acute 10‐d or chronic 28‐d bioassays [31,34,35]. These sediments were sealed in Nalgene® (United States Plastic Corporation, Lima, OH, USA) polymethylpen‐tane containers and stored overnight at 4°C.…”

“…The evaluation of whole‐sediment toxicity assessed through bioassays and related to ecotoxicological impacts has lead to the establishment of sediment quality guidelines. These guidelines were developed to protect biological resources and humans from the effects of contaminated sediment ([6,14,16,22,26,27,30–33]; http://www.ene.gov.on.ca/envision/gp/B1-3.pdf; http://response.restoration.noaa.gov/book_shelf/121_sedi_qual_guide.pdf). Contaminant levels at or below a concentration rarely showing adverse biological effects typically are classified as either the effects‐range low or the threshold‐effects level [32–35].…”

A Review of the Microtox® Toxicity Test System for Assessing the Toxicity of Sediments and Soils

“…Microtox has been incorporated into both informal and traditional triad designs in a limited number of studies. For instance, Porebski et al (1999) used a combination of bioassays that included Microtox pore water and solid-phase tests, sample chemistry and benthic community structure to assess pollution along a gradient in Belledune Harbour, New Brunswick. A similar approach had been adopted earlier by Day et al (1995).…”