International Dredging Review

International Dredging Review

Researchers gave several presentations related to toxicity testing of dredged material and other sediments at the 25th Meeting of the Society of Environmental Toxicology and Chemistry (SETAC) meeting in Portland Oregon November 14-18.

SETAC is a non-profit professional society with a mission to support the development of principles and practices to protect enhance and manage sustainable environmental quality and ecosystem integrity. It has long been at the forefront of critical review of scientific research related to contaminants and other environmental stressors and aggressively promotes the use of science in the development environmental policy.

SETAC sponsors an annual North American meeting where professionals present and discuss research in a variety of different fields. This year’s Portland Oregon meeting was also the 4th World Congress meeting and attracted scientists environmental managers and students from all over the world. The breadth of research presented this year was staggering ranging from the use of DNA biomarkers to discussions of sustainable economies.

The majority of presentations focused on studies with water column organisms. This focus is reflective of toxicity testing in general which has concentrated on water studies primarily because of the commercial recreational and aesthetic value of streams rivers lakes and the fish that live in them. However ecologists have long recognized that benthic organisms including crustaceans mussels and insects may also be subject to adverse effects from contaminated sediments due to their intimate contact with sediments and interstitial water.

Tests with benthic organisms began in earnest in the late 1970s with studies using mayflies (e.g. Hexagenia limbata) and the larval midge Chironomus sp. Most of the early sediment testing was focused on the potential effects of the disposal of dredged material. The U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency developed guidance documents for testing of dredged material for disposal in both marine and freshwater environments. Procedures in both the marine (the Green Book) and inland testing manuals follow a tiered approach for evaluating dredged materials with toxicity testing using benthic organisms falling under Tier III and IV. Toxicity evaluation of dredged materials includes whole sediment testing as well as an evaluation of elutriate (water-extractable) fractions.

There were more than 100 presentations at the SETAC meeting that had direct or indirect relevance to the testing of dredged material. Some of the more critical ones included:

Field Validation of Chronic Sub-lethal Dredged Material Laboratory Bioassays: A 3 Year Summary by D.W. Moore (MEC Analytical) and others. Described U.S. Army Corps of Engineers research into the development of two chronic sublethal bioassays with the marine polychaete Neanthes arenaceodentata and the estuarine amphipod Leptocheirus plumulosus. Studies in the laboratory and in the field suggest that laboratory tests may provide overly conservative estimates of potential impacts to the benthic community.

Sensitivity and Performance of Chronic Sediment Toxicity Tests in Dredged Material Management by A.J. Kennedy and others. Chronic (28-day) tests using Leptocheirus plumulosus and Neanthes arenaceodentata and acute (10-day) tests using Americamysis bahia Ampelisca abdita and Leptocheirus were conducted using contaminated (4000 – 19000 ppb PAHs) sediment from New York Harbor. Despite the longer test period and sublethal endpoints chronic tests were not necessarily more sensitive to the contaminated sediments. Mysid shrimp (A. bahia) was relatively insensitive to the sediments.

Development of a Classification System for Marine-Dredged Material Proposed for Disposal in the Netherlands by C.A. Schipper and H. Verhaar. Because of a growing need to incorporate toxicity endpoints into the assessment of marine dredged material Netherlands is switching from the Uniform Content Test (UGT) to the Chemistry Toxicity Test (CTT). The CTT in addition to considering the chemistry of dredged material also uses tests with 1) the mud shrimp Corophium volutator 2) the Microtox SP™ test using the bacterium Vibrio fisheri and 3) the DR-CALUX bioassay which uses genetically modified rat liver cells to identify compounds with a dioxin-like action.

Changes in the United States Biological Testing Framework for Dredged Material Evaluations by J.A. Steevens. Describes recent changes in the guidance document Evaluation of Dredged Material Proposed for Discharge in Waters of the United States. The changes reflect some of the issues raised in the recent SETAC Pellston Workshop on sediment quality guidelines and incorporate multiple lines of evidence (sediment toxicity tests bioaccumulation studies analytical chemistry physical data and predictive models) into the sediment disposal decision-making process.

Many other presentations related to sediment toxicity testing were also given. Some of this information will eventually be published in Environmental Toxicology and Chemistry one of the professional journals of SETAC. Researchers will continue to conduct focused studies on sediment toxicity issues and will no doubt present some of that information at the 26th SETAC meeting will be held in Baltimore Maryland Nov. 13-17 2005.

About the Author: David Pillard is a Certified Senior Ecologist environmental toxicologist and Technical Director at the ENSR International Environmental Laboratory Fort Collins Colorado. He specializes in aquatic and terrestrial toxicology aquatic ecology risk assessment and general water resources. Dr. Pillard received his Ph.D. in Biology/Ecology in 1988 from the University of North Texas Denton Texas.