Indicators: Sediment Toxicity

What is sediment toxicity? 

Toxicity is the ability of a substance to cause harmful health effects to an organism. Sediment toxicity is a term used to refer to the potential for negative effects on aquatic organisms arising from contaminants in sediment. Sediment toxicity is evaluated by exposing laboratory test organisms to sediment samples collected from the bottoms of lakes, estuaries or other water bodies. Test organisms (usually organisms that are sensitive to their environment) are exposed to both potentially contaminated sediment samples and known clean sediment samples under controlled laboratory conditions. At the end of the test, the number of organisms surviving in the contaminated sediment are compared to the number of organisms surviving in the control sediment. The sediment sample is identified as toxic if the survival in the field samples is significantly less than in control samples. 

Why is sediment toxicity testing important? 

Many different contaminants may be present together in an aquatic environment. Testing for each potential contaminant can be challenging. Researchers test the overall toxicity of a sediment sample to determine if the sediment may be in degraded condition due to a combination of known and unknown contaminants. 

What can sediment toxicity testing tell us about the water? 

Sediment toxicity testing can tell us if there are conditions in the sediment that may lead to decreased survival of organisms. When sediment dwelling organisms face adverse impacts due to a contaminated environment, they may pass toxic substances into their predators and subsequently, the food web. In addition, if toxic conditions impact the survival of sediment organisms, it can reduce the population of prey for organisms further up the food web and lead to negative consequences throughout the ecosystem. 

How is this indicator used in NARS? 

The National Coastal Condition Assessment collects data on sediment toxicity and is available on the NARS data page. Below the table you access assessment information in current reports. 

National Coastal Condition Assessment Web Report – Coming Soon.