Sediment contact with benthic organisms

Sensitivity of biotests in terms of uncertainty considerations refers to the potential of a test system to indicate or to predict correctly the effects of contaminants in the sediment, thereby minimising false positive (nontoxic sample inconectly classified as toxic) and false negative (toxic sample incorrectly classified as nontoxic) results. Ingersoll et al. (1997) pointed out that whole-sediment tests with benthic organisms and acute measurement endpoints showed a high degree of certainty in this respect. This has also been shown by Ronnpagel et al. (1998) for a bacteria contact test which correlated well with the autochthonous microbial activity in experiments with spiked sediments. 

The ecological risk to local benthic organisms from potential exposure to POPs through direct contact with marine sediment was also assessed. Direct contact with the contaminated sediment was the most significant pathway of exposure for benthic organisms. The use of chemical specific... 

Thus far, quality objectives for chemical substances are derived from the most sensitive organisms in acute and chronic toxicity test batteries that determine NOEC values for different trophic levels. The pT-method similarly determines specific sample dilution levels that are devoid of adverse effects toward (micro)organisms of a standardized test battery. Common to both approaches is the more frequent use of water-column test organisms as opposed to benthic-dwelling organism that reflect more intimate contact with sediment. This practice is primarily based on the fact that standardized bioassays capable of appraising sediment porewaters and elutriates are presently more numerous than solid-phase tests for whole-sediment assessment. As more of these latter tests become developed and standardized (see Chapters 12 and 13, volume 1 of this book on amphipod and chironomid tests), their more frequent use will contribute to a better understand of the toxic effects of sediment-bound contaminants. 

PAHs tend to accumulate in the bottom sediments, which can become a constant source of toxic contaminants putting in danger, continuously, the biota health and viability, mainly, of the benthic organisms that suffer constant expositions to PAHs by the direct contact with the soil (Bihari et al., 2006 Boscolo et al., 2007). 

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