Grandidierella lignorum (Amphipoda: Aoridae) can be used for assessing the toxicity of sediment with varying grain sizes and low organic content
Sediment grain size and organic matter influences the distribution of macrozoobenthic fauna. These parameters also influence bioavailability and toxicity of contaminants in aquatic systems, because sediment is the sink and source for most contaminants. These sediment parameters therefore potentially confound sediment toxicity results when using inappropriate toxicity test organisms and/or test conditions. Grandidierella lignorum is being developed as a sediment toxicity test organism for South African coastal waters and it is crucial that its preference for sediment grain size and organic matter is determined with the aim of defining test conditions for sediment toxicity tests. G. lignorum were offered a choice of six sediment grades and two types of organic matter of varying concentrations (0–8%) to determine their preference thereof. Very coarse sediment grade and mud were consistently the least selected particle sizes in all experiments. Sediment with low organic matter (<0.5%), was also consistently selected by G. lignorum and this was not influenced by sediment particle size. G. lignorum can therefore be used for the toxicity testing of sediment with a wide grain size variation, although results may be confounded in sediment samples largely comprised of very coarse or muddy sediment.
Keywords: confounding factors, defining test condition, sediment toxicity testing, toxicity test organism