In the SITAR project the nanoinjection technique was used to inject sediment extracts into newly fertilised rainbow trout (Oncorhynchus mykiss) eggs, whereupon disorders in the developing embryos and larvae were recorded as a measure of potential toxicity.
The potential toxicity of munitions dumped on the seabed or buried beneath the sediment surface depends largely on the characteristics of the toxic substances. Earlier studies of the toxicity of dumping areas have focused mainly on the acute toxicity of hydrophilic (polar) substances and found very little toxicity, if any (Halsband, 1976; MHLCAKL, 1986; FLGWC, 1993; Russian Federation, 1993; HELCOM CHEMU, 1994; Henriksson et al., 1996; Muribi, 1997; Muribi and Eriksson, 1997). A vast number of environmental pollutants are, however, lipophilic and many of these are not acutely toxic, but give rise to effects first after a long exposure period and/or long after the exposure. These environmental pollutants include well-known model pollutants, such as dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs), dioxins and dibenzofurans. Such persistent organic pollutants may bioaccumulate both by bioconcentration (directly from the water phase) and by biomagnification (via the food web). The parent substances are not necessarily toxic in themselves, but toxic metabolites may be formed during intracellular metabolism. These factors explain why adverse biological effects may not only be found at sites where these kinds of pollutants are released.
Exposure to lipophilic organic pollutants in the aquatic environment occurs in at least three ways: (i) by maternal transmission, (ii) by direct uptake from the water phase and (iii) by food consumption. With the nanoinjection technique used within SITAR all the above routes of exposure are taken into consideration. With nanoinjection, very roughly speaking, we refer to the introduction ("nanoinjection") of extracts from seabed samples of the study area in fertilized fish eggs. The growth disorders percentage observed in injected eggs from the study site with respect to a reference site
gives a relative measure of accumulated potential toxicity at the site. The relevance of the method can be explained in the following way: surficial sediment is a relevant abiotic matrix for measurement of potential toxicity; extraction with toluene gives a relevant selection of lipophilic xenobiotics that are potentially bioaccumulated; nanoinjection of the extracts into newly fertilised rainbow trout eggs offers a relevant, sensitive biological system with characteristic vertebrate metabolism; and selected subcellular biomarker responses confirm relevant uptake over the cell membrane when a dose-response relationship is found after relevant chronic exposure.
As a positive control to the SITAR study area we also measured the potential toxicity along an 84-km-long pollution gradient through the Stockholm Archipelago (Sweden, Baltic Sea) with the city of Stockholm as a point source. The choice of control was motivated by documented toxic effects in adult feral perch (Perca fluviatilis) in this gradient (Balk et al., 2003a, b). In addition to the biotoxicity measurement selected PCBs and polycyclic aromatic hydrocarbons (PAHs) were quantified in sediments from the stations of the Stockholm Archipelago gradient, including one site in the central part of the munitions dumping area.