A simple continuous-flow toxicity test system for microscopic life stages of aquatic organisms

Comparison of Acute Aquatic Effects of the Oil Dispersant Corexit 9500 with Those of Other Corexit Series Dispersants

“…In past testing, delayed mortality seen in mysids suggested that these animals might possess protective structures, such as thick epithelial cuticles, that could limit exposure or were able to ameliorate biochemical toxicity through physiological pathways, such as biotransformation and depuration (Swedmark et al, 1971). This is borne out by the observation that juvenile Holmesimysis have been seen to survive in constant dispersant exposures of up to 30 ppm for up to 48 hr before significant mortality occurred (Singer et al, 1990). It appears, though, that the effects of Corexit 9500 in mysids may be more biochemical than those of the other Corexits, as evidenced by the relatively long lag time before the onset of significant mortality (Table 3), which may imply a greater solvent role in its toxicity.…”

“…Because sealed conditions can be maintained throughout toxicity tests, solution chemistry can be rigidly controlled, which is especially important when testing complex volatile and/or unstable mixtures. In order to monitor water quality within the test yet still maintain tight chemical control, 125-ml sampling flasks are located downstream of one chamber in each test treatment (Singer et al, 1990). Because these flasks directly drain the test chambers, it is possible to characterize, in real time, the water quality conditions that exist within the test without disturbing the chambers themselves.…”

“…The various components of the system have been described previously (Singer et al, 1990(Singer et al, , 1991(Singer et al, , 1993. The system utilizes sealed glass exposure chambers (≈260 ml) with integral fritted glass disks for containing microscopic test organisms in flowthrough conditions (Singer et al, 1993).…”

“…have been widely used in the state for regulatory testing over the past several years (Anderson et al, 1990;Singer et al, 1990Singer et al, , 1991.…”

“…Indeed, the lack of standardization of methods in the field of oil and dispersant toxicity testing has led to an unfortunate lack of comparability of data sets, and a lack of coherent conclusions, even after more than two decades of research (National Research Council, 1989;Markarian et al, 1995). Over the past several years, an exposure system has been developed that allows the testing of complex, volatile mixtures using microscopic organisms under precisely controlled, flowthrough conditions (Singer et al, 1990(Singer et al, , 1993. Standardized procedures have also been developed for testing dispersants, and oils, in a modeled-exposure regime that provides useful insight into effects that might be expected in the field (Singer et al, 1991).…”