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Freshwater Invertebrate Tests

Cladoceran (Ceriodaphnia dubia)

Cladocerans are used extensively internationally for aquatic toxicity testing and have been found to adapt well to laboratory conditions (Environment Canada 1992; USEPA 1993; Hall and Golding 1998). The functional role of cladocerans in a freshwater community favours them as test animals. They have an important role in converting phytoplankton and bacteria into nutritionally valuable food for species higher up the food chain.

Acute and chronic test methodologies have been developed (e.g. Environment Canada 1992; ASTM 1997) and applied to both pure chemical and industrial wastewater discharges (USEPA 1985). The chronic three-brood test method was introduced for use in effluent and ambient water evaluations, and is one of several methods used by the USEPA and Environment Canada for regulatory monitoring programs.

Ceriodaphnia dubia

Acute 48h survival test

Juveniles (<24h old) are exposed to various concentrations of a test substance under defined conditions. The survival of the organisms after 48h exposure is compared to the survival of the organisms in an appropriate control. A test substance is considered toxic when a statistically significant, dose-dependent effect on survival of the organisms is observed.

Chronic 7d survival and reproduction test

Juveniles (<24h old) are exposed to various concentrations of a test substance in a static-renewal test system for a minimum of 7days. The survival of the exposed organisms is compared to the survival in an appropriate control. The number of offspring produced in three broods during this exposure for different concentrations of the test substance is compared to the number of offspring produced during exposure to an appropriate control.

Amphipod (Paracalliope fluviatilis)

Paracalliope fluviatalis

The freshwater amphipod Paracalliope fluviatilis is potentially one of the most useful indigenous freshwater species for toxicity testing. It is common throughout New Zealand and usually found in flowing waters, inhabiting sediment and weed beds along the edges of streams. Previous studies have found them to be sensitive to a wide range of contaminants (e.g Burnett 1972; Hunt 1974; Hickey and Vickers 1994; Hall and Golding 1998) and their relative sensitivity suggests that P. fluviatilis may be one of the most vulnerable species to contaminants.

Acute 48h survival test

Juveniles aged between 0 and 7 days are exposed in a static system to various concentrations of a test substance for 48h. The survival of the amphipods exposed to the test substance is compared to the survival of the amphipods in an appropriate control. A test substance is considered toxic when a statistically significant, dose-dependent effect on amphipod survival occurs.

Chronic 30d survival and reproduction test

Juveniles between 1-3mm length are exposed in a flow through test system to various concentrations of a test substance for 30 days. At the completion of the test exposure, the number of surviving adults and juveniles are counted and compared to the number of adults and juveniles in an appropriate control.

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