Artemia bioassay

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Effects on Aquatic Organisms

Abamectin is highly toxic to fish and aquatic invertebrates (7). Its 96-hour LC50 in rainbow trout is 3.2 ppb, 9.6 ppb in bluegill sunfish, 15 ppb in sheepshead minnow, 24 ppb in channel catfish, and 42 ppb in carp. Its 48-hour LC50 in Daphnia magna, a small freshwater crustacean, is 0.34 ppb. The 96-hour LC50 for abamectin in pink shrimp (Panaeus duorarum) is 1.6 ppb, 0.022 ppb in mysid shrimp, 430 ppb in eastern oysters, and 153 ppb in blue crab (6).

While the above LC50 values are quite low, indicating a high level of toxicity to aquatic organisms, actual concentrations of abamectin in surface waters (fresh water) adjacent to treated areas are expected to be low. Application rates of 0.025 pounds of abamectin per acre (the highest recommended rate) should result in concentrations no higher than 26 parts per trillion in adjacent surface waters one day after the application. Rapid photodegradation and adsorption to sediments should produce even lower concentrations within days. The degradation products of abamectin are less toxic to aquatic organisms than abamectin itself (6).

Abamectin did not bioaccumulate in bluegill sunfish exposed to 0.099 ppb for 28 days in a flow-through tank. On day 28, the concentration of residues in the fish was 6.8 ppb, but this rapidly decreased to 0.32 ppb by day 42. The BCF value calculated from this study is 52, indicating that abamectin does not accumulate or persist in fish (6).

  • Brine shrimp (Artemia salina) as a convenient bioassay for avermectin analogs [[1]]


Effects on Aquatic Organisms

The toxicity of imidacloprid to fish is moderately low. The 96-hour LC50 of imidacloprid is 211 mg/l for rainbow trout, 280 mg/l for carp, and 237 mg/l for golden orfe. In tests with the aquatic invertebrate Daphnia, the 48- hour EC50 (effective concentration to cause toxicity in 50% of the test organisms) was 85 mg/l (3). Products containing imidacloprid may be very toxic to aquatic invertebrates.