| Summary: | Nearly every continent has species of crawfish that inhabit wetlands or are near coastal areas where petroleum and other oils are produced, transported, and accidentally released. Most crawfish cannot tolerate polluted water. Thus, they could serve as biomonitors of fossil fuel, biofuel, and other oil releases and assess potential negative impacts such oils have on wetland and coastal ecosystems.
The objectives of this study were to estimate the acute toxicity of three oils to juvenile crawfish and determine if toxicity was due to poisoning or interference with oxygen transfer across the gills. Juvenile crawfish (Procambarus clarkii) were tested for acute toxicity (96-h) using South Louisiana crude, peanut and mineral oils. Pairs of randomized tanks, with ten crawfish per tank or twenty per treatment concentration, were used in each experiment. Temperature (22°C±1) and standard water quality parameters were maintained constant based on ASTM protocols. The acute toxicity of South Louisiana crude oil was compared with peanut oil, a representative of biofuels and similar biologically-based oils, and mineral oil, which has a higher molecular weight and represents the heavier components of crude oil and biofuels.
Two sets of experiments showed crude oil is acutely toxic to juvenile crawfish from 50 to 100 mg/L, with 84 mg/L being the LC50 (median lethal concentration at 96-h). Peanut oil acute toxicity, identified by another pair of experiments, was approximately one order-of-magnitude lower (LC50 = 600 mg/L) than crude oil. The heavier mineral oil produced another order-of-magnitude lower mortality, with the LC50 exceeding 10,000 mg/L. The gills of crawfish exposed to crude oil did not appear to be coated with hydrocarbons and the mortality observed is putatively due to poisoning, Peanut oil mortality appeared to be due to poisoning plus smothering, whereas mineral oil mortality appeared to be due primarily to smothering. This work suggests possible engineering techniques to reduce the toxic effects of oils and points to toxicity considerations of biofuels. Additional laboratory and field-based studies using juvenile crawfish are needed to provide understanding of the mechanisms of acute and chronic toxicity by hydrocarbon and biologically-based oils in sensitive wetland and coastal ecosystems.
Key words: crawfish, crude oil, biofuel, toxicity, ecology, engineering
|
|---|
