Assessment of the impact of naphthalene contamination on mangrove fauna using behavioral bioassays

Pollution of the marine and estuarine environments by petroleum hydrocarbons is a world wide phenomenon (Connell and Miller 1980) and whilst large scale crude oil spills are the most obvious source of pollution, since the 1970's the impact of chronic, low level hydrocarbon input from sources such as oil refineries has been recognised as having long term ecological consequences, even when there may be no visible evidence of acute effects (Connell and Miller 1980). Mangroves are perhaps the dominant and most important intertidal habitat along subtropical and tropical coastlines and estuaries and as such are located in areas of high risk of acute or chronic petroleum hydrocarbon pollution. Further, once contamination occurs, high levels of hydrocarbons may be expected to remain in mangrove sediments as conditions are not favorable for hydrocarbon depletion by sediment transport or degradation by aerobic bacteria. Much research has focused on determining the acute toxicity of the water soluble fraction of crude or fuel oil to aquatic fauna but relatively little attention has been given to individual hydrocarbons. The medium to low boiling point aromatics such as naphthalene and its alkyl derivatives are the most toxic petroleum fraction to marine organisms (Anderson et al. 1974; Moore and Dwyer 1974) and they are known to provoke behavioral responses in marine animals at sublethal concentrations (Hargrave and Newcomb 1973; Linden 1977; Nagarajah et al. 1985). The goal of this investigation was to investigate the effects of a single aromatic petroleum hydrocarbon, naphthalene, in a subtropical mangrove environment, through the use of behavioral bioassays. The test organism chosen was the intertidal gastropod Ophicardelus quoyi, which is abundant in mangroves throughout eastern Australia.