Zooplankton avoidance behaviour as a response to point sources of hydrocarbon-contaminated water

Abstract

Hydrocarbon contamination is a pernicious threat for marine ecosystems as non-lethal effects on the plankton propagate through the food chain and accumulate in the tissues of top predators, ultimately putting human health at risk. The swimming behaviour of the calanoid copepods Eurytemora affinis and Temora longicornis was investigated in relation to point-source contamination by five different-sized patches of the water-soluble fraction of diesel oil diluted at 1 : 100, 1 : 1000 and 1 : 10 000 in estuarine and coastal waters. Both species consistently showed avoidance of the contaminated patches, irrespective of their size and concentration. Specifically, E. affinis exhibited similar sensory abilities irrespective of contaminant concentrations. In contrast, T. longicornis more efficiently identified high-density contaminated patches than low-density ones, and exhibited a negative exponential density dependence of its sensing abilities to the intensity of the chemical cues. Although the conclusions from this experiment need to be generalised to a variety of hydrocarbon contaminants, the present work indicates that zooplankton organisms have the potential to avoid hydrocarbon-contaminated waters, and also suggests that zooplankton swimming behaviour could potentially be used as an endpoint for a toxicity bioassay to assess the presence of toxic chemicals in estuarine and coastal waters.