Effects of a dimethylnaphthalene-contaminated food source and daily fluctuating temperatures on the survival potential of the estuarine shrimp Palaemonetes pugio

The biological effects of a naturally occurring perturbation were compared with one which may be induced by man's activities in the coastal zone. The estuarine shrimp Palaemonetes pugio was exposed for 32 d to fluctuating (18°–22°C) temperatures (FT) and/or 2,6-dimethylnaphthalene (DMN)-contaminated food at a concentration of 0.24 g DMN g^-1 wt food. After exposure, relative survival rates were evaluated in a matrix of environmental challenge tests. Low salinity (2 S) had little overall effect on survival. Survival at elevated temperatures (33°C) was significantly lower than in reduced salinity and was independent of the treatment effects. Resistance to the challenge of hypoxia+reduced salinity, however, in contrast to the other tests, was significantly reduced by exposure to FT and DMN-contaminated food. The influence of FT was much stronger and obscured the effects of DMN-contaminated food when shrimp were exposed to both perturbations at the same time. The persistent, residual effects of FT and DMN-contaminated food on the survival of P. pugio during exposure to hypoxia were evaluated after a 16-d recovery period with stable temperatures and uncontaminated food. The initial deleterious effects of FT appeared to be ameliorated by the stable temperatures. On the other hand, shrimp which had ingested DMN-contaminated food, prior to the clean food, exhibited enhanced survival during exposure to hypoxia. After ingesting contaminated food for 32 d, P. pugio contained concentrations of DMN approximately 1 order of magnitude greater than that in the food. Shrimp kept in FT generally had higher concentrations of DMN than shrimp held in stable temperatures. Feeding uncontaminated food to contaminated shrimp for 16 d resulted in a significant reduction of DMN in the tissues.Virginia Institute of Marine Science Contribution No. 983