Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


The effects of chlorinated sea water on the blue crab, Callinectes sapidus Rathbun, were evaluated through measurements of acute toxicity, serum constituents (protein, total ninhydrin positive substances, chloride, osmotic, sodium, potassium, calcium, and magnesium concentrations), oxygen consumption and ventilation rates in whole crabs, and oxygen consumption of excised gills. Histological examination of gills was also performed. The 96-hr LC50 for female blue crabs exposed to chlorinated sea water at 21�C and 14('0)/00 was 0.86 mgCl(,2)/l CIO (chlorine induced oxidants). The value for males under similar conditions was 0.84 mgCl(,2)/l CIO. Mortality was uncommon below 0.61 mgCl(,2)/l, but reached 100% with as little as 1.15 mgCl(,2)/l. Exposure of adult females to 0.79 mgCl(,2)/l CIO for two hours in a flow-through respirometer caused decreases in oxygen consumption. These decreases were interpreted as short-term reactions to sensing the chlorinated water, since 96-hr exposures of crabs to 0.99 MgCl(,2)/l CIO caused no consistent changes in statistically measured oxygen consumption of whole crabs or excised gills relative to controls. In addition, except for short-term reactions, the same levels of CIO had no effects on crab ventilation rates. Histological examination of gills revealed no observable damage from exposure to CIO. CIO levels ranging from 0.36 to 1.04 mgCl(,2)/l had no consistent effects on any of the serum constituents, except for magnesium. Hyporegulation of this ion was disrupted (serum magnesium concentration increased relative to controls and approached external medium levels) during 96-hr exposures of crabs to CIO levels of 0.47 mgCl(,2)l and higher. The magnitude of the effect was directly related to dose. The effect of CIO on blue crab serum magnesium is the same as that found for other crabs exposed to CIO and chlorinated hydrocarbon pesticides. It is hypothesized that increased serum magnesium levels interfere with neural activity, causing death. Since magnesium regulation in the blue crab occurs at the bladder wall, the implication is that CIO acts on the crab at this internal site. This possibility compounds the already difficult problem of toxicant identification when using CIO.



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