Effects of Acute Exposure to Bleached Kraft Pulpmill Effluent on Carbohydrate Metabolism of Juvenile Coho Salmon (Oncorhynchus kisutch) During Rest and Exercise

Abstract

In the static study (no exercise), liver glycogen stores were unchanged during 12-h exposure to 0.8 of the 96-h LC50; longer exposures caused a progressive decrease to levels one fifth those of controls at 72 h. Plasma glucose levels in fish held in 0.8 LC50 effluent for 3–96 h were elevated; at 96 h, glucose had increased threefold. Mean values for plasma lactate were elevated significantly at 3, 6, 24, 72, and 96 h.In the exercise (swimming one body length per second)–rest study, muscle glycogen levels decreased 53–78% during exercise in water or effluent (0.7 LC50) for 4–12 h, and did not recover during 12-h rest in water. Muscle glycogen for fish exercised for 12 h in effluent and then rested for 4 or 12 h in effluent was lower compared to values for fish exercised in effluent and then rested in water. There was no difference in liver glycogen levels offish exercised in effluent or water for 4–12 h. Values of liver glycogen for fish exercised in effluent for 12 h and then rested for 4, 8, or 12 h in effluent decreased 60–70% compared to fish exercised in water for 12 h and then rested in water and by 55–65% from fish exercised in effluent for 12 h and rested in water for 4–12 h. Plasma glucose levels were elevated one- to fourfold during exercise in water or effluent. Fish resting in water for 4, 8, or 12 h following exercise in water had relatively stable glucose levels; whereas for fish exercised and then rested in effluent the glucose levels increased twofold during resting. Plasma lactate levels were elevated five- to sixfold during exercise in water or effluent for 4–12 h, declining to values 1–2 times those of stock fish within 4-h rest. Plasma lactate levels for fish exercised in effluent and then rested in effluent or water were continually higher than those for fish exercised and rested in water.It was concluded that measurement of carbohydrate metabolites, particularly blood sugar levels, in unexercised fish could prove useful as a rapid method for measuring toxicity of pulpmill effluents and other pollutants.