Some Effects of Simultaneous Variation in Salinity, Temperature and Dissolved Oxygen on the Resistance of Young Coho Salmon to A Toxic Substance

Abstract

Median resistance times of juvenile coho salmon (Oncorhynchus kisutch) acclimated to fresh water at 12oC were investigated at 3 mg/l of sodium pentachlorophenate over combinations of levels of salinity, temperature and dissolved oxygen using factorial schemes developed by Box and associates. For the relationship: [image] = [phi](x1, x2,x3,...,xK) a true response [image] is regarded as a function of combinations of levels of k quantitative factors x1, x2, x3,..., xk. The relationship was approximated by a polynomial in x for the three coded factors: salinity (x1), %; temperature (x2), [degree]C; and dissolved oxygen (X3), mg/1. The experimental data were fitted to a second-order polynomial: Y = 59.9319 + 9.5469x1 - 10.8943x2 + 0.1746x3 - 2.2690x1 2 - 4.4291x2 2 -4.0143x3 2 -X2360X1X2 + 2.5328X1X3 - 0.2671x2X3 This was transformed to its canonical form, from which ellipsoidal response surfaces were constructed. Alternative levels of salinity, temperature and dissolved oxygen were computed for general evaluation of the manner in which these variables altered the response to the pentachlorophenate. A maximum response time was computed for the response surfaces, associated with levels of the three variables at 17.68% salinity, 4.86[degree]C and 7.66 mg/l, O2. The use of multivariable experimental techniques is discussed as a means of considering the significance of alteration in the levels of associated environmental factors in evaluation of experimental or environmental situations involving water quality alteration.