The viscosity of seawater decreases considerably with rise of temperature and increases slightly with increase of salinity. The coefficient of dynamic viscosity is a measure of the drag exerted on moving objects in a fluid. In seawater of salinity 35%o at 00C the coefficient of dynamic viscosity is 18.9 X 10~9N per cm2 per unit velocity gradient, and at 300C is only 8.7 X 10~9. These values indicate that resistance to movement is over twice as great in the coldest parts of the sea as in the warmest. Viscosity influences both sinking and swimming speeds, and in many organisms must also have effects on feeding rates and respiration.
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