JURY, Steven H.*; BETKA, Marlies; LINELY, Tim; HARRIS, H.W.; MariCal, Inc.: The interaction of low pH, aluminum, and calcium on olfaction of Atlantic salmon (Salmo salar)

The interaction of pH, aluminum (Al) and calcium (Ca) on olfactory nerve activity and Na/K ATPase in olfactory lamellae was determined for Atlantic salmon (Salmo salar). Parr were reared in either ambient (Ca, <0.1 mM) or hard (Ca, 1 mM) freshwater and subsequently transferred to one of the following conditions: 1) control (pH 7, <0.1 mM Ca, no Al); 2) simulated limed river (SLR- pH 7, 1 mM Ca, 10 uM Al); or 3) simulated acidic river (SAR- pH 5, <0.1 mM Ca, 10 uM Al). Under SAR conditions, Na/K ATPase activity in olfactory lamellae and gills was significantly lower than control conditions for both the ambient and hard water acclimated fish. Electrical responses recorded from the olfactory nerves of fish reared under the ambient conditions and subsequently exposed to control, SLR, or SAR were determined by exposing the olfactory epithelia to stimuli for 10 s each at pH 5 or 7. Aluminum stimuli (>=10 uM) caused an inhibition of background activity when delivered at pH 5 but not pH 7. As reported by others, the responses to amino acid stimuli at low pH were reduced when tested under control conditions, however this was not the case when tested under SLR or SAR conditions. Conversely, the response to a polyamine stimulus, 100 uM spermine, at low pH under control conditions was not reduced. However, the response to spermine was greatly reduced at both pHs under the higher Ca SLR conditions. Interestingly, Al when presented together with either the amino acid or polyamine stimuli at either pH did not appear to directly affect the response to the odorants but it did inhibit the response to 1 mM Ca. These results suggest that ecologically relevant levels of Al have complex pharmacological effects on salmon olfaction in addition to the documented toxic effects on gill physiology. An understanding of the interaction of low pH, Al, and Ca in natural and mitigated salmon rivers is crucial to identify potential impacts on olfactory-mediated behaviors.