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A physical and chemical study of Tofino Inlet, Vancouver Island, British Columbia. Coote, Arthur R.


The distribution of the physical and chemical properties in Tofino Inlet is examined in this study. The presence of shallow thresholds in the entrances to the inlet prevents the exchange of deep water in the inlet with oceanic water of the same depth and restricts the intrusion of oceanic water to that of the surface layer. Replacement of the bottom water of the inlet occurs in the summer, when the density of the oceanic surface water is highest for the year, and accounts for the relatively high bottom temperatures, which are observed throughout the year. Between replacements the bottom water in the upper basins of Tofino stagnates and becomes anoxic. Under these stagnant conditions the oxygen supply of this water is used up. Eventually heterotrophic bacteria use sulphate as hydrogen acceptor for the oxidation of organic matter and produce hydrogen sulphide and carbon dioxide. The production of these substances results in an increase In the alkalinity and a decrease in the pH of the water. Using certain assumptions regarding the oxidative processes, calculations are made which suggest that the observed anomalous increase in alkalinity is mainly due to the dissolution of calcium carbonate in these relatively acidic waters. A rate of oxygen utilization is calculated for the deep basin water and is used to determine whether or not replacement of the bottom water was likely during the summer of 1959.

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