Oxygen and hydrogen sulfide concentration of Nootka Sound bottom water

Senior thesis written for Oceanography 445

[author abstract] Nootka Sound is a narrow fjord located at the west side of the Vancouver Island that have little investigation been done. It has a large sill that could potentially trap ocean water. Along with steep salinity and other geological reasons, Nootka Sound is susceptible to oxygen depletion in water, which is detrimental to benthic communities and fisheries. In this study, oxygen concentrations were measured with oxygen probe on CTD instrument. Oxygen data was calibrated with titration of water sample from CTD, with Winkler Method. Water samples was analyzed to show its nutrient concentration, specifically nitrate, nitrite and ammonia concentrations. Results shows that at the time of the study, water below 350 meters in depth is oxygen depleted. At one of the station, water sample had a strong rotten egg smell, which means there was a lot of dissolved hydrogen sulfide. Hydrogen sulfide is a great indicator of sulfate reduction, which only happens when no oxygen and nitrate exists. The condition of Muchalat Inlet is similar to Sannich Inlet and Hood Canal in terms of the mechanisms that causes oxygen depletion.

University of Washington School of Oceanography