The Hood Canal is a long, narrow and deep fjord like body of water. It is often referred to as a ”Dead Zone”. It is an area that is literally suffocating due to lack of oxygen. There are many contributors to this problem in the Puget Sound. One is the underwater topography of the canal. It has an entrance which is very shallow of 150 feet. This creates a sill like effect making water exchange throughout seasons and tides difficult. Another contributing factor is [[Nitrification]]the --supply largeof amountsnutrients, primarily nitrate, to the euphotic zone. There are both natural and anthropogenic sources of nitrogennutrients. present The primary natural source is in theocean water that flushes Hood Canal. NitrificationisAnthropogenic causedsources byinclude leaking septic systems, storm water runoff, agriculture and various other sources. TheseThe high levelspresence of nitrogennutrients leadleads to excessive algae growth, which consumes oxygen when the algae begin to die and decompose, creatingcontributing anaerobicto the low oxygen conditions in these waters. PoorLow oxygen concentrations due to poor tidal exchange and nitrificationhigh productivity are what have characterized the Hood Canal as a “Dead Zone”. The poor tidal exchange in Puget Sound is due to a few factors. These include the flushing time, and the shape of the sound. Flushing time depends on the volume of the estuary, the volume of the tidal prism, and the number of tidal cycles per day. The tidal prism is known as the difference in the volume of the estuary at high and low tide. An equation for an approximate flushing time is: (Flushing time = Volume of estuary/ Volume of tidal prism) Puget Sound has a rather long flushing time, because it is rather large compared to its tidal prism. The shape of the sound prevents many of the inlets in the sound from flushing much at all; there is a lot of water movement in these inlets, but much of the water returns to the same inlet over and over again, and pollution and nutrients keep building up in this same area of water. (Emerick)
