Friday, July 16, 2010

Will there be a fish kill in Lower Hood Canal this year?

Recent media reports, like this one in the Kitsap Sun, describe oxygen depletion in Hood Canal. Researchers are concerned that if the oxygen deficit increases, fish kills may occur within “dead zones.”

This week, members of the House Ecology & Parks Committee got an update on current conditions in Hood Canal, and heard about ongoing research to track “dead zones” and determine what effect humans (mainly via residential on-site septic systems) have on lower oxygen levels in the water. Dr. Jan Newton, from the University of Washington, gave a presentation showing annual variations in oxygen levels at various spots along Hood Canal. Dr. Newton heads the Hood Canal Dissolved Oxygen Program, which has determined so far that although the input of nitrogen into Hood Canal from residential septic systems is small compared to the marine input (nitrogen from ocean water coming into the canal),it is enough to potentially cause a “tipping point” depending on the background concentration of nitrogen for that year. In other words, some years it might not make a difference, and other years it most definitely could.

This year, oxygen levels in Lower Hood Canal are at the lowest levels based on record-keeping, which means 2010 could be the year of sudden fish kills within the Canal. It’s too early yet to tell if that will happen, but what is clear is that minimizing human input of nitrogen into Hood Canal is important. This is an issue that the Committee will continue to track during the interim, because the economies of many communities along Hood Canal are dependent on a healthy marine environment for fishing, shellfish harvesting, and recreation.