Check out this great video from UW's Applied Physics Lab
to learn how our network of ORCA (Oceanic Remote Chemical Analyzer)
buoys has helped scientists track the "blob" and it's effects in local
waters, including fish kills in Hood Canal.
From Jan Newton, Allad Devol and Wendi Ruef, University of Washington:
A fish kill occurred in late August in Hood Canal, documented by observations from the Skokomish Tribe and by ORCA buoy oxygen measurements by the University of Washington. The fish kill was most severe on 29 August, but with stress and some mortality observed both before and after.
Seth Book and others from the Skokomish Tribe DNR observed thousands of dead fish and crab on Friday, which was covered by the media. On Saturday-Sunday, we anticipated even more fish kill, due to sustained southerly winds, but the lowest oxygen waters stayed deep, below ~10 m. Videos show the fish and crabs confined to a narrow surface layer, which maintained sufficient oxygen.
A couple things to clarify from the media reports:
- Worst year? The low oxygen levels in southern Hood Canal were the most extreme we have measured, even worse than in 2006 and 2010. However, the fish kill events in 2003, 2006 and 2010 appear to have been worse than this year, at least so far.
- Blob effect? The effect of the blob (warmer than typical NE Pacific ocean waters) was last fall, when the ocean waters entering Puget Sound were warmer (less dense) and did not flush the southern reach of Hood Canal. The year 2015 started with hypoxic waters in southern Hood Canal. The blob, still offshore now, is not affecting current conditions. Strong coastal upwelling during June is what is flushing Hood Canal now. This seasonal intrusion started about a month earlier than normal, which is lucky because oxygen conditions would have worsened until the flushing started.
Oxygen conditions in Hood Canal appear to be improving as flushing continues. Conditions today at Hoodsport show the entire water column is above hypoxic levels; at Twanoh there is severe hypoxia (less than 1 mg/L) at 10 m depth, but the deepest waters now have oxygen concentrations above this.
Visit ORCA and NANOOS for more information on hypoxia in Washington waters.
Lingcod from the 2006 Hood Canal fish kill event. Photo credit: Hood Canal Dissolved Oxygen Program
Fish kills in Hood Canal occur when hypoxic waters are rapidly upwelled
to the surface, usually when seasonal southerly wind storms push surface waters aside to be replaced with less oxygenated water from below. The rapid upward movement of low oxygen water to the surface traps fish, suffocating them.
The abnormal
weather and oceanic conditions which we've seen this year (the 'blob,' drought, etc.) have resulted in extreme hypoxia in Hood
Canal. But these anomalies have also set up Hood Canal for early seasonal flushing from oceanic intrusions, which could replenish oxygen levels.
Fish kill risk depends on whether seasonal storms or
complete flushing occur first, which is especially relevant at the moment with southerly winds expected in Hood Canal over the weekend. Which will win? Hopefully the fish!
Find out more from the Oceanic Remote Chemical Analyzer (ORCA) Fish Kill Advisory and
follow real-time oxygen levels monitored in Hood Canal on NVS.
Dead ratfish from the 2010 Hood Canal fish kill event. Photo credit: Ron Figlar-Barnes
