Over the past many years, it had become accepted wisdom that fish kills and related problems in Hood Canal were caused by humans, especially human waste coming from septic systems. However, a new comprehensive review of the science dispels that idea as a myth. It has lessons for us here in the San Juans about jumping to the "blame the people" conclusion, especially since it turns out to be wrong for poorly-circulated Hood Canal with 60,000 people, whereas we are fewer than 16,000 people living within the very well-circulated Straits of Georgia.
I encourage you to read the linked article for yourself. Here are some excerpts:
But in 2002, 2003, 2004, 2006 and 2010, periods of low oxygen were so extreme that fish died in massive numbers. In most of those years, thousands of fish from more than two dozen species were killed. Underwater photographs captured wolf eels seeming to pant and rockfish by the hundreds gathering near the water's surface, where oxygen was more plentiful. Dead lingcod washed ashore.
While no one formally tracked fish kills through history, the events of the last decade unnerved many scientists.
Fish kills have hammered Hood Canal off and on at least as far back as the 1920s, if not earlier. A 2008 study of core samples found that oxygen levels in much of the canal were actually lower before 1900 than they were for most of the 20th century.
When several studies, including by both Newton and Brett, showed significant nutrient loading from human waste found its way to Hood Canal, that seemed to offer an explanation.
But there was debate about scale. Even though hundreds of tons of nutrients washed into the canal, that remained a fraction of the nitrogen coming from natural sources. The chief question remained: Were human sources enough to push the system over the edge?
"The biggest source is the Pacific Ocean," said Mindy Roberts, who led the new review for Ecology. But in Lynch Cove, in particular, "some evidence is showing humans are contributing. Other evidence is saying no."
The two watchdog agencies — along with an exhaustive review by outside experts — concluded that human sources of nitrogen contributing to low-oxygen events in the mainstem of Hood Canal were "insignificant," while evidence linking humans to oxygen problems in the more troubled area near the canal's end in Lynch Cove "is not strong."
The overwhelming causes of fish kills, the agencies concluded, are the geography of the canal and ocean conditions.