The Seattle Times reports on a scientific study that debunks the long standing belief that septic systems caused major kills of fish and other marine life in Hood Canal on Washington’s Puget Sound. Researchers had claimed that nutrients from septic systems were killing sculpins, rockfish, perch, sea stars and many other creatures.
The paper reported that a new joint report by the U.S. EPA and the state Department of Ecology “determined the link between human activity and the hooked fjord's low-oxygen problems wasn't solid enough to warrant setting new strict pollution limits. 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’...The overwhelming causes of fish kills, the agencies concluded, are the geography of the canal and ocean conditions.
“Some believe that people are still a significant source of the problem, but that technology and monitoring capability aren't yet sensitive enough to prove it. Scott Brewer, executive director of the Hood Canal Coordinating Council, which represents local counties trying to figure out what they should do to keep the canal clean and safe, agreed. ‘To me it didn't negate the idea that there are human impacts there," he said. "I think there are.’
“But some colleagues, such as Michael Brett, a University of Washington environmental engineering professor who evaluated nitrogen runoff from vegetation and septic tanks into Hood Canal, said that while climate change or other human-caused impacts may play a role, the study should put to rest the link between housing development and fish kills.”
Fish kills in the canal occur because while parts of it are deep, the entrance is shallow, and water circulates poorly in and out and from surface to bottom. Plants and algae bloom die and decay, and rivers carry nutrients in; all of that depletes oxygen. Fish kills have happened as early as the 1920s and were extreme in several years of the last decade.
Read more at http://seattletimes.com/html/localnews/2019193768_hoodcanal19m.html.
