Nitrate levels have been on the rise in Puget Sound since 2000. What exactly, might you ask, are nitrates? And furthermore, why should you care?
Nitrates are naturally occurring chemical compounds left over after the break down of animal and human waste.
So, how are nitrates getting into Puget Sound? Sure, some of it comes from the rich coastal upwellings of nutrients that make their way in to these protected waters. But scientists think it’s no accident that the rise in nitrate levels in the past dozen years corresponds with population growth around Puget Sound.
The uptick in nitrate levels has mainly come via the runoff from fertilized or agriculturally used landscapes. Putting fertilizers rich in ammonia or using manure on your property is a surefire way to ensure that the next time it rains you’re contributing to the rising nitrate levels in Puget Sound. Another way: let your septic tank get out of date and start leaking.
Scientists don’t know how much of the nitrate boom comes from septic tanks vs. livestock vs. surface runoff. But they do know this: algae love nitrates.
And from what Christopher Krembs, an oceanographer with the Washington Department of Ecology, is seeing from the air, things are looking good right now in the world of algae.
“If you have more nutrients you will have more blooms, longer lasting blooms, larger blooms,” Krembs explains.
On a recent flight over Puget Sound (see video above), Krembs says, he saw more blooms than he’s ever seen in the two and a half years he’s been doing these water quality monitoring flights for Ecology.
credit: Department of Ecology Marine Monitoring Unit
“Definitely this is worth noting,” he says. “It’s normally always occurring that we have phytoplankton blooms in the spring time and sometimes in the fall but we are interested in how often they occur, how long they persist and what magnitude they have.”
Below us the blooms of algae tint the water different shades of light blue, green and even rust. Their expanding swathes of color are accented by white frothy lines, marking where different currents and fronts intermingle in Puget Sound.
The recent stretch of warm weather combined with lots of sunshine, low winds and LOTS of spring run-off from the rivers and streams that feed into the Sound have made for the perfect growing conditions for algae.
Krembs says these algae probably aren’t toxic (though ground crews will go out and test to make sure). They’re most likely native species of algae and diatoms that just happen to be going gang busters right now.
But while these blooms may not be toxic, they are contributing to a big problem in Puget Sound: Acidification.
Here’s how: when these mats of algae die and sink to the bottom they’ll consume oxygen and release carbon dioxide (CO2) in the decomposition process. That CO2 reacts with sea water forming new compounds like carbonic acid and releasing hydrogen ions that lower the pH of the water making it hostile to some forms of life, such as larval shellfish.
So, that big global ocean acidification problem not only has very local effects – it could also have a local source: you and me.
Scientists are still trying to figure out just how much of the nitrates in Puget Sound are naturally occurring and how much are from human land use like fertilized lawns, livestock and leaky septic tanks, but no matter where the nitrates are coming from they’re making life easy for algae and those algae are contributing to the acidification of the water in Puget Sound.
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