9/26/16 – Reverse nutrient flow?

9/26/16 – When you think of nutrient flow, I hope you are thinking about the nutrients that flow downstream and collect in large bodies of water. But there is another kind of nutrient flow that might not be as obvious. This is the flow of nutrients from the oceans, upstream, out of the water and onto the land, and then into various plants and animals. How does this happen? The answer is salmon!

Salmon spend their lives in the oceans growing and storing nutrients in their bodies. Then, when salmon move up the streams to spawn the nutrients from the ocean are carried inside the salmon far up the rivers and streams, deep into the forests. Nitrogen is one important element that is brought into the terrestrial ecosystem by salmon. Many, many different things feed upon the salmon, from Orcas, to Brown and Black bears, Bald eagles, and even various species of insects and trees. So many different things not only eat salmon, but heavily depend on them for survival, that salmon are considered a ‘keystone’ species.

Bears catch salmon in Katmai National Forest. Image courtesy of Explore Live Bear Cam.
Bears catch salmon in Katmai National Forest 7/9/15. Image courtesy of Explore Live Bear Cam.

Bears are an important link in the flow of nutrients from the salmon into the terrestrial system, where it can be used by trees like Sitka Spruce, Douglas Fir, and Western Hemlock. Bears sometimes drag salmon out of the water and eat only part of the body, leaving some behind to directly enter the soils, or to be eaten by something else. Much of the nitrogen that comes from the salmon that bears eat, shall I say ‘flows or drops’ out of the bear and onto the ground to be incorporated into the soils and then into the plants. The other animals fertilize the plants in the same way, but bears move by far the greatest amount of nutrients. The result is healthy forests with large trees and a variety of plant types. These healthy forests, in turn, result in healthy streams, which are necessary to grow, you guessed it – salmon!

If you have been watching the Explore live bear cams from Katmai National Park you have been seeing this phenomenon in action. You can learn more about the bears you have been seeing on the live camera. Don’t forget to watch the live chat with Ranger Leslie on Monday September 26 at 11:00 Alaska time!

Bears fishing in Katmai National Forest 9/21/16. Image courtesy Explore Live Bear Cam.
Bears fishing in Katmai National Forest 9/21/16. Image courtesy Explore Live Bear Cam.

But all is not well with the salmon, and this spells trouble for the bears, and for many of us. Salmon numbers have dropped precipitously for decades. Humans have dramatically altered the landscape, overfished, and introduced foreign genes into the wild stocks of the Pacific Northwest. When a keystone species is in decline then all the things that depend on them are in trouble too. Because the salmon are a link between the oceans and the forests, management practices in both areas have implications on the other area. That is why is is important to manage salmon in ocean fisheries as well as stream pollution in the Pacific Northwest. If you want to learn more about protecting salmon and all the species that depend on them, check out the Wild Salmon Center.

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