Biologist: stream habitat critical

Riparian zone along anadromous streams important to salmon

A local stream ecologist and biology professor contends the near shore habitat of anadromous streams is a critical component of the health of that water body which supports the insects, fish and salmon fry living there.

 

David Wartinbee, Kenai Peninsula College professor of biology, said riparian habitat -- trees, shrubs and other vegetation along a river -- provides nutrients and energy to drive the system, stabilize the area under the stream salmon need for spawning and has added benefits as in-stream habitat and as a filter. Those roles are interconnected and are needed to support the health of the river and fish, Wartinbee said.

Twenty-five rivers and streams on the Kenai Peninsula currently have rules in place to protect that habitat while still allowing for some property owner development. Protections go 50 feet up the bank from the ordinary high water mark.

The anadromous streams ordinance passed by the borough assembly in late June 2011 and now listed in borough code under KPB 21.18 added 2,317 stream miles to the 602 stream miles previously included in the district. However, the ordinance added 871 privately-owned parcels to the previously managed 2,797 privately-owned parcels. The other 1,035 parcels added by the ordinance are owned by federal, borough, municipal, Native or state entities.

Over the last several months as the Kenai Peninsula Borough administration and Donald E. Gilman River Center staff worked to enact the anadromous streams ordinance expansion, those current and future protections have come under criticism from property owners who feel they are onerous. Implementation for the east side of Cook Inlet was pushed back until 2013.

Questions have surfaced recently about why the near stream habitat of these streams -- and to the surprise of some -- and lakes needs protection.

Wartinbee, using the Kenai River as an example, said the river is productive in terms of fish directly because of the riparian vegetation living in the 50 foot set back area. If there is less riparian vegetation, there would be fewer bugs and insects and therefore less fish that feed on them, Wartinbee said.

"If I was czar of the world, we would have a 100-foot set back because that is so important and if people want to be good stewards along the riparian areas, by all means don't cut the trees down," he said. "Leave them there. One, it stabilizes your bank so it doesn't wash away, two it provides nutrients for our young salmon."

When examining a river system, Wartinbee said one should consider where the energy driving the system comes from. Some river systems are driven by energy -- sugars called glucose -- made from algae.

"Streams that have no riparian vegetation, their only source of energy is from the algae, light hitting the algae enabling them to photosynthesize," Wartinbee said.

Some slow-moving bodies of water or rivers use energy from rooted aquatics like lilies and reeds. But in a riparian habitat, the trees and shrubs around the stream producing leaves, twigs, bark and other organics that fall into the stream in turn become very important energy sources, Wartinbee said.

"The streams that provide the greatest number of fish and the greatest diversity are those streams that have lots of riparian vegetation," he said.

Fallen leaves and other organic matter are chopped up and used by a whole suite of insects and invertebrates in the stream that are also the food source for salmon fry.

"We fully recognize that the more time that our young salmon ... can spend in a stream that has lots of insects in it, and is shallow and well-protected, the bigger they get and the more likely they are to return," he said.

Wartinbee said salmon and fish carcasses are also highly important as insects, organisms, bacteria and fungi are "geared up" to process them.

"What's happening is those carcasses are there and they in turn deposit lots of slowly released nutrients: potassium, nitrogen and phosphorous -- the same stuff you put in your garden -- that in turn get picked up by the algae, the in-stream vegetation and, most importantly, the roots from the riparian vegetation," he said.

The riparian vegetation also provides protection for young salmon to escape from predators, additional habitat, filtering effects and bank stabilization.

However, another critical aspect of the riparian zone is its importance to the hyporheic zone, which extends below and to the sides of the river. The hyporheic area, which is full of gravel, is important for salmon spawning, Wartinbee said.

"If you have no hyporheic zone, that is these gravels in there, you'll have no salmon spawning," he said. "If it is plugged up with fine mineral deposits, you'll have no spawning. The salmon know there is water going down into those gravels and coming back up."

Roots of the riparian zone stabilize the gravels in the hyporheic so the water can move laterally.

"By stabilizing the bank and everything that's underneath there, you now have this river reaching laterally, in some cases hundreds of yards ... and in many cases, tens of feet in depth," he said.

Wartinbee said he was surprised to hear about lakes being included in the anadromous streams ordinance because lakes are "a different breed of cat."

"Some of the players are the same, but the fluxes in terms of what's moving in and out is quite different," he said. "I think it is kind of a stretch to extend the anadromous stream protection to lakes."

While Wartinbee said he considers protection for lakes important, as they are just as easily damaged, he said they should have their own specific rules, especially considering how some lakes are differ greatly from one another.

Wartinbee said it is important to remember that while small changes made to the riparian habitat might not be immediately noticeable or damaging, they can add up over time.

"If we only do a small amount, a few percentage points of removal, then it's a very small almost immeasurable amount," he said. "But when you multiply that times thousands and thousands of land owners each doing some small amount, there is no question there has been some impact."

When asked about how serious damage to riparian habitat might be, Wartinbee used habitat in Oregon and Washington and their rivers' respective decline in salmon habitat as an example.

"Those folks are crying about what they've destroyed," he said. "They raped and pillaged their streams and bulldozed down the vegetation and so forth and now they wish they had it back."

Wartinbee said he hopes the borough and residents will be "farsighted enough" to maintain the habitat in place.

"If you talk to people from Oregon and Washington, they'll tell you, 'Hey, save it while you can,'" he said. "I have heard that more times than I want to think about."

Brian Smith can be reached at brian.smith@peninsulaclarion.com.

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