Watery Webs Of Life -- An Icy Stream Bubbles With Vitality And Challenges To Our Vision
IMAGINE A PLANET of bone-chilling cold.
A place with a howling wind so fierce that inhabitants have to cling to stones or risk being swept away.
A world shaped like a ribbon that expands and contracts, warms and cools, and loses or gains oxygen as the seasons turn.
Imagine, in other words, a clear, cold stream.
Pools like champagne, a bottom that looks lacquered and a purity that seems sterile.
Look again. Our Northwest creeks and rivers are long, sinewy ropes of life. When University of Washington graduate students flipped over a couple of rocks at Carnation's Griffin Creek this winter and netted what was clinging below, a thousand swimming insects filled their pan. The inhabitants ranged from an adult stonefly the size of a Chinese noodle to baby mayflies no bigger than a comma.
A river that looks empty to us hosts forests of algae, empires of bacteria, legions of insects and an underground stratum of crayfish, clams, worms and snails. Fish called sculpin skim the bottom, trout and salmon hide in the shadows, and frogs and salamanders emerge on the banks in spring. Tiny birds called dippers plunk themselves underwater on the coldest days, feeding on a cornucopia of bugs that we can barely see.
These biological ribbons are relatively rare: Only one millionth of the world's water is in streams and rivers. (Ninety-nine percent of Earth's water is ocean and most of the rest Antarctic ice.) Despite their rarity, rivers are environmentally
vital - the threads that stitch ecosystems together.
They're also coveted by humans. Worldwide, the amount of river water used for agriculture, drinking and industry has soared four times since 1950.
We're just learning how important the last undisturbed creeks are.
Even in its natural state a stream is a chaotic place, always changing depth, temperature, course and shape as it swells with rain and snow melt. It is fed by falling vegetation and dying animals (a local trout was found with 50 ants in its belly, swallowed from a regiment falling off a log) and dammed with logs and branches. Gravel and sediment are flushed in and out.
Life has evolved to thrive in this uncertainty. Animals have developed ingenious strategies to stay anchored in the current and hatch in stages that avoid flood and drought. A comprehensive study of Breitenbach Creek in central Germany identified about 1,100 separate insect and worm species in just a few kilometers. That doesn't count algae, fungi, bacteria, plankton, mollusks and fish.
We in the Northwest, however, are pushing this diversity to its limits. After a hundred years of "improving" streams by dredging, riprapping, channeling, clearing and cleaning, we've increased the volume of winter floods, prolonged the period of summer drought, and turned once-meandering waterways of alternating pools and rapids into sediment-choked chutes that run like freeways to the sea.
"The major change we've made is to homogenize streams into a continuous riffle," explained Tom Sibley, a professor at the University of Washington's Center for Streamside Studies. He pointed to Griffin Creek as an example. "We don't know what normal is anymore."
A graduate student, Jamie Glasgow, is studying the two forks of the Tolt River - one of them dammed to supply Seattle with drinking water - and their variations in flow.
"Life evolved to some swings," Glasgow said. "The question is whether we're increasing the swings." The volume of the Tolt's flow can jump 100 times now in a winter storm. What such a cataclysm does to the creatures within is barely understood.
Glasgow has found that trout in the undammed fork grow faster and bigger than those below the dam, presumably because the insect life - and thus food - is richer.
The question is not academic. Some of the hundreds of millions of dollars about to be spent to restore endangered salmon will go toward putting streams back toward what they once were. How to do that is hotly debated.
The good news is that if we simply leave a strip of undisturbed land on either bank, forest and stream will combine to slowly put things back. The bad news is that we don't really know how much land. One Tulalip Indian study showed clear benefits from buffers as wide as 90 feet, but uncertain gains after that. Seattle is proposing 600-foot buffers on its watershed streams.
Attempts to set a standard in Olympia have run into a buzzsaw of environmental and economic doubt. With Western Washington veined with creeks, the stakes for timber companies, housing developers and road builders could run into billions of dollars.
WE MISMANAGE STREAMS because they seem so alien. One of the first surprising things is that their critters like that shocking cold: It helps them rest and breathe.
Water molecules include atoms of oxygen, but it is so tightly bonded that animals can't breathe it. Instead they depend on oxygen from the air that diffuses into water through the turbulence of waves and rapids, or oxygen produced by water plants. As a result, oxygen is about 30 times less available in water than air.
The diving beetle gets around this by actually carrying an air bubble underwater with it, surfacing when its natural scuba tank gives out. Other stream inhabitants aren't so ingenious; they need oxygen dissolved in the water.
As water warms, it loses its ability to hold oxygen. Meanwhile, the metabolism of its cold-blooded fish, insects, mollusks and worms speeds up. Timber clear-cutting that robs a stream of shade can raise its temperature an average of 6 to 7 degrees Celsius. Each degree warmer accelerates a fish's respiration rate 10 percent.
Warm a creek, and to a panting fish it's the equivalent to being locked in a trunk or stuck on an accelerating treadmill.
Streams also like to take their time, gobbling, restoring and flooding land as they go, making side channels and swamps. From the air they look rubbery and indecisive, and we humans think the way to fix one is to straighten it out. What a meandering stream is doing, however, is losing its own excess energy and restoring its structure by going the long way.
When Germans decided to hurry flood waters downstream by straightening the Rhine in 1817, for example, the suddenly impatient river cut its channel 20 feet deeper, drying up orchards and wells. Straightened streams gather fewer nutrients from the land, have fewer pools and sloughs, and have less-hospitable bottoms.
Thirty years ago, Washington's land managers ordered logging companies to remove tree trunks and wood debris from creeks, believing it choked off habitat for fish. Now we pay loggers to put trees in because they slow a river's flow, create pools and aerating ripples, and support a skin of bacteria, fungi and plankton that are the base of the stream's food chain and oxygen supply.
IT ALL STARTS with slime, you see. Ever tried to wade a swift stream? The rocks are slicker than a greased cookie sheet, and the reason is they support a "biofilm" of the same stuff that grows on wet logs. This is the river's garden, the microscopic plants and animals that larger insects and worms eat before becoming food themselves.
Bacteria are so small that they are protected from turbulence by the relatively thick sludge of surrounding water molecules: To them, swimming is like corkscrewing through honey or tapioca pudding. At their scale, there can be millions of bacteria in a thimble-full of water.
Single-celled protozoa, microscopic creatures more complex than bacteria, also exist in countless numbers. One study showed a stream bed the size of a moderate room could grow a pound of protozoa a year.
Greenish-brown algal scum is more visible and serves the same function as a forest: converting sunlight, water and carbon dioxide into sugar and oxygen through photosynthesis.
Even big stream plants, vital in their own right, are covered by this productive slime. Stroke the stem of a lily pad and you bulldoze a microscopic garden.
This tiny life has evolved ingenious strategies. Diatoms, which are single-celled algal plants, encase themselves in crystal greenhouses. Made of silica, the same material found in glass, the tiny boxes protect the microscopic plant while allowing sunlight and selected molecules to come inside.
More food comes into the stream from fallen leaves, which are rapidly colonized by bacteria and fungi. An alder leaf can lose a quarter of its weight its first 24 hours in the water just from leaching of its nutrients, and the rest is devoured within weeks.
Dead animals contribute: The thick brush and big trees next to some streams were fertilized by the bodies of spawned-out salmon.
The water is also full of "dissolved organic matter" - molecules of plants and animals that have been completely broken down, like composted soil, and washed into the river.
In sum, a stream may look and taste clean but you're really drinking thin organic soup in a dilute solution of calcium bicarbonate, a kind of salt. If it flows by farms or fertilized lawns you can count on a good dose of nitrogen as well. One study in Ireland showed a third of the nation's fertilizer is washed into its streams before feeding any plants.
GRIFFIN CREEK, which flows through a Weyerhaeuser tree farm, was originally logged to its banks early in this century. At the second harvest in the 1980s the company left alone a strip of young alder and cedar that had grown up on the banks. As a result the creek is healthier than many foothill streams, supporting coho salmon that swim to it from the Snoqualmie River.
The creek is being studied by UW scientists, with the support of the company, to determine how to improve it even more. Upstream beaver dams that trap and pond flood waters have been left undisturbed. Whole logs and bundles of small poles - because big tree trunks are increasingly rare - have been put in the stream to see if they help create pools, eddies and small falls. The latter help push oxygen into the water.
The complexity of Griffin Creek begins to become apparent when scientists stretch a fine mesh net in the current and let it strain water. In less than an hour it yields a fistful of "dirt" - needles, pieces of leaves, floating insects and even a stray crayfish, possibly kicked off the bottom by a human foot.
The water is full of insects. Species such as mayflies, caddis flies and stoneflies spend most of their life underwater, breathing through gills, before emerging into the air as adults to breed and die. The dance of insects observed above the water in summer gives some idea of the density of juveniles growing in the water in winter.
Their life cycle keeps stream biology in equilibrium. Adults tend to fly upstream to deposit their eggs, helping repopulate stream areas from which insects have drifted downstream. Their wing color changes after egg-laying, and Glasgow has discovered that trout prefer the color of bugs that have already laid their eggs - an instinct that helps ensure the fish a future food supply.
We must also remember a stream is bigger than it looks. The water can extend below the bed we see for several feet, creating an underground river called the hyporheal zone. Insects, worms, crayfish and fresh-water mollusks inhabit this corridor.
The water also extends sideways. When you walk on a river bank, part of the stream may be flowing beneath your feet. So wide is this zone that aquatic insects have been found a quarter mile from Montana's Flathead River. They have migrated to the edges of the underground river before popping to the surface.
Insects that live in the current have evolved a variety of strategies to survive. Some species of waterbugs skate on top of the water, using the surface tension like a film of ice to keep from falling in. Down at the bottom of a stream, the current greatly slackens a few millimeters from the rocks because of friction: Insects crawl in this calm zone. Some mayflies have a streamlined shape that lets the current slip by them, and a sucker on their belly to hold on to the rocks.
Caddis flies - there are 1,359 known species of this aquatic insect in North America alone - anchor themselves with silk. Like the fibers produced by silkworms or spiders, this silk is stronger than steel for its width and weight, and is used to build a house to protect its occupant. Sand, tiny rocks, conifer needles, bits of wood and scraps of leaves may all be wound together with the silk to make a kind of cocoon. Looking like bits of sticky twig, these can often be found stuck to river rocks.
Many of these insects graze like contented cows. There are scrapers that mow the rocks, collectors that filter out whatever is flowing by, shredders, piercers, predators and so on.
Fish are usually the sole occupants of the water column itself, and to other stream inhabitants they are like vast, predatory blimps floating overhead to feed on the bottom or snatch at insects on the surface or in the air. Many fish are homebodies. While studies have shown some trout migrate a good distance up and downstream, brown trout and arctic grayling tend to stick to the same 50 or 100 feet of stream.
Salmon, in contrast, migrate to and from the sea. Some species like coho spend the first year or more of their life in a stream, and others, like chinook, leave quickly. When they spawn and die, their carcasses feed not only big animals like bear and eagle but the tiniest ones as well, down to bacteria.
A dam or dike or culvert that cuts off this migration starves a stream of nutrients.
LEARNING HOW NORTHWEST streams work takes patience and gumption. The water is freezing to scientists, the brush and insects miserable, and the climate dark and rainy half the year. Much of the biological activity, such as when trout feed, goes on at night.
Yet a healthy stream becomes a core refuge and corridor of biological diversity. Restoring it is one of the most dramatic environmental improvements possible.
Accordingly, graduate student Jennifer O'Neal periodically dons a dry suit and goes snorkeling at dusk to check on the life of frigid Griffin Creek. Why?
"The beauty, the camouflage and the life histories of these animals," she explained. "I'm fascinated."
So she dives into part of our Northwest most of us hardly suspect is there.
William Dietrich, author and former Seattle Times reporter, writes Our Northwest for Pacific Northwest magazine. Tom Reese is a Times staff photographer. Mark Nowlin is a Times news artist.
Published Correction Date: 04/25/99 - A Tulalip Tribes Study Of The Effects Of Leaving Trees Standing Beside Streams During Logging Concluded That Buffers At Least 200 Feet Wide Helped Protect Water Quality And Fish Habitat. This In Pacific Northwest Magazine Mischaracterized Findings Of The Study.
Copyright (c) 1999 Seattle Times Company, All Rights Reserved.