Casting a Wide Net for Science

A puzzle with a lot of pieces” is how Doug Markle, an Oregon State University fisheries biologist, describes Upper Klamath Lake and its two endangered species of fish. OSU researchers—from engineers to social scientists—are slogging through wetlands, modeling lake currents, and even visiting housing developments to fit the pieces together. What they learn will help people manage the land and water better.

Markle has been monitoring Lost River and shortnose sucker populations in Upper Klamath Lake for 11 years, but only recently have people appreciated the complexity of the system. “At first, everybody focused on relationships between lake levels and sucker populations, but it’s not that simple,” said Markle. “You have to look at the whole system, and that takes a lot of people and a lot of collaboration.”

Adult sucker die-offs, such as those in 1995, 1996, and 1997, are one piece of the puzzle. Tammy Wood, a U.S. Geological Survey (USGS) researcher, has found that wind-driven currents

move water around the lake in a circle. Markle suspects that when the circular movement is strong, stale water keeps recirculating, while fresh water entering from springs and the Williamson River is carried downstream into the Klamath River. The resulting changes in water quality may partly explain fish die-offs.

The system doesn’t stop at the water’s edge. “We’re finding a correlation between larval sucker populations and climate data,” said Markle. He has his eye on the Pacific Decadal Oscillation, an alternating, roughly decade-long pattern of warmer and cooler ocean temperatures in the northern Pacific Ocean. With data for one climate cycle so far, the results are tantalizing. If the oscillation explains low larval populations, Markle expects the numbers to rebound within a couple of years.

Dave Simon, an OSU fisheries researcher, heads toward a breach in a dike that inadvertently returned several thousand acres of farmland to wetlands. Photo: Lynn Ketchum

Being a larval sucker is a risky business. Most are born in the Sprague River and float down the Williamson to Upper Klamath Lake. During their first few weeks of life, the tiny larvae are easy pickings for predators; more than 90 percent probably don’t make it through their first month in the lake.

One threat to larvae may be fathead minnows, a non-native fish. Markle has found that when fathead minnows are abundant in the lake, suckers are not. “There are a couple of possible reasons,” he said. “Maybe fathead minnows and suckers react differently to some lake condition, and their numbers move in opposite directions. Or, fathead minnows might have a negative effect on suckers.” When Markle’s field data are combined with laboratory experiments by Larry Dunsmoor of the Klamath Tribes, evidence points to the latter.

Larvae also can be swept out of the lake on the downstream current, ending up in Lake Ewauna or the Klamath River. Research by one of Markle’s graduate students, Sue Reithel, has found that more than 50 percent of larvae leave the lake in a three- to four-week period. “Once they’re out of the lake, they probably don’t live long because of low summer oxygen levels in Lake Ewauna and the river,” said Markle.

OSU researchers are following the migration patterns of endangered Lost River suckers, such as this five-month-old juvenile. Photo: Lynn Ketchum

Trying to understand what keeps larval suckers in the lake has led Markle to the delta where the Williamson River empties into Upper Klamath Lake. Historically marshy, the delta was diked and drained decades ago. Now, in a cloud of dust and bulldozers, The Nature Conservancy (TNC) is returning 5,000 acres to wetlands. Eventually, 27 miles of levee will be removed, and the river will reflood the delta.

The resulting marshes should be prime larval sucker habitat. Working with TNC, USGS, and OSU colleagues Sue Reithel and Mark Terwilliger, Markle has found that larvae can get hung up in the marshes for about a week, protecting them from predators and swift passage out of the lake. “Stalling them for a week can make a real difference and keep more larvae in the system,” he said. “This research has enabled us to quantify the payoff from marsh restoration.”

Other questions remain unanswered, however. For instance, naturally high levels of phosphorus and years of fertilizer use have loaded the soil in the Williamson delta with phosphorus, said Desiree Tullos, an OSU bioengineer. What happens to that phosphorus after flooding could affect water quality in Upper Klamath Lake, where phosphorus is one culprit in deadly algae blooms. During flooding, soil oxygen is replaced by water, leaving soil microbes desperate for air, said Tullos. “They’ll chew up molecules containing phosphorus and oxygen to pull off the oxygen, freeing phosphorus to enter the water,” she said.

An algal bloom along the shore of Upper Klamath Lake poses a threat to endangered fish when the bloom dies and dissolved oxygen levels plummet. Photo: Lynn Ketchum

Each year, up to 25 tons of phosphorus enter the lake by pumping the delta’s fields dry in winter and flooding them during summer. Returning 5,000 acres of natural hydrology to the delta should reduce phosphorus inputs into the lake. The exact biogeochemistry of phosphorus releases under TNC management is unclear, however. “We expect to see a substantial spike in phosphorus [in the water] after flooding,” said Tullos. What isn’t clear is the timing and magnitude of that spike. It may depend on the time of year when the flooding occurs, so Tullos will be looking for seasonal patterns as she samples soil and water before and after the first major phase of flooding. What she learns will help TNC and other agencies reduce the likelihood of excess external phosphorus entering the lake.

Tullos is also part of a team of OSU researchers studying a very different piece of the puzzle—one that relates to the effects of population growth and changes in land use. “In many ways, what’s happening in Klamath Falls is mimicking what has happened in Bend,” said Tullos. “A lot of people are moving into a water-limited area, placing new demands on the land and water.”

“There’s been a recent boom in amenity migration from California and other urban areas,” said Hannah Gosnell, a geographer in the OSU Department of Geosciences. These newcomers are mostly retirees and “equity refugees”—people looking for a rural lifestyle, great views, good weather, and a lower cost of living—and they are changing the face of land use in the Klamath Basin. “We’re starting to see a shift from traditional irrigated agriculture to hobby farming and ranching,” said Gosnell.

What does this have to do with water and fish? A lot, according to Gosnell and Tullos. Changing land use patterns can affect both water quantity and quality. Understanding the rate of those changes, their patterns, and their potential implications will help land use planners and water resource managers better prepare for change.

It seems nothing is simple in the Klamath Basin. In Markle’s words, “When you finally put something together, it’s another little piece of the puzzle.”