Streamflows, algae and aquatic plants, and invertebrate animals drive water quality and fish disease dynamics in the Klamath River, but gaps exist in our understanding on how they are all linked. The dam removals presented an opportunity to collect unique data on how these processes are connected. The ecology team is researching relationships between water quality, fish disease risk, and the aquatic plants and animals (worms!) that influence them. Results are relevant to a variety of landscape-scale changes that impacts streamflows, temperatures, and sediment and nutrients loads, including future dam removals, wildfires, and flow management.
These components also directly link to concepts of river health that are being examined with the Community Experiences and Knowledge Co-Production components of the project.
Algae and Rooted Aquatic Plants
Algae and aquatic plants provide the basis for aquatic food webs, influence water quality, and control carbon cycling in rivers. Despite the importance of algae and plants to freshwater ecosystems, increased growth and accumulation of algae, cyanobacteria, and aquatic plants beyond historic levels is a growing problem in rivers. Excess growth of algae and aquatic plants in the Klamath River impedes tribal fishing practices, restricts river access, and causes extreme fluctuations in dissolved oxygen and pH.
We are documenting growth and accumulation of algal and aquatic plants before and after dam removal and investigating their seasonal growth to understand how environmental changes caused by dam removal affect algae and aquatic plants. These changes are summarized in the diagram below, which illustrates the hypotheses we had about changing streamflows and sediment on plants and algae.
Evaluating these hypotheses involves high-frequency sampling of the plants and algae over the growing season. The data are also being analyzed to examine how production by the plants and algae has responded to changes in sediment concentrations, nutrients, and peak flows. Production is a measure of how fast and how much the plants and algae grow in the river and it is important because the plants and algae can control several aspects of water quality in the river, including pH and dissolved oxygen. Those data will be used to develop a new food-web model that will be used to simulate a range of potential management actions (changing peak flows, sediment loads, etc.).
2024 Research Updates
In our year 2 of field surveys, we sampled two sites downstream of Iron Gate Dam over this summer 2024 during dam removal, with each survey taking place bi-weekly from June through August. At each site we measured ~80 different locations (quads) throughout the site each time we surveyed.
At our upriver site, Tree of Heaven Campground, plants were already well established at the beginning of the summer despite the muddy, turbid river. The lack of spring peak flows seemed to have helped them overwinter and suggesting that peak flows may be more important than abundant light availability at the start of summer.
At our downriver site, Big Bar, we observed little to no growth at the beginning of the summer. The tributaries between the two sites add a lot of water to the river, and peak flows in the lower river were elevated this year. This annecdotally reinforces the importance of peak flows.
At both sites, continuous high turbidity later in the summer seemed to result in algae decaying and dying off as water levels also dropped and the river contracted, as was observed by dried algae along the dried out banks.
Source: OSU Media
Salmon parasites
The myxozoan parasite Ceratonova shasta (C.shasta) causes mortality (up to 90% in some years) in outmigrating juvenile salmon. The parasite alternately infects annelid (worm) and salmon hosts in order to complete its life cycle. The annelid hosts release the (short-lived) parasite stage that infects the salmon so understanding the factors that drive the distribution and density of infected annelids is central to managing of disease risk in juvenile and adult salmon. This study informs our knowledge of annelid host ecology by describing diets of the suspension feeding annelids, and how reservoir removal and subsequent changes in the algae and aquatic plants in the river in turn affect annelid host density or distribution.
2024 Research Updates
Salmonid risk of C. shasta in 2024 was elevated downstream from Iron Gate dam during juvenile outmigration season, and annelid host densities (preliminary) in this reach were high in winter and spring but declined in summer and fall. Proposed mechanism to explain decline is 1) composition of suspended sediments and 2) deposition of fine sediments/burial.
- Preliminary models built describing relationships between water quality variables and annelid variables have been built using data collected 2021-2023.
- Characterization of annelid gut contents in annelids from infectious zone is ongoing, but preliminary data show there are differences in composition of gut contents in 2024 relative to pre-dam.
Dissolved Oxygen
Dissolved oxygen is necessary for the survival of fish and other wildlife in rivers. In the Klamath River, the amount of dissolved oxygen can be affected my several environmental factors, such as temperature, primary production, turbulence, and sediment pulses.
During sediment pulses, large quantities of sand, silt, clay, and organic matter (like dead plants or algae) can get pushed through the river by landslides, fires, heavy rain, or the removal of dams. These sediment pulses can block sunlight from reaching the riverbed, inhibiting photosynthesis and affecting the amount of oxygen being produced in the river. Additionally, sediment pulses contain organic matter, such as plant and algae particles. These particles attract microorganisms, such as bacteria, that decompose the organic matter. These microorganisms breathe in oxygen just like us, and can consume significant quantities of oxygen from the river.
When the dam is removed, the sediment currently trapped behind the dam will be flushed into the river, and will remain the river for up to one year. This part of the study aims to quantify the amount of dissolved oxygen consumed by the sediment pulse and model the recovery of dissolved oxygen as the sediment pulse makes its way out of the Klamath River.
2024 Research Updates
Between January and May 2024, we sampled three sites downstream of the former Iron Gate Dam to the confluence with the Shasta River. Field work involved collecting samples of water and sediment to bring back to the lab, making measurements of water quality parameters and velocity, and babysitting some sensors that we left in the river to continuously measure dissolved oxygen and temperature.
During that period, there were four occurrences during which dissolved oxygen dropped during reservoir drawdown. Two of these drops were to levels considered lethal for most fish species. Evidence suggests that these drops were caused by multiple mechanisms, including biological oxygen demand from the organic matter stored in the reservoir bed sediment, chemical oxygen demand from the reduced minerals in the sediment, and anoxic (no-oxygen) water present just above the sediment bed in the former reservoir. Data analysis is underway!
Meet the Ecology Team
Desiree Tullos, PhD, PE (OR)
Professor, Water Resources Engineering
Oregon State University
Julie Alexander, PhD
Assistant Professor (Senior Research)
Oregon State University, Department of Microbiology
Laurel Genzoli, PhD
Postdoctoral scholar
University of Nevada
Kristine Alford
PhD Student
Oregon State University
Issi Tang
MS Student
Oregon State University
