Kootenai River
The Kootenai River in southeastern British Columbia has been a subject of great interest to aquatic ecologists for several decades. The ecosystem of this body of water is in dire need of rehabilitation, as it has been degraded due to the loss and impoundment of wetlands, leading to major nutrient deficiencies and a collapse of the aquatic food web. To address this issue, researchers from the International Kootenai River Ecosystem Restoration Team (IKERT) collaborated to determine nutrient replacement would be a potential solution to restore the collapsed food web.
More about the Kootenai River
Along with Lake Koocanusa acting as a nutrient sink, the Libby Dam has interrupted the natural dynamics of the Kootenai River since it was built in the early 1970s. The Iimpoundment that forms behind the dam has caused the river to lose many of its natural characteristics, including large amounts of sediment and nutrients, negatively affecting species that depend on the habitat to survive.
The extremely low levels of nitrogen and phosphorous running downstream of the Libby Dam have led to ultra-oligotrophic conditions in the Kootenai River. The macroinvertebrate populations, as well as the chlorophyll levels, are well below average compared to other regional rivers of similar sizes. Macroinvertebrate biomass declines more with greater distance from the dam, as a result of deficiencies in nutrients and, in effect, a decrease in the habitat complexity and diversity.
About the study
The study, "Effects of nutrient replacement on benthic macroinvertebrates in an ultraoligotrophic reach of the Kootenai River," which was published in the December 2014 issue of the journal Freshwater Science, delved into the issue of nutrient deficiency in the river. The scientists developed a program to add nutrients to the Kootenai River downstream from Libby Dam, which they hypothesized would add moderate increases richness, abundance and biomass of macroinvertebrates with little change to the species assemblage structure. The target concentration post-addition is 5 milligrams per liter of phosphorous. Before this project, the phosphorus levels are barely detectable in the body of water
The researchers then measured the responses of benthic invertebrate communities to the experimental addition using a before-after control-impact (BACI sampling design. Benthic, macroinvertebrate samples were collected pre- and post-treatment from both fertilized and unfertilized reaches, with collections taking place July to early November between 2003 and 2010.
The findings
After the nutrition addition program was implemented, the findings revealed an improvement in benthic macroinvertebrate levels, including:
Mean modified total abundance increased 72 percent, excluding Oligochaeta and Chironomidae subtaxa
Mean total abundance increased 69 percent
Mean biomass increased 48 percent
Total invertebrate taxa richness increased nearly 80 percent
Specifically, the findings showed abundance of Ephemeroptera, which is the main insect order in the Kootenai River area of study, boosted 66 percent. Additionally, abundance of filter feeder showed an increase, which signified a rise in the amount of suspended organic matter as well as forms consumed by other benthic macroinvertebrates.
What does this mean for the Kootenai River ecosystem?
Benthic invertebrate taxonomy specialists have long known that these invertebrates play critical roles in rivers and streams. They regulate the flow of energy and nutrients, among other materials, along freshwater ecosystems, contributing to the foundation of food chains involving terrestrial invertebrate and fish as well as avian and mammalian assemblages. They not only consume trophic organisms at lower levels but also support production among higher trophic levels.
By acting as an intermediary, the organism also serves as a way for the invertebrate taxonomy field to characterize flowing, fresh water ecosystems and a tool for monitoring responses to large-scale changes in these lotic environments. That means researchers can use benthic macroinvertebrates to determine the environmental costs and benefits of certain measures aimed at restoring the ecosystem as a whole. This will mean not only a more productive and biologically varied ecosystem in the Kootenai River, but also the survival of fisheries and livelihood of populations that rely on fish caught from this body of water for sustenance.
EcoAnalysts and the Kootenai River Nutrient Replacement Program
The experts at EcoAnalysts conducted the annual field sampling as well as the lab analysis from this study. However, this is not the first time the bioassessment leader has worked to improve the health and biological diversity of the Kootenai River. The organization has been actively involved in the Kootenai River Nutrient Replacement Program in Montana and Idaho over the years, contributing services from bioassessment laboratories to raise nutrition levels in the river and restore it to its natural health and vitality.