Bug Flows: Community science in action
Experimental flows informed by light trapping
What you take away: A Colorado River reflection
A young woman reflects on her Partners in Science trip through Grand Canyon
Aquatic insects are important components of riverine foodwebs as they are prey for fish, birds, bats, lizards, and spiders. The closure of Glen Canyon Dam in 1963 fundamentally altered the hydrology, water temperature, and turbidity of the Colorado River through Grand Canyon. These changes, along with competition with invasive species and limited food availability have led to the decline and extirpation of native fish. Monitoring aquatic insects is critical for understanding population dynamics of fish and other predators in Grand Canyon.
Conducting research in Grand Canyon is logistically challenging.The river is deep, swift, cold, and access to most field sites requires multi-day rafting expeditions. To access these remote sites, we collaborate with river guides, private boaters, and educational groups to collect data on emergent aquatic insects, fish, bats, and water quality on their expeditions. Data from these efforts are yielding fundamentally new insights into the Colorado River ecosystem.
If you are interested in including science on your next river trip in Grand Canyon, please send an email with your trip dates to science_the_river@usgs.gov
Sampling Aquatic Insects with Light Traps
Aquatic insects are a key component of the aquatic and terrestrial food web in and around rivers. Understanding their abundance and distributions over time and space is important to understanding the health of an ecosystem. However, sampling aquatic insects on a large scale, over long periods of time, is impossible for typical research groups of only a few people. However, working cooperatively with people who are on the river every day (professional river guides and private boaters), our group has been able to collect samples throughout 250+ miles of Grand Canyon, throughout the year. The dataset, based on light traps set at the river’s edge every evening that collect adult aquatic insects, currently contains several thousand samples and several million insects. This community science effort allows us to ask and answer questions about the Colorado River in Grand Canyon that are truly unprecedented in scale, such as how hydropower releases from Glen Canyon Dam affect aquatic insect populations, how the phenology (seasonal timing) of aquatic insects varies by species and with distance downstream from the Dam, and how aquatic insect populations vary from year-to-year throughout the entire Grand Canyon.
Methods
Every night in camp, collectors set out a light trap at the river’s edge for one hour at dusk. Traps consist of a fluorescent black light placed on top of a plastic pan containing ethanol. At the end of the hour, the sample is poured into a bottle, and eventually brought back to the lab where its contents are counted and identified by USGS personnel.
Results
Our results demonstrate that the abundance and diversity of aquatic insects in the Colorado River is constrained by hydropower production at Glen Canyon Dam. Hydropower production at Glen Canyon Dam causes large hourly changes in river discharge, and these discharge waves create an artificial intertidal zone along river margins that is present >250 miles downstream where the Colorado River enters its next reservoir, Lake Mead. Our light trap data show that at places in the Grand Canyon where the Colorado River experiences daily low flows at dusk, aquatic insects are over 3 times more abundant compared to places where the daily high flows happen at dusk. Using a series of other experiments and modeling, we found that differential mortality of insect eggs laid along river margins is the underlying cause of these differences in adult insect abundance. These results inform the design of environmental flow experiments ('Bug Flows') that could mitigate mortality of aquatic insect eggs while still allowing for the production of renewable hydropower that society needs.
Recording Bat Acoustic Activity
Community scientists have recorded 19 different species of bats foraging along the Colorado River in Grand Canyon using ultrasonic acoustic detectors. We supply collectors with specialized microphones that connect with tablets, providing a live visual feed of bat foraging activity. By pairing acoustic data of bats with our light trap sampling, we have learned that aquatic insects, particularly aquatic flies in the family Chironomidae, are important prey for bats common to the river corridor.
Bug Flows: Improving Food Web Health on the Colorado River
Insect Drift
Aquatic Insects
Aquatic insects are important components of riverine foodwebs as they are prey for fish, birds, bats, lizards, and spiders. The closure of Glen Canyon Dam in 1963 fundamentally altered the hydrology, water temperature, and turbidity of the Colorado River through Grand Canyon. These changes, along with competition with invasive species and limited food availability have led to the decline and extirpation of native fish. Monitoring aquatic insects is critical for understanding population dynamics of fish and other predators in Grand Canyon.
Conducting research in Grand Canyon is logistically challenging.The river is deep, swift, cold, and access to most field sites requires multi-day rafting expeditions. To access these remote sites, we collaborate with river guides, private boaters, and educational groups to collect data on emergent aquatic insects, fish, bats, and water quality on their expeditions. Data from these efforts are yielding fundamentally new insights into the Colorado River ecosystem.
If you are interested in including science on your next river trip in Grand Canyon, please send an email with your trip dates to science_the_river@usgs.gov
Sampling Aquatic Insects with Light Traps
Aquatic insects are a key component of the aquatic and terrestrial food web in and around rivers. Understanding their abundance and distributions over time and space is important to understanding the health of an ecosystem. However, sampling aquatic insects on a large scale, over long periods of time, is impossible for typical research groups of only a few people. However, working cooperatively with people who are on the river every day (professional river guides and private boaters), our group has been able to collect samples throughout 250+ miles of Grand Canyon, throughout the year. The dataset, based on light traps set at the river’s edge every evening that collect adult aquatic insects, currently contains several thousand samples and several million insects. This community science effort allows us to ask and answer questions about the Colorado River in Grand Canyon that are truly unprecedented in scale, such as how hydropower releases from Glen Canyon Dam affect aquatic insect populations, how the phenology (seasonal timing) of aquatic insects varies by species and with distance downstream from the Dam, and how aquatic insect populations vary from year-to-year throughout the entire Grand Canyon.
Methods
Every night in camp, collectors set out a light trap at the river’s edge for one hour at dusk. Traps consist of a fluorescent black light placed on top of a plastic pan containing ethanol. At the end of the hour, the sample is poured into a bottle, and eventually brought back to the lab where its contents are counted and identified by USGS personnel.
Results
Our results demonstrate that the abundance and diversity of aquatic insects in the Colorado River is constrained by hydropower production at Glen Canyon Dam. Hydropower production at Glen Canyon Dam causes large hourly changes in river discharge, and these discharge waves create an artificial intertidal zone along river margins that is present >250 miles downstream where the Colorado River enters its next reservoir, Lake Mead. Our light trap data show that at places in the Grand Canyon where the Colorado River experiences daily low flows at dusk, aquatic insects are over 3 times more abundant compared to places where the daily high flows happen at dusk. Using a series of other experiments and modeling, we found that differential mortality of insect eggs laid along river margins is the underlying cause of these differences in adult insect abundance. These results inform the design of environmental flow experiments ('Bug Flows') that could mitigate mortality of aquatic insect eggs while still allowing for the production of renewable hydropower that society needs.
Recording Bat Acoustic Activity
Community scientists have recorded 19 different species of bats foraging along the Colorado River in Grand Canyon using ultrasonic acoustic detectors. We supply collectors with specialized microphones that connect with tablets, providing a live visual feed of bat foraging activity. By pairing acoustic data of bats with our light trap sampling, we have learned that aquatic insects, particularly aquatic flies in the family Chironomidae, are important prey for bats common to the river corridor.