A novel strategy to help stream communities recover
This project aimed to jump-start the ecological recovery of several historically degraded King County streams by seeding them with a diverse community of macroinvertebrates – or “stream bugs” - from healthy streams. Typically, healthy streams support a diverse stream bug community, including many types of sensitive mayfly, stonefly, and caddisfly larvae, as well as a suite of other insect larvae, snails, worms, crayfish and clams. The Benthic Index of Biotic Integrity, or B-IBI, is largely based on counts of the different types of sensitive taxa, and when conditions degrade and they disappear, B-IBI scores decline.
How did we seed bugs?
In the summer of 2018, we seeded – or translocated - a collection of macroinvertebrates from healthy streams to four streams where many sensitive species were no longer found. Despite restoration efforts or otherwise good habitat in the four basins, there were few sensitive species and their B-IBI scores remained low. We suspected one reason might have been that the streams were isolated with no nearby source of sensitive taxa. The lack of healthy macroinvertebrate communities in the urban basins surrounding these sites may have limited recovery of these streams, even when conditions were suitable. By reintroducing these sensitive native species, we hoped to accelerate recovery of the stream community.
Thanks to our enthusiastic team, the translocation went as planned. We moved approximately 46,000 macroinvertebrates from two healthy streams to each of the four “recipient” streams. The recipient streams include Taylor Creek in Seattle, Gold Creek near Woodinville, Miller Creek in the City of Normandy Park, and a tributary of Yarrow Creek in the City of Bellevue. Samples collected in the recipient streams prior to seeding confirmed there were few sensitive species present before the experiment, and B-IBI scores were typically poor or very poor. Samples collected from the healthy streams indicated that on average, the translocation added 15 new mayfly taxa, 9 new stonefly taxa and 13 new caddisfly taxa to each stream. While it was not expected that all of these new taxa would persist in the recipient streams, the persistence of even a few new taxa would suggest the recipient streams could support a more diverse and sensitive suite of taxa.
Did it work?
The primary result of the project is that seeding streams appears to have been partially successful. In all four recipient streams, at least one new or possibly new taxon was found in 2019, one year post-seeding. In two of the four streams, B-IBI scores increased in part because of those new taxa. We conclude the project was only partially successful because many taxa that were added were not found in post-seeding samples, and for those new taxa that were found, we do not yet know if they will thrive there for many generations.
Summary of results by stream, one year after seeding:
- Gold Creek: Three new or possibly new taxa were found, including a stonefly, caddisfly and a fly, but most surprising was the 37 point increase in B-IBI score a year after seeding.
- Taylor Creek: Three possibly new taxa were found, including a beetle, midge, and a caddisfly, and the B-IBI score increased 16 points a year after seeding.
- Yarrow Creek tributary: One new stonefly was found a year after seeding, but the B-IBI score did not improve.
- Miller Creek: Four new or possibly new taxa were found, including a mayfly, midge, crane fly and stonefly, but the B-IBI score did not improve.
The results suggest bug seeding is a plausible action, that when done carefully and in appropriate locations, can help restore diverse macroinvertebrate communities.
Don’t do this on your own
Although bug seeding may be appropriate in some cases, do not transplant invertebrates on your own. Moving any organisms from one stream to another requires permits and careful planning to ensure no pathogens or non-native species are added unintentionally.
Although we do not recommend seeding any bugs on your own, there are many things you can do to help restore water quality and improve stream habitats. Activities include installing rain gardens at your home, as well as encouraging local planners to implement effective stormwater controls. Reducing the delivery of contaminants and fine sediments, protecting riparian areas, and restoring natural stream flows are all key factors needed to protect and restore freshwater quality.
Funding for this project was from the US Environmental Protection Agency’s National Estuary Program and was administered by the Washington State Department of Ecology. For more information, please contact Kate Macneale at firstname.lastname@example.org.
- Final report – Bug Seeding: A Possible Jump-start to Stream Recovery, June 2020
- Quality Assurance Project Plan: Invertebrate Supplementation as Restoration Action in Select B-IBI Basins
- Poster presented at Symposium on Urbanization and Stream Ecology, in Austin, Texas, February 2020
- Figure 1: Map of donor and recipient sites and recent B-IBI scores from those and other sites in King County
- Figure 2: Colonization baskets, used to collect bugs in Webster
- Figure 3: Collecting colonization baskets on moving day
- Figure 4: Releasing bugs in Miller Creek in 2018
- Figure 5: A stonefly nymph that survived a year in Gold Creek
This project has been funded wholly or in part by the United States Environmental Protection Agency under assistance agreement 01J18101 to King County. The contents of this document do not necessarily reflect the views and policies of the Environmental Protection Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.