Jared Meek and Faculty Mentor: C. Riley Nelson, Brigham Young University, Biology Department
The Provo River in central Utah flows from its headwaters in the Uinta Mountains, down the heavily agricultural Heber Valley, through the urban center of Provo and Orem, and out into Utah Lake. Beginning in the 1950s, the Provo River underwent significant alterations as part of a large-scale water reclamation project throughout central Utah1, including the channelization and straightening of its middle section. In addition to these alterations, the river had two dams constructed along its course: the Deer Creek Dam (1941) and the Jordanelle Dam (1993). To remedy the ecological impairment that these manipulations caused, the Utah Reclamation Mitigation and Conservation Commission (URMCC) was tasked with restructuring a stretch of the Provo River to restore fish and aquatic insect habitat and diversity2.
The Provo River Restoration Project was conducted between 1999-2008 on the middle reach of the river. To understand the aquatic insect diversity in the pre-restored river, benthic macroinvertebrate samples were collected from multiple sites by Shiozawa et al.3 Using the same methods and sampling sites reported by Shiozawa et al., we collected macroinvertebrate samples to evaluate the long-term result of this restoration project through a comparison of macroinvertebrate diversity. Considering the abundance of data demonstrating that currently accepted methods of river restoration are not as effective as previously thought4, we predicted that the current aquatic macroinvertebrate diversity in the Middle Provo River would not be greater than the recorded pre-restored diversity.
Materials & Methods
To retain comparative integrity between the pre-restored and contemporary samples, Shiozawa et al.’s benthic sampling methods were followed exactly. Macroinvertebrate samples were collected at four of Shiozawa et al.’s original sampling sites between February 25 – March 31, 2017. At each sampling site, equally spaced transects were marked at 10 meter intervals along the riverbank, and samples were collected from the stream benthos at 2 meter intervals along each transect. Modified nets (253-micron mesh on 17.5 cm metal frame) were used to gather a total of 50 kick-net macroinvertebrate samples at each site (200 total samples over the four sites). These transect intervals enabled sampling of diverse habitats along at least 70m of river length.
The contents of each net were carefully washed into a Whirl-Pak®, preserved in 70% ethyl alcohol. The preserved samples were transported to a lab on the Brigham Young University campus where they were stored in a refrigerator for later identification and counting.
Macroinvertebrates were identified down to the Family or Genus level using An Introduction to the Aquatic Insects of North America5. After all samples from a site were identified, the total number of species per site was found, and the number of species among all sites was determined.
For analysis, total species richness was compared between three sampling years: 1999, 2002, and 2017 (Figure 1). The highest species richness among all sites (44 species) was found in the pre-restored Site 4 from 1999, and the lowest species richness (13 different species) was observed in post-restored Sites 4 and 7 from 2017. In total, 118 different macroinvertebrate species were
identified by Shiozawa et al. identified from 1999-2002 sampling efforts, and 28 different species were identified in the 2017 sampling efforts (Figure 4), demonstrating a clear decrease in aquatic macroinvertebrate diversity following restoration efforts.
While the effects of many restoration projects have been assessed throughout North and South America, this was the first comparative analysis conducted in Utah4. In combination with the findings that increased habitat heterogeneity has not resulted in increased macroinvertebrate diversity4, our results question whether increasing habitat heterogeneity should be the focus of future restoration projects. By returning to Shiozawa et al.’s sampling sites fifteen years after his final sampling, we have provided comparative evidence to answer this important question, adding to our understanding of river restoration both in Utah and throughout the world. We concluded that the Provo River Restoration Project, while an important step towards ecological restoration in the Middle Provo River, has not fully succeeded in returning the river to its pre-channeled conditions, especially in terms of macroinvertebrates. While some of the project’s goals were fulfilled, such as increased diversity of vegetation and habitat, this increase in habitat heterogeneity has not bolstered the diversity of macroinvertebrate species.
These results are worrisome considering the amount of time and resources invested into the Provo River Restoration Project2. Recent research has concluded that biodiversity strengthens ecosystem processes and stability, which in turn provides more ecosystem services6. Thus, the observable decrease in macroinvertebrate diversity in the Middle Provo River may be indicative of declining ecosystem health.
The Provo River Restoration Project’s efforts to restore habitat heterogeneity through meanders, side channels, and riparian habitat may have made the ecosystem appear healthier, but the lack of species richness shows that restoring habitat heterogeneity is not enough to revitalize a river harmed by dam obstruction and pollution.
We recommend that the restructured sites along the Provo River Restoration Project be continually monitored. Such monitoring will provide a clearer understanding of what is happening to this system, and has the potential of informing water managers and restoration ecologists of practices that maintain species diversity. If current restoration methods are not alone successful in restoring macroinvertebrate diversity, we need to identify other causes of diversity loss, such as inconsistent stream flow, barriers to migration7, and multiple sources of pollution. By re-evaluating current restoration methods, we can eventually achieve the desired results of biodiversity increase and sustainability.
1. Ashley J. & Jones R. L. (2002) The Central Utah Project. J. Land Resources & Envtl. L., 22, 273.
2. Utah Reclamation Mitigation and Conservation Commission. (1997) Provo River Restoration Project: Final Environmental Impact Statement. http://www.mitigationcommission.gov/prrp/pdf/prrp_eis.pdf
3. Shiozawa D.K., Weibell B.J. & McLaughlin E. (2002) The investigation of the macrobenthos of the Provo River between Jordanelle and Deer Creek Reservoirs. Part I: A Report to the Utah Reclamation Mitigation and Conservation Commission.
4. Palmer M.A., Menninger H.L. & Bernhardt E. (2010) River restoration, habitat heterogeneity, and biodiversity: a failure of theory or practice? Freshwater Biology 55, 1: 205-222.
5. Merritt R. W., Cummins K. W. & Berg M. B. (2008) An introduction to the aquatic insects of North America. Kendall Hunt.
6. Mori A. S., Lertzman K. P. & Gustafsson L. (2017) Biodiversity and ecosystem services in forest ecosystems: a research agenda for applied forest ecology. Journal of Applied Ecology, 54(1), 12-27.
7. Stanford J. A., Ward J. V., Liss W. J., Frissell C. A., Williams R. N., Lichatowich J. A. & Coutant C. C. (1996) A general protocol for restoration of regulated rivers. River Research and Applications, 12(4‐5), 391-413.