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Dr. Alison Purcell O’Dowd

Associate Professor, Environmental Science Program Coordinator
Graduate Faculty

My teaching and research interests include environmental science, ecological restoration and aquatic ecology. I teach courses from the freshman-level through graduate students and work hard to get to know my students and help them reach their academic and career goals. My research primarily involves the use of benthic macroinvertebrates and fish to explore topics related to stream and wetland restoration, invasive species, wildfire, and step-pool sequences in steep, mountain streams.

I am thrilled to teach and conduct research in the fascinating and diverse ecological environment of the California North Coast. Environmental issues are definitely at the forefront of people’s minds in this area and students are passionate about improving ecosystems and repairing nature.

Contact Information
  • Natural Resources (NR) Building, Rm. 213
  • (707) 826-3438
  • .(JavaScript must be enabled to view this email address)
Specialty Area

Ecological Restoration, Aquatic Ecology


Ph.D. University of California, Berkeley (Environmental Science, Policy, and Management/Aquatic Ecology)
B.S. University of Oregon, Eugene (Environmental Science)

Courses Taught

I teach courses in environmental science and ecological restoration. These courses investigate ways to understand and address anthropogenic impacts and disturbances on ecosystems. I try to promote a learning atmosphere that allows students to interact with the natural environment and learn structural and functional processes first-hand. Therefore, I try to get my students outside and interacting with the environment as often as possible so they can fully experience the topic.

ENVS 111 – Environmental Science Freshman Seminar
ENVS 110 – Introduction to Environmental Science
ENVS 230 – Environmental Problem Solving
ENVS 350 – Principles in Ecological Restoration
ENVS 410 – Environmental Science Senior Capstone
ENVS 450 – Applied Ecological Restoration


My research interests are within the areas of aquatic ecology and ecological restoration. Specifically I study stream and wetland restoration, the ecology and eradication of invasive species, the impacts of wildfire on stream communities, and the biological significance of step-pool sequences in mountain streams. My research methods focus on using benthic macroinvertebrates as indicators of water quality in urban and natural freshwater ecosystems.  I conduct much of my research through Humboldt State University’s River Institute

More specifically my research explores how biological stream communities respond to disturbance within a watershed. My bioassessment research uses benthic macroinvertebrates as indicators of water quality to develop indices for the management of water bodies. One of my research projects examined ways to analyze long-term bioassessment data for the Lake Tahoe Basin. Another project compared urban gradients and aquatic biological indicators of urbanization in three climatic regions of the United States: San Jose, CA (west coast); Baltimore, MD (Mid-Atlantic); and Cleveland, OH (Midwest). The biological indicators of urbanization developed for these three regions were intended to help water agencies prioritize restoration and conservation efforts in urban watersheds. My research has also involved several post- project assessments of urban stream restoration projects in the San Francisco Bay Area in order to evaluate their success. These assessments included biological, habitat, and sociological assessments of several urban stream restoration projects to determine the condition of each site over time.

I am interested in the ecological significance of mountain step-pool streams. I am collaborating with a professor at the University of Colorado, Denver to compare biological communities in step-pool streams of northern California (Smith River) and Colorado.  We are also examining the bio-physical impacts of wildfire on high-gradient mountain streams.

Some of my research at Humboldt State University involves wetland ecosystems. My graduate students are exploring research questions related to an invasive non-native plant species (Spartina densiflora) in the salt marshes of Humboldt Bay.


Kinoshita, A.M., A. Chin, G.L. Simon, C. Briles, T.S. Hogue, A.P. O’Dowd, A.K. Gerlak, and A.U. Albornoz.  2016. Wildfire, Water, and Society: Toward Integrative Research in the “Anthropocene.” Anthropocene. 16:16-27.

O’Dowd, A. P. and A. Chin. 2016. Do bio-physical attributes of steps and pools differ in high-gradient mountain streams? Hydrobiologia. DOI: 10.1007/s10750-016-2735-5

O’Dowd, A.P., W. Trush, D. Colvin, R. Lavery, D. Ichien, and O. Abi-Chahine. 2014. Annual hydrograph assessment for steelhead migration in the Santa Ynez River. Report for the National Marine Fisheries Service, National Oceanic and Atmospheric Administration.

Chin A., O’Dowd A.P., and Gregory K.J. 2013. Urbanization and River Channels. In: John F. Shroder (ed.) Treatise on Geomorphology, Volume 9, pp. 809-827. San Diego: Academic Press.

Resh, V.H., L. Beche, J. Lawrence, R. Mazor, E.P. McElravy, A.P. O’Dowd, and S. Carlson. 2013. Long-term patterns in fish and benthic macroinvertebrates in northern California mediterranean-climate streams. Hydrobiologia 719(1):93-111. DOI: 10.1007/s10750-012-1373-9

O’Dowd, A.P., A. Stubblefield. 2013. Stream condition assessment of the Lake Tahoe Basin in 2009 and 2010 using the river invertebrate prediction and classification system (RIVPACS). Prepared for the Bureau of Land Management and Tahoe Regional Planning Agency. Report P079.

O’Dowd, A.P. 2011. Encouraging salmon recovery and restoring ecosystem function. California Forests Magazine 15(2):14-15.

O’Dowd (Purcell), A. P. 2011. Encouraging salmon recovery and restoring ecosystem function. California Forests Magazine 15(2):14-15.

Roy, A.H., A. H. Purcell, C. J. Walsh, and S. J. Wenger. 2009. Advances in urban stream ecology: an introduction to the series. Journal of the North American Benthological Society 28(4):908-910.

Carter, J. L., A. H. Purcell, S. V. Fend, and V. H. Resh. 2009. Development of a local-scale urban stream assessment method using benthic macroinvertebrates: an example from the Santa Clara Basin, California. Journal of the North American Benthological Society 28(4):1007-1021.

Wenger, S. J., A. H. Roy, C. R. Jackson, E. S. Bernhardt, T. L Carter, S. Filoso, C. A. Gibson, N. B. Grimm, W. C. Hession, S. S. Kaushal, E. Martí, J. L. Meyer, M. A. Palmer, M. J. Paul, A. H. Purcell, A. Ramirez, A. D. Rosemond, K. A. Schofield, E. Sudduth, and C. J. Walsh. 2009. Twenty-six key research questions in urban stream ecology: an assessment of the state of the science. Journal of the North American Benthological Society 28(4):1080-1098.

Chin, A., A. H. Purcell, J. Quan, and V.H. Resh. 2009. Assessing geomorphological and ecological responses in restored step-pool systems. In James, L.A., S.L. Rathburn, and G.R. Whittcar (eds.). Management and Restoration of Fluvial Systems with Broad Historical Changes and Human Impacts: Geological Society of America Special Paper 451, p. 199-217.

Bressler, D. W., M. J. Paul, A. H. Purcell, M. T. Barbour, E. Rankin, and V. H. Resh. 2009. Assessment tools for urban catchments: developing stressor gradients. Journal of the American Water Resources Association 45(2):291-305.

Purcell, A. H., D. W. Bressler, M. J. Paul, M. T. Barbour, E. Rankin, J. L. Carter, and V. H. Resh. 2009. Assessment tools for urban catchments: developing biological indicators using benthic macroinvertebrates. Journal of the American Water Resources Association 45(2):306- 319.

Paul, M. J., D. W. Bressler, A. H. Purcell, M. T. Barbour, E. Rankin, and V. H. Resh. 2009. Assessment tools for urban catchments: defining observable biological potential. Journal of the American Water Resources Association 45(2):320-330.

Mazor, R., A. H. Purcell, and V. H. Resh. 2009. Long-term variability in benthic macroinvertebrate bioassessments: A 20-year study from two northern Californian streams. Environmental Management 43:1269-1286.

Chin, A., S. Anerson, A. Collison, E. Ellis-Sugai, J.P. Haltiner, J.B. Hogervorst, G.M. Kondolf, L.S. O’Hirok, A.H. Purcell, A.L. Riley, and E. Wohl. 2009. Linking theory and practice for restoration of step-pool streams. Environmental Management 43:645-661.

Purcell, A. H., A. Hoffmann, and V. H. Resh. 2008. Life history of a dipteran predator (Scathophagidae: Acanthocnema) of insect egg masses in a northern California stream. Freshwater Biology 53:2426-2437.

Presentations & Posters

(*indicates graduate or undergraduate student co-author)

O’Dowd, A.P. and A. Chin. 2014. “Do bio-physical attributes of steps and pools differ in high gradient mountain streams?”  Joint Aquatic Sciences Meeting. Portland, OR.

Valasco, K.Z.*, P.K. Mendez, A.P. O’Dowd, R. Leventhal, and A. Chin. 2014. “Benthic macroinvertebrate community response of self-organizing step-pool restoration in Wildcat Creek (Alameda Co., CA, USA).” Joint Aquatic Sciences Meeting. Portland, OR.

Degenstein, E.*, J. Graham, and A.P. O’Dowd. 2014. “Modeling velvetgrass (Holcus lanatus) habitat suitability in Kings Canyon and Sequoia National Parks.” UCGIS Symposium. Pasadena, CA.

O’Dowd, A.P. and W.J. Trush. 2014. “A perfect match for self-renewal: steelhead and the Santa Ynez River Ecosystem.” 32nd Annual Salmonid Restoration Federation Conference. Santa Barbara, CA.

Chin, A., A.P. O’Dowd, R. Storesund, A. Parker*, and C. Roberts-Niemann*. 2013. “Response of step-pool mountain channels to wildfire under changing climate-fire regimes.” American Geophysical Union Annual Fall Meeting. San Francisco, CA.

Chin, A., L. Laurencio*, A. Parker*, A.P. O’Dowd and R. Storesund. 2013. “Initial response of step-pool streams to wildfire.” Geological Society of America Annual Meeting. Denver, CO.

O’Dowd, A.P., A. Stubblefield, C. Praul, and R. Mazor. 2012. “Stream condition in the Lake Tahoe Basin using River Invertebrate Prediction and Classification System (RIVPACS).”  Tahoe Science Conference; Incline Village, NV.

Koski, I.* and A.P. O’Dowd. 2012. “Landscapes in transition: Private lands oak woodland management in the Klamath-Siskiyou bioregion.” The California Society for Ecological Restoration (SERCAL) Conference; Davis, CA.

Mitchell, M.* and A.P. O’Dowd. 2012. “A comparison of terrestrial invertebrate communities of invaded and restored salt marsh of Humboldt Bay.” Humboldt Bay Symposium; Eureka, CA. Poster

Lagarde, L.* and A.P. O’Dowd. 2012. “Invasive Spartina densiflora Reduces Primary Productivity in a Northern California Salt Marsh.” Humboldt Bay Symposium; Eureka, CA. Poster

O’Dowd, A.P. and A. Chin. 2012. “Biological-physical interactions in step-pool streams: a guide for future restoration efforts.” River Restoration Northwest’s Stream Restoration Symposium; Stevenson, WA.

Purcell (O’Dowd), A.H. 2010. “Dipteran larvae as predators of macroinvertebrate egg masses.” Humboldt State University’s Ecology Seminar Series; Arcata, CA.


Graduate Students
Prospective Graduate Students

If your research interests are in the areas of stream ecology, bioassessment, or restoration ecology, and you are interested in working on a thesis (developing research questions and hypotheses, collecting and statistically analyzing the data), and you will work to publish your research results in a journal, here are some things you should know and some steps you should take.

Understand that space is limited and competition can be strong. I generally accept only one to two new graduate students each year. If you are interested in working with me, I strongly encourage you to do two things: 1) .(JavaScript must be enabled to view this email address) stating why you are a good fit for my lab, a summary of your research-related experience (if any), and what topic/area you would like to explore for your Masters thesis (this can be broad or specific); 2) if at all possible, visit campus and meet with me in person.

Look over my current and former graduate students’ research descriptions below to see the types of projects students that work with me pursue.

Current Graduate Students
Emily Cooper
Estimating potential habitat and Carrying Capacity of Anadromous Salmonid Habitat in the Upper Eel River, California

Emily’s research will quantify anadromous salmonid spawning and rearing habitat and estimate potential carrying capacity in the mainstem Eel River watershed upstream of Scott Dam for Coho salmon, Chinook salmon, and steelhead trout if the Potter Valley Project were either modified or removed. Fish passage barriers upstream of Scott Dam will be identified, and streams within the designated study site will be stratified into reach types that will then be subsampled for implementing habitat assessment field surveys. Ground survey data, aerial imagery, and LiDar data will be combined to create a three-dimensional geospatial fish population model to estimate capacity. Implications of this project have the potential to provide evidence for dam removal, as well as demonstrating advances in applying high-resolution topographic data from LiDar technology to instream habitat modeling and carrying capacity estimation. This will assist researchers and managers in adapting watershed management practices that combine field-based methods and technological advances to support both human and freshwater systems.

Lara Jansen
Ecological implications of dam flow diversions on the Upper Eel River

Lara’s research will quantify the downstream impacts of the Potter Valley Project diversion on Upper Mainstem Eel River in terms of both ecosystem health and salmonid food availability through a comparative study with the unregulated Middle Fork Eel River over the spring and summer when most of the flow diversion occur. The potential outcomes of this project are identifying the extent that the diversions may not only be limiting salmon recovery in terms of physical habitat, but also food supply. A food-web scale approach can provide management with a more complete picture of how the recovery of salmonids may be impaired under current regulated flow regime.

Monique Silva Crossman
Effects of manual and mechanical Ammophila arenaria removal techniques on coastal dune plant communities and morphology

Monique’s research examines the effects of two treatment types for removing Ammophila arenaria (European beachgrass) from coastal sand dunes. Her study will quantify the effects of manual and mechanical removal of A. arenaria on the native plant population as well as look at any changes to the overall morphology of the dunes between invaded and restored areas. Native vegetation populations will be determined by vegetation surveys at Little River, Prairie Creek and Tolowa Dunes State Parks. Elevation will be determined by RTK and UAV measurements at the same parks. This will assist land managers to choose the removal technique that affords the best long term benefit to the non-target parameters.

Former Graduate Students
Erin Degenstein - Graduated 2015
A Model to Predict the Future Distribution and Spread of Invasive Plants in Wilderness Areas of Kings Canyon and Sequoia National Parks, California

Erin’s research explored non-native invasive velvet grass (Holcus lanatus) that disrupts natural ecosystems in the Sierra Nevada of California. Several species are encroaching on wilderness landscapes in Sequoia and Kings Canyon National Parks, and resources to control these invasions are limited. This study will use habitat suitability modeling to predict potential distributions for Holcus lanatus. The maps produced by this research can inform early detection surveys for Holcus lanatus so that National Park Service staff can maximize available resources. A spatial visualization of potential habitat can allow managers to best utilize their limited resources to help preserve and protect wilderness ecosystems.

Emily Ferrell - Graduated 2015
Post-Fire Pulses of Aquatic Production: Investigating the Midterm Effects of High-Severity Fire on Headwater Streams in Northwestern California

Emily’s graduate research seeks to understand the mechanisms underlying aquatic community changes caused by riparian fire 5-10 years following a fire. Her study will assess both aquatic macroinvertebrate communities and periphyton production in the headwaters of the mid-Klamath region that were burned in the 2008 Klamath Theater Complex fire.

Kelsey McDonald - Graduated 2014
Tidal Seed Dispersal Potential of Spartina densiflora in Humboldt Bay (Humboldt County, California)

Kelsey’s research examined the tidal dispersal potential of the invasive cordgrass Spartina densiflora from saltmarshes in Humboldt Bay (Humboldt County, California) by demonstrating the net direction and quantity of seeds drifting in tidal creeks in the saltmarshes. Kelsey also measured the buoyancy duration of S. densiflora seeds in still water and compare this with seeds in an orbital shaker to simulate bay and ocean conditions. The results of the buoyancy study will help to estimate how long S. densiflora seeds can float and therefore how far they might be able to travel in ocean and bay currents to invade other regions along the West Coast.

Iris Koski - Graduated 2012
Landscapes in Transition: Private lands oak woodland management in the Klamath-Siskiyou bioregion

Iris’ thesis was entitled "Landscapes in Transition: Private lands oak woodland management in the Klamath-Siskiyou bioregion" and explored the factors that influence oak woodland management and ecosystem restoration for private landowners in this region. Iris conducted fieldwork and analysis at various sites and surveyed hundreds of private landowners and land managers to obtain data related to oak woodland management and restoration. She hopes to continue this analysis and develop guidelines and criteria for management of remaining oak woodlands, which tend to be ecologically significant and biodiverse.

Matt Mitchell - Graduated 2012
Community Structure of Terrestrial Invertebrates and Habitat Complexity Relationships in Spartina-Invaded and Restored Humboldt Bay Salt Marshes

Matt’s research compared terrestrial invertebrate communities in Spartina densiflora-invaded and restored salt marshes along Humboldt Bay. Results showed significant differences in invertebrate community structure in S. densiflora invaded marsh when compared to samples taken in restored marsh. Richness and evenness of epibenthic and low canopy invertebrates was highest in the restored marsh. Both the invasive snail Myosotella myosotis and the native snail Littorina subrotundata displayed a strong association with invaded sites, while the native talitrid amphipod genus Orchestia was associated with restored sites. In restored Distichlis spicata dominated salt marsh, individuals in the order Hemiptera represented nearly 100% of all invertebrates sampled, the most abundant of which was in the family Delphacidae. The long-jawed orb weaver spider family Tetragnatha was found in relatively high abundance at invaded sites, but was nearly absent from Salicornia pacifica and D. spicata vegetation at restored sites. The taller height of S. densiflora (compared to native salt marsh vegetation) provides habitat niches and refugium at high tide not found in native salt marsh, and disrupts existing co-evolved relationships between invertebrates and native vegetation.

Luc Lagarde - Graduated 2012
Invasive Spartina densiflora Brongn. Reduces primary productivity in a northern California salt marsh

Luc’s research explored the impact of the invasive dense-flowered cordgrass (Spartina densiflora) on the primary productivity of a Humboldt Bay (California) salt marsh using above and belowground biomass measurements coupled with paired closed-chamber carbon dioxide flux measurements. Although samples dominated by S. densiflora displayed higher aboveground net primary productivity compared to samples dominated by native vegetation, samples dominated by S. densiflora also displayed lower belowground net primary productivity, net primary productivity, and net ecosystem exchange measurements compared to samples dominated by native vegetation; therefore, S. densiflora colonization reduced primary productivity. In plots dominated by S. densiflora, less benthic macroalgae was present and less photosynthetically active radiation reached the substratum. Therefore, increased shading of the sediment surface in plots dominated by S. densiflora contributed to lower net ecosystem exchange measurements. Luc’s research contributed to understanding the impact of S. densiflora on the primary productivity of Humboldt Bay salt marsh ecosystems.