Grantee Research Project Results
2007 Progress Report: Quantifying Ecological Thresholds And Resilience In Stream Ecosystems
EPA Grant Number: R832444Title: Quantifying Ecological Thresholds And Resilience In Stream Ecosystems
Investigators: Hilderbrand, Robert H. , Raesly, Richard L.
Institution: University of Maryland - College Park , Frostburg State University
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 2006 through December 31, 2007
Project Period Covered by this Report: January 1, 2007 through December 31, 2008
Project Amount: $295,079
RFA: Exploratory Research: Understanding Ecological Thresholds In Aquatic Systems Through Retrospective Analysis (2004) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Water
Objective:
Our overall objectives are to assess the consequences of landscape change on stream ecosystem structure and function and conduct futures scenarios of ecosystem change. Specifically, the objectives are to: 1) assess stream ecosystem state shifts across gradients of landscape change, 2) quantify ecosystem resilience and vulnerability to forms of landscape change, 3) identify and quantify landscape alteration thresholds causing ecosystem state shifts, and 4) develop a rigorous predictive framework to forecast changes in stream ecosystems as landscape alterations continue within watersheds.
Progress Summary:
The last 12 months have been productive for the project. We spent considerable time exploring the nature of reference communities inhabiting minimally disturbed watersheds. There are essentially no minimally disturbed watersheds in the piedmont of Maryland and few in the coastal plain, so we have had to relax our disturbance criteria some, especially regarding the amount of agriculture, to get a suitable number of sites. However, analyses indicate that agriculture has little detectable effect on communities until it approaches 40% of the watershed. We have identified a number of reference communities for fish in each of the three general geographic regions of Maryland and are nearing completion for the invertebrates. Preliminary results indicate that fish reference communities exist as a continuum across different stream channel types rather than as discrete alternate states. However, we are able to classify with very high accuracy, the identity of fish reference communities solely from physical watershed attributes that do not respond to human actions; classification accuracy in piedmont watersheds was 100% across three reference communities, 60% across four communities in the coastal plain, and 80% across two communities in the highlands. Our classification success suggests that restoration endpoints for fishes may be predicted from watershed variables for degraded sites. With the determination of reference communities and minimally disturbed watersheds, we are now moving forward with identifying ecological thresholds that shift communities from intact to degraded states. To this end, we have determined that fish communities in the piedmont have substantially different resilience/vulnerability to urbanization and impervious surfaces with some communities tolerating a maximum of 6% urbanization before being altered compared to other communities capable of tolerating substantially more urbanization before changing organizational structure.
Finally we have extended to fish, the method developed last year for assessing taxon responses to stressors by comparing cumulative frequency distributions of observed and expected responses across a stressor gradient. In addition to a presence/absence analysis, the fish data are analyzed using abundances. Preliminary results indicate that both presence/absence and abundance data usually produce very similar results. However, the abundance data allow us to identify sites that are probable sinks or taxa that appear to facing an extinction debt despite still being present at a site.
Future Activities:
We anticipate project completion in one year. Remaining tasks include refinement of stressor thresholds for each community, analysis of stream temperatures in relation to community structure, development of a stream condition predictive model, and development of stream vulnerability/resilience maps.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
| Other project views: | All 5 publications | 4 publications in selected types | All 4 journal articles |
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Ulz R, Hildebrand R, Boward D. Identifying regional differences in threshold responses of aquatic invertebrates to land cover gradients. ECOLOGICAL INDICATORS 2009;9(3):556-567. |
R832444 (2007) |
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Ulz R, Hildebrand R, Raesly R. Regional differences in patterns of fish species loss with changing land use. BIOLOGICAL CONSERVATION 2010;143(3):688-699. |
R832444 (2007) |
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Ulz R, Hildebrand R. Interregional variation in urbanization-induced geomorphic change and macroinvertebrate habitat colonization in headwater streams. JOURNAL OF THE NORTH AMERICAN BENTHOLOGICAL SOCIETY 2011;30(1):25-37. |
R832444 (2007) |
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Ulz R, Eshleman K, Hildebrand R. Variation in physicochemical responses to urbanization in streams between two Mid-Atlantic physiographic regions. ECOLOGICAL APPLICATIONS 2011;21(2):42-415. |
R832444 (2007) |
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Supplemental Keywords:
risk assessment, agriculture, ecology, Mid-Atlantic, Maryland, MD, EPA Region 3,, RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Aquatic Ecosystem, Aquatic Ecosystems & Estuarine Research, Ecological Risk Assessment, Ecology and Ecosystems, Environmental Monitoring, environmental history, water quality, anthropogenic impact, estuarine research, ecological thresholds, ecosystem indicators, modeling ecosystem change, ecosystem response, ecosystem stress, riverine ecosystems, trophic interactions, land use, aquatic ecosystems, landscape changeRelevant Websites:
The webpage that we have created to disseminate general information, project goals, and preliminary results and publications related to the research has logged over 300 visits in the last 12 months. Although I do not update it as much as I should, it is current with our research. The link to the homepage can be found at http://www.al.umces.edu/~bhilderbrand/research/asters%20project/asters%20home.html Exit .
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.