Grantee Research Project Results
2004 Progress Report: Influence of Bio-Pollution on Ecosystem Processes: The Impact Introduced Lake Trout on Streams and Terrestrial Predators in Yellowstone National Park
EPA Grant Number: R829426E02Title: Influence of Bio-Pollution on Ecosystem Processes: The Impact Introduced Lake Trout on Streams and Terrestrial Predators in Yellowstone National Park
Investigators: Hall, Robert O. , Ben-David, Merav
Institution: University of Wyoming
EPA Project Officer: Chung, Serena
Project Period: July 15, 2002 through September 30, 2004
Project Period Covered by this Report: July 15, 2003 through September 30, 2004
Project Amount: $160,610
RFA: EPSCoR (Experimental Program to Stimulate Competitive Research) (2001) RFA Text | Recipients Lists
Research Category: EPSCoR (The Experimental Program to Stimulate Competitive Research)
Objective:
Invasive species can impact populations and ecosystem processes within the recipient ecosystem, but their impacts outside of this ecosystem are rarely considered. Lake trout (Salvelinus namaycush) have invaded Yellowstone Lake and, if left unchecked, are predicted to substantially lower native cutthroat trout (Oncorhynchus clarki bouvieri) populations. The impact of fewer native cutthroat trout almost certainly will extend beyond the lake to trout spawning tributary-streams. The objective of this research project is to investigate the role of cutthroat trout in structuring stream ecosystems, their importance to river otters (Lontra canadensis), and possible links to terrestrial plants, thus integrating instream and terrestrial processes. For the element cycling component of this study, we will focus on nitrogen (N), because it limits production in streams and terrestrial ecosystems. These observations will enable us to make initial predictions on how streams, trout predators, and the terrestrial landscape will be affected following cutthroat trout demise. Upon completion, this study will provide insights into potential ecosystem changes in other systems where reductions in anadromous salmonids may occur.
Progress Summary:
The Science and Engineering Environmental Research component of the Wyoming Environmental Protection Agency/Experimental Program to Stimulate Competitive Research project has already met many of the goals stated in the objectives:
Between January 1, 2003-November 15, 2004, two graduate students completed several laboratory analyses with the assistance of four undergraduate students. In addition, one full field-season (May to October) was conducted for the in-stream processes where N excretion by trout and N cycling in streams were measured. Also, sampling for biofilm and stream invertebrates was conducted. Eight sampling sessions for chlorophyll, phytoplankton, zooplankton, and invertebrates were conducted within Yellowstone Lake during the same period. For the river otter component, all stable isotope analyses of foliage were completed as well as all analyses and sample preparation of tree rings. Also, more than 300 (of anticipated 500) fecal samples were analyzed for diet composition.
For the in-stream component, three streams were monitored and sampled intensively. One hundred and twenty-six samples of biofilm and invertebrates were collected for isotope analysis and to estimate invertebrate secondary production. Between 20 and 80 water samples were collected for analyses of ammonium (NH4) and nitrate (NO3) concentrations and N excretion by cutthroat trout. In the lake, between 72 and 96 samples of invertebrates, zooplankton, and phytoplankton were collected. A similar number of samples were collected for analyses of NH4 and NO3 concentrations. Three lake trout were used to estimate N excretion for that species. Additionally, the East Fire burnt most of the basin in two of the watersheds. We fortunately had collected baseline N concentration data before and after the fire, which will provide valuable insight on N export following fire and a large flood.
Both graduate students have made progress in data analysis and manuscript writing. Lusha Tronstad contributed data and writing to a multiauthor manuscript entitled “Improving the fluorometric ammonium method by accounting for matrix effects with standard additions”. We used this method in all of the NH4 analyses in this work, and as part of this project we have extensively modified this method to improve its accuracy and precision. That manuscript was submitted to the Canadian Journal of Fisheries and Aquatic Sciences in October. Jamie Crait finished a manuscript entitled “Nutrient transports in an inland system: effects of river otter activity on plant growth and community composition in Yellowstone Lake”. This manuscript will be submitted to Ecological Monographs by December 31, 2004.
Our results for the project (including data obtained and analyzed in the previous year) indicate that recent N transports from a lake to streams are substantially lower than historical values with the reductions in cutthroat trout. This observation was more pronounced in 2004, when only 1,000 spawners (or 25% of the number spawning in that stream in 2003) entered Clear Creek. We could not detect elevated NH4 concentrations at the stream outlet during 2004. The effects of such lower N input on in-stream invertebrates are still being evaluated. Cutthroat trout excreted an average of 6 mg NH4/fish/hour and lake trout excreted 9.4 mg NH4/fish/hour; however, the excretion rate did not depend on the sex, mass, condition, water temperature, or length of the trout.
The East Fire of 2003 increased NH4 and NO3 concentrations in the burnt Cub and Little Cub Creeks in 2004, but not in the mostly intact Clear Creek. A large flood on July 18, 2004, strikingly increased NH4 concentrations and reduced chlorophyll stocks in all three streams. Otter surveys suggest that although activity levels of river otters in Yellowstone Lake and tributaries are similar to other systems in the intermountain west, the actual abundance of otters may be lower. Otters exhibited a seasonal change in activity patterns in response to the spawning migrations of cutthroat trout. In addition, trout remains were found in 90-100 percent of all feces collected at latrines along the lakeshores throughout the summer in both years. Trout also were the most frequent (> 90%) prey remains in feces collected along tributary streams in May and June but were less frequent (50-60%) in July and August when longnose sucker (Catostomus catostomus) became more prevalent. In 65 samples sent to a specialized laboratory, remains of only 3 lake trout were identified. These data suggest that cutthroat trout are an important food item for otters in Yellowstone Lake.
Our stable isotope results support the hypothesis that river otters transport aquatically derived N onto latrine sites, and in turn, fertilize plants at these locations. To explore whether site characteristics rather than otter activity affects isotopic values in plants, habitat selection models were developed and δ15N values of plants on correctly and incorrectly classified sites were compared. The prediction that latrines correctly classified as latrines and latrines mis-classified as random sites will have the same isotopic values under otter fertilization was supported by the data. Otter fertilization had a positive effect on growth of currant (Ribes spp.) shoots, after controlling for light limitation. Also, although diversity did not significantly differ between sites, eight plants were more prevalent on latrines, and one was more prevalent on random sites. The completed analyses suggest that tree-ring widths alone are not a reliable proxy for temporal changes in cutthroat trout abundance and otter activity. We are currently analyzing tree cores for δ15N to relate temporal changes in N isotope values to historical cutthroat populations. Data from Yellowstone National Park, combined with results from our study, suggest that a significant decline in cutthroat trout abundance has already occurred and that such a decline already resulted in changes in the structure of streams, the abundance of otters, and the transport of nutrients to the riparian ecosystem.
To supplement funding for this project, the principal investigators submitted proposals to several granting agencies and were able to secure an additional $6,750. In-kind support was provided by Yellowstone National Park.
A press release describing this project was printed in more than 50 newspapers nationwide, including The New York Times, The Oregonian, and The Seattle Intelligencer.
Future Activities:
Drs. Hall and Ben-David submitted a proposal to EPA/Science to Achieve Results entitled “Regime shift in the Yellowstone Lake Ecosystem: retrospective comparisons of in- and out of lake impacts”. This project is designed to continue the work on the effects of cutthroat declines in Yellowstone Lake beyond the funding period provided by this award.
Data from Yellowstone National Park, combined with results from our study, suggest that a significant decline in cutthroat trout abundance has already occurred. This decline, in turn, resulted in changes in the structure of streams, the abundance of otters, and the transport of nutrients to the riparian ecosystem. Therefore, continuation of this project is crucial because this study will provide insights into potential ecosystem changes in other systems where reductions in anadromous salmonids may occur. We are in the process of seeking additional funds to expand and continue this work from a variety of sources, the U.S. National Park Service, the University of Wyoming-National Park Service Research Center, including the U.S. Geological Survey, the U.S. Fish and Wildlife Service, and the National Science Foundation.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 24 publications | 4 publications in selected types | All 4 journal articles |
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Crait JR, Ben-David M. River otters in Yellowstone Lake depend on a declining cutthroat trout population. Journal of Mammalogy 2006;87(3):485-494. |
R829426E01 (2004) R829426E01 (Final) R829426E02 (2004) R829426E02 (Final) |
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Crait JR, Ben-David M. Effects of river otter activity on terrestrial plants in trophically altered Yellowstone Lake. Ecology 2007;88(4):1040-1052. |
R829426E01 (2004) R829426E02 (2004) R829426E02 (Final) |
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Supplemental Keywords:
ecological effects, ecosystem, indicators, terrestrial, aquatic, analytical, surveys, western states, cutthroat trout, invasive species, limnology, nitrogen, nutrient transports, river otters, stream invertebrates, tree cores, Yellowstone, anthropogenic stress, aquatic biota, aquatic ecosystems, bioassessment, biodiversity, bioindicators, biological impairment, biological indicators, biopollution, conservation, conservation planning, diagnostic indicators, ecosystem indicators, ecosystem monitoring, ecosystem response, ecosystem stress, lake trout, lakes, land use, nitrogen uptake, nutrient transport, restoration planning, watershed assessment, watershed classification, watershed management, watershed restoration, ecosystems, ecosystem protection/environmental exposure and risk, international cooperation, water, aquatic ecosystem, aquatic ecosystems and estuarine research, ecology, ecology and ecosystems, ecosystem protection, ecosystem/assessment/indicators, environmental monitoring, terrestrial ecosystems, water and watershed, water quality monitoring, watersheds, Yellowstone Park, anthropogenic processes, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, ECOSYSTEMS, Water, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, Water & Watershed, Ecology, Ecosystem/Assessment/Indicators, Aquatic Ecosystem, Water Quality Monitoring, Ecological Effects - Environmental Exposure & Risk, Monitoring/Modeling, Terrestrial Ecosystems, Environmental Monitoring, Ecology and Ecosystems, Watersheds, anthropogenic stress, bioassessment, anthropogenic processes, watershed classification, nutrient transport, lake trout, ecosystem monitoring, watershed management, biodiversity, biopollution, Yellowstone Park, conservation, diagnostic indicators, ecosystem indicators, lakes, aquatic ecosystems, bioindicators, watershed sustainablility, invasive species, water quality, biological indicators, ecosystem stress, watershed assessment, conservation planning, nitrogen uptake, ecosystem response, aquatic biota, land use, restoration planning, watershed restorationRelevant Websites:
http://www.uwyo.edu/bhall Exit
http://uwadmnweb.uwyo.edu/Zoology/faculty/Ben-David 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.