Grantee Research Project Results
1997 Progress Report: Evaluation of Rangeland Stream Condition and Recovery Using Physical and Biological Assessments of Nonpoint Source Pollution
EPA Grant Number: R823487Title: Evaluation of Rangeland Stream Condition and Recovery Using Physical and Biological Assessments of Nonpoint Source Pollution
Investigators: Herbst, David B.
Current Investigators: Herbst, David B. , Knapp, Roland A.
Institution: University of California - Santa Barbara
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 1995 through August 31, 1998
Project Period Covered by this Report: September 1, 1996 through August 31, 1997
Project Amount: $249,647
RFA: Exploratory Research - Environmental Biology (1995) RFA Text | Recipients Lists
Research Category: Biology/Life Sciences , Human Health , Aquatic Ecosystems
Objective:
The research has several objectives: (1) to compare the usefulness of physical habitat and biological monitoring techniques in detecting grazing impacts and associated nonpoint source pollution, (2) to compare the recovery of stream ecosystems under different grazing practices (exclosures), and (3) develop biological indicators for streams in overgrazed watersheds.Progress Summary:
Overgrazing resulting in the loss of riparian vegetation often leads to unstable streambanks and widespread erosion and sediment release into waterways. This type of nonpoint source (NPS) pollution associated with grazing has been especially problematic for establishing contamination effects and limits. The health of Great Basin streams is of concern because of their small size, limited protective cover, and prolonged exposure to grazing. Flowing water in the arid desert is a vital natural resource for wildlife of all kinds and excessive clogging and sedimentation in channels can choke aquatic life. Though drinking water standards based on chemical toxicity and disease have been used widely, the beneficial uses of water for aquatic ecosystems have been more difficult to define and apply to resource management.In order to apply the technology of macroinvertebrate bioassessment to nonpoint source pollution related to livestock grazing problems, there is a need to develop (1) reference stream standards, (2) a baseline for trend comparisons in invertebrate communities exposed to varied grazing management practices, and (3) a database on sediment-polluted streams that can be used to analyze invertebrate associations and develop a tolerance scoring system for indicator fauna specific to grazing-related impacts. The approach of the research supported by this grant has been to apply the technique of bioassessment to identifying NPS grazing pollution problems and compare this system with traditional monitoring methods that have relied on external stream features such as channel geomorphology and riparian vegetation.
Now in the final year, project results to date are based on (1) a pilot project comparing seasonal differences in physical habitat conditions, aquatic invertebrate communities, and fish populations among 9 stream reaches including a single ungrazed reference reach, and (2) an expanded study designed to (i) establish multiple reference stream reaches, (ii) initiate a set of sites for baseline trend monitoring, and (iii) obtain a data set from varied habitat conditions to be used for developing invertebrate indicator groups of NPS pollution related to grazing impacts.
During the pilot project phase of the study habitat features for each site remained essentially constant between spring and fall sampling seasons. The ungrazed reference reach always scored highest in physical habitat quality and also possessed the best overall bioassessment scores (summed over all seasons of comparison) and had the greatest densities of adult trout. Grazed sites with the poorest channel and riparian conditions always had the lowest bioassessment rank while sites of intermediate quality were variable. Pairing the ungrazed reference with its adjacent grazed site, bioassessment scores were much lower on the grazed site in the fall, toward the end of the grazing season, but were similar in spring (before grazing). This suggests that bioassessment may detect short-term and local grazing impacts, but that single-season bioassessment measures are inadequate to capture the range of variation. Moreover, post-grazing recovery may reset conditions for aquatic life by spring, providing the potential for rapid ecological renewal. The sites with the poorest habitat conditions, however, showed little or no tendency for recovery in the spring. The initial project phase has revealed differences between an ungrazed site and NPS-polluted grazed sites, and permitted contrasts and derivation of monitoring indicators, but also shown limitations due to low sample sizes and redundant measures. Fish sampling was eliminated from further study after 1995.
Sampling was expanded during the summers of 1996 and 1997 (July-September) and 445 macroinvertebrate samples taken from 89 stream study reaches (5 replicates per site) have now been processed. Detailed taxonomic analysis of the samples includes identification of midges (chironomidae), a group often ignored in bioassessment but found here to have nearly the same amount of taxonomic diversity as all other invertebrate groups combined. This will add great predictive power to indicator group analysis. Habitat descriptions for each study reach include complete geomorphic profiles from 15 transects, substrates, embedding, current, cover, slope, water chemistry, algal chlorophyll biomass, and coarse and fine particulate organic matter. With more than half the samples processed and counted, patterns are already evident in the higher diversity and types of organisms associated with reference reaches versus low diversity at sites where overgrazing was evident. In addition to a direct environmental gradient analysis of community data, paired-comparisons of ungrazed exclosures with adjacent grazed land will also permit an evaluation of land management in producing aquatic habitat recovery.
Future Activities:
Plans for 1998 Field Season: The scope of the study will continue to be expanded this summer so that sufficient data is available for rigorous statistical analysis (115 total stream reach samples over a diversity of stream types and conditions, including 15 stations selected for annual baseline trends, and >20 reference reaches). Classification and ordination analysis of invertebrate data from study reaches will permit species clustering into indicator groups along environmental gradients related to grazing impacts. The data analysis will also use canonical correspondence analysis as a contrast with multi-metric methods of impact assessment. Results will provide a diagnostic technique for biomonitoring of rangeland streams and guidance of resource management. An experimental treatment of grazed and ungrazed streams with sediment additions is also planned for this summer. Results will be used to test for differential resistence in short-term responses of community structure to the sediment erosion component of grazing impacts.Supplemental Keywords:
agriculture, pesticides, water quality, Great Basin., RFA, Scientific Discipline, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, Water & Watershed, Contaminated Sediments, exploratory research environmental biology, Environmental Chemistry, Ecosystem/Assessment/Indicators, Chemical Mixtures - Environmental Exposure & Risk, Ecosystem Protection, Chemistry, Ecological Effects - Environmental Exposure & Risk, Ecological Effects - Human Health, Biology, Watersheds, Ecological Indicators, ecological exposure, rangeland, aquatic biota , ecosystem assessment, landscape indicator, erosion, stream ecosystems, contaminated sediment, land use effects, runoff, ecological impacts, aquatic ecosystems, assessment methods, bioassay, environmental stress, water quality, vegetationProgress 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.