Grantee Research Project Results
2001 Progress Report: Environmental Factors That Influence Amphibian Community Structure and Health as Indicators of Ecosystems
EPA Grant Number: R825867Title: Environmental Factors That Influence Amphibian Community Structure and Health as Indicators of Ecosystems
Investigators: Beasley, Val , Richards, Carl , Johnson, Lucinda , Piwoni, Marvin , Schoff, Pat , Cole, Rebecca
Current Investigators: Beasley, Val , Richards, Carl , Schotthoefer, Anna , Lieske, Camilla , Johnson, Catherine , Murphy, Joe , Johnson, Lucinda , Piwoni, Marvin , Schoff, Pat , Cole, Rebecca
Institution: University of Illinois Urbana-Champaign , USGS National Wildlife Health Center , University of Minnesota
Current Institution: University of Illinois Urbana-Champaign , Illinois Waste Management and Research Center , United States Geological Survey , University of Minnesota - Duluth
EPA Project Officer: Packard, Benjamin H
Project Period: June 1, 1998 through May 31, 2001 (Extended to September 30, 2002)
Project Period Covered by this Report: June 1, 2000 through May 31, 2001
Project Amount: $1,299,991
RFA: Ecosystem Indicators (1997) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration
Objective:
The primary objective of this research project is to assess the relative influence of landscape patterns, biotic interactions, water quality, and contaminants on the health and community structure of amphibians. The specific objectives are to evaluate: (1) the relative influence of wetland- and watershed-scale factors (i.e., landscape and ecological data) on amphibian community structure and health; and (2) whether amphibian community structure and health are indicative of ecological integrity.
Progress Summary:
Spatial and Ecological Assessments. Sixty-four wetlands in 13 regional watersheds, representing a range of human disturbance levels in northern Illinois, Wisconsin, and central Minnesota were studied. Landscape-level spatial data (e.g., land cover, hydrography, roads, soils, quaternary geology, and wetland mapping) were collected for each watershed and for areas within a 2 km and a 10 km radius around each wetland. Amphibian calling surveys were conducted at all wetlands during 1998-2000, to determine the number of species and the abundance of each species. Relationships among anuran species occurrences, wetland morphology, water chemistry, and landscape metrics were analyzed, and habitat models were developed for four frog species based on the analysis. These species showed a wide range of associations with wetland-specific and landscape (1-2 km and 10 km) metrics, but no single environmental factor had an overriding influence on anuran distributions. Relationships between explanatory variables and species occurrences varied as a function of scale, and multi-scale models were better predictors of species occurrences than models based on wetland-specific or landscape variables alone.
Subsequent studies involved more intensive data collection, focusing on 20 of the Minnesota Wetlands included in the earlier studies, and 16 new sites in that vicinity. Calling surveys were conducted annually at all sites in Minnesota, as were dipnet surveys, and water chemistry measurements. Detailed, time- and area-constrained macroinvertebrate surveys were performed in 1999, with samples returned to the laboratory to determine general abundances of different taxa. Quantitative vegetation assessments were performed in all wetlands during 1999. Water and sediment cores were collected for chemical analysis in 1999 and 2000. Spatial data were derived from aerial photointerpretation and geographic information systems (GIS) analysis for the 36 wetlands to supplement the broad landscape data previously collected, and were summarized for varying scales, including wetland buffers of 10 m to 5 km in width. We found strong relationships among several wetland attributes and surrounding land use types. Like the habitat models discussed above, the form and strength of these relationships varied with the spatial scale of the landscape assessed. Invertebrate species richness was correlated negatively with agriculture in the landscape at nearly all spatial scales examined, while the percent organic matter in the soil was correlated positively with agricultural land use. Cattail (Typha)-dominated wetlands were associated significantly with high levels of agriculture in the local landscape, but the vegetative community overall showed no strong relationship to the broader landscape conditions. Anuran species richness was strongly associated with landscape metrics only at the broadest scales examined, however, all nine study wetlands with the highest species richness (> 6 species) were bordered at least partially by woodland, indicating that forest cover is very important to certain anuran species. Our results indicate that several wetland attributes (e.g., biotic community metrics, water and soil metrics) may prove useful as indicators of overall wetland condition, as affected by the surrounding landscape conditions.
Parasitology Studies. An environmental data matrix, consisting of uncorrelated variables, including percentage of land classified as agriculture, forest or wet forest, distance to nearest neighbor, and contagion was evaluated. A local habitat data matrix also was evaluated considering wetland size, water pH, minimum dissolved oxygen, and percentage of open water. Stepwise analysis were conducted at the local wetland, 2 km, and 10 km scales to identify predictor variables for the abundance of commonly encountered larval parasite groups, specifically, echinostomes and Fibricola sp. Also, statistical analysis was used to identify environmental variables associated with the presence of Ribeiroia ondatrae, the larval trematode known to cause limb malformations in developing frogs. This initial analysis suggests that the percentages of forest and wet forest will be important predictor variables for the parasite taxa examined. Our preliminary analysis, examining whether richness of parasite taxa at a wetland was associated with richness of macroinvertebrates, snails, and vegetation species, found no significant correlations.
Gross and Microscopic Pathology Studies on Frogs. Separate databases are maintained for the 1999 and 2000 frogs. Information collected included sex, weight (intact animal and selected organs), snout-to-vent length, and the presence and severity of abnormalities. The 1999 database has been completed; the 2000 database is 90 percent complete and in review for histologic diagnosis. Batrachochytrium dendrobatidis (which causes cutaneous fungal infections implicated in frog die-offs worldwide) was identified in 27 frogs from 6 sites in 1999. Species affected were Rana septentrionalis (mink frog) and R. sylvatica (wood frog). No chytrid organisms were identified in R. pipiens (our target species) even at sites where other frog species were affected. We evaluated species other than, or in addition to, R. pipiens at only 10 of 30 sites. Thus, chytrids in Minnesota wetlands could be prevalent and warrant future study. The pathology data will be evaluated in conjunction with landscape and local habitat variables, as well as contaminant data, to identify habitat characteristics that influence health outcomes.
Malformations. Malformation rates for several frog species were determined from our set of randomly selected wetland sites over the three field seasons (1998-2000). Malformations were identified in metamorphic frogs by examination in the field and by bone and cartilage staining. Malformed frogs were found in clustered sites in all 3 years, but the cluster locations were not the same year to year. The malformation rates observed were higher than the 0.3 percent rate determined for metamorphic frogs collected from similar sites in Minnesota in the 1960s, and thus there appears to be an elevation relative to that time frame.
Water Quality Assessments. Data on dissolved oxygen, pH, and temperature were examined in connection with the presence and abundance of coontail (Ceratophyllum demersum), a common aquatic plant, as well as with the numbers of metamorphic leopard frogs caught at each study pond within a defined period of time and effort (catch success). A positive correlation was found among ample dissolved oxygen concentrations, large quantities of coontail, and high catch success. This seems to suggest that abundant oxygen, and/or the presence of aquatic plants early in the season, may be needed for a pond to support leopard frogs at a time between fertilization and metamorphosis.
Contaminant Analyses. Organic analysis data for base neutral organic compounds were completed for pond waters and sediments collected in 2000, and acid herbicide data for 2000 are in final review. Metals analysis was completed for all sediment samples collected in 1999 and 2000. We continued to note very limited contamination in the study ponds. Our surveys of pond stewards indicated that many farmers in this area of central Minnesota rely substantially on crop rotation for weed control, and/or, are involved in organic agriculture. These methods, in combination with buffers, seem to result in low pesticide burdens in the aquatic environment. The 2000 pond water base neutral analytical data include very few samples above the detection limits of the assays. Atrazine and degradation products were only found at near detection limits in a few of the ponds. The 2000 sediment results revealed low levels of several polycyclic aromatic hydrocarbon compounds in several ponds. Some pesticides, and their degradation products, e.g., atrazine and dichloro-diphenyl-trichlorethane (DDT), were found in a few pond sediments, but only at very low concentrations. No polychlorinated biphenyls (PCBs) were detected in the pond waters or sediments. Metals concentrations were at or near background levels in the 2000 sediments, and ranged only modestly among the ponds. The only elevated value was for zinc in one sample at 480 mg/kg of dry sediment, and this does not, in our view, represent a definitive contamination situation. No other metals of toxicologic interest were found at elevated concentrations, although additional examinations of the data are pending.
Future Activities:
Parasitology Studies. The aim of the parasitology component of the project is to determine how frog-parasite interactions are influenced by environmental factors at varying spatial scales. To address this aim, we determined distributions and abundances of parasites in juvenile frogs collected in 1999 and 2000. These data will be analyzed to determine: (1) how frog parasite communities vary with land use, including agriculture and wetland characteristics; (2) whether different parasites respond differently to environmental factors at varying scales; and (3) whether parasite abundances correlate with frog size and indicators of ecological conditions. Analysis will focus on relationships among species occurrences or abundances and environmental variables that indicate agricultural impact, such as percentage of land within an area around each wetland that is used for agriculture, presence of row crops at the wetland's edge, water pH, dissolved oxygen, and the detection of agricultural pesticides in water or sediment. To assess the effects of scale, we will conduct analysis at the 1, 2, and 10 km scales used in our landscape analysis. It is expected that the analysis will produce models that describe relationships between parasite species and environmental variables. These models then will be used to predict which parasite species are most indicative of frog population health or disease, as well as environmental condition.
Pathology Studies. The objectives of the pathology studies include: (1) assessment of the condition of individual frogs at each site; (2) determination of the frequency and severity of specific health problems at each site; (3) identification of objective endpoints antemortem and postmortem that can be utilized as indicators of frog health; and (4) identification of habitat factors that are linked to adverse impacts on frog health. The first two objectives are encompassed in the database and include results from gross and histologic evaluations. The final two objectives will be accomplished via statistical analysis in an effort to identify associations among measurable health endpoints, indicators of water quality, contaminant exposure and load, and landscape factors at different spatial scales.
Analytical Toxicology. Metals analysis of the 1999 and 2000 tissue samples is expected to be completed by the end of February 2002. Organic analysis on tissues is expected to be completed by the end of March 2002. Results on acid herbicide analysis on the 2000 sediments also are expected in this time frame. After completion of the water, sediment, and tissue contaminant analysis, the data will be examined to identify relationships among detections and levels of contaminants and other elements in the water, sediments and frog tissues with catch success at each study pond. Employing GIS analysis, these data sets also will be analyzed within the greater context of landscape level features to examine potential interactions at the pond, watershed, and region levels.
Journal Articles:
No journal articles submitted with this report: View all 47 publications for this projectSupplemental Keywords:
watersheds, sediments, risk assessment, health effects, ecological effects, chemicals, toxics, metals, organics, ecosystem, indicators, aquatic, habitat, integrated assessment, Midwest, Minnesota, MN, Illinois, IL,Wisconsin, WI, agriculture., RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Ecosystem/Assessment/Indicators, exploratory research environmental biology, Ecological Effects - Environmental Exposure & Risk, Microbiology, Ecological Risk Assessment, Biology, Ecological Indicators, ecological exposure, pesticide exposure, aquatic biota , landscape indicator, watersheds, amphibians, ecosystem integrity, parasitic infection, multiple spatial scales, biotic integrity, contaminant impact, water qualityRelevant Websites:
http://www.nrri.umn.edu/cwe/hostedpages/amphweb.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.