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2002 Progress Report: Interactive Effects of Climate Change, Wetlands, and Dissolved Organic Matter on UV Damage to Aquatic Foodwebs

EPA Grant Number: R829643
Title: Interactive Effects of Climate Change, Wetlands, and Dissolved Organic Matter on UV Damage to Aquatic Foodwebs
Investigators: Bridgham, Scott D. , Johnston, Carol A. , Lamberti, Gary A. , Lodge, David M. , Maurice, Patricia A. , Shmagin, Boris A.
Current Investigators: Bridgham, Scott D. , Frost, Paul C , Johnston, Carol A. , Lamberti, Gary A. , Lodge, David M. , Maurice, Patricia A. , Shmagin, Boris A.
Institution: University of Notre Dame , South Dakota State University , University of Oregon
Current Institution: University of Oregon , Natural Resources Research Institute (Center for Water and the Environment) , Trent University , University of Notre Dame
EPA Project Officer: Jones, Brandon
Project Period: June 24, 2002 through June 23, 2005 (Extended to June 23, 2006)
Project Period Covered by this Report: June 24, 2002 through June 23, 2003
Project Amount: $897,307
RFA: Assessing the Consequences of Global Change for Aquatic Ecosystems: Climate, Land Use, and UV Radiation (2001)
Research Category: Global Climate Change , Ecological Indicators/Assessment/Restoration

Description:

Objective:

Understanding the factors controlling ultraviolet radiation (UVR) flux into aquatic ecosystems is critical given its deleterious effects on many ecological processes. UVR is strongly attenuated in aquatic ecosystems by dissolved organic matter (DOM). Previous research suggests that the quantity and quality of DOM at the landscape scale is controlled primarily by: (1) vegetation community and soil type, with wetland areas being of particular significance; (2) flow paths through soil; (3) the discharge regimes of rivers and streams; and (4) intra-system DOM degradation and production mechanisms. Climate change likely will affect each of these DOM control factors in complex ways. Whereas a significant amount of previous research has focused on the separate roles of DOM and UVR in aquatic ecosystems, much less is known about the interactive effects of climate change, landscape, DOM, UVR, and aquatic foodwebs.

The objectives of this project are to: (1) relate via multivariate analysis the DOM concentration and chemical characteristics in various tributaries of a relatively pristine watershed in the Lake Superior drainage basin (Ontonagon River in northern Michigan) to discharge, wetland landscape characteristics, upland landscape characteristics, and stream order; (2) determine interactions among UVR intensity and DOM chemistry, photodegradation, photoaggregation, and biodegradation; and (3) determine the response of stream foodwebs to the interactions among UVR intensity and DOM quantity and quality.

Progress Summary:

We completed an initial survey of DOM concentration and chemistry, in addition to other water-quality parameters, for 60 streams in the Ontonagon River watershed in September 2003. We also performed an initial landscape assessment using a geographic information system (GIS) of the watershed. We used the results to: (1) examine relationships between landscape characteristics and stream DOM concentration and chemistry; and (2) choose 35 streams to sample more intensively. To date, we have sampled each of these 35 sites 9 times for DOM and related water chemical variables and found considerable variation in stream DOM concentration and chemistry among sites and among seasons (fall versus spring). UVR was measured in 30 streams from the Ontonagon River watershed during the summer of 2003. Concurrent with each measurement, stream DOM and its UV absorbtivity were measured. UVR attenuation and penetration in our study streams showed considerable variation and relate strongly to stream DOM concentration.

We also examined the role of microbial community structure on DOM biodegradation by reciprocally transplanting bacterial inocula from three different aquatic sites into DOM from those sites. Results suggest that microbial communities are adapted to degrade the DOM of their native habitats. A second experiment demonstrated the important effects of bacteria on DOM chemistry from both physical sorption and biodegradation mechanisms.

Two stream foodweb experiments were completed in the summer of 2003. Before experiments could be conducted, an artificial stream facility comprising 24 channels had to be constructed. The first stream experiment manipulated stream DOM concentration and UV-B exposure to colonizing periphyton. There was a strong positive effect of DOM on stream chlorophyll and particulate carbon, indicative of greater algal growth in these treatments. UV-B exclusion had relatively weaker effects on algae. A second experiment examined the effects of UVR on periphyton that had colonized clay tiles in low UV environments (high DOM streams) versus low UV environments (low DOM streams).

Future Activities:

In the next year, we will continue to measure stream DOM concentrations and chemistry, discharge, and other water quality variables at 35 sites in the Ontonagon River watershed every 2 months. To better understand the role of soils and site-specific geology on stream DOM, soil samples will be collected across the watershed in conjunction with our stream survey. Detailed GIS analysis of watershed geology and soils will be completed, and UV radiation will be mapped across the watershed. We will take seasonal samples from 5-10 streams and measure biodegradation rates of the DOM and bacterial growth rates, with and without prior photodegradation. Two additional stream foodweb experiments are planned for the summer of 2004. In one experiment, we will assess whether DOM stimulates primary producers through its effects on UV-A or through its effects on stream nutrient supply. A second experiment will expose producers and an array of their consumers to different UV environments.

Journal Articles:

No journal articles submitted with this report: View all 52 publications for this project

Supplemental Keywords:

groundwater, soil, land, global climate, chemical transport, ecological effects, bioavailability, stressor, bacteria, discharge, scaling, terrestrial, environmental chemistry, biology, engineering, ecology, hydrology, geology, limnology, Great Lakes, Midwest, Michigan, MI, EPA Region 5, watersheds, ultraviolet radiation, UVR, UV-A, UV-B, solar radiation, dissolved organic carbon, DOC, dissolved organic matter, DOM, precipitation, wetlands, forest, stream, river, foodwebs, algae, invertebrates, watershed slope, lake, molecular weight, absorbtivity, GIS, geographic information system. , Water, Air, Geographic Area, Scientific Discipline, RFA, Water & Watershed, climate change, Ecological Risk Assessment, Atmospheric Sciences, EPA Region, Hydrology, Watersheds, State, water quality, UV radiation, Global Climate Change, hydrologic models, ecological research, aquatic food web, Lake Superior, land use, vulnerability assessment, wetlands, vegetation models, environmental monitoring, Region 5, climate models, anthropogenic processes, aquatic ecosystems, climate variability, land and water resources, global change, watershed sustainablility, regional hydrologic vulnerability, water resources, dissolved organic matter, aquatic ecology
Relevant Websites:

http://www.d.umn.edu/~cjohnsto/Recon.htm exit EPA

Progress and Final Reports:
Original Abstract
2003 Progress Report
2004 Progress Report
Final Report

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The 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.

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