Grantee Research Project Results
1999 Progress Report: Microbial indicators of biological integrity and nutrient stress for aquatic ecosystems
EPA Grant Number: R825868Title: Microbial indicators of biological integrity and nutrient stress for aquatic ecosystems
Investigators: Grover, James P. , Chrzanowski, Thomas H.
Institution: The University of Texas at Arlington
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 1997 through August 31, 2000
Project Period Covered by this Report: September 1, 1998 through August 31, 1999
Project Amount: $748,000
RFA: Ecosystem Indicators (1997) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Aquatic Ecosystems
Objective:
Our research explores the connections between biological integrity and nutrient supply and limitation, focusing on the microbial component of lakes and reservoirs. Microbial indicators should respond rapidly to increased nutrient supply and alterations in supply ratios of different nutrients. We examine two reservoirs in north Texas year round and two lakes in the Experimental Lakes Area (Ontario, Canada) during the ice-free growing season. One of the Canadian lakes is pristine; the other has been experimentally eutrophied with phosphorus additions for about 30 years. Indicators that emphasize connections between processing of materials (e.g., nutrients) and the population and community dynamics of microorganisms are being studied. We currently focus on: (1) seston chemistry, particularly the C:N:P ratio (seston is a surrogate for microflora); (2) species- and community-level responses of algae to dilution bioassays of nutrient limitation; (3) community-level responses of bacteria to dilution bioassays of nutrient limitation; (4) community structure of algae in situ, as it relates to shifting nutrient limitation; and (5) community structure of bacteria in situ, as it relates to shifting nutrient limitation. We seek to test several hypotheses concerning patterns and correlations among these indicators, and to assess their spatiotemporal and inter-regional variability.Progress Summary:
Sampling and experimental work in two Texas reservoirs has been continual since March 1998. Sampling and experimental work in two Canadian lakes was completed as planned during the summers of 1998 and 1999. Data collection from the first year of the study is complete, except for some of the algal species counts. Some of the data collection from the second year of sampling is complete. At present, we have analyzed seasonal patterns and made comparisons between lakes for the first year of sampling.
We hypothesized that stoichiometric indicators of nutrient limitation based on the C:N:P composition of seston would agree with growth responses in dilution bioassays. When N or P is deficient in seston (e.g., high C:N or C:P ratio), this nutrient is inferred to be deficient in cells of bacteria and algae, and experimental enrichment with N or P should stimulate growth of algae and bacteria. We calculated the "effect size" in factorial bioassay experiments as the average increment-to-growth rate in treatments receiving a particular nutrient, versus growth in those treatments without the nutrient. In the Texas lakes, temporal correlations between indicators of P-limitation and C:P and N:P ratios in the seston are all in the hypothesized directions and significant. Correlations between indicators of N-limitation often are opposite to the hypothesized directions. We tentatively conclude that indicators of P-limitation perform more consistently than indicators of N-limitation, and hypothesized that algal and bacterial nutrient limitation would be positively correlated, due to competition for the same nutrient pool. This proved to be the case for both P and N, in the Texas lakes.
We have had continuing difficulties with bioassay experiments in the Canadian lakes, where there is high variability, and a number of unexpected negative effects from nutrient enrichment. The generally good performance of similar experiments and analyses in Texas suggests that biological properties render such experimental designs inappropriate to Canadian lakes. To obtain greater insight from the stoichiometric indicators, size-fractionated sampling of seston in Canada was instituted during 1999, although these data are not yet available.
We hypothesized that bacterial community structure shifts in response to nutrient limitation. We constructed physiological profiles of bacterial communities based on use of 95 carbon substrates on Biolog microtiter plates. Principal components analyses of the first year of data reveal several interesting patterns. In the two Canadian lakes, bacterial substrate use in spring and early summer is similar in oligotrophic Lake 239 and eutrophic Lake 227, with high responses to several amino acids. After the collapse of a blue-green bloom in eutrophic Lake 227 in midyear, the two lakes diverge with Lake 239 characterized by high response to leucine, and Lake 227 characterized by high response to carbohydrates. In the two Texas lakes, samples taken during cool seasons (late autumn, winter, and early spring) show high response to several amino and carboxylic acids, while those taken in warm weather show high response to carbohydrates. A combined analysis reveals strong relative growth response to amino and carboxylic acids in the Canadian lakes, and strong relative growth responses to carbohydrates in the Texas lakes. Seasonal trends are superimposed on this regional pattern: in all lakes, amino and carboxylic acids are used more strongly in cool seasons, and carbohydrates in warm seasons, with a greater amplitude to this pattern in more eutrophic lakes.
Future Activities:
An additional year of sampling is planned for the Texas reservoirs, as is one summer field season in Canada. As more data become available, we will address issues of interannual variability. We also will conduct more extensive ordination analyses of bacterial community data (Biolog CLPP) and algal community structure. We should be able to use canonical ordination to relate community structure to the environmental variables that are measured. We are considering instituting size-fractionated determinations of seston stoichiometry to our procedures for Texas lakes, although in these lakes detritus concentrations are sometimes large and may interfere with size separation.Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 25 publications | 3 publications in selected types | All 3 journal articles |
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Chrzanowski TH, Grover JP. Effects of mineral nutrients on the growth of bacterio- and phytoplankton in two southern reservoirs. Limnology and Oceanography 2001;46(6):1319-1330. |
R825868 (1999) R825868 (2000) R825868 (Final) |
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Supplemental Keywords:
water, bacteria, indicators, aquatic, limnology, south central, TX, eutrophication algae, nutrients., RFA, Scientific Discipline, Water, Ecosystem Protection/Environmental Exposure & Risk, Nutrients, Limnology, Aquatic Ecosystems & Estuarine Research, Ecosystem/Assessment/Indicators, Ecosystem Protection, exploratory research environmental biology, Ecological Effects - Environmental Exposure & Risk, Microbiology, Aquatic Ecosystem, Ecological Risk Assessment, Aquatic Ecosystem Restoration, Ecological Indicators, eutrophication, hydrological stability, nutrient supply, ecological exposure, aquatic, biological activity, ecological condition, ecological effects, interactive stressors, nutrient loading, algae, adverse impacts, aquatic biota , ecosystem assessment, wetland eutrophication, bioavailability, algal growth, demographic factors, ecosystem condition, molecular detection, Seston C:N:P ratio, wetland habitat, biological integrity, nutrient stress, lakes, biotic integrity, ecosystem indicators, water quality, aquatic ecosystems, environmental indicators, ecosystem, ecosystem health, environmental stress, ecological stoichiometry, biological indicators, nitrogen, nutrient management, interactive aquatic ecosystem indicatorRelevant Websites:
http://www.uta.edu/chrzanowskihttp://www.uta.edu/grover
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.