Grantee Research Project Results
2000 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.
Current 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, 1999 through August 31, 2000
Project Amount: $748,000
RFA: Ecosystem Indicators (1997) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Aquatic Ecosystems
Objective:
Our research explores 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 latter lakes is pristine, while the other has been experimentally eutrophied with phosphorus additions for about 30 years. We study indicators that emphasize connections between processing of materials (e.g., nutrients) and the population and community dynamics of microorganisms. We currently focus on the following: seston chemistry, particularly the C:N:P ratio (seston is a surrogate for microflora); species and community-level responses of algae to dilution bioassays of nutrient limitation; community level responses of bacteria to dilution bioassays of nutrient limitation; community structure of algae in situ, as it relates to shifting nutrient limitation; 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 1998-2000. Data collection from the first two years of the study is nearly completed. At present, we have analyzed seasonal patterns and made comparisons between lakes for the first one to two years of sampling. The two Texas lakes are similar in many physical characteristics, but Eagle Mountain Lake has a consistently higher abundance of algae and bacteria than Joe Pool Lake. Seasonal patterns also differ, in that Joe Pool Lake has episodic blooms of high algal abundance, while Eagle Mountain Lake shows a consistent seasonal pattern of high abundance through mid to late summer. Both lakes show similar degrees of nutrient limitation of algal and bacterial growth, as determined from bioassay experiments that estimate the in situ growth rates of these populations, and their potential growth rates if nutrients were at high supply. In both lakes, algae and bacteria are consistently nutrient limited from late spring to late summer. In our current data analyses, we focus on the extent to which bacterial and algal growth rates are limited by inorganic nitrogen and phosphorus. Our results indicate that joint limitation by these nutrients occurs, that the algae are usually more severely nutrient-limited than the bacteria, and that rapid shifts in degree of limitation are more common in Joe Pool Lake, where algal growth appears more episodic than in Eagle Mountain Lake. We have previously presented evidence that during this period of nutrient-limited growth, bacterial utilization of organic carbon substrates changes from the patterns seen during cooler times of year. To quantify these changes, we have calculated indices of utilization of three broad substrate classes?carbohydrates, amino acids, and (non-amino) carboxylic acids. The utilization index for carbohydrates rises dramatically during summer in both lakes, while indices for the two other substrate classes are depressed, relative to values seen during early spring, late autumn, and winter.
In the two Canadian lakes, much of our data confirms well-established differences between the pristine Lake 239, and the experimentally eutrophied Lake 227. Thirty years of phosphate enrichment have produced much more abundant algal and bacterial populations in the latter, with pronounced spring and summer blooms. Unfortunately, the design of bioassay experiments that we use to assess nutrient limitation has not worked in these lakes, although we can make inferences about nutrient limitation from our data on the nutrient composition of seston. These show, as expected from classical studies of this long running experiment, that both nitrogen and phosphorus are severely limiting to algal growth in Lake 239, with phosphorus probably more limiting than nitrogen. Nutrient limitation is less severe in Lake 227, where nitrogen limitation emerges occasionally during the growing season. We have found that bacterial substrate utilization shows seasonal differences in these lakes: there is an increase in the index of carbohydrate utilization in late summer, and declines in indices of amino and carboxylic acid utilization. This pattern has much greater amplitude in Lake 227, and we suggest that the magnitude of carbohydrate utilization is coupled to the production of algae in the summer. This would make high carbohydrate utilization by bacteria a symptom indicative of eutrophication. During our last summer of field work in Canada, we added studies of additional lakes. Though we are not sampling these as intensively through time as Lakes 239 and 227, we should be able to determine whether the late summer shift to carbohydrate utilization is a general pattern in this region, and whether it correlates to algal abundance as we hypothesize.
Future Activities:
We now have completed most of the planned sampling for this project, although we intend to continue sampling the Texas reservoirs until the current warm weather season is concluded, which is expected in November. As the last year of this study continues, we will analyze and process all remaining samples, and conduct statistical analysis. We have several working hypotheses that we will formally test, involving correlations and associations between seston nutrient composition, nutrient limitation of algal and bacterial growth, and community composition and productivity of algae and bacteria. In addition to examining a number of specific hypotheses, our analyses will address a broader goal of characterizing seasonal and interannual variation of a number of indicators in the lakes we study, so that natural variations of these quantities will be better understood.Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 25 publications | 3 publications in selected types | All 3 journal articles |
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Type | Citation | ||
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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) |
Exit Exit |
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Grover JP, Chrzanowski TH. Seasonal patterns of substrate utilization by bacterioplankton: case studies in four temperate lakes of different latitudes. Aquatic Microbial Ecology 2000;23(1):41-54. |
R825868 (2000) R825868 (Final) |
Exit Exit |
Supplemental Keywords:
water, ecological effects, metabolism, ecosystem, indicators, ecology, limnology, analytical, Central, Texas, TX, Canada., 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.