Grantee Research Project Results
2002 Progress Report: Biogeochemical Indicators of Watershed Integrity and Wetland Eutrophication
EPA Grant Number: R827641Title: Biogeochemical Indicators of Watershed Integrity and Wetland Eutrophication
Investigators: Reddy, Konda R. , Lowe, E. F. , DeBusk, William F. , Fisher, M. M. , Graham, William M. , Prenger, Joseph P. , Ogram, A.
Current Investigators: Reddy, Konda R. , Lowe, E. F. , DeBusk, William F. , Fisher, M. M. , Graham, William M. , Prenger, Joseph P. , Keenan, L. W. , Ogram, A.
Institution: University of Florida , St. Johns River Water Management District
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1999 through September 30, 2002
Project Period Covered by this Report: October 1, 2001 through September 30, 2002
Project Amount: $639,410
RFA: Ecological Indicators (1999) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Aquatic Ecosystems
Objective:
The overall objective of this research project is to develop sensitive, reliable, rapid, and inexpensive indicators of ecological integrity for use in large-scale ecosystem management and restoration. In many areas, wetlands more efficiently will indicate the ecological integrity of the entire watershed than will any other portions of the landscape because: (1) wetlands are critical areas of the landscape. Many species depend upon wetlands for successful completion of their life cycle, and most species require, or benefit from, nearby aquatic habitat. If the integrity of a wetland decreases, the effects on the biota eventually will be far-reaching; (2) wetlands, as low lying areas in the landscape, receive inputs from all adjacent uplands. If the integrity of an upland area is compromised, it most likely will soon be reflected in the integrity of the associated wetlands; and (3) the response of a wetland to inputs from the uplands is patterned, indicating areas within the landscape which are experiencing degradation or improvement. Unlike lakes, which will show a generalized response to inputs due to mixing or streams, which rapidly transport materials to other areas, wetlands absorb inflowing pollutants and nutrients proximal to the points of inflow. Biogeochemical processes are good indicators of ecological integrity because they are potentially very sensitive. They also are likely to be highly reliable in the sense that ecological changes at such a fundamental level will affect all species utilizing the ecosystem. Changes at higher levels (e.g., population changes) may be due to factors that affect only a small portion of the biota, whereas changes in biogeochemical processes portend comprehensive alteration of the biota.
The central hypothesis of this research is that rates of biogeochemical cycling of carbon, nitrogen, and phosphorus (C, N, and P) in wetlands can be used to indicate the ecological integrity of wetlands, and that the concentrations of certain forms of these elements can accurately predict the rates of ecologically important processes. The specific objectives of this research project are to: (1) identify the key biogeochemical processes impacted by nutrient loading and measure the rates of these processes along the nutrient gradient; (2) develop relationships between a process and its related, easily measurable indicator; (3) determine the spatial and temporal distribution of easily measurable indicators for a test wetland ecosystem; (4) determine the spatial variations in biogeochemical processes, and develop spatial maps for various processes to determine the extent of impact and risk assessment; and (5) validate the predictability of empirical relationships by making independent measurements of biogeochemical processes in different wetland ecosystems.
We will test the hypotheses presented above in the Blue Cypress Marsh Conservation Area (BCMCA) located within Upper Saint Johns River Basin, FL. Some areas of the BCMCA have been impacted by nutrient loading from adjacent uplands, resulting in distinct nutrient and vegetation gradients. The BCMCA provides the benefit of established gradients of high-nutrient (impacted) to low-nutrient systems (unimpacted), to test our hypotheses.
Progress Summary:
Determination of Spatial Variability and Interrelationships of Biogeochemical Processes and Efficient Indicators. Based on preliminary data from January 2000, soil-sampling grids were established in two impacted areas, and one reference area. Soil sampling for the first task was planned for June 2000. However, because of drought conditions in the headwater region of the St. Johns River, this sampling was not accomplished until September 11-26, 2000. Samples were obtained from a grid that will provide maximum information for spatial and geostatistical analyses. Each sample was the composite of two soil cores, and detritus samples were collected at each coring site. Approximately 120 soil and 120 detritus samples were obtained for use in batch incubation experiments, and for routine soil analysis. Biogeochemical processes related to carbon, nitrogen, and phosphorus cycling were measured in plant litter and soil samples; all samples were characterized for basic physicochemical properties, and a subset of samples were analyzed for microbial indicators. These analyses indicate a substantial difference between soil and detritus in the various areas and vegetation communities.
Multivariate statistical procedures were used to evaluate relationships among sensitive biogeochemical indicators, and between indicators and biogeochemical processes. These results indicate that soil biogeochemical measurements can be used to discriminate between low impact and high impact regions, and vegetation type (which can be used as a measure of ecosystem disturbance). The establishment of discriminant functions for these groups makes it possible to assign new samples to membership in these groups. Additionally, geostatistical analyses can extend such information over space. However, further work is needed to refine the present results, especially focusing on the comparison of appropriate approaches in clustering variables and validation of the discriminant function analysis using an independent data set.
Temporal Variability of Biogeochemical Processes and Indicators. Based on the results obtained from the spatial variability studies, two stations in each area (total of six stations) were established to determine temporal variability of key biogeochemical processes and associated indicators. One area in the NE was chosen as a transitional impacted area for its slightly elevated Total Phosphorus (TP) values in remnant native Cladium vegetation. At each station, three plots (2 x 2 m area) were established in March 2001, and were monitored every 2 months for 1 year (through January 2002). The plots were instrumented for continuous monitoring of soil temperature, and redox potential was measured at four depths (5, 10, 20, and 30 cm) during each sampling period. Water level continuously was monitored at two recording stations within the marsh. Soil cores (one composite sample of four cores/plot) were obtained once every 2 months. Detritus samples (400 cm2) were collected at each coring site. All samples were characterized for the following parameters: bulk density, pH, moisture content, loss on ignition (LOI), (TN), (TP), (TC), total inorganic P (TPi), total organic P (TPo), SRP, total labile organic P (TLOP), MBP, TKN, total labile organic N (TLON), PMN, denitrifying enzyme activity (DEA), extractable NH4+, CO2 production, CH4 production, soil oxygen demand (SOD), TOC, total labile organic (TLOC), acid phosphatase activity (APA), ß-glucosidase activity, dehydrogenase activity.
Total phosphorus significantly was higher in soil and detritus of the impacted sites, while TP in soils and detritus from the NECladium area were not significantly higher than the NW reference sites. APA levels did show a clear difference in detritus between NECladium and the NW reference areas. Soil APA values exhibit a slight but non-significant difference between the NW reference sites and NE and SW sites. MBC significantly was lower in soil of the NE sites, possibly due to less aerobic conditions, because the NE sites did not burn in January 2001. MBC in both soils and detritus declined with the onset of flooding and anaerobic conditions. ß-glucosidase increased over the course of the growing season, probably because of increased availability of carbon from plant exudates and detritus.
Canonical Coefficient Analysis indicates that for soil, 61.3 percent of the variation in microbial metabolism is controlled by ß-glucosidase activity. However, in detritus, microbial metabolism is influenced mainly by APA, with 47 percent of variance in microbial metabolism attributable to the enzymes assayed, in this case dominated by APA.
Diversity and Composition of Prokaryotic Groups Related to C, N, and, P Cycling in Wetland. The diversity and composition of key assemblages of prokaryotes, which are responsible for crucial steps in carbon cycling in BCM soil samples, were investigated with an emphasis on the syntrophic bacteria and methanogens. Our approach was to use polymerase chain reaction (PCR)-based cloning and sequencing, or analytical techniques such as Terminal Restriction Fragment Length Polymorphism (T-RFLP). PCR reactions were optimized for these specific groups of anaerobic microbes at different temperatures, cycles, and with different primers (specific for hydrogenotrophs or acetoclastic methanogens). Amplification and analysis is ongoing.
Shifts in composition of methanogens were investigated by microcosm studies. In the absence of sulfate, propionate conversion is thermodynamically possible only at a low partial hydrogen pressure, and with a low formate concentration. These conditions are met in syntrophic consortia, where the syntrophs convert propionate and/or butyrate into acetate, CO2, hydrogen and/or formate that subsequently are used by the methanogens. In the presence of sulfate, sulfate-reducing bacteria like Desulfobulbus spp. can convert propionate into acetate and hydrogen sulfide. However, recent studies revealed that syntrophic propionate-oxidizing bacteria, such as Syntrophobacter spp., are themselves capable of oxidizing propionate by sulfate reduction. Results indicate competition between the sulfate reducing bacteria (SRBs) and the syntrophs for carbon donors (propionate and or butyrate). However, in the non-impacted NW Cladium site, exogenous addition of sulfate completely inhibited methanogenesis, indicating the greater involvement of SRBs there.
DNA extraction, PCR amplification, and cloning of bacterial and archaeal 16S rDNAs in enrichment cultures were performed, followed by T-RFLP and phylogenetic studies. These rDNA clones were grouped into operational taxonomic units based on their RFLP patterns. Representative clones having different and similar RFLP patterns then were sequenced, compared, and aligned, and a phylogenetic tree was constructed. Remarkable differences were obtained in the archaeal RFLP patterns with 2 different restriction enzymes in the impacted (NE) and the non-impacted (NW) sites. Commonalities also were seen with soils from impacted sites spiked with propionate and butyrate, but clear differences were obtained in the non-impacted sites enriched with the same substrates. A high diversity was observed in the bacterial community, and there were few similarities in the impacted and the non-impacted sites. In general, the methanogenic community in the non-impacted regions mainly is comprised of sarcinas, but Methanosaeta can survive, as well and is essentially dependent on the acetate flux. The evidence suggests that when the system is challenged with butyrate, there is a shift towards syntrophic conversion of butyrate, giving rise to acetate and hydrogen. Hydrogen, in turn, would then be consumed by the hydrogenotrophs, forming high levels of methane and, because acetoclastic methanogens are lacking here, acetate should accumulate. Interestingly, when we analyzed acetate concentrations in these samples, the level of acetate was found to be four to five times higher than in other samples where it must have been consumed by the acetoclastic methanogens sarcina and saeta.
Spatial Distribution of Biogeochemical Indicators in Water, Litter, and Soil. Based on the results obtained from the preliminary geostatistical analyses in the first task, a large-scale monitoring network was developed in March 2002, to characterize the spatial distribution of biogeochemical indicators in water, litter, and soil throughout the study site. Approximately 300 sample locations were identified at 400 m intervals on a regular grid throughout the marsh, and detritus and soil samples were obtained from 273 of these sites. Most of the chemical/physical analyses of these samples have been completed, and data analysis will begin when complete. A map of soil and detritus characteristics for the entire marsh will be developed based on these analyses. Additional data on vegetation type and presence of invasive species also were obtained for a detailed description of the approximately 8000 ha marsh.
Future Activities:
Our investigation will continue, and the experiments and analysis of data will be more carefully examined.
Task 5: Validation of Predictive Equations Using Independent Measurements. The predictive relationships between the biogeochemical processes and parameters will be evaluated in a variety of ways. First, a snapshot including approximately 120 sets of processes and parameters has been collected over the site in Task 1. From this data, 60 sets of measured processes and parameters have been used to develop the empirical relationships, while the remaining 60 will be used to evaluate the accuracy of using the relationship at different sites within the same wetland. As a second measure of the robustness of the predictive relationships, the temporal biogeochemical data collected in Task 2 will be used to test the models developed in Task 1. This analysis will test the applicability of extending the model to predict biogeochemical processes using biogeochemical indicators measured at different times and over different seasons of the year.
A final measure of the validity of the relationships developed between the processes and parameters will be determined by sampling 12 sites in selected wetlands in the southeastern United States. Site selection will be made after discussion with the U.S. Environmental Protection Agency's (EPA) Environmental Monitoring and Assessment Program (EMAP) wetland resource group. At each site, a minimum of three stations will be sampled. Both the processes and the soils parameters listed in Task 1 will be determined at these locations. This should demonstrate that the biogeochemical process and parameter relationships are valid, and that the magnitude of the processes measured can be used as a reliable indicator of the extent to which a wetland has been impacted by nutrient loading. Sampling methods, data analysis, and modeling will be similar to that outlined in Task 1.
Journal Articles:
No journal articles submitted with this report: View all 26 publications for this projectSupplemental Keywords:
geostatistical analyses, nutrient cycling, microbial, diversity, landscape scale., RFA, Scientific Discipline, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Nutrients, Environmental Chemistry, Ecosystem/Assessment/Indicators, Ecosystem Protection, State, Ecological Risk Assessment, Ecology and Ecosystems, Ecological Indicators, nutrient supply, risk assessment, wetlands, nutrient transport, eutrophication, aquatic ecosystem, biogeochemical indicators, watersheds, wetland vegetation, nutrient gradiants, soil, ecosystem indicators, vegetation gradients, aquatic ecosystems, GIS, water quality, nutrient cycling, Florida, nutrient fluxes, spatial and temporal patterns, nitrogen, statistical evaluationRelevant Websites:
http://wetlands.ifas.ufl.edu/research/wbl2.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.