projects > spatial and temporal patterns and ecological effects of canal-water intrusion into the A.R.M. Loxahatchee National Wildlife Refuge > work plan
U.S. Geological Survey, Greater Everglades Priority Ecosystems Science (GE PES)Fiscal Year 2006 Study Work PlanStudy Start Date: February 2004 Study End Date: February 2007 Web Sites: None Location (Subregions, Counties, Park or Refuge): A.R.M. Loxahatchee National Wildlife Refuge Funding Source: USGS Greater Everglades Priority Ecosystems Science (GE PES) Other Complementary Funding Source(s): BRD funds Funding History: FY04 Project Investigators: Paul McCormick (pmccormick@usgs.gov, 304.724.4478) and Bill Orem (borem@usgs.gov, 703.648.6273) Overview & Objective(s): Alterations to groundwater and surface-water hydrology and water chemistry in south Florida have contributed to increased flows of mineral-rich (i.e., high conductivity) canal water into historically rainfall-driven (low conductivity) areas of the Everglades. The Loxahatchee National Wildlife Refuge has largely retained its historic low conductivity or soft-water condition, which supports a characteristic periphyton community, wetland plant species that may also be adapted to soft-water conditions, and lower rates of key ecosystem processes (e.g., decomposition) than in areas of the Everglades exposed to canal discharges. Recent monitoring data indicate a trend towards increased intrusion of canal water into the Refuge interior, but the causes (e.g., changing water management strategies, weather patterns) and magnitude of ecological effects resulting from this intrusion are not clear. This study is part of a coordinated effort between USGS and the Refuge to understand causes and predict patterns of canal-water intrusion and to assess effects on sensitive wetland biota and functions. Synoptic surveys, monitoring along canal-water gradients, and field experimentation were initiated in FY04 with the following objectives:
Specific Relevance to Major Unanswered Questions and Information Needs Identified: (Page numbers below refer to DOI Science Plan.) Projects that improve the quantity, timing, and distribution of water supplies to the natural system are at the core of Everglades restoration efforts. This study addresses a major DOI concern that the quality of water available for these projects may be inadequate to support natural ecosystem functioning (p. 14). While phosphorus impacts on Everglades populations and processes have been extensively studied, the environmental effects of other major water quality changes remain poorly understood. This study will improve understanding of the effects of elevated marsh concentrations of water quality constituents other than P resulting from increased supplies of canal water to the natural system. Thus, this project directly supports DOI's science program to support the assessment and management of contaminants that could be introduced into the system as an indirect effect of water engineering projects (p. 17). This study supports the Arthur R. Marshall Loxahatchee NWR Internal Canal Structures Project (p. 39) as it helps understand spatiotemporal patterns and ecological effects on Refuge resources of changing water quality and its relation to restoration activities. This project will provide answers to 3 of the 4 major unanswered questions for the Refuge in the DOI Science Plan (p. 37) by addressing: (1) links between hydrology, water quality, and ecology; (2) ecological responses to hydrologic change; and (3) water quality criteria that must be achieved for agricultural and urban water diverted into the Refuge. Results of this study are also relevant to projects in other areas of the Everglades that may be affected by changing water quality as a result of increasing canal-water inputs including the Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement Project (p. 66). Information gained from this study will support the Landscape Scale Modeling Project (p. 81) as it: (1) provides data to improve the accuracy and precision of hydrologic models for the Refuge; (2) provides data that facilitate the simulation of nutrient transport and biogeochemical cycling in the soil and water column (p. 81); (3) facilitates Everglades Landscape Model (ELM) development (p. 82) by providing data on how periphyton respond to changes in water quality, which can be incorporated into the model to improve its accuracy in predicting landscape responses to different water management scenarios; and (4) facilitates Regional Simulation Model (RSM) ecological module development (p. 82) by providing data on how biota respond to water quality changes produced by restoration efforts. Status: A Refuge-wide synoptic survey of surface-water conductivity and marsh soil and plant nutrient levels at 130 sites was completed in February 2004 in coordination with the SFWMD. Additional samples were collected at each site to assess whether stable isotope compositions of soil and vegetation and soil uranium concentrations could provide useful environmental markers of the extent and effects of canal-water intrusion. Laboratory nutrient and stable isotope analyses have been completed and data interpretation is underway. A 12-station transect monitoring network was established in May 2004, and measurements of water soil and plant chemistry and periphyton and macrophyte communities began in August 2004. A transect-wide decomposition experiment was initiated in August 2004. Results from these studies are pending. A field fertilization experiment consisting of 15 walled plots (3.7 m x 1.2 m) was constructed during the fall of 2004 to quantify chemical and biological responses to mineral enrichment. Monthly dosing of experimental plots was initiated in March 2005. Triplicate plots are being dosed with a mineral solution to produce mineral pulses that approximate 0 (control), 12, 25, and 50% of canal mineral levels. Soil and plant tissue chemistry and periphyton and plant community composition were monitored in these plots during FY05. Laboratory bioassays were initiated during FY05 to understand microbial and plant responses to nutrient and mineral gradients in the Refuge. Aerobic microbial respiration was found to be strongly C limited across these gradients, with no evidence of P or mineral effects. The response of a common interior slough-wet prairie macrophyte, Xyris stricta, to nutrient and mineral enrichment was assessed in a series of laboratory experiments. Selective enrichment with common limiting nutrients (N, P, and/or K) elicited no strong growth response from seedlings of this species. Enrichment with an artificial canal-water (mineral) solution elicited a significant negative growth response from this species. Germination of this species from interior soil samples and initial seedling growth also declined with increasing mineral levels. The negative response of this species to mineral enrichment may explain its distribution in the Refuge, where it is restricted to the soft-water interior. A white paper was begun to review ecological effects of mineral enrichment on peatlands such as the Everglades. A literature search was conducted to compile available information on ecosystem changes along mineral gradients in peatlands. A draft document was prepared that reviewed this information and compared it with existing evidence for ecological effects of mineral enrichment in the Everglades. Recent Products: Results of the synoptic survey were presented at the National Conference on Ecosystem Restoration in Orlando in December 2004. Two manuscripts were prepared using data from this project. These manuscripts will be submitted to peer-review journals in FY06. Planned Products: Reports, peer-review manuscripts, a white paper, and technical presentations. WORK PLAN Title of Task 1: Continue monitoring water and soil chemistry along canal-water gradients Work to be undertaken during the proposal year and a description of the methods and procedures: This task supports efforts under the A.R.M. Loxahatchee National Wildlife Refuge Enhanced Water Quality Monitoring and Research Plan. This task will also provide information to support other tasks focusing on the ecological effects of water-quality changes caused by canal-water intrusion on Refuge resources. Specific Task Product(s): These data will be used to interpret transect biological sampling (see Tasks 2 and 3) and will be included in reports and peer-review manuscripts containing those data. The Refuge is also including this information in their Enhanced Water Quality Monitoring database. Title of Task 2: Field experiment to quantify changes in litter decomposition and nutrient flux rates along canal-water gradients Work to be undertaken during the proposal year and a description of the methods and procedures: Decomposition bags will be collected in August 2006 (24 months of incubation). Samples will be processed in the laboratory to measure rates of plant mass and nutrient loss. Initial results suggest that differences in hydroperiod among sites may be influencing decomposition rates. Additional bags will be placed at two sites, an interior low-conductivity site and a moderately canal influenced site, to test for hydroperiod effects. At each site, one set of bags will be placed just above the soil and a second set of bags will be placed approx. 5 cm above the soil. Bags elevated farther above the soil will dry out more frequently, thereby mimicking a shorter hydroperiod. Replicate bags from each location will be collected after 6, 12, and 24 months. Specific Task Product(s): Data collection and analysis will be completed in FY07. Results will be compiled into a report, which will then be converted into a peer-review manuscript. Results will also be included in scientific presentations. Title of Task 3: Field measurements to document changes in vegetation composition and production along canal-water gradients Work to be undertaken during the proposal year and a description of the methods and procedures: Surveys of slough vegetation will be performed quarterly to develop a plant inventory for each transect site. Initial observations performed during FY05 showed that this level of monitoring is necessary to capture different slough-wet prairie taxa during flowering to allow identification. Periphyton samples will also be collected quarterly to monitor taxonomic composition. Sawgrass regrowth rate measurements begun in FY05 will continue. Production measurements of sawgrass and selected slough-wet prairie taxa (e.g., Rhyncospora inundata and R. tracyii) will continue to be developed and implemented. Vegetation measurements will be correlated with soil and water chemistry and site hydrology to develop hypotheses concerning the environmental factors affecting Refuge vegetation along canal gradients. These hypotheses will be tested as part of a separate GE PES project slated to begin in FY07. Specific Task Product(s): Data collection and analysis will be completed in FY06. Results will be compiled into a report, which will then be converted into a peer-review manuscript. Results will also be included in scientific presentations. Title of Task 4: Field experiment to quantify ecological effects of additions of high conductivity waters to the Refuge interior Work to be undertaken during the proposal year and a description of the methods and procedures: Monthly dosing will continue with the assistance of Refuge staff. Measurements of soil, porewater, and vegetation mineral accumulation and macrophyte and periphyton composition begun in FY05 will continue. Microbial enzyme measurements initiated in collaboration with investigators from the SFWMD will also continue. Soil microbial measurements (e.g., aerobic and anaerobic respiration) are also planned. Specific Task Product(s): Data collection and analysis will be completed in FY07. Preliminary results will be compiled into a report at the end of FY06 and then a final report after task completion. These results will then be converted into a peer-review manuscript and included in scientific presentations. Title of Task 5: Laboratory experiments to determine the effects of water quality and hydrology on soil phosphorus retention and release Work to be undertaken during the proposal year and a description of the methods and procedures: Controlled laboratory experiments will be conducted to measure P fluxes from soils from different transect sites under different hydrologic and water quality conditions. In phase 1, controlled laboratory experiments will be conducted wherein soil cores from selected transect sites will be incubated under different hydrologic conditions to measure levels of potentially bioavailable P. Replicate soil cores will be incubated under flooded, saturated, and drained (drying) conditions for an extended period (1-2 months) under controlled temperature conditions. Incubation chambers will then be replenished with fresh low-P water and filtered to measure release of soluble reactive P (SRP). In phase 2, soils from a minimally impacted location will be incubated in water containing different conductivity levels (i.e., a laboratory solution containing major ions at concentrations similar to those in canal waters) but the same background concentration of P. Initially, small soil samples will be incubated in test tubes for short periods (several days), drained and then agitated in distilled water, and filtered to measure SRP. Longer term experiments will involve incubating larger soil cores in the same water quality treatments and then treating them as described for phase 1 experiments. Microbial respiration and biomass will also be measured to understand the role of microbial activity in P release. In phase 3, a final set of experiments will be conducted wherein soil cores from the same minimally impacted location will be exposed to low P waters of varying conductivity prior to replenishment with waters containing a specified concentration of SRP. Incubation containers will be slowly shaken (minimum speed for shaker table) for a 24-h period and rates of SRP loss will be measured via periodic sampling. Microbial respiration and biomass will also be measured to understand the role of microbial activity in P retention. This task will provide critical information on how hydrologic and water quality changes affect microbial processes that retain and release P from Refuge sediments, which likely represents the primary source of water-column P in interior areas. The findings of this work will hopefully allow the Refuge and other environmental managers to better understand the natural and human factors that affect surface-water P concentrations within the Refuge. Specific Task Product(s): Data collection and analysis will be completed in FY07. Preliminary results will be compiled into a report at the end of FY06 and then a final report after task completion. These results will then be converted into a peer-review manuscript and included in scientific presentations. Title of Task 6: Field and laboratory experiments to determine the effect of canal-water pulses on nutrient accumulation in the Refuge interior Work to be undertaken during the proposal year and a description of the methods and procedures: Surface soils from an interior Refuge location will be exposed to continuous and pulsed dosing of an artificial canal-water solution in laboratory microcosms to measure patterns of nutrient accumulation and loss. In the field, soil cores will be exchanged between interior locations receiving minimal and significant canal influence to measure rates of nutrient accumulation and loss. Specific Task Product(s): Data collection and analysis will be completed in FY06. Results will be compiled into a report during FY07. It is anticipated that these result will be included in a peer-review manuscript and included in scientific presentations. Title of Task 7: Scoping study to assess the efficacy of different geochemical methods for reconstructing historic water quality conditions across the Refuge Work to be undertaken during the proposal year and a description of the methods and procedures: Piston coring of peat sediments will be conducted to assess downcore geochemistry. Trends in organic elemental composition (C, N, P, and S) and atomic ratios (C/N, C/P, C/S, N/P) can often provide useful information on paleoecology. For example, changes in atomic C/N may be indicative of changes in N-fixing periphyton abundance, but may be complicated by diagenetic effects. Similarly, S in soils may be indicative of the historical amounts of sulfate entering the Refuge. Some metals (Fe, Mn, Cu) may be indicative of historical levels of agriculturally-derived inflow and/or inputs of Lake Okeechobee/Kissimmee River inflow. Downcore changes in concentrations of Si may provide information on sawgrass abundance. Organic marker compounds (lignin phenols, plant sterols) may also be used to provide paleoecological information. Scoping studies in FY06 will emphasize simple organic and inorganic elemental compositional studies, with later work emphasizing more sophisticated (and expensive) analyses, once the utility of this approach has been established. Specific Task Product(s): Data collection and analysis will be completed in FY06. Results will be compiled into a report that will include an assessment of the efficacy of these geochemical methods and, pending the outcome of this work, additional measurements that could be performed to improve understanding of past water quality conditions in the Refuge. Title of Task 8: Complete laboratory experimentation and sample processing proposed under an addendum to the FY05 work plan Work to be undertaken during the proposal year and a description of the methods and procedures: Specific Task Product(s): A report will be submitted to the Refuge during FY06 that conveys the findings of this work. These findings may also be included in peer review manuscripts and in scientific presentations. Title of Task 9: Complete white paper and continue data integration and synthesis Work to be undertaken during the proposal year and a description of the methods and procedures: The primary goal of this task is to complete a draft paper for external peer review by December 2006 and a final version for public distribution before the end of FY06. Data entry, QA/QC, and analysis will continue with the assistance of technical staff. Submission of 2 peer-review publications and 1-2 presentations at scientific meetings are also planned for FY06. Specific Task Product(s): Completed white paper, peer-review publications, scientific presentations |
U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 09 June, 2006 @ 01:40 PM(TJE)