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projects > spatial and temporal patterns and ecological effects of canal-water intrusion into the A.R.M. Loxahatchee National Wildlife Refuge > work plan

Project Work Plan

U.S. Geological Survey, Greater Everglades Priority Ecosystems Science (GE PES)

Fiscal Year 2006 Study Work Plan

Study Title: Spatial and temporal patterns and ecological effects of canal-water intrusion into the A.R.M. Loxahatchee National Wildlife Refuge
Study 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)
Supporting Organizations: A.R.M. Loxahatchee National Wildlife Refuge
Associated / Linked Studies: A.R.M. Loxahatchee National Wildlife Refuge Enhanced Water Quality Monitoring and Research Plan

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:

  1. document spatial and temporal patterns of canal-water intrusion into the Refuge;
  2. quantify nutrient concentrations and shifts in the nature and degree of nutrient limitation along canal-water gradients;
  3. quantify changes in key microbial, periphyton, and plant processes along these gradients;
  4. link changes in biota and process rates to water chemistry changes caused by canal-water intrusion through field experimentation.

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
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: Paul McCormick
Phone: 304.724.4478
FAX: 304.724.4465
Task Status: Active
Task priority: High
Time Frame for Task 1: FY04-FY07
Task Personnel: Paul McCormick
Task Summary and Objectives: The Refuge has established a conductivity monitoring network to document spatial and temporal patterns of canal-water intrusion. Twelve of these monitoring sites, located along an east-west gradient of canal influence across the center of the Refuge, were selected for more intensive sampling, including characterization of soil and porewater nutrients, nutrient cycling rates, and periphyton and plant communities and productivity. The objective of this sampling is to understand ecological changes associated with different levels of canal influence.

Work to be undertaken during the proposal year and a description of the methods and procedures:
Dataloggers will continue to be deployed to obtain nearly continuous measurements of surface-water conductivity. The Refuge will continue monthly water-quality sampling. Levels of total and available soil nutrients will be measured using a combination of methods (e.g., extractions, ion-exchange membranes, porewater sampling). These measurements will build on soil N and P fractionations performed in FY04 and provide additional information for assessing changes in nutrient availability and its contribution to vegetation shifts along this gradient (see task 3 below).

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
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: Paul McCormick
Phone: 304.724.4478
FAX: 304.724.4465
Task Status: Active
Task priority: High
Time Frame for Task 2: FY04-FY07
Task Personnel: Paul McCormick
Task Summary and Objectives: Sawgrass litter was collected from all 12 transect stations in May 2004, air dried and weighed in the lab, and used to fill mesh bags that were returned to the sites in August. Litter collected from each site was returned to the same site to measure site-specific decomposition (loss of mass) and nutrient recycling (loss of N and P content) rates over a 3-year period. Litter from the lowest conductivity site (LOX8), which is believed to have the lowest nutrient content (to be determined in the lab) due to the lack of canal influence, was also placed at 4 other sites with increasing levels of canal influence to assess the effect of water chemistry (i.e., increasing nutrient concentrations) on these rates. Finally, litter from these other four sites was also placed at LOX8 to assess the influence of litter chemistry (i.e., increasing nutrient content related to canal-water intrusion) on these rates. Sawgrass decomposition rates are typically quite slow, and it will be 1-2 years before patterns will emerge from this study. In order to obtain a “quick and dirty” assessment of the effects of canal-water intrusion on potential decomposition rates, strips of standardized cotton (i.e., cellulose) fabric were deployed in sawgrass and slough habitats in August 2004. This procedure has been widely used for this same purpose in other wetland studies. The hypothesis being tested is that increasing levels of canal influence (i.e., higher conductivity) result in faster rates of decomposition and N and P recycling as a result of increased nutrient inputs.

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
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: Paul McCormick
Phone: 304.724.4478
FAX: 304.724.4465
Task Status: Proposed
Task priority: High
Time Frame for Task 3: FY05-FY06
Task Personnel: Paul McCormick
Task Summary and Objectives: While P appears to be the primary nutrient limiting primary productivity in the Refuge interior, it is possible that other elements such as N, K, and micronutrients may be co-limiting to plant growth. Increased mineral loading may indirectly affect the bioavailability of P and other plant nutrients by affecting microbial and geochemical processes that sequester P. Mineralization may also inhibit the growth of soft-water plant and periphyton species that are intolerant of high mineral concentrations. Changes in limiting nutrient and mineral concentrations may thus affect vegetation composition and production and, consequently, landscape patterns (e.g., shifts in the proportion of emergent vs. open-water habitat).

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
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: Paul McCormick
Phone: 304.724.4478
FAX: 304.724.4465
Task Status: Active
Task priority: High
Time Frame for Task 4: FY05-FY07
Task Personnel: Paul McCormick
Task Summary and Objectives: Controlled mineral additions will be initiated at a minimally impacted location in the Refuge interior to experimentally determine effects of varying levels and durations of canal-water intrusion on marsh processes and vegetation patterns. The information gained from this experiment will be critical to establishing cause-effect relationships between canal-water intrusion and ecological changes. Fifteen experimental plots have been dosed monthly since March 2005 with a mineral solution containing the major ions Ca, Cl, K, Mg, N, Na and S in a ratio similar to that for canal water. 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.

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
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: Paul McCormick
Phone: 304.724.4478
FAX: 304.724.4465
Task Status: Active
Task priority: High
Time Frame for Task 5: FY06-FY07
Task Personnel: Paul McCormick
Task Summary and Objectives: The effects of canal-water intrusion on P cycling rates at interior (i.e., P generally at background levels) Refuge locations will be examined using a series of laboratory incubations beginning in FY06. This work was originally slated to begin in FY05 but was postponed in order to begin preparation of a white paper on peatland responses to increased mineral loading at the request of the Refuge (see FY05 task 5 above). The occurrence of temporarily elevated P concentrations or “excursions” at some interior Refuge locations, generally those with the lowest conductivity levels, in recent years is of great concern to Refuge and water managers and has potentially significant regulatory and legal implications that could affect Everglades restoration. One hypothesis to be tested here is that interior sites with elevated conductivity levels exhibit greater P limitation and, therefore, tighter P cycling than low conductivity sites. If true, this would explain the tendency for P excursions to occur at the most interior locations. It is also likely that hydrology (e.g., flooded vs. saturated vs. drying soil conditions) affects the potential for soil P 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
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: Paul McCormick
Phone: 304.724.4478
FAX: 304.724.4465
Task Status: Active
Task priority: Medium
Time Frame for Task 6: FY06-FY07
Task Personnel: Paul McCormick, Bill Orem
Task Summary and Objectives: Results of the synoptic survey (FY04) indicated that nutrient levels in the surface soil-litter layer may be a more sensitive indicator of the effects of canal-water intrusion on Refuge chemistry compared with routine measurements of water chemistry. This is especially true for areas that receive periodic pulses of canal water as opposed to continue exposure. At such sites, elevated nutrient levels may persist in the surface soils despite a rapid return of surface-water chemistry to ambient conditions. Experiments will be performed to assess the potential for surface soils to accumulate P and non-P nutrients (e.g., Ca, N, S) in response to pulsed vs. continuous exposure to canal water. These experiments will test the perception that transient water-quality excursions (e.g., temporarily elevated concentrations of P or other nutrients) in the Refuge interior have no lasting effect on marsh biogeochemistry. If initial experiments during FY06 show the potential for significant accumulation and retention of soil nutrients in response to pulsed dosing, then additional experiments will be designed in FY07 to understand the ecological significance of this enrichment.

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
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: Bill Orem
Phone: 703.648.6273
FAX:
Task Status: Active
Task priority: High
Time Frame for Task 7: FY06
Task Personnel: Bill Orem, Paul McCormick
Task Summary and Objectives: The purpose of this scoping study will be to examine changes in chemical constituents through time in soil cores as a means of reconstructing historic water quality conditions in the Refuge. Wetland soils often provide a record of past environmental conditions through storage of chemical (inorganic and organic) and biological (pollen, shells) markers. Interpretation of this record is not usually straightforward, however, and may be hampered by an absence of modern analog studies, and resetting of chemical signals by diagenetic processes. Nevertheless, paleoecological studies have frequently been successful at providing important information on past conditions. Such information can provide managers with concrete goals for restoring and maintaining water quality.

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
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: Paul McCormick
Phone: 304.724.4478
FAX: 304.724.4465
Task Status: Active
Task priority: High
Time Frame for Task 8: FY05-FY06
Task Personnel: Paul McCormick
Task Summary and Objectives: Additional sampling and experimentation was proposed during FY05 to fill selected data gaps identified during the initial development of the white paper. Field sampling under this task was completed in FY05.

Work to be undertaken during the proposal year and a description of the methods and procedures:
Samples from this work still need to be processed and analyzed using ICP (under contract) and for NCS (in-house). An greenhouse experiment examining effects of soil mineral enrichment on sawgrass growth will be conducted during the fall of FY06 as proposed in the FY05 addendum.

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
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: Paul McCormick
Phone: 304.724.4478
FAX: 304.724.4465
Task Status: Active
Task priority: High
Time Frame for Task 9: FY05-FY07
Task Personnel: Paul McCormick
Task Summary and Objectives: Substantial data collection occurred during FY05 and attention will be focused in FY06 on entering, interpreting, and disseminating these data in peer-review manuscrips and scientific presentations. At the request of the Refuge, a document is being prepared that reviews available information on peatland ecology with respect to mineral gradients and relates it to existing evidence for the ecological effects of mineral enrichment in the Everglades.

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



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