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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 2005 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
Principal Investigator: Paul McCormick, pmccormick@usgs.gov, 304.724.4478
Study Personnel: Carol Kendall ckendall@usgs.gov, 650.329.5603
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 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. A 12-station transect monitoring network was established in May 2004, and measurements of water chemistry and soil and plant nutrients began in August 2004. A transect-wide decomposition experiment was also initiated in August 2004. A field fertilization experiment is being designed and will be initiated in October 2004.

Recent Products:

Two abstracts summarizing results from the synoptic survey have been submitted for presentation at the National Conference on Ecosystem Restoration in Orlando in December 2004.

Planned Products:

Reports, peer-review manuscripts, 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
Budget and Time Frame for Task 1: FY04-FY07
Task Personnel:

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 be deployed semi-continuously throughout the year (when at least 10 cm of surface water is present) at each transect site to record water level, temperature, conductivity, pH, and dissolved oxygen. Refuge staff will assist with data logger deployments and maintenance. Soil and porewater nutrient chemistry will be sampled during February and August 2005. Ecological effects sampling will be conducted in Tasks 2, 3, and 6.

This task supports efforts A.R.M. under the 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):

September 2004 Begin data logger deployments
February 2005 Dry season sampling of soil and porewater chemistry
May 2005 Preliminary report on transect water quality and soil chemistry
August 2005 Wet season sampling of soil and porewater chemistry

Title of Task 2: Field experiment to quantify changes in decomposition and nutrient recycling 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
Budget and Time Frame for Task 2: FY04-FY07
Task Personnel:

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:

Cotton strips will be collected in September 2004 (after approximately 30 days of incubation) and tested in the lab to measure the loss of the fabric's tensile strength (due to microbial decomposition) in order to provide an indication of rates of microbial metabolism along the gradient of canal-water influence. Decomposition bags will be collected in November 2004 (month 3) and in February (month 6) and August 2005 (month 12). Samples will be processed in the laboratory to measure rates of plant mass and nutrient loss.

This task will provide information to help understand the ecological effects of water-quality changes caused by canal-water intrusion on Refuge resources.

Specific Task Product(s):

November 2004 Effects of water quality on wet season decomposition rates for cotton strips (surrogate substrate)
April 2005 Effects of water quality on dry season decomposition rates for cotton strips
September 2005 Preliminary report on effects of water quality on mass and nutrient loss rates for sawgrass litter

Title of Task 3: Field measurements to document changes in periphyton and plant productivity and species composition 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
Budget and Time Frame for Task 3: FY05-FY06
Task Personnel:

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. Furthermore, effects of increased nutrient levels on microbial processes (to be investigated in Task 5) may indirectly affect the bioavailability of P and other plant nutrients. Increasing levels of nutrient availability and primary productivity often result in shifts in vegetation composition (e.g., increased dominance of species capable of rapid growth at high nutrient levels) and landscape patterns (e.g., encroachment of macrophyte stands into open-water slough areas).

Work to be undertaken during the proposal year and a description of the methods and procedures:

This work will be performed in collaboration with the University of Florida at all 12 transect sites during the summer of 2005. The suite of measurements that will be used to measure rates of plant growth and primary productivity is still being developed but will likely include regrowth rates of sawgrass and slough vegetation in clip plots, tagging stems of fast growing species such as water lily to measure leaf turnover rates, and light-dark bottle incubations to measure periphyton productivity. Slough macrophyte and periphyton biomass and species composition at each transect site will also be characterized.

Specific Task Product(s):

January 2005 Develop collaborative work plan with University of Florida
June-September 2005 Conduct wet season field work

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
Budget and Time Frame for Task 4: FY04-FY07
Task Personnel:

Task Summary and Objectives:

Controlled additions of different nutrient combinations 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. The experiment will be designed to understand the effects of low and high levels of canal water intrusion in both the presence and absence of elevated P. Rather than attempting to recreate the exact chemical composition of canal water, we will focus on the effects of enrichment with a suite of major ions including Ca, Cl, K, Mg, N, Na and S. The experiment is not designed to quantify the ecological effects of specific nutrient concentrations, but rather to link increasing levels and durations of enrichment to changes in key ecological processes.

Work to be undertaken during the proposal year and a description of the methods and procedures:

Field enclosures and associated walkway structures are scheduled for completion in October 2004. Enclosures will be 3.7 m long and 1.2 m wide and will be established along a sawgrass-slough fringe such that a portion of each habitat is enclosed and exposed to dosing. Dosing will be initiated in November 2004 and performed monthly with the assistance of Refuge field staff. The dosing treatments are still being developed. Soils, plants and periphyton will be sampled prior to the first dosing event to document baseline nutrient levels and species composition in each plot. Plots will be sampled again in August and September 2005 for these same parameters and for rates of periphyton and microbial metabolism. Decomposition rates will also be measured at that time using standardized cotton strips (see description under Task 2). An effort will be made to involve other researchers in this experimental effort, e.g., USGS investigators studying effects of sulfur on marsh processes, SFWMD scientists with an interest in microbial enzyme activity and periphyton and plant processes, and University of Florida researchers with an interested in soil microbial processes.

Specific Task Product(s):

October 2004 Construct experimental plots
November 2004 Conduct baseline measurements and initiate dosing
Summer 2005 Begin periodic sampling to quantify ecological changes in response to dosing
Fall 2005 Preliminary assessment of ecological effects of mineralization on Refuge resources

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
Budget and Time Frame for Task 5: FY04-FY07
Task Personnel:

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 FY05. The occurrence of temporarily elevated P concentrations or “excursions” at some interior Refuge locations, generally those with the lowest conductivity levels, is of great concern to Refuge and water managers and has potentially significant regulatory and legal implications that could affect Everglades restoration. A major hypothesis of this study 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 P release to the water column and that water conditions during the past few years (including periods of extreme drought) have been conducive to this release, thus explaining the increased occurrence of elevated P at interior locations.

Work to be undertaken during the proposal year and a description of the methods and procedures:

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 for 24-h and filtered through a 0.2 um filter 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):

January 2005 Initiate experimentation
May 2005 Initial results concerning effects of hydrology on bioavailable P release from soils along canal-water gradients (phase 1)
July 2005 Initial results concerning effects of simulated water quality changes on bioavailable P release (phase 2)

Title of Task 6: Evaluating stable isotopes as indicators of biogeochemical and trophic shifts in response to canal-water intrusion
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task Leaders: Carol Kendall
Phone: 650.329.5603
FAX:
Task Status: Active
Task priority: Medium
Budget and Time Frame for Task 6: FY04-FY07
Task Personnel:

Task Summary and Objectives:

Stable isotope techniques have been used successfully in conjunction with other information to examine aquatic ecosystem responses (e.g., variations in food web base, trophic structure, and marsh biogeochemistry) to variations in hydrology and contaminant loading. Selected techniques will be applied here to detect changes in nutrient sources and food web structure along canal-water gradients and in response to experimental dosing of canal-water constituents (see Task 4).

Work to be undertaken during the proposal year and a description of the methods and procedures:

Sampling under this task will be finalized in October 2005, but will likely included analysis of N, C and S isotopic compositions of soils and biota (macrophytes, periphyton, and fauna) collected as part of transect and field experiment sampling.

This work will be focused on developing sensitive indicators of canal influence on biogeochemical processes and trophic structure within the Refuge interior. It is anticipated that such indicators will be applicable to other areas of the Everglades as well.

Specific Task Product(s):

To be determined.

Title of Task 7: 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
Budget and Time Frame for Task 7: FY04-FY07
Task Personnel:

Task Summary and Objectives:

This task accounts for travel and GE PES-funded salary related to the dissemination of the results of the other tasks described in this work plan.

Work to be undertaken during the proposal year and a description of the methods and procedures:

Results of work conducted during FY04 will be presented at the National Conference on Ecosystem Restoration (NCER) in Orlando, FL in December 2004. New data collected during FY05 will be analyzed as time allows in an effort to provide the Refuge with frequent brief reports on study progress and findings.

Specific Task Product(s):

Presentation of study findings at NCER conference in Orlando, FL in December 2004, various reports produced through the year as listed for previous tasks.



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