Florida Coastal Everglades LTER - Current Working Groups

Florida Coastal Everglades Long Term Ecological Research

Florida Coastal Everglades LTER - Current Working Groups
Current Working Groups

The current phase of the FCE LTER program is organized into four working groups and four cross-cutting themes. Each working group or cross-cutting theme focuses on a set of key research questions and/or major processes being quantified by the LTER program.

Working Groups

• Primary Production
• Trophic Dynamics and Community Structure
• Biogeochemical Cycling
• Organic Matter Dynamics

Cross-cutting Themes

• Modeling and Synthesis
• Human Dimensions
• Climate and Disturbance
• Hydrology

View Former Working Groups
(FCE I, 2000-2006)

Untitled Document

Primary Production Working Group

Findings

To investigate primary production, or the amount of living material produced when nutrients and energy from sunlight are used to create plant tissues, researchers collected data along two of the Everglades� major drainage basins: Shark River Slough, which empties into the Gulf of Mexico, and Taylor Slough, which drains to Florida Bay. Previous work had shown that the estuarine ecotone at the end of the Shark River Slough drainage basin is characterized by higher rates of plant and animal productivity than upstream oligotrophic, or nutrient-poor, marshes due to the presence of phosphorus-rich marine water. But FCE-LTER scientists believed that the Taylor Slough/Florida Bay estuarine ecotone would exhibit a lower rate of productivity compared to the Shark River Slough/Gulf of Mexico ecotone because Florida Bay has dense seagrass beds that can sequester phosphorus and low tidal action that can inhibit marine phosphorus from entering the estuarine ecotone. The hypothesis, however, proved to be incorrect; productivity in the Taylor Slough ecotone was higher than expected.

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Detailed Findings:

Sharon Ewe sampling seedling regeneration in a forest gap

Tagged tree damaged by Hurricane Wilma

A. The role of "gaps" or canopy openings in mangrove forests is apparently critical in shaping the structural properties of mangrove forest, particularly in forests where tree height is greater than 8m (Shark River). Since these gaps are created by lighthing and hurricanes, which are common natural disturbances in the ENP, FCE LTER scientists will evaluate how forest gaps affect nutrient and carbon cycling at different temporal and spatial scales in the ecotone zone. The recent effect of hurricane Wilma (August 2005) in some sampling stations along Shark River allows the design of experiments to test hypotheses related to succession, zonation, and productivity patterns in mangrove forest of subtropical latitudes.

B. Peaks in mangrove production in the oligohaline zone are driven by soil P availability (Chen & Twilley 1999) that may be supplemented by shallow coastal groundwater discharge (Price et al., 2006). Soil P content in lower Taylor Slough is low at TS/Ph-6 (upper ecotone) and higher at TS/Ph-7 and 8 (lower ecotone; Mancera-Pineda 2003; Chambers & Pederson 2006), while porewater soluble reactive P (SRP) concentrations from these two sites are similar (Rivera-Monroy unpubl.data). Fine root biomass at TS/Ph ecotone sites is higher than at the SRS sites, suggesting increased plant "foraging" for P, a subsurface P source, or both. Ratios of fine root biomass to aboveground biomass (FRB:ABG) are also greater in sites with the lowest bulk soil P content. New isotopic evidence from the TS/Ph ecotone suggests a strong groundwater influence in aboveground mangrove tissues, compared with no groundwater signal in sawgrass growing at the same site. Productivity and biomass allocation measurements will continue at all mangrove sites using refined methods for estimating aboveground net primary productivity (ANPP) in the dwarf red mangrove (Rhizophora mangle L.) trees. FCE researchers are also planning a small-scale fertilization experiment to better understand how P availability controls dwarf R. mangle productivity and biomass allocation.

C. Primary production at freshwater FCE sites is dominated by sawgrass and periphyton, with highest rates of turnover occurring near the oligohaline ecotone, particularly along the TS/Ph transect (Ewe et al. 2006; Iwaniec et al. 2006). Very high rates of periphyton production have been measured near the TS/Ph ecotone (up to 18000 g C m-2 yr-1; Iwaniec et al. 2006). FCE LTER scientists expect that these hydrologic changes resulting from water management will lead to a decline in sawgrass ANPP (Childers et al. 2006b) and a shift from soil-associated periphyton communities (where P supply is relatively enhanced) to water column or plant-associated communities (where P supply is relatively depleted). Measurements of sawgrass ANPP and periphyton productivity will continue at freshwater FCE sites as per Childers et al. (2006b) and Iwaniec et al. (2006), with modifications suggested by Ewe et al. (2006). Specifically, FCE LTER scientists have found that quantifying periphyton productivity requires a variety of approaches, including biomass accumulation on artificial substrates and light-dark bottle biological oxygen demand (BOD), but with added emphasis on the latter method because it generates the lowest variance in estimates (Hall et al. 2006).

References

Chambers, R.M. and K.A. Pederson, 2006. Variation in soil phosphorus, sulfur, and iron pools among south Florida wetlands. Hydrobiologia, 569(1): 63-70.

Chen, R. and R.R. Twilley, 1999. Patterns of mangrove forest structure associated with soil nutrient dynamics along the Shark River estuary. Estuaries, 22(4): 955-970.

Childers, D.L., D. Iwaniec, D. Rondeau, G.A. Rubio, E. Verdon, and C.J. Madden, 2006. Responses of sawgrass and spikerush to variation in hydrologic drivers and salinity in southern Everglades marshes. Hydrobiologia, 569(1): 273-292.

Ewe, S.M.L., E.E. Gaiser, D.L. Childers, D. Iwaniec, V.H. Rivera-Monroy, and R.R. Twilley, 2006. Spatial and temporal patterns of aboveground net primary productivity (ANPP) along two freshwater-estuarine transects in the Florida Coastal Everglades . Hydrobiologia, 569(1): 459-474.

Hall, R.O., S.E. Thomas, and E.E. Gaiser, 2007. Measuring primary production in freshwater ecosystems . In T.J. Fahey and A.K. Knapp, (eds.) Principles and Standards for Measuring Net Primary Production in Long-Term Ecological Studies. Oxford University Press.

Iwaniec, D., D.L. Childers, D. Rondeau, C.J. Madden, and C.J. Saunders, 2006. Effects of hydrologic and water quality drivers on periphyton dynamics in the southern Everglades. Hydrobiologia, 569(1): 223-235.

Mancera-Pineda, Jose Ernesto 2003. The Contribution of Mangrove Outwelling to Coastal Food Webs as a Function of Environmental Settings. Ph.D. dissertation, University of Louisiana at Lafayette.

Price, R.M., P.K. Swart, and J.W. Fourqurean, 2006. Coastal groundwater discharge - an additional source of phosphorus for the oligotrophic wetlands of the Everglades. Hydrobiologia, 569(1): 23-36.

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This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DEB-1237517, #DBI-0620409, and #DEB-9910514. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
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