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publications > paper > phosphorus cycling and partitioning in an oligotrophic Everglades wetland ecosystem: a radioisotope tracing study
Phosphorus cycling and partitioning in an oligotrophic Everglades wetland ecosystem: a radioisotope tracing study
Gregory B. Noe*, Leonard J . Scinto*, Jonathan Taylor*,‡, Daniel L. Childers*,† and Ronald D. Jones*,†
*Southeast Environmental Research Center, Florida International University, Miami, FL, U.S.A.
†Department of Biological Sciences, Florida International University, Miami, FL, U.S.A.
‡Present address: Everglades National Park, Daniel Beard Research Center, Homestead, FL, U.S.A.
Correspondence: Gregory B. Noe, U.S. Geological Survey,
430 National Center, Reston, VA 20192, U.S.A.
E-mail: gnoe@usgs.gov
Summary
- Our goal was to quantify short-term phosphorus (P) partitioning and identify the
ecosystem components important to P cycling in wetland ecosystems. To do this, we
added P radiotracer to oligotrophic, P-limited Everglades marshes. 32PO4 was added to the
water column in six 1-m2 enclosed mesocosms located in long-hydroperiod marshes of
Shark River Slough, Everglades National Park. Ecosystem components were then
repeatedly sampled over 18 days.
- Water column particulates (>0.45 µm) incorporated radiotracer within the first minute
after dosing and stored 95-99% of total water column 32P activity throughout the study.
Soluble (<0.45 µm) 32P in the water column, in contrast, was always <5% of the 32P in
surface water. Periphyton, both floating and attached to emergent macrophytes, had the
highest specific activity of 32P (Bq g-1 31P) among the different ecosystem components.
Fish and aquatic macroinvertebrates also had high affinity for P, whereas emergent
macrophytes, soil and flocculent detrital organic matter (floc) had the lowest specific
activities of radiotracer.
- Within the calcareous, floating periphyton mats, 81% of the initial 32P uptake was
associated with Ca, but most of this 32P entered and remained within the organic pool
(Ca-associated = 14% of total) after 1 day. In the floc layer, 32P rapidly entered the
microbial pool and the labile fraction was negligible for most of the study.
- Budgeting of the radiotracer indicated that 32P moved from particulates in the water
column to periphyton and floc and then to the floc and soil over the course of the 18 days
incubations. Floc (35% of total) and soil (27%) dominated 32P storage after 18 days, with
floating periphyton (12%) and surface water (10%) holding smaller proportions of total
ecosystem 32P.
- To summarise, oligotrophic Everglades marshes exhibited rapid uptake and retention of
labile 32P. Components dominated by microbes appear to control short-term P cycling in
this oligotrophic ecosystem.
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| Figure 1. Specific activity of 32P in unfiltered surface water (total) and partitioning of total surface water activity into the particulate and
soluble fractions (fractions) (mean ± 1 SE) through time. [larger version] |
Related information:
SOFIA Project: Effect of Water Flow on Transport of Solutes, Suspended Particles, and Particle-Associated Nutrients in the Everglades Ridge and Slough Landscape
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