Phosphorus cycling and partitioning in an oligotrophic Everglades wetland ecosystem: a radioisotope tracing study

Abstract

Summary 1. 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. 2. 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−131P) 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. 3. 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. 4. 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 day 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. 5. 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.

Variation in soil phosphorus, sulfur, and iron pools among south Florida wetlands

“…sources from coastal ocean water, terrestrial runoff and groundwater, atmospheric deposition), much of the variation in soil storage of phosphorus is due to variation in the carbonate-bound P pool (Zhang et al 2004), even though short-term P storage occurs in organic plant and periphyton pools (McCormick et al 1996;Dodds 2003;Noe et al 2003). …”

Local Biomass Control on the Composition and Reactivity of Particulate Organic Matter in Aquatic Environments

“…In the wetlands of the FCE, detritus is expected to play a dominant role in carbon and energy flows. Noe et al (2003) found that floc is a strong regulator of phosphorus cycling in this oligotrophic environment. Noe et al (2002) tested the response of several ecosystem components to continuous, low-level phosphorus additions.…”

“…In the Everglades, floc has been defined as a heterogeneous mixture containing senescing periphyton, decaying macrophyte tissue, soil particles, algae and bacteria (DeBusk et al, 2001;Noe et al, 2003). A biomarker-based study by showed that floc composition in the FCE is regulated regionally by local vegetation inputs, particularly from periphyton, emergent and submerged plants and terrestrial plant detritus such as mangroves.…”

Dynamics of Ecosystem Metabolism and Flocculent Detritus Transport in Estuarine Taylor River

“…In oligotrophic ecosystems, such as Everglades wetlands, nutrients are often found immobilized in organic forms and are quickly recycled following remineralization , Noe et al 2003). Thus, mobile organic compartments of these ecosystems provide a means by which nutrients can be transported across the landscape.…”

“…Nutrients therefore spend little time in inorganic forms in oligotrophic ecosystems, such as the extremely phosphorus (P)-deficient Taylor River estuary . Several studies have linked Everglades floc organic matter (OM) to local wetland primary producers , including periphyton , Noe et al 2003, a complex associate of algae, bacteria, and fungi abundant throughout the Everglades, and submerged aquatic vegetation, particularly free-floating bladderwort (Utricularia spp. ;…”