Abstract
BackgroundEvaluation of carbon (C), nitrogen (N), and phosphorus (P) ratios in aquatic and terrestrial ecosystems can advance our understanding of biological processes, nutrient cycling, and the fate of organic matter (OM) in these ecosystems. Eutrophication of aquatic ecosystems can change the accumulation and decomposition of OM which can alter biogeochemical cycling and alter the base of the aquatic food web. This study investigated nutrient stoichiometry within and among wetland ecosystem compartments (i.e., water column, flocculent, soil, and aboveground vegetation biomass) of two subtropical treatment wetlands with distinct vegetation communities. Two flow-ways (FWs) within the network of Everglades Stormwater Treatment Areas in south Florida (USA) were selected for this study. We evaluated nutrient stoichiometry of these to understand biogeochemical cycling and controls of nutrient removal in a treatment wetland within an ecological stoichiometry context.ResultsThis study demonstrates that C, N, and P stoichiometry can be highly variable among ecosystem compartments and between FWs. Power law slopes of C, N, and P within surface water floc, soil, and vegetation were significantly different between and along FWs.ConclusionsAssessment of wetland nutrient stoichiometry between and within ecosystem compartments suggests unconstrained stoichiometry related to P that conforms with the notion of P limitation in the ecosystem. Differences in N:P ratios between floc and soil suggest different pathways of organic nutrient accumulation and retention between FWs. Surface nutrient stoichiometry was highly variable and decoupled (or close to decoupled as indicated by < 25% explained variation between parameters), in particular with respect to P. We hypothesize that decoupling may be the imprint of variability in inflow nutrient stoichiometry. However, despite active biogeochemical cycles that could act to restore nutrient stoichiometry along the FW, there was little evidence that such balancing occurred, as the degree of stochiometric decoupling in the water column did change with distance downstream. This information is only the beginning of a larger journey to understand stoichiometric processes within wetland ecosystems and how they relate to ecosystem function.
Highlights
The study of nutrient stoichiometry, pioneered by Redfield (1934, 1958), laid the foundation of two important biogeochemical principles that later became basic tenets of ecological stoichiometry: (1) organisms have consistent carbon (C), nitrogen (N), and phosphorus (P) molar ratios and (2) the abundance of C, N, and P in a system is regulated by interactions between organisms and their environment
Our objective is to evaluate overall nutrient relationships (i.e., C × N, C × P, and N × P) within surface water, soil flocculent material, recently accreted soil, and vegetation live aboveground biomass (AGB) between two FWs, one dominated by emergent aquatic vegetation (EAV) and the other by submerged aquatic vegetation (SAV)
Everglades stormwater treatment areas (STAs) treatment cells are comprised of a mixture of EAV and SAV communities in several configurations including EAV and SAV treatment cells arranged in parallel or in series (Chen et al 2015)
Summary
The study of nutrient stoichiometry, pioneered by Redfield (1934, 1958), laid the foundation of two important biogeochemical principles that later became basic tenets of ecological stoichiometry: (1) organisms have consistent carbon (C), nitrogen (N), and phosphorus (P) molar ratios and (2) the abundance of C, N, and P in a system is regulated by interactions between organisms and their environment. These principles were supported by the similarity of measured N and P concentrations in marine plankton relative to the ratio of mineral forms of N (as nitrate [NO3]), P (as phosphate [PO4]), and non-calcite inorganic C in deep ocean water (Redfield 1934, 1958). We evaluated nutrient stoichiometry of these to understand biogeochemical cycling and controls of nutrient removal in a treatment wetland within an ecological stoichiometry context
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