Carbon pool trends and dynamics within a subtropical peatland during long-term restoration

Abstract

Introduction: The Florida Everglades has undergone significant ecological change spanning the continuum of disturbance to restoration. While the restoration effort is not complete and the ecosystem continues to experience short duration perturbations, a better understanding of long-term C dynamics of the Everglades is needed to facilitate new restoration efforts. This study evaluated temporal trends of different aquatic carbon (C) pools of the northern Everglades Protection Area over a 20-year period to gauge historic C cycling patterns. Dissolved inorganic C (DIC), dissolved organic C (DOC), particulate organic C (POC), and surface water carbon dioxide (pCO 2(aq) ) were investigated between May 1, 1994 and April 30, 2015. Results: Annual mean concentrations of DIC, DOC, POC, and pCO 2(aq) significantly decreased through time or remained constant across the Water Conservation Areas (WCAs). Overall, the magnitude of the different C pools in the water column significantly differed between regions. Outgassing of CO 2 was dynamic across the Everglades ranging from 420 to 2001 kg CO 2 year −1 . Overall, the historic trend in CO 2 flux from the marsh declined across our study area while pCO 2(aq) largely remained somewhat constant with the exception of Water Conservation Area 2 which experienced significant declines in pCO 2(aq) . Particulate OC concentrations were consistent between WCAs, but a significantly decreasing trend in annual POC concentrations was observed. Conclusions: Hydrologic condition and nutrient inputs significantly influenced the balance, speciation, and flux of C pools across WCAs suggesting a subsidy-stress response in C dynamics relative to landscape scale responses in nutrient availability. The interplay between nutrient inputs and hydrologic condition exert a driving force on the balance between DIC and DOC production via the metabolism of organic matter which forms the base of the aquatic food web. Along the restoration trajectory as water quality and hydrology continues to improve, it is expected that C pools will respond accordingly.

The relative importance of photodegradation and biodegradation of terrestrially derived dissolved organic carbon across four lakes of differing trophic status

“…Differences between the responses observed in the Arctic and our temperate and subtropical lakes are most likely explained by the initial concentration and quality of terrestrially derived DOC and time. In the Arctic, glacial meltwater can be highly photolabile and dominated by seasonal inputs of DOC from shallow or deep soils (Cory et al, 2014;Spencer et al, 2014;and Kaiser et al, 2017). In temperate regions, DOC tends to contain more humic and fulvic acids derived from soils, which may be less photolabile than Arctic DOC.…”

“…However, DOC concentrations in Greenland lakes C. M. Dempsey et al: The relative importance of photodegradation and biodegradation (Saros et al, 2015) and the Mississippi River (Duan et al, 2017) have been decreasing. A long-term study of the Florida Everglades showed that some study sites were decreasing in DOC concentration, but the majority of sites were not changing (Julian et al, 2017). As DOC inputs into aquatic ecosystems have increased, stabilized, or decreased, long-term studies have focused on understanding the mechanisms behind the change, but less research has addressed the fate of DOC once it enters a lake.…”

Evaluation of nutrient stoichiometric relationships among ecosystem compartments of a subtropical treatment wetland. Do we have “Redfield wetlands”?

“…Water column parameters such as total P (TP), total N (TN), and dissolved organic C (DOC) were analyzed for these samples. In the Everglades system, the organic C pool is predominately composed of the DOC fraction with low particulate OC concentrations (Julian et al 2017), therefore the bias of not including particulates in the C analysis is small. Individual soil samples were collected along the flow transects twice during the dry and wet seasons between 2015 and 2016 using the push-core method consistent with prior wetland soil studies (Bruland et al 2007;Osborne et al 2011a;Newman et al 2017).…”

Stoichiometric homeostasis of wetland vegetation along a nutrient gradient in a subtropical wetland. Understanding stoichiometric mechanisms of nutrient retention in wetland macrophytes

“…For this study we used the water column parameters total P (TP), total N (TN), and dissolved organic C (DOC) (Villapando and King 2018). In the Everglades system, the surface water organic C pool is predominately composed of the DOC fraction with low particulate OC concentrations (Julian et al 2017), therefore total OC is assumed to be equivalent to DOC concentrations. We also made use of soil samples collected along the flow transects twice during the dry and wet seasons between 2015 and 2016 and analyzed for TP, TN, and TC.…”