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Title: Long-term patterns and trends in water column biogeochemistry in a changing environment
Water column nutrient concentrations and autotrophy in oligotrophic ecosystems are sensitive to eutrophication and other long-term environmental changes and disturbances. Disturbance can be defined as an event or process that changes the structure and response of an ecosystem to other environmental drivers. The role disturbance plays in regulating ecosystem functions is challenging because the effect of the disturbance can vary in magnitude, duration, and extent spatially and temporally. We measured changes in total nitrogen (TN), dissolved inorganic nutrient (DIN), total phosphorus (TP), soluble reactive phosphorus (SRP), total organic carbon (TOC), and chlorophyll-a (Chl-a) concentrations throughout the Everglades, Florida Bay, and the Florida Keys. This region has been subjected to a variety of natural and anthropogenic disturbances including tropical storms, fires, eutrophication, and rapid increases in water levels from sea-level rise and freshwater restoration. We hypothesized that the rate of change in water quality would be greatest in the coastal ecotone where disturbance frequencies and marine P concentrations are highest, and in freshwater marshes closest to hydrologic changes from restoration. We applied trend analyses on multi-decadal data (1996–2019) collected from 461 locations distributed from inland freshwater Everglades (ridge and slough) to outer marine reefs along the Florida Keys, USA. Total Organic Carbon decreased throughout the study area and was the only parameter with a systematic trend throughout the study area. All other parameters had spatially heterogeneous patterns in long-term trends. Results indicate more variability across a large spatial and temporal extent associated with changes in biogeochemical indicators and water quality conditions. Chemical and biological changes in oligotrophic ecosystems are important indicators of environmental change, and our regional ridge-to-reef assessment revealed ecosystem-specific responses to both long-term environmental changes and disturbance legacies. more »« less
Park, Joseph; Saberski, Erik; Stabenau, Erik; Sugihara, George
(, PLOS ONE)
Doi, Hideyuki
(Ed.)
A central tenant of the Comprehensive Everglades Restoration Plan (CERP) is nutrient reduction to levels supportive of ecosystem health. A particular focus is phosphorus. We examine links between agricultural production and phosphorus concentration in the Everglades headwaters: Kissimmee River basin and Lake Okeechobee, considered an important source of water for restoration efforts. Over a span of 47 years we find strong correspondence between milk production in Florida and total phosphate in the lake, and, over the last decade, evidence that phosphorus concentrations in the lake water column may have initiated a long-anticipated decline.
Sarker, Shishir K.; Kominoski, John S.; Gaiser, Evelyn E.; Scinto, Leonard J.; Rudnick, David T.
(, Restoration Ecology)
Wetland restoration requires managing long‐term changes in hydroperiod and ecosystem functions. We quantified relationships among spatiotemporal variability in wetland hydrology and total phosphorus (TP) and its stoichiometric relationships with total organic carbon (TOC:TP) and total carbon (TC:TP) and total nitrogen (TN:TP) in water, flocculent organic matter (floc), periphyton, sawgrass (Cladium jamaicense), and soil during early phases of freshwater wetland restoration—water year (WY) 2016 (1 May, 2015 to 30 April, 2016) to WY 2019—in Everglades National Park (ENP, Homestead, FL, U.S.A.). Wetland hydroperiod increased by 87 days, following restoration actions and rainfall events that increased median stage in the upstream source canal. Concentrations of TP were highest and most variable at sites closest (<1 km) to canal inputs and upstream wetland sources of legacy P. Surface water TOC:TP and TN:TP ratios were highest in wetlands >1 km downstream of the canal in wet season 2015 with spatial variability reflecting disturbances including droughts, fires, and freeze events. The TP concentrations of flocculent soil surface particles, periphyton, sawgrass, and consolidated soil declined, and TC:TP and TN:TP ratios increased (except soil) logarithmically with downstream distance from the canal. We measured abrupt increases in periphyton (wet season 2018) and sawgrass TP (wet season 2015 and 2018) at sites <1 km from the canal, likely reflecting legacy TP loading. Our results suggest restoration efforts that increase freshwater inflow and hydroperiod will likely change patterns of nutrient concentrations among water and organic matter compartments of wetlands as a function of nutrient legacies.
Kominoski, John S.; Gaiser, Evelyn E.; Castañeda‐Moya, Edward; Davis, Stephen E.; Dessu, Shimelis B.; Julian, II, Paul; Lee, Dong Yoon; Marazzi, Luca; Rivera‐Monroy, Victor H.; Sola, Andres; et al
(, Ecology)
Abstract Long‐term ecological research can resolve effects of disturbance on ecosystem dynamics by capturing the scale of disturbance and interactions with environmental changes. To quantify how disturbances interact with long‐term directional changes (sea‐level rise, freshwater restoration), we studied 17 yr of monthly dissolved organic carbon (DOC), total nitrogen (TN), and phosphorus (TP) concentrations and bacterioplankton productivity across freshwater‐to‐marine estuary gradients exposed to multiple disturbance events (e.g., droughts, fire, hurricanes, and low‐temperature anomalies) and long‐term increases in water levels. By studying two neighboring drainages that differ in hydrologic connectivity, we additionally tested how disturbance legacies are shaped by hydrologic connectivity. We predicted that disturbance events would interact with long‐term increases in water levels in freshwater and marine ecosystems to increase spatiotemporal similarity (i.e., synchrony) of organic matter, nutrients, and microbial activities. Wetlands along the larger, deeper, and tidally influenced Shark River Slough (SRS) drainage had higher and more variable DOC, TN, and TP concentrations than wetlands along the smaller, shallower, tidally restricted Taylor River Slough/Panhandle (TS/Ph) drainage. Along SRS, DOC concentrations declined with proximity to coast, and increased in magnitude and variability following drought and flooding in 2015 and a hurricane in 2017. Along TS/Ph, DOC concentrations varied by site (higher in marine than freshwater wetlands) but not year. In both drainages, increases in TN from upstream freshwater marshes occurred following fire in 2008 and droughts in 2010 and 2015, whereas downstream increases in TP occurred with coastal storm surge from hurricanes in 2005 and 2017. Decreases in DOC:TN and DOC:TP were explained by increased TN and TP. Increases in bacterioplankton productivity occurred throughout both drainages following low‐temperature events (2010 and 2011) and a hurricane (2017). Long‐term TN and TP concentrations and bacterioplankton productivity were correlated (r > 0.5) across a range of sampling distances (1–50 km), indicating spatiotemporal synchrony. DOC concentrations were not synchronized across space or time. Our study advances disturbance ecology theory by illustrating how disturbance events interact with long‐term environmental changes and hydrologic connectivity to determine the magnitude and extent of disturbance legacies. Understanding disturbance legacies will enhance prediction and enable more effective management of rapidly changing ecosystems.
Net ecosystem carbon balance is a comprehensive assessment of ecosystem function that can test restoration effectiveness. Coastal peatlands are globally important carbon sinks that are vulnerable to carbon loss with saltwater intrusion. It is uncertain how wetland carbon stocks and fluxes change during freshwater restoration following exposure to saltwater and elevated nutrients. We restored freshwater to sawgrass (Cladium jamaicense) peat monoliths from freshwater marshes of the Everglades (Florida, U.S.A.) that had previously been exposed to elevated salinity (approximately9 ppt) and phosphorus (P) loading (1 g P m−2year−1) in wetland mesocosms. We quantified changes in water and soil physicochemistry, plant and soil carbon and nutrient standing stocks, and net ecosystem productivity during restoration. Added freshwater immediately reduced porewater salinity from >8 to approximately 2 ppt, but elevated porewater dissolved organic carbon persisted. Above‐ and belowground biomass, leaf P concentrations, and instantaneous rates of gross ecosystem productivity (GEP) and ecosystem respiration (ER) remained elevated from prior added P. Modeled monthly GEP and ER were higher in marshes with saltwater and P legacies, resulting in negative net ecosystem productivities that were up to 12× lower than controls. Leaf litter breakdown rates and litter P concentrations were 2× higher in marshes with legacies of added saltwater and P. Legacies of saltwater and P on carbon loss persisted despite freshwater restoration, but recovery was greatest for freshwater marshes exposed to saltwater alone. Our results suggest that restoration in nutrient‐limited freshwater wetlands exposed to saltwater intrusion and nutrient enrichment is a slow process.
Dissolved organic matter (DOM) drives biogeochemical processes in aquatic ecosystems. Yet, how hydrologic restoration in nutrient‐enriched ecosystems changes DOM and the consequences of those changes for the carbon cycle remain unclear. To predict the consequences of hydrologic restoration on carbon cycling in restored wetlands, we need to understand how local environmental factors influence production, processing, and transport of DOM. We collected surface water samples along transects in restored peat (organic‐rich, macrophyte‐dominated) and marl (carbonate, periphyton‐dominated) freshwater marshes in the Everglades (Florida, U.S.A.) that varied in environmental factors (water depth, phosphorus [P] concentrations [water, macrophytes, periphyton, and soil], and primary producer biomass) to understand drivers of dissolved organic carbon (DOC) concentrations and DOM composition. Higher water depths led to a “greening” of DOM, due to increasing algal contributions, with decreasing concentrations of DOC in peat wetlands, and a “browning” of DOM, due to increasing humic contributions, with increasing DOC concentrations in marl wetlands. Soil total P was positively correlated with DOC concentrations and microbial contributions to DOM in peat wetlands, and periphyton total P was positively correlated with algal contributions to DOM in marl wetlands. Despite large variations in both vegetation biomass and periphyton biovolume across transects and sites, neither were predictors of DOC concentrations or DOM composition. Hydrologic restoration differentially alters DOM in peat and marl marshes and interacts with nutrient enrichment to shift proportions of green and brown contributions to surface water chemistry, which has the potential to modify wetland food webs, as well as the processing of carbon by micro‐organisms.
Julian, Paul, Fourqurean, James W, Davis, Stephen E, Surratt, Donatto, Gaiser, Evelyn E, Kominoski, John S, Troxler, Tiffany G, Boyer, Joseph N, Thomas, Serge, Briceño, Henry O, Madden, Christopher J, Montes, Enrique, and Kelble, Chris R. Long-term patterns and trends in water column biogeochemistry in a changing environment. Retrieved from https://par.nsf.gov/biblio/10534389. Estuarine, Coastal and Shelf Science 306.C Web. doi:10.1016/j.ecss.2024.108896.
Julian, Paul, Fourqurean, James W, Davis, Stephen E, Surratt, Donatto, Gaiser, Evelyn E, Kominoski, John S, Troxler, Tiffany G, Boyer, Joseph N, Thomas, Serge, Briceño, Henry O, Madden, Christopher J, Montes, Enrique, & Kelble, Chris R. Long-term patterns and trends in water column biogeochemistry in a changing environment. Estuarine, Coastal and Shelf Science, 306 (C). Retrieved from https://par.nsf.gov/biblio/10534389. https://doi.org/10.1016/j.ecss.2024.108896
Julian, Paul, Fourqurean, James W, Davis, Stephen E, Surratt, Donatto, Gaiser, Evelyn E, Kominoski, John S, Troxler, Tiffany G, Boyer, Joseph N, Thomas, Serge, Briceño, Henry O, Madden, Christopher J, Montes, Enrique, and Kelble, Chris R.
"Long-term patterns and trends in water column biogeochemistry in a changing environment". Estuarine, Coastal and Shelf Science 306 (C). Country unknown/Code not available: Elsevier. https://doi.org/10.1016/j.ecss.2024.108896.https://par.nsf.gov/biblio/10534389.
@article{osti_10534389,
place = {Country unknown/Code not available},
title = {Long-term patterns and trends in water column biogeochemistry in a changing environment},
url = {https://par.nsf.gov/biblio/10534389},
DOI = {10.1016/j.ecss.2024.108896},
abstractNote = {Water column nutrient concentrations and autotrophy in oligotrophic ecosystems are sensitive to eutrophication and other long-term environmental changes and disturbances. Disturbance can be defined as an event or process that changes the structure and response of an ecosystem to other environmental drivers. The role disturbance plays in regulating ecosystem functions is challenging because the effect of the disturbance can vary in magnitude, duration, and extent spatially and temporally. We measured changes in total nitrogen (TN), dissolved inorganic nutrient (DIN), total phosphorus (TP), soluble reactive phosphorus (SRP), total organic carbon (TOC), and chlorophyll-a (Chl-a) concentrations throughout the Everglades, Florida Bay, and the Florida Keys. This region has been subjected to a variety of natural and anthropogenic disturbances including tropical storms, fires, eutrophication, and rapid increases in water levels from sea-level rise and freshwater restoration. We hypothesized that the rate of change in water quality would be greatest in the coastal ecotone where disturbance frequencies and marine P concentrations are highest, and in freshwater marshes closest to hydrologic changes from restoration. We applied trend analyses on multi-decadal data (1996–2019) collected from 461 locations distributed from inland freshwater Everglades (ridge and slough) to outer marine reefs along the Florida Keys, USA. Total Organic Carbon decreased throughout the study area and was the only parameter with a systematic trend throughout the study area. All other parameters had spatially heterogeneous patterns in long-term trends. Results indicate more variability across a large spatial and temporal extent associated with changes in biogeochemical indicators and water quality conditions. Chemical and biological changes in oligotrophic ecosystems are important indicators of environmental change, and our regional ridge-to-reef assessment revealed ecosystem-specific responses to both long-term environmental changes and disturbance legacies.},
journal = {Estuarine, Coastal and Shelf Science},
volume = {306},
number = {C},
publisher = {Elsevier},
author = {Julian, Paul and Fourqurean, James W and Davis, Stephen E and Surratt, Donatto and Gaiser, Evelyn E and Kominoski, John S and Troxler, Tiffany G and Boyer, Joseph N and Thomas, Serge and Briceño, Henry O and Madden, Christopher J and Montes, Enrique and Kelble, Chris R},
}
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