This dataset includes field and laboratory measurements of surface waters, pore waters, sediment, and fish from Water Conservation Areas and adjacent canals of the Florida Everglades (USA). Water, sediment, and fish samples were collected from Water Conservation Areas 1 (Arthur R. Marshall Loxahatchee National Wildlife Refuge), 2, and 3 and neighboring canals between 2012 and 2019. The sites sampled in Water Conservation Areas 2 and 3 follow hydrologic flow paths. Field measurements reported for surface and pore waters include specific conductance, pH, dissolved oxygen (DO) concentration, and oxidation-reduction potential (ORP). Pore waters were filtered (quartz fiber filter) and measured for major cations, inorganic anions, inorganic sulfide, dissolved organic carbon (DOC) concentration, dissolved organic matter (DOM) ultraviolet and visible light (UV-Vis) absorption and fluorescence, total mercury (HgT), and methylmercury (MeHg)concentrations. Surface water samples were collected and filtered (quartz fiber filter); particulate concentrations of MeHg and HgT were measured, and filtered aliquots were measured for major cations, inorganic anions, inorganic sulfide, DOC concentration, DOM UV-Vis and fluorescence, HgT and MeHg. Sediments were collected by push-core and measured for HgT, MeHg, organic matter content by loss on ignition (LOI), and percent dry weight. Resident mosquitofish (Gambusia holbrooki) were collected and measured for HgT and MeHg.

Several canals in southern Florida run from Lake Okeechobee through the Everglades Agricultural Area (EAA) and feed water to the northern Everglades. Agricultural and water-management practices affect the water quality of these canals. Fertilizers added in the EAA flow into the canals and are transported to treatment areas which remove much of the phosphorous in the water, but are not as effective in removing dissolved sulfate. Elevated sulfate concentrations, found downstream in the Water Conservation Areas in the northern Everglades, can stimulate sulfur-reducing bacteria which can also convert inorganic mercury to methyl mercury, a bioaccumulative neurotoxin. Chemistry data at 25 canal sites in southern Florida were sampled for water properties (temperature, pH, specific conductance), sulfur isotopes, major anions and cations, nutrients (including ammonium and orthophosphate), and trace metals. Data collection began in 1996 with a small subset of sites, and has continued through 2019. Funding for this data collection was provided by the USGS Priority Ecosystems Studies Program for South Florida (Nick Aumen, Program Executive).

Several canals in southern Florida run from Lake Okeechobee through the Everglades Agricultural Area (EAA) and feed water to the northern Everglades. Agricultural and water-management practices affect the water quality of these canals. Fertilizers added in the EAA flow into the canals and are transported to treatment areas which remove much of the phosphorous in the water, but are not as effective in removing dissolved sulfate. Elevated sulfate concentrations, found downstream in the Water Conservation Areas in the northern Everglades, can stimulate sulfur-reducing bacteria which can also convert inorganic mercury to methyl mercury, a bioaccumulative neurotoxin. Chemistry data at 25 canal sites in southern Florida were sampled for water properties (temperature, pH, specific conductance), sulfur isotopes, major anions and cations, nutrients (including ammonium and orthophosphate), and trace metals. Data collection began in 1996 with a small subset of sites, and has continued through 2019. Funding for this data collection was provided by the USGS Priority Ecosystems Studies Program for South Florida (Nick Aumen, Program Executive).

The data in this data release includes results from the analysis of water and fish from 76 sites in the Everglades National Park (ENP). Water and particulate matter samples were collected from 2008 to 2018 and analyzed for total mercury (THg) and methylmercury (MeHg). Filtered water samples were also analyzed for dissolved organic carbon (DOC), specific ultraviolet absorbance (SUVA), and major anions. Fish samples (Eastern Mosquitofish, Flagfish, African Jewelfish, Golden Topminnow, and Mayan Cichlid species) were collected from 2007 to 2018 and analyzed for THg and MeHg and carbon and nitrogen stable isotopes. These data are important for analyzing hydrologic and geochemical controls on MeHg distribution and production in the ENP.

The data in this data release includes results from the analysis of water and fish from 76 sites in the Everglades National Park (ENP). Water and particulate matter samples were collected from 2008 to 2018 and analyzed for total mercury (THg) and methylmercury (MeHg). Filtered water samples were also analyzed for dissolved organic carbon (DOC), specific ultraviolet absorbance (SUVA), and major anions. Fish samples (Eastern Mosquitofish, Flagfish, African Jewelfish, Golden Topminnow, and Mayan Cichlid species) were collected from 2007 to 2018 and analyzed for THg and MeHg and carbon and nitrogen stable isotopes. These data are important for analyzing hydrologic and geochemical controls on MeHg distribution and production in the ENP.

This data was collected as part of a laboratory study examining the effects of sea level rise on mercury (Hg) methylation and demethylation rates in peat cores collected from the Florida Everglades. Peat cores were collected from a freshwater region of the Everglades, Water Conservation Area 3, in 2022 and taken to the University of California-Davis for methylation and demethylation studies. Prior to the incubations peat cores were inundated with water of different salinities (0.16 parts-per-thousand (ppt), 0.25 ppt, 0.50 ppt, 1.0 ppt, 6.0 ppt) to simulate saltwater intrusion in coastal regions of Everglades National Park. Incubations were run for 20 days. An enriched isotope tracer of inorganic Hg (201Hg) was added to the cores to track the methylation process. In tandem isotopically enriched methylmercury (204MeHg) was tracked to examine demethylation. Porewater and peat material were collected from the incubations and analyzed for Hg and MeHg. Additional parameters such as dissolved organic carbon concentration and quality, reduction-oxidation potential, major cation and anions, and other metals were monitored during the incubations to examine the controlling variables dictating Hg methylation. Across all salinity treatments, porewaters became increasingly anoxic, sulfate concentrations decreased, and MeHg concentrations increased over the course of 20 days. The findings highlight the potential for enhanced production and mobilization of MeHg in coastal wetlands of the Florida Everglades due to the onset of saltwater intrusion.

Mercury concentrations in various environmental media, as well as water quality characteristics, from survey samples taken in the Florida Everglades. Portions of this dataset are inaccessible because: will add after peer review. They can be accessed through the following means: will add after peer review. Format: will add after peer review. This dataset is associated with the following publication: Kalla, P., M. Cyterski, D. Scheidt, and J. Minucci. Spatiotemporal effects of interacting water quality constituents on mercury in a common prey fish in a large, perturbed, subtropical wetland. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, NETHERLANDS, 792: 148321, (2021).

Soil porewater (30cm and 60cm depth) was sampled for specific conductance, salinity and temperature in the southwest coastal Everglades, Everglades National Park from 1997-2012 at four sampling locations. Principal sampling location (HR) was located adjacent the Harney River and had five sampling sites (~ 60m apart) along a 300m N-S transect in a coastal mangrove fringe forest sampled from 1997-2011. Porewater was sampled from 2002-2012 at three secondary locations: Tarpon Bay (TB), Shark River (SR) and Shark Slough (SS). At each of these sampling locations, there were at least three 30cm and three 60cm porewater sampling pipes.

Florida Bay has been exposed to a series of events in the past that has led to major ecological changes. Beginning with the seagrass die-off of 2015, water quality began to deteriorate, and a subsequent phytoplankton bloom began in the late wet season of 2016. Since then, Hurricane Irma along with other wind and rain events appear to have contributed to the persistence and intensification of these blooms. During the last decade, Everglades National Park (EVER) has conducted extensive monitoring and research of the Florida Bay ecosystem to document long term trends in water quality and to gain insights into the dynamics of these phytoplankton blooms. Monitoring typically occurs every other month beginning in January over the course of 5 days.