Everglades National Park Research Articles

Emergence potential of mosquito-borne arboviruses from the Florida Everglades.

The Greater Everglades Region of South Florida is one of the largest natural wetlands and the only subtropical ecosystem found in the continental United States. Mosquitoes are seasonally abundant in the Everglades where several potentially pathogenic mosquito-borne arboviruses are maintained in natural transmission cycles involving vector-competent mosquitoes and reservoir-competent vertebrate hosts. The fragile nature of this ecosystem is vulnerable to many sources of environmental change, including a wetlands restoration project, climate change, invasive species and residential development. In this study, we obtained baseline data on the distribution and abundance of both mosquitos and arboviruses occurring in the southern Everglades region during the summer months of 2013, when water levels were high, and in 2014, when water levels were low. A total of 367,060 mosquitoes were collected with CO2-baited CDC light traps at 105 collection sites stratified among the major landscape features found in Everglades National Park, Big Cypress National Preserve, Fakahatchee State Park Preserve and Picayune State Forest, an area already undergoing restoration. A total of 2,010 pools of taxonomically identified mosquitoes were cultured for arbovirus isolation and identification. Seven vertebrate arboviruses were isolated: Everglades virus, Tensaw virus, Shark River virus, Gumbo Limbo virus, Mahogany Hammock virus, Keystone virus, and St. Louis encephalitis virus. Except for Tensaw virus, which was absent in 2013, the remaining viruses were found to be most prevalent in hardwood hammocks and in Fakahatchee, less prevalent in mangroves and pinelands, and absent in cypress and sawgrass. In contrast, in the summer of 2014 when water levels were lower, these arboviruses were far less prevalent and only found in hardwood hammocks, but Tensaw virus was present in cypress, sawgrass, pinelands, and a recently burned site. Major environmental changes are anticipated in the Everglades, many of which will result in increased water levels. How these might lead to the emergence of arboviruses potentially pathogenic to both humans and wildlife is discussed.

First person – Jillian Josimovich

ABSTRACTFirst Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping early-career researchers promote themselves alongside their papers. Jillian Josimovich is first author on ‘ Clutch may predict growth of hatchling Burmese pythons better than food availability or sex’, published in BiO. Jillian is a biologist in the lab of Dr Andrea Currylow at Geological Survey, Fort Collins Science Center, South Florida Field Station in Everglades National Park, USA, investigating applied research that can inform management efforts for imperiled species and ecosystems, with a particular focus on herpetological ecology and conservation.

Integrating Aquatic Metabolism and Net Ecosystem CO2 Balance in Short- and Long-Hydroperiod Subtropical Freshwater Wetlands

How aquatic primary productivity influences the carbon (C) sequestering capacity of wetlands is uncertain. We evaluated the magnitude and variability in aquatic C dynamics and compared them to net ecosystem CO2 exchange (NEE) and ecosystem respiration (Reco) rates within calcareous freshwater wetlands in Everglades National Park. We continuously recorded 30-min measurements of dissolved oxygen (DO), water level, water temperature (Twater), and photosynthetically active radiation (PAR). These measurements were coupled with ecosystem CO2 fluxes over 5 years (2012–2016) in a long-hydroperiod peat-rich, freshwater marsh and a short-hydroperiod, freshwater marl prairie. Daily net aquatic primary productivity (NAPP) rates indicated both wetlands were generally net heterotrophic. Gross aquatic primary productivity (GAPP) ranged from 0 to − 6.3 g C m−2 day−1 and aquatic respiration (RAq) from 0 to 6.13 g C m−2 day−1. Nonlinear interactions between water level, Twater, and GAPP and RAq resulted in high variability in NAPP that contributed to NEE. Net aquatic primary productivity accounted for 4–5% of the deviance explained in NEE rates. With respect to the flux magnitude, daily NAPP was a greater proportion of daily NEE at the long-hydroperiod site (mean = 95%) compared to the short-hydroperiod site (mean = 64%). Although we have confirmed the significant contribution of NAPP to NEE in both long- and short-hydroperiod freshwater wetlands, the decoupling of the aquatic and ecosystem fluxes could largely depend on emergent vegetation, the carbonate cycle, and the lateral C flux.

Microbial Respiration and Enzyme Activity Downstream from a Phosphorus Source in the Everglades, Florida, USA

Northeast Shark River Slough (NESS), lying at the northeastern perimeter of Everglades National Park (ENP), Florida, USA, has been subjected to years of hydrologic modifications. Construction of the Tamiami Trail (US 41) in 1928 connected the east and west coasts of SE Florida and essentially created a hydrological barrier to southern sheet flow into ENP. Recently, a series of bridges were constructed to elevate a portion of Tamiami Trail, allow more water to flow under the bridges, and attempt to restore the ecological balance in the NESS and ENP. This project was conducted to determine aspects of soil physiochemistry and microbial dynamics in the NESS. We evaluated microbial respiration and enzyme assays as indicators of nutrient dynamics in NESS soils. Soil cores were collected from sites at certain distances from the inflow (near canal, NC (0–150 m); midway, M (150–600 m); and far from canal, FC (600–1200 m)). Soil slurries were incubated and assayed for CO2 emission and β-glucoside (MUFC) or phosphatase (MUFP) activity in concert with physicochemical analysis. Significantly higher TP contents at NC (2.45 times) and M (1.52 times) sites than FC sites indicated an uneven P distribution downstream from the source canal. The highest soil organic matter content (84%) contents were observed at M sites, which was due to higher vegetation biomass observed at those sites. Consequently, CO2 efflux was greater at M sites (average 2.72 µmoles g dw−1 h−1) than the other two sites. We also found that amendments of glucose increased CO2 efflux from all soils, whereas the addition of phosphorus did not. The results indicate that microbial respiration downstream of inflows in the NESS is not limited by P, but more so by the availability of labile C.

Spatiotemporal effects of interacting water quality constituents on mercury in a common prey fish in a large, perturbed, subtropical wetland

We present results of a multiyear study of the Everglades (Florida, USA) detailing how differences in environmental variables can alter mercury concentrations in the food web. About 1000 random locations throughout the freshwater Everglades marsh have been sampled for the United States Environmental Protection Agency's Everglades Regional Environmental Monitoring and Assessment Program (“REMAP”) since 1995. REMAP sampling is synoptic and multimedia, including an abundant prey fish (eastern mosquitofish, Gambusia holbrooki) as an indicator of mercury bioaccumulation. Amplifying an approach we reported to Everglades National Park, we used Generalized Boosted Models on the REMAP data to estimate how much of the mercury concentration in mosquitofish could be explained by water quality constituents or indicators of ecological health (covariates). The resulting model accounts for 60% of the environmental influence on variation in mosquitofish mercury, a robust outcome for a large, disturbed ecosystem such as the Everglades, given its seasonal, annual, and spatial differences. Of the eight most influential covariates, two were methyl mercury in periphyton and water, two can be indicators of trophic state (alkaline phosphatase and chlorophyll-a), one can be a marker of stormwater transport (conductivity), and two can be enablers of mercury methylation (sulfate in soil and water). While these covariates had an average individual influence ranging from 4.0% to 10.1%, together they accounted for 52.2% of the total relative influence. Water with low phosphorus, but with sulfur and carbon above background, moved into the less disturbed parts of the Everglades via modifications to the existing water management system, could increase mercury bioaccumulation in those parts of the marsh.

Mapping CO2 fluxes of cypress swamp and marshes in the Greater Everglades using eddy covariance measurements and Landsat data

Wetlands play a critical role in the global carbon (C) budget by sequestering carbon dioxide (CO2) and storing significant amounts of C, but climate change is altering C dynamics in these ecosystems. Therefore, predicting and mapping net ecosystem exchange (NEE) of CO2 in wetlands has emerged as a focus of research to better understand where, how, and when biogeochemical cycles will be modified by human and natural disturbances like climate change. To address this, we developed an object-based machine learning ensemble approach to upscale eddy covariance (EC) CO2 flux measurements across two major wetland ecosystems (cypress swamp and freshwater marshes) in the Greater Everglades of south Florida. We linked 30-m Landsat, water depth, and air temperature data with EC flux measurements using the temporally composite concept for model development, and mapped fluxes within Big Cypress National Preserve (BCNP) and Everglades National Park (ENP) to characterize two distinct seasonal flux patterns. Using an ensemble analysis of three machine learning model outputs (Artificial Neural Network, Support Vector Machine, and Random Forest), our models of NEE at BCNP had a high predictive power with a R2 greater than 0.8, while NEE was predicted at ENP with a R2 greater than 0.5. We also generated an uncertainty map to quantify the prediction diversity caused by application of multiple models in upscaling. This uncertainty map identifies regions that are either easy or challenging to predict from model based analyses. We conclude that integration of Landsat, water depth, and air temperature data is valuable for quantifying CO2 exchange between the atmosphere and Everglades ecosystems, and the developed paradigm is promising for upscaling EC flux measurements in wetlands to study and mitigate disturbances to wetland ecosystem services such as hurricanes, fires, water management and/or climate change.

Coastal Ecosystem Vulnerability and Sea Level Rise (SLR) in South Florida: A Mangrove Transition Projection

We used static, elevation and land cover data to estimate sea level rise impacts (SLR) to urban, developed lands and coastal wetland systems in Everglades National Park and the East and West coastal regions in South Florida. Maps and data tables estimating potential state change to open water were compiled through overlay analysis of elevation, land cover, and SLR masks with future land cover projected using a land cover transition threshold model. Analysis was based on a 2–5-km-wide longitudinal band along the SW and SE coasts of Florida where sea-level rise has no surface impediments to inundation and will likely cause coastline transgression and wetland migration. Analysis used three different projections; 0.27 m (0.9 ft), 0.76 m (2.5 ft) and 1.13 m (3.7 ft) greater than current sea level by 2070 estimated by NOAA and IPCC. Under a 0.27 m SLR projection 51% of the coastal land cover may be impacted. Under 0.76 and 1.13 m projected SLR, coastal land cover areas were impacted by 56.5 and 59.1%, respectively. Migration of coastal wetlands from their current location into more inland areas in response to increased water depths and as a function of empirically derived marsh and mangrove accretion rates were also evaluated. With a SLR of 0.76 m by 2070, without accretion, 1,160 sq km of wetland became open estuarine water. However, with accretion values of 0.211 m (4.1 mm yr–1) and 0.55 m (11 mm yr–1) by 2070, there was a transition of wetland cover to open estuarine water of only 349 and 41 sq km, respectively. Under a low SLR of 0.27 m by 2070 scenario with accretion, the coastal mangroves were able to migrate inland while maintaining the current coastline. It was only under the more extreme scenario of 1.13 m SLR by 2070 that accretion was not able to compensate for inundation and there was a loss of wetland coastline everywhere.

Mapping the Extent of Mangrove Ecosystem Degradation by Integrating an Ecological Conceptual Model with Satellite Data

Anthropogenic and natural disturbances can cause degradation of ecosystems, reducing their capacity to sustain biodiversity and provide ecosystem services. Understanding the extent of ecosystem degradation is critical for estimating risks to ecosystems, yet there are few existing methods to map degradation at the ecosystem scale and none using freely available satellite data for mangrove ecosystems. In this study, we developed a quantitative classification model of mangrove ecosystem degradation using freely available earth observation data. Crucially, a conceptual model of mangrove ecosystem degradation was established to identify suitable remote sensing variables that support the quantitative classification model, bridging the gap between satellite-derived variables and ecosystem degradation with explicit ecological links. We applied our degradation model to two case-studies, the mangroves of Rakhine State, Myanmar, which are severely threatened by anthropogenic disturbances, and Shark River within the Everglades National Park, USA, which is periodically disturbed by severe tropical storms. Our model suggested that 40% (597 km2) of the extent of mangroves in Rakhine showed evidence of degradation. In the Everglades, the model suggested that the extent of degraded mangrove forest increased from 5.1% to 97.4% following the Category 4 Hurricane Irma in 2017. Quantitative accuracy assessments indicated the model achieved overall accuracies of 77.6% and 79.1% for the Rakhine and the Everglades, respectively. We highlight that using an ecological conceptual model as the basis for building quantitative classification models to estimate the extent of ecosystem degradation ensures the ecological relevance of the classification models. Our developed method enables researchers to move beyond only mapping ecosystem distribution to condition and degradation as well. These results can help support ecosystem risk assessments, natural capital accounting, and restoration planning and provide quantitative estimates of ecosystem degradation for new global biodiversity targets.

American crocodiles (Crocodylus acutus) as restoration bioindicators in the Florida Everglades.

The federally threatened American crocodile (Crocodylus acutus) is a flagship species and ecological indicator of hydrologic restoration in the Florida Everglades. We conducted a long-term capture-recapture study on the South Florida population of American crocodiles from 1978 to 2015 to evaluate the effects of restoration efforts to more historic hydrologic conditions. The study produced 10,040 crocodile capture events of 9,865 individuals and more than 90% of captures were of hatchlings. Body condition and growth rates of crocodiles were highly age-structured with younger crocodiles presenting with the poorest body condition and highest growth rates. Mean crocodile body condition in this study was 2.14±0.35 SD across the South Florida population. Crocodiles exposed to hypersaline conditions (> 40 psu) during the dry season maintained lower body condition scores and reduced growth rate by 13% after one year, by 24% after five years, and by 29% after ten years. Estimated hatchling survival for the South Florida population was 25% increasing with ontogeny and reaching near 90% survival at year six. Hatchling survival was 34% in NE Florida Bay relative to a 69% hatchling survival at Crocodile Lake National Wildlife Refuge and 53% in Flamingo area of Everglades National Park. Hypersaline conditions negatively affected survival, growth and body condition and was most pronounced in NE Florida Bay, where the hydrologic conditions have been most disturbed. The American crocodile, a long-lived animal, with relatively slow growth rate provides an excellent model system to measure the effects of altered hydropatterns in the Everglades landscape. These results illustrate the need for continued long-term monitoring to assess system-wide restoration outcomes and inform resource managers.

A dry future for the Everglades favors invasive herpetofauna

The Greater Everglades Ecosystem is a globally important ecoregion, home to 68 threatened or endangered species and the largest designated wilderness area in the Eastern United States. Anthropogenic manipulations of the natural hydrology have led to widespread degradation of this ecosystem and monitored population declines across multiple taxa. Simultaneous introductions of hundreds of non-native species into South Florida and their subsequent invasion into the Everglades has further impacted native Everglades communities. Predictions for future climate change suggest that the Everglades is headed towards a drier future, making it crucial to understand how changes in hydrological regimes will impact both native and non-native fauna. Our study combines the results of a landscape-scale experimental manipulation conducted to assess the impact of differing hydrological regimes at the Loxahatchee Impoundment Landscape Assessment between 2018 and 2020 with a community composition analysis of data collected across multiple habitat types throughout Everglades National Park between 2000 and 2002. Both datasets used a variety of survey methods to extensively characterize the amphibian and reptile amphibian assemblage across habitat types and hydrological regimes. An NMDS analysis indicated that variation in hydrology is the primary axis structuring reptile and amphibian habitat usage across the Everglades, with non-native species more likely to be indicators of drier habitat types. This result concurred with those from the landscape-scale manipulation, in which non-native species were significantly favored by drier hydrological conditions. Taken together, these results suggest that a drier future within the Greater Everglades Ecosystem may facilitate further spread of South Florida’s diverse non-native amphibian and reptile assemblage.

Interactive effects of hydrology and fire drive differential biogeochemical legacies in subtropical wetlands

AbstractFire is an important component of many ecosystems, as it impacts biodiversity, biogeochemical cycles, and primary production. In wetlands, fire interacts with hydrologic regimes and other ecosystem characteristics to determine soil carbon (C) gains or losses and rates of nutrient cycling. However, how legacies of fire interact with wetland hydroperiod to affect soil chemistry is uncertain. We used the Florida Everglades as a model landscape to study how fire regimes, hydroperiod, and soil types collectively contribute to long‐term C, nitrogen (N), and phosphorus (P) concentrations and stoichiometric mass ratios (C:N, C:P, N:P) in both short‐ and long‐hydroperiod subtropical wetlands that consist of marl and peat soils, respectively. We used fire records from 1948 to 2018 and hydroperiod from 1991 to 2003, and analyzed these data together with soil chemistry data collected during two extensive field surveys (n = 539) across different ecosystem and soil types throughout Everglades National Park. We also analyzed macrophyte and periphyton P concentrations (n = 150) collected from 2003 to 2016 in fire‐impacted wetland sites. Hydroperiod was the main driver of soil C concentration in both marl and peat soils, but fire played a substantial role in nutrient cycling. Particularly in marl soils, soil P concentrations were affected by the absence of fire. In the first decade post‐fire, we observed an amplification of P cycling with decreased soil C:P ratios by 95% and N:P ratios by 45%. After more than a decade post‐fire, soil P became increasingly depleted (41% lower). Macrophyte P tissue concentration was 50% higher only in the first year post‐fire, whereas periphyton P did not change. By recycling nutrients and through removal of litter accumulation, which forms a physical obstacle to photosynthesis, fire likely helps maintain high levels of macrophyte aboveground live biomass as well. Given its substantial effect on nutrient cycling, we advocate for fire management that uses fire return intervals that minimize depletion of soil nutrients and promote positive feedbacks to productivity in wetland ecosystems. In addition, coordinated management of fire return intervals and wetland hydroperiod can be used to set priorities for wetland soil nutrient concentrations and ratios.

Irruptive White Ibis breeding is associated with use of freshwater crayfish in the coastal Everglades

AbstractAs avian reproductive success is generally prey limited, identifying important prey types or sizes and understanding mechanisms governing prey availability are important objectives for avian conservation ecology. Irruptive White Ibis (Eudocimus albus) nesting at coastal colonies in the southern Everglades numbered over 100,000 nests in the 1930s. A century of drainage and altered hydrologic patterns reduced aquatic prey availability and eliminated large nesting events; nesting activity in recent decades has been typically less than 5% of historical peaks. Hydrologic restoration is expected to increase ibis nesting activity, but which prey types will support high nesting effort is less clear. In 2017 and 2018, we collected food boluses from White Ibis chicks at coastal colonies in Everglades National Park. We also monitored regional nesting activity from 1999 to 2018. In 2017, the region had 1,075 nests, typical of the past several decades; but in 2018, there were 30,420 nests, representing the highest recorded nesting activity in 87 yr. Prey composition varied between years; estuarine crabs dominated nestling boluses in 2017, while crayfish and fish were dominant prey in 2018. Crayfish, especially Procambarus alleni, were heavily exploited by ibis early in the 2018 breeding season, while fish were used more at the end. Crayfish abundances in wetlands near the colonies were higher prior to 2018, and more crayfish-producing short-hydroperiod wetlands remained available for ibis foraging in 2018. Our results support previous studies indicating that crayfish are important prey for breeding ibises and suggest that unprecedented, extensive flooding of seasonal wetlands promoted crayfish production and initiated the irruptive breeding in 2018. Our observations indicate that rehydration of the southern Everglades could restore ibis nesting activity at coastal colonies, but further investigations of hydrologic variation, crayfish production, and ibis foraging and nesting activity will be helpful to understand these dynamics and the importance of short-hydroperiod wetlands.

Accelerometry to study fine-scale activity of invasive Burmese pythons (Python bivittatus) in the wild

BackgroundThe establishment of Burmese pythons (Python bivittatus) in Everglades National Park, Florida, USA, has been connected to a > 90% decline in the mesomammal population in the park and is a major threat to native reptile and bird populations. Efforts to control this population are underway, but are hampered by a lack of information about fine-scale activity cycles and ecology of these cryptic animals in the wild. We aimed to establish a technique for monitoring the activity of Burmese pythons in the wild using acceleration data loggers (ADLs), while attempting to identify any behavioral patterns that could be used to help manage this invasive species in the Greater Everglades and South Florida.ResultsWe obtained continuous acceleration and temperature data from four wild snakes over periods of 19 to 95 days (mean 54 ± 33 days). Snakes spent 86% of their time at rest and 14% of their time active, including transiting between locations. All snakes showed at least one period of continuous transiting lasting 10 h or more, with one animal transiting continuously for a period of 58.5 h. Acceleration data logger-derived transiting bout duration was significantly correlated with the distance snakes traveled per hour for two snakes that also carried GPS loggers. Snakes were most active in midday or early-night depending on individual and time of year, but all snakes were least likely to be active in the early mornings (0400–0700 h local time). Very little movement took place at temperatures below 14 °C or above 24 °C, with most movement taking place between 15° and 20 °C. One animal showed a highly unusual rolling event that may be indicative of a predation attempt, but this could not be confirmed.ConclusionsFine-scale activity and some behaviors were apparent from ADL data, making ADLs a potentially valuable, unbiased tool for monitoring large-bodied snakes in the wild. Snakes spent the majority of their time resting, but also moved continuously for several hours at a time during bouts of transiting. Results suggest that individuals may shift their diel activity pattern based on season. Understanding seasonal differences in activity levels can improve the accuracy of population estimates, help detect range expansion, and improve managers’ ability to find and capture individuals.

Garden Hoe

Garden Hoe Dana Wildsmith (bio) It's not as sharp as it used to be. I hearfriends say the same of themselves, but Ibelieve that I've grown sharper through my yearsof gardening, at least in ways that Iconsider worthy. Now I notice wheremy herb beds migrate to, and feed the dirtaccordingly. I've learned if nothing's there,amend or move along. It never hurtsto sow for your own needs, plus more to share,I've also learned. And how a drought can lendyou time to think and plan. How rain repairsso quickly you forgive the wait. And whento be as blunt as my old chopping hoe,or when to plow loss under, let it go. [End Page 90] Dana Wildsmith Dana Wildsmith is the author of a novel, Jumping, and an environmental memoir, Back to Abnormal: Surviving With An Old Farm in the New South, which was Finalist for Georgia Author of the Year. She is also the author of five collections of poetry. Wildsmith has served as Artist-in-Residence for Grand Canyon National Park and will serve as Artist-in-Residence for Everglades National Park. She lives with her family on an old farm in north Georgia, and works as an English Literacy Instructor at Lanier Technical College. Her widely followed blog, http://www.danawildsmith.com/blog, focuses on the life of a working writer. Copyright © 2021 Berea College

Mangroves as a Source of Greenhouse Gases to the Atmosphere and Alkalinity and Dissolved Carbon to the Coastal Ocean: A Case Study From the Everglades National Park, Florida

AbstractMost research evaluating the potential of mangroves as a sink for atmospheric carbon has focused on carbon burial in sediments. However, the few studies that have quantified lateral exchange of carbon and alkalinity indicate that the dissolved carbon and alkalinity export may be several‐fold more important than burial. This study aims to investigate rates and drivers of alkalinity, dissolved carbon, and greenhouse gas fluxes of the mangrove‐dominated Shark River estuary located in the Everglades National Park in Florida, USA. Spatial surveys and 29‐hr time series were conducted to assess total alkalinity (TAlk), organic alkalinity (OAlk), dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) dynamics. Dissolved carbon and greenhouse gas concentrations were coupled to porewater input, which was examined using radon‐222. Shark River was a source of CO2 (92 mmol/m2/day), CH4 (56 μmol/m2/day), and N2O (2 μmol/m2/day) to the atmosphere. Dissolved carbon export (DIC = 142 mmol/m2/day, DOC = 39 mmol/m2/day, normalized to mangrove area) was several‐fold higher than previously reported carbon burial rates in the study area (~28 mmol/m2/day). The majority of the DIC was exported as TAlk (97 mmol/m2/day), which remains dissolved in the ocean for millennia and, therefore, represents a long‐term sink for atmospheric carbon. By integrating our results with previous studies, we argue that alkalinity, dissolved carbon, and greenhouse gas fluxes should be considered in future blue carbon budgets.

Linking Hydrology and Dissolved Organic Matter Characteristics in a Subtropical Wetland: A Long‐Term Study of the Florida Everglades

AbstractDissolved organic matter (DOM) acts as an important biogeochemical component of aquatic ecosystems that controls nutrient cycling, influences water quality, and links terrestrial and oceanic carbon pools, yet long‐term studies of how changing environmental drivers alter its abundance and composition are rare. Using a 10‐year, spatially explicit data set from Everglades National Park, a globally significant wetland, we investigated the relationships between DOM quality/quantity and hydrologic/climatic drivers along two contrasting marsh‐estuarine transects based on generalized linear modeling and a cumulative sums analysis. Analyses revealed distinct spatial, seasonal, and interannual patterns in variability of DOC and optical properties. Landscape‐scale seasonal patterns showed an enrichment in microbial‐like and protein‐like DOM during the dry season relative to the wet season. While some compositional constituents varied with the solar calendar, responsive to temperature and photoperiod, others varied with the hydrologic calendar. Independent water level and discharge effects indicated strong hydrologic control on DOM quality that differed between the two transects, evidencing differences in their connectivity to areas of high agricultural activity. Across all sites, a significant long‐term increasing trend in the fluorescence index was observed, associated with a positive correlation with precipitation and also potential changes in agricultural inputs, with other features associated with drought and hurricanes. Lastly, the cumulative sums analysis revealed differences between the two transects in the sensitivity of DOM composition to decreased water levels associated with 30‐year climate scenarios, with the less hydrologically dynamic transect exhibiting greater potential sensitivity.

Seasonal Variations in Dissolved Carbon Inventory and Fluxes in a Mangrove‐Dominated Estuary

AbstractTwo experiments were performed during the wet and dry seasons to quantify dissolved carbon dynamics and fluxes in the Shark River, a tidal estuary flowing through the largest contiguous mangrove forest in North America (Everglades National Park, Florida, USA). During these experiments, between 80% and 87% of the total dissolved carbon pool consisted of inorganic carbon (DIC). Carbon inputs from mangroves to the estuary were slightly higher during the wet season, whereas alkalinity inputs were comparable during the two experiments. Longitudinal dissolved carbon fluxes to the coastal ocean were slightly higher during the wet season (13.53 ± 0.76 × 105 mol day−1 during the wet and 11.70 ± 0.32 × 105 mol day−1 during the dry), whereas longitudinal alkalinity flux was comparable during both experiments (10.64 ± 0.74 in the wet vs. 9.88 ± 0.30 × 105 mol day−1 during the dry season). Overall, DIC production in surface water, porewater, and groundwater was dominated by oxic mineralization of mangrove‐derived organic matter and carbonate dissolution. Carbonate dissolution was the most important alkalinity production process in the system. The experiments show that regardless of the season and hydro‐climatic conditions, Shark River receives large inputs of dissolved carbon from the upstream marsh, mangroves, and carbonate dissolution, and that per area, it exports a greater amount of dissolved carbon than many other mangrove‐dominated estuaries in the world.

Quantifying effects of increased hydroperiod on wetland nutrient concentrations during early phases of freshwater restoration of the Florida Everglades

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.

Conspecific chemical cues facilitate mate trailing by invasive Argentine black and white tegus.

Squamate reptiles (snakes and lizards) rely on chemical cues from conspecifics to search the environment for potential mates. How such cues are used by invasive species to facilitate reproduction, especially seasonally, is a key question that can inform management practices. The Argentine black and white tegu (Salvator merianae) is an invasive reptile species in south Florida threatening native fauna in biodiverse regions such as Everglades National Park. While some information exists on the reproductive ecology of this species in its native range in South America, the chemical ecology of S. merianae is unclear especially in its invasive range. By testing both male (n = 7) and female (n = 7) tegus in a Y-maze apparatus, we assessed if either sex follows chemical trails left by conspecifics and if behaviors were sex- or season-specific. We conducted three types of trials where conspecifics created odor trails: Male-only (male scent only in base and one arm of Y), Female-only, and Male vs. female. Males did not preferentially follow scent trails from either sex, but they did differentially investigate conspecific scent from both sexes. Seasonally, males showed increased rates of chemosensory sampling (rates of tongue-flicking) during the spring (breeding season; March-May) compared to fall (non-breeding season; September-November). Males also had reduced turning and pausing behavior while trailing in the spring. Female tegus exhibited stronger conspecific trailing abilities than males, following both male and female scent trails, and they explored the maze less before making an arm choice. Females also investigated the scent trails intensely compared to males (more passes in scented arms, more time with scent trails). Our results demonstrate for the first time that females of an invasive reptile species can follow conspecific scent trails. Given the strong female responses to odor, sex-specific targeting of tegus via application of a conspecific chemical cue in traps could enhance removal rates of females during the breeding season.

A Geochemical Record of Late‐Holocene Hurricane Events From the Florida Everglades

AbstractA 5.25‐m sediment core SRM‐1 and 45 surface samples from mangrove forests at the Shark River Estuary in the Everglades National Park, Florida, were examined by using X‐ray fluorescence and carbon isotopic analyses to study the history of intense hurricane landfall during the Late‐Holocene. Significance testing of the surface samples in relation to storm deposits from Hurricane Wilma suggests that elemental concentration of Sr and Cl and the ratio of Cl/Br are the most sensitive indicators for major hurricane events in our study area. The geochemical data sets of core SRM‐1 identified five active periods of intense hurricane activities during the last 3,500 years at ~3,400–3,000, ~2,200–1,500, ~1,000–800, ~600–300, and ~150 calibrated years before present to present. This is the longest paleohurricane record to date from South Florida. Our results are consistent with the view that intense hurricane activities in South Florida were modulated by Intertropical Convergence Zone (ITCZ) movements, El Niño/Southern Oscillation (ENSO) activities, and North Atlantic Oscillation (NAO) strength. This study contributes to the methodological advancement in paleotempestological studies by demonstrating that geochemical signals, particularly signals of saltwater intrusions, can be preserved in the sediment profiles on millennial time‐scale and measured by X‐ray fluorescence techniques, thereby enabling more storm records to be produced from otherwise suboptimal sand‐limited coastal systems such as the Florida Everglades. More work needs to be done to explore the use of geochemical and stable isotopic analyses in detecting storm signals from sand‐limited coastal environments.