Chambers, L. G., Guevara, R., Boyer, J. N., Troxler, T. G., & Davis, S. E. (2016). Effects of Salinity and Inundation on Microbial Community Structure and Function in a Mangrove Peat Soil. Wetlands, 36(2), 361–371.
Abstract: Shifts in microbial community function and structure can be indicators of environmental stress and ecosystem change in wetland soils. This study evaluated the effects of increased salinity, increased inundation, and their combination, on soil microbial function (enzyme activity) and structure (phospholipid fatty acid (PLFA) signatures and terminal restriction fragment length polymorphisms (T-RFLP) profiles) in a brackish mangrove peat soil using tidal mesocosms (Everglades, Florida, USA). Increased tidal inundation resulted in reduced soil enzyme activity, especially alkaline phosphatase, an increase in the abundance and diversity of prokaryotes, and a decline in number of eukaryotes. The community composition of less abundant bacteria (T-RFLPs comprising 0.3-1 % of total fluorescence) also shifted as a result of increased inundation under ambient salinity. Several key biogeochemical indicators (oxidation-reduction potential, CO2 flux, porewater NH4 (+), and dissolved organic carbon) correlated with measured microbial parameters and differed with inundation level. This study indicates microbial function and composition in brackish soil is more strongly impacted by increased inundation than increased salinity. The observed divergence of microbial indicators within a short time span (10-weeks) demonstrates their usefulness as an early warning signal for shifts in coastal wetland ecosystems due to sea level rise stressors.
|
Charles, S. P., Kominoski, J. S., Troxler, T. G., Gaiser, E. E., Servais, S., Wilson, B. J., et al. (2019). Experimental Saltwater Intrusion Drives Rapid Soil Elevation and Carbon Loss in Freshwater and Brackish Everglades Marshes. Estuaries and Coasts, 42(7), 1868–1881.
Abstract: Increasing rates of sea-level rise (SLR) threaten to submerge coastal wetlands unless they increase soil elevation at similar pace, often by storing soil organic carbon (OC). Coastal wetlands face increasing salinity, marine-derived nutrients, and inundation depths from increasing rates of SLR. To quantify the effects of SLR on soil OC stocks and fluxes and elevation change, we conducted two mesocosm experiments using the foundation species sawgrass (Cladium jamaicense) and organic soils from freshwater and brackish Florida Everglades marshes for 1 year. In freshwater mesocosms, we compared ambient and elevated salinity (fresh, 9 ppt) and phosphorus (ambient, + 1 g P m(-2) year(-1)) treatments with a 2 x 2 factorial design. Salinity addition reduced root biomass (48%), driving 2.8 +/- 0.3 cm year(-1) of elevation loss, while soil elevation was maintained in freshwater conditions. Added P increased root productivity (134%) but also increased breakdown rates (k) of roots (31%) and leaves (42%) with no effect on root biomass or soil elevation. In brackish mesocosms, we compared ambient and elevated salinity (10, 19 ppt) and inundated and exposed conditions (water level 5-cm below and 4-cm above soil). Elevated salinity decreased root productivity (70%) and root biomass (37%) and increased k in litter (33%) and surface roots (11%), whereas inundation decreased subsurface root k (10%). All brackish marshes lost elevation at similar rates (0.6 +/- 0.2 cm year(-1)). In conclusion, saltwater intrusion in freshwater and brackish wetlands may reduce net OC storage and increase vulnerability to SLR despite inundation or marine P supplies.
|
|
Dessu, S. B., Price, R. M., Troxler, T. G., & Kominoski, J. S. (2018). Effects of sea-level rise and freshwater management on long-term water levels and water quality in the Florida Coastal Everglades. Journal of Environmental Management, 211, 164–176.
|
|
Díaz, P., Morley, K. M., & Yeh, D. H. (2017). Resilient urban water supply: preparing for the slow-moving consequences of climate change. Water Pract Technol, 12(1), 123–138.
|
Drury, A. J., John, C. M., & Shevenell, A. E. (2016). Evaluating climatic response to external radiative forcing during the late Miocene to early Pliocene: New perspectives from eastern equatorial Pacific (IODP U1338) and North Atlantic (ODP 982) locations: Late Miocene-Early Pliocene Variability. Paleoceanography, 31(1), 167–184.
Abstract: Orbital-scale climate variability during the latest Miocene-early Pliocene is poorly understood due to a lack of high-resolution records spanning 8.0-3.5Ma, which resolve all orbital cycles. Assessing this variability improves understanding of how Earth's system sensitivity to insolation evolves and provides insight into the factors driving the Messinian Salinity Crisis (MSC) and the Late Miocene Carbon Isotope Shift (LMCIS). New high-resolution benthic foraminiferal Cibicidoides mundulus O-18 and C-13 records from equatorial Pacific International Ocean Drilling Program Site U1338 are correlated to North Atlantic Ocean Drilling Program Site 982 to obtain a global perspective. Four long-term benthic O-18 variations are identified: the Tortonian-Messinian, Miocene-Pliocene, and Early-Pliocene Oxygen Isotope Lows (8-7, 5.9-4.9, and 4.8-3.5Ma) and the Messinian Oxygen Isotope High (MOH; 7-5.9Ma). Obliquity-paced variability dominates throughout, except during the MOH. Eleven new orbital-scale isotopic stages are identified between 7.4 and 7.1Ma. Cryosphere and carbon cycle sensitivities, estimated from O-18 and C-13 variability, suggest a weak cryosphere-carbon cycle coupling. The MSC termination coincided with moderate cryosphere sensitivity and reduced global ice sheets. The LMCIS coincided with reduced carbon cycle sensitivity, suggesting a driving force independent of insolation changes. The response of the cryosphere and carbon cycle to obliquity forcing is established, defined as Earth System Response (ESR). Observations reveal that two late Miocene-early Pliocene climate states existed. The first is a prevailing dynamic state with moderate ESR and obliquity-driven Antarctic ice variations, associated with reduced global ice volumes. The second is a stable state, which occurred during the MOH, with reduced ESR and lower obliquity-driven variability, associated with expanded global ice volumes.
|
Her, Y. G., Boote, K. J., Migliaccio, K. W., Fraisse, C., Letson, D., Mbuya, O., et al. (2017). Climate change impacts and adaptation in Florida's agriculture. In E. P. Chassignet, J. W. Jones, V. Misra, & J. Obeysekera (Eds.), Florida's climate: Changes, variations, & impacts (pp. 235–267). Gainesville, FL: Florida Climate Institute.
Abstract: In this chapter, we describe Florida�s agriculture, the vulnerability of its crops and livestock to climate change and possible adaptation strategies. Much of Florida�s agricultural success is linked to its moderate climate, which allows vegetable and fruit crop production during the winter/spring season as well as the production of perennial crops such as citrus and sugarcane. In addition, there is a substantial livestock industry that uses the extensive perennial grasslands. While rising CO2 is generally beneficial to crop production but detrimental to nutritional quality, increase in temperature will cause mostly negative effects on yield. Florida�s agriculture faces additional challenges from climate change characterized by sea level rise and intensified extreme climate events, affecting land and irrigation water availability, livestock productivity and pest and disease pressure. New technologies and adaptation strategies are needed for sustainable agricultural production in Florida, including increased water and nutrient use efficiency in crops, crop and livestock breeding for heat stress, pest and disease resistance and reduced exposure of livestock to high temperature. Irrigation is a favored adaptation, but places an even greater burden or potential conflict between agriculture and community use of water resources.
|
|
Hu, M., Ren, H., Ren, P., Li, J., Wilson, B. J., & Tong, C. (2017). Response of gaseous carbon emissions to low-level salinity increase in tidal marsh ecosystem of the Min River estuary, southeastern China. Journal of Environmental Sciences, 52, 210–222.
|
Liu, C., Liang, X., Ponte, R. M., Vinogradova, N., & Wang, O. (2019). Vertical redistribution of salt and layered changes in global ocean salinity. Nature Communications, 10(1).
Abstract: Salinity is an essential proxy for estimating the global net freshwater input into the ocean. Due to the limited spatial and temporal coverage of the existing salinity measurements, previous studies of global salinity changes focused mostly on the surface and upper oceans. Here, we examine global ocean salinity changes and ocean vertical salt fluxes over the full depth in a dynamically consistent and data-constrained ocean state estimate. The changes of the horizontally averaged salinity display a vertically layered structure, consistent with the profiles of the ocean vertical salt fluxes. For salinity changes in the relatively well-observed upper ocean, the contribution of vertical exchange of salt can be on the same order of the net surface freshwater input. The vertical redistribution of salt thus should be considered in inferring changes in global ocean salinity and the hydrological cycle from the surface and upper ocean measurements.
|
Mazzei, V., Wilson, B. J., Servais, S., Charles, S. P., Kominoski, J. S., & Gaiser, E. E. (2019). Periphyton as an indicator of saltwater intrusion into freshwater wetlands: insights from experimental manipulations. Ecol Appl, 30(3), e02067.
Abstract: Saltwater intrusion has particularly large impacts on karstic wetlands of the Caribbean Basin due to their porous, carbonate bedrock and low elevation. Increases in salinity and phosphorus (P) accompanying saltwater intrusion into these freshwater, P-limited wetlands are expected to alter biogeochemical cycles along with the structure and function of plant and algal communities. Calcareous periphyton is a characteristic feature of karstic wetlands and plays a central role in trophic dynamics, carbon storage, and nutrient cycling. Periphyton is extremely sensitive to water quality and quantity, but the effects of saltwater intrusion on these microbial mats remain to be understood. We conducted an ex situ mesocosm experiment to test the independent and combined effects of elevated salinity and P on the productivity, nutrient content, and diatom composition of calcareous periphyton from the Florida Everglades. We measured periphyton total carbon, nitrogen, and P concentrations and used settlement plates to measure periphyton accumulation rates and diatom species composition. The light and dark bottle method was used to measure periphyton productivity and respiration. We found that exposure to ~1 g P.m(-2) .yr(-1) significantly increased periphyton mat total P concentrations, but had no effect on any other response variable. Mats exposed to elevated salinity (~22 kg salt.m(-2) .yr(-1) ) had significantly lower total carbon and tended to have lower biomass and reduced productivity and respiration rates; however, mats exposed to salinity and P simultaneously had greater gross and net productivity. We found strong diatom species dissimilarity between fresh- and saltwater-treated periphyton, while P additions only elicited compositional changes in periphyton also treated with saltwater. This study contributes to our understanding of how the ecologically important calcareous periphyton mats unique to karstic, freshwater wetlands respond to increased salinity and P caused saltwater intrusion and provides a guide to diatom indicator taxa for these two important environmental drivers.
|
Meyers, S. D., Wilson, M., & Luther, M. E. (2015). Observations of hysteresis in the annual exchange circulation of a large microtidal estuary. J. Geophys. Res. Oceans, .
Abstract: A nonlinear relation between the salinity field and the subtidal exchange circulation in the Tampa Bay estuary is demonstrated using observational data from 1999-2011. The data are averaged to form mean monthly climatological values of total freshwater discharge (Q), axial and vertical salinity gradients, and subtidal vertical shear. Well-known steady-state solutions indicate the exchange circulation is linearly proportional to the horizontal salinity gradient, assuming a constant vertical eddy viscosity (Aeff). The exchange flow is found to be multi-valued with respect to the horizontal salinity gradient, forming a hysteresis loop in parameter space that passes through three dynamical regimes. Regime I is relatively dry with weak salinity gradients and exchange circulation. Regime II is the wet season (June-September) in which all quantities rapidly increase. In regime III the exchange flow persists even though Q and the axial salinity gradient are again low. Gradient Richardson numbers and Simpson numbers also form a loop in parameter space with Ri remaining subcritical (turbulent) until the wet season when Ri rises above criticality (weak vertical mixing) where it remains through the end of regime III. The Simpson number is in a narrow range around 0.2, indicating that the horizontal salinity gradient is always a driver of the exchange circulation. The Aeff, estimated from a parameterization of the Richardson number, decreases by almost an order of magnitude from regime I to II. It remains low during III, indicating the persistent stratification is insulating the exchange flow from destruction by tidal mixing during this time period.
|
Moore, J. F., Pine III, W. E., Frederick, P. C., Beck, S. /, Moreno, M., Dodrill, M. J., et al. (2020). Trends in Oyster Populations in the Northeastern Gulf of Mexico: An Assessment of River Discharge and Fishing Effects over Time and Space. Mar Coast Fish, 12(3), 191–204.
Abstract: Within the Big Bend region of the northeastern Gulf of Mexico, one of the least developed coastlines in the continental USA, intertidal and subtidal populations of eastern oysterCrassostrea virginica(hereafter referred to as "oyster") are a critical ecosystem and important economic constituent. We assessed trends in intertidal oyster populations, river discharge, and commercial fishing activity in the Suwannee River estuary within the Big Bend region using fisheries-independent data from irregular monitoring efforts and publicly available environmental data. We used generalized linear models to evaluate counts of oysters from line-transect surveys over time and space. We assessed model performance using simulation to understand potential bias and then evaluated whether these counts were related to freshwater inputs from the Suwannee River and commercial oyster fishing effort and landings at different time lags. We found that intertidal oyster counts have declined over time and that most of these declines are found in inshore intertidal oyster bars, which are becoming degraded. We also found a significant relationship between oyster counts and a 1-year lag on mean daily Suwannee River discharge, but including commercial fishery trips or landings did not improve model fit. It is unclear whether declines in intertidal oyster bars are offset by formation of new oyster reefs elsewhere. These results quantify rapid declines in intertidal oyster reefs in a region of coastline with high conservation value that can be used to inform ongoing and proposed restoration projects in the region.
|
Ogurcak, D. E., & Price, R. M. (2019). Groundwater geochemistry fluctuations along a fresh-saltwater gradient on the carbonate islands of the lower Florida Keys. Chemical Geology, 527.
Abstract: Climate change will have long-lasting effects on the availability of fresh water on small, carbonate islands that have isolated fresh groundwater lenses, particularly as sea level rises and rainfall regimes shift. The carbonate islands of the Florida Keys provide an ideal location to study the effect of variable rainfall on the aqueous geochemistry of the islands' groundwater. In a rainfall-driven carbonate system, the expectation is that limestone dissolution will occur within the vadose zone resulting in increased ions in the groundwater. However, geochemical processes are also affected by the salinity of groundwater and the extent of the mixing zone between fresh and salt water. We chose two islands to conduct the study of the shallow groundwater: the largest island in the lower Florida Keys, Big Pine Key (BPK), and a smaller island, Upper Sugarloaf Key (SLK). From May 2011 through April 2012, monthly groundwater samples were collected from 24 shallow (1 m deep) wells located along a fresh to saline gradient on both islands. Groundwater chemistry was compared with rainfall amounts from a weather station on BPK. Saturation indices for aragonite and calcite, generated with geochemical modeling in PHREEQC, were compared to conservative mixing between Gulf of Mexico water and freshwater. Equilibrium to supersaturated conditions with respect to carbonate minerals dominated in all of the groundwater samples. Saturation indices varied with rainfall with the most supersaturated samples observed after a large rain event and samples approaching equilibrium after the longest period without rainfall. Calcium in excess of what would be expected from conservative mixing of fresh water and seawater was observed in all groundwater samples and was elevated at near-shore locations, especially on BPK. Contrary to expectations, dissolution resulting from mixing of freshwater and seawater was not supported in the shallow groundwater. Instead, dissolution within the narrow vadose zone from rain events likely resulted in the excess calcium in the groundwater. Seasonal fluctuations in groundwater composition were primarily observed on the smaller island and were related to the fresh water balance, changing rapidly after a heavy rain event, and suggest that a size threshold has been surpassed for a stable lens. Rising seas will further decrease lens extent and vadose zone depth, reducing the potential for future limestone dissolution.
|
Putland, J. N., Mortazavi, B., Iverson, R. L., & Wise, S. W. (2014). Phytoplankton Biomass and Composition in a River-Dominated Estuary During Two Summers of Contrasting River Discharge. Estuaries and Coasts, 37(3), 664–679.
Abstract: Estuaries located in the northern Gulf of Mexico are expected to experience reduced river discharge due to increasing demand for freshwater and predicted periods of declining precipitation. Changes in freshwater and nutrient input might impact estuarine higher trophic level productivity through changes in phytoplankton quantity and quality. Phytoplankton biomass and composition were examined in Apalachicola Bay, Florida during two summers of contrasting river discharge. The < 20 mu m autotrophs were the main component (92 +/- 3 %; n = 14) of phytoplankton biomass in lower (< 25 psu) salinity waters. In these lower salinity waters containing higher dissolved inorganic nutrients, phycocyanin containing cyanobacteria made the greatest contribution to phytoplankton biomass (69 +/- 3 %; n = 14) followed by < 20 mu m eukaryotes (19 +/- 1 %; n = 14), and phycoerythrin containing cyanobacteria (4 +/- 1 %; n = 14). In waters with salinity from 25 to 35 psu that were located within or in close proximity to the estuary, > 20 mu m diatoms were an increasingly (20 to 70 %) larger component of phytoplankton biomass. Lower summer river discharges that lead to an areal contraction of lower (5-25 psu) salinity waters composed of higher phytoplankton biomass dominated by small (< 20 mu m) autotrophs will lead to a concomitant areal expansion of higher (> 25 psu) salinity waters composed of relatively lower phytoplankton biomass and a higher percent contribution by > 20 mu m diatoms. A reduction in summer river discharge that leads to such a change in quantity and quality of estuarine phytoplankton available will result in a reduction in estuarine zooplankton productivity and possibly the productivity of higher trophic levels.
|
|
Robbins,, & Lisle,. (2018). Regional Acidification Trends in Florida Shellfish Estuaries: a 20+ Year Look at pH, Oxygen, Temperature, and Salinity. Estuaries and Coasts, 41(5), 1268–1281.
|
Saha, A. K., Moses, C. S., Price, R. M., Engel, V., Smith, T. J., & Anderson, G. (2012). A Hydrological Budget (2002-2008) for a Large Subtropical Wetland Ecosystem Indicates Marine Groundwater Discharge Accompanies Diminished Freshwater Flow. Estuaries and Coasts, 35(2), 459–474.
Abstract: Water budget parameters are estimated for Shark River Slough (SRS), the main drainage within Everglades National Park (ENP) from 2002 to 2008. Inputs to the water budget include surface water inflows and precipitation while outputs consist of evapotranspiration, discharge to the Gulf of Mexico and seepage losses due to municipal wellfield extraction. The daily change in volume of SRS is equated to the difference between input and outputs yielding a residual term consisting of component errors and net groundwater exchange. Results predict significant net groundwater discharge to the SRS peaking in June and positively correlated with surface water salinity at the mangrove ecotone, lagging by 1 month. Precipitation, the largest input to the SRS, is offset by ET (the largest output); thereby highlighting the importance of increasing fresh water inflows into ENP for maintaining conditions in terrestrial, estuarine, and marine ecosystems of South Florida.
|
|
Schettini, C. A. F., Valle-Levinson, A., & Truccolo, E. C. (2017). Circulation and transport in short, low-inflow estuaries under anthropogenic stresses. Regional Studies in Marine Science, 10, 52–64.
|
Stachelek, J., Kelly, S. P., Sklar, F. H., Coronado-Molina, C., Troxler, T., Bauman, L., et al. (2018). In situ simulation of sea-level rise impacts on coastal wetlands using a flow-through mesocosm approach. Methods Ecol Evol, 9(8), 1908–1915.
Abstract: 1. The impact of sea level rise (SLR) on coastal wetlands is dependent on the net effects of increased inundation and saltwater intrusion. The need for accurate projections of SLR impacts has motivated several experimental mesocosm studies aimed at detailed investigations on wetland biogeochemical cycling. However, the degree with which they accurately reproduce field conditions remains unknown because they have primarily been laboratory based using relatively small sediment volumes (10-200 L) treated over short time periods.
2. As a first step towards addressing these issues, we present a novel mesocosm device and portable methodology for long-term SLR simulation via in situ saltwater additions to relatively large sediment volumes (approximately 1,000 L). The device (chamber) consists of two interlocking polycarbonate cylinders with an internal diameter of 1.4 m. Each cylinder has holes drilled in the side to facilitate water exchange. The outer cylinder (collar) can be rotated to one of two possible positions. The first position produces alignment of the inner cylinder holes with the collar holes, whereas the second position offsets the holes to eliminate water exchange and contain salt additions (doses).
3. Our device design and dosing scheme produced higher porewater salinities in the sediments of treatment mesocosms relative to control mesocosm sediments. In addition, we observed low incidence of elevated porewater salinity outside of the chamber walls and no measurable salt contamination of control plots.
4. Widespread SLR simulations in a variety of geographical settings, whether with our proposed design or some other design, would likely help reduce some of the general uncertainties regarding the sensitivity of coastal wetlands to SLR and saltwater intrusion.
|
Talley, L. D., Feely, R. A., Sloyan, B. M., Wanninkhof, R., Baringer, M. O., Bullister, J. L., et al. (2016). Changes in Ocean Heat, Carbon Content, and Ventilation: A Review of the First Decade of GO-SHIP Global Repeat Hydrography. Annu. Rev. Mar. Sci., 8(1), 185–215.
Abstract: Global ship-based programs, with highly accurate, full water column physical and biogeochemical observations repeated decadally since the 1970s, provide a crucial resource for documenting ocean change. The ocean, a central component of Earth's climate system, is taking up most of Earth's excess anthropogenic heat, with about 19% of this excess in the abyssal ocean beneath 2,000 m, dominated by Southern Ocean warming. The ocean also has taken up about 27% of anthropogenic carbon, resulting in acidification of the upper ocean. Increased stratification has resulted in a decline in oxygen and increase in nutrients in the Northern Hemisphere thermocline and an expansion of tropical oxygen minimum zones. Southern Hemisphere thermocline oxygen increased in the 2000s owing to stronger wind forcing and ventilation. The most recent decade of global hydrography has mapped dissolved organic carbon, a large, bioactive reservoir, for the first time and quantified its contribution to export production (similar to 20%) and deep-ocean oxygen utilization. Ship-based measurements also show that vertical diffusivity increases from a minimum in the thermocline to a maximum within the bottom 1,500 m, shifting our physical paradigm of the ocean's overturning circulation.
|
|
Tynan, S., Opdyke, B., Dutton, A., & Walczak, M. (2017). Late Holocene inter-annual temperature variability reconstructed from the [delta][super:18]O of archaeological_Ostrea angasi_shells. Australian Journal of Earth Sciences, 64(6), 779–791.
|
|
Wang, C., Tong, C., Chambers, L. G., & Liu, X. (2017). Identifying the Salinity Thresholds that Impact Greenhouse Gas Production in Subtropical Tidal Freshwater Marsh Soils. Wetlands, 37(3), 559–571.
|
