Hilary D. Flower

Public support for restoration in sensitive ecosystems like the Everglades depends in part on individual-level concern and perceptions of impact from environmental threats. This study examines how environmental knowledge and ideological and political factors (IPFs)– cultural worldview (CWV), political ideology, and voting behavior – influence Floridians’ concern for the Everglades and their perceptions of impact for six different threats to the Everglades. Two of these threats, sea level rise and changes in precipitation, relate directly to climate change and thus are more likely to evoke ideological or political responses from participants. Analysis of our sample of 1437 Floridians reveals that: (1) Of the IPFs, CWV had the largest influence on environmental concern and perceptions of impact, except for in the case of sea level rise, for which voting behavior superseded CWV, (2) environmental knowledge had a larger influence on perceptions of impact for environmental threats that are not ideologically entangled (e.g. water quality), (3) IPFs had a larger influence on perceptions of impact from threats that are ideologically entangled (i.e. sea level rise and changes in precipitation), and (4) those with Communitarian-Egalitarian worldviews held higher levels of concern and perceived greater risk impacts on all but one of the threats (invasive species), although some differences vary across the distribution of environmental knowledge. These findings improve our understanding of how environmental knowledge and IPFs shape public concern for and perceptions of threats to the Greater Everglades ecosystem. These insights can help in developing communication strategies that generate public support for restoration.

One of the most important ecological consequences of saltwater intrusion into coastal aquifers is that water-rock interactions result in a spike in phosphorus (P) in ambient groundwater, which can then be discharged to overlying estuaries. Although this phenomenon is well-documented globally, the geochemistry of the process has remained a matter of speculation. Laboratory experiments paired with geochemical modeling can provide insight into the thermodynamically favorable mechanisms behind observed phenomena. It is particularly important to understand the mechanism for seawater-induced desorption from calcite, because this mineral is the main component of limestone, a common bedrock of coastal aquifers globally. We conducted batch experiments with calcite that had pre-adsorbed P, immersing it in freshwater, seawater, or a range of mixtures of the two, and measuring the P released to solution after equilibration. These empirical results provide input to geochemical software that was programmed to allow Ca2+-P ion pairs (CaPO4- and CaHPO40) to adsorb to the mineral surface at positively charged calcium sites in competition with common seawater ligands (CO32-, SO42-, and H2O). This allowed us to compare the viability of possible surface complexation reactions in simulating our laboratory results, and calibrate association constants for plausible reactions. Based on the surface complexation reactions that could successfully simulate our empirical observations of saltwater-induced P-desorption from calcite, we identified a "push" and "pull" mechanism. In our model, P is "pulled" from the calcite surface due to the high concentrations of dissolved Mg2+ in seawater, which strongly scavenges surface P to form aqueous Mg2+-P ion pairs (MgHPO40 and particularly MgPO4-). To a lesser extent, P may be "pushed" from the calcite surface due to competition by seawater CO32-. Although SO42- has been suggested as a possibly important competitor for P at the mineral surface, our model provided no support for this mechanism. This study is the first to successfully model seawater-induced P desorption from any mineral. Our study provides association constants for surface complexation reactions which can be used in future modeling of phosphorus release caused by saltwater intrusion into coastal carbonate aquifers.

One of the primary drivers of Phosphorus (P) limitation in aquatic systems is P adsorption to sediments. Sediments adsorb more P in freshwater compared to other natural solutions, but the mechanism driving this difference is poorly understood. To provide insights into the mechanism, we conducted batch experiments of P adsorption to calcite in freshwater and seawater, and used computer software to develop complexation models. Our simulations revealed three main reasons that, combining together, may explain the greater P adsorption to calcite in freshwater vs. seawater. First, aqueous speciation of P makes a difference. The ion pair CaPO4− is much more abundant in freshwater; although seawater has more Ca2+ ions, MgHPO40 and NaHPO40 are more thermodynamically favored. Second, the adsorbing species of P make a difference. The ion pair CaPO4− (the preferred adsorbate in freshwater) is able to access adsorption sites that are not available to HPO42− (the preferred adsorbate in seawater), thereby raising the maximum concentration of P that can adsorb to the calcite surface in freshwater. Third, water chemistry affects the competition among ions for surface sites. Other ions (including P) compete more effectively against CO32− when immersed in freshwater vs. seawater, even when the concentration of HCO3−/CO32− is higher in freshwater vs. seawater. In addition, we found that under oligotrophic conditions, P adsorption is driven by the higher energy adsorption sites, and by the lower energy sites in eutrophic conditions. This study is the first to model P adsorption mechanisms to calcite in freshwater and seawater. [Display omitted] •A model of phosphorus adsorption to calcite in natural waters is presented.•Immersion in freshwater enhances phosphorus adsorption to the calcite mineral surface.•Phosphorus preferentially adsorbs to calcite as CaPO4− in freshwater.•Abundance of dissolved CaPO4− in freshwater enhances phosphorus adsorption.•Phosphorus competes with CO32− at the calcite surface more effectively in freshwater compared to seawater.

In the subtropics, climate change is pushing woody mangrove forests into herbaceous saltmarshes, altering soil carbon (C) and nitrogen (N) pools, with implications for coastal wetland productivity and C and N exports. We quantified total C and N pools, and mobile fractions including extractable mineral N, extractable organic C and N, and active (aerobically mineralizable) C and N, in surface soils (top 7.6 cm) of adjacent mangrove (primarily Avicennia germinans) and saltmarsh (Juncus roemerianus) vegetation zones in tidal wetlands of west-central Florida (USA). We tested whether surface-soil accumulations of C, N, and their potentially mobile fractions are greater in mangrove than in saltmarsh owing to greater accumulations in the mangrove zone of soil organic matter (SOM) and fine mineral particles (C- and N-retaining soil constituents). Extractable organic fractions were 39-45% more concentrated in mangrove than in saltmarsh surface soil, and they scaled steeply and positively with SOM and fine mineral particle (silt + clay) concentrations, which themselves were likewise greater in mangrove soil. Elevation may drive this linkage. Mangrove locations were generally at lower elevations, which tended to have greater fine particle content in the surface soil. Active C and extractable mineral N were marginally (p < 0.1) greater in mangrove soil, while active N, total N, and total C showed no statistical differences between zones. Extractable organic C and N fractions composed greater shares of total C and N pools in mangrove than in saltmarsh surface soils, which is meaningful for ecosystem function, as persistent leaching of this fraction can perpetuate nutrient limitation. The active (mineralizable) C and N fractions we observed constituted a relatively small component of total C and N pools, suggesting that mangrove surface soils may export less C and N than would be expected from their large total C and N pools. (c) 2021 Elsevier B.V. All rights reserved.

Scenarios modeling can be a useful tool to plan for climate change. In this study, we help Everglades restoration planning to bolster climate change resiliency by simulating plausible ecosystem responses to three climate change scenarios: a Baseline scenario of 2010 climate, and two scenarios that both included 1.5 degrees C warming and 7% increase in evapotranspiration, and differed only by rainfall: either increase or decrease by 10%. In conjunction with output from a water-use management model, we used these scenarios to drive the Everglades Landscape Model to simulate changes in a suite of parameters that include both hydrologic drivers and changes to soil pattern and process. In this paper we focus on the freshwater wetlands; sea level rise is specifically addressed in prior work. The decreased rainfall scenario produced marked changes across the system in comparison to the Baseline scenario. Most notably, muck fire risk was elevated for 49% of the period of simulation in one of the three indicator regions. Surface water flow velocity slowed drastically across most of the system, which may impair soil processes related to maintaining landscape patterning. Due to lower flow volumes, this scenario produced decreases in parameters related to flow-loading, such as phosphorus accumulation in the soil, and methylmercury production risk. The increased rainfall scenario was hydrologically similar to the Baseline scenario due to existing water management rules. A key change was phosphorus accumulation in the soil, an effect of flow-loading due to higher inflow from water control structures in this scenario.