Water Conservation Area Research Articles

Screening Historical Water Quality Monitoring Data for Chemicals of Potential Ecological Concern: Hazard Assessment for Selected Inflow and Outflow Monitoring Stations at the Water Conservation Areas, South Florida

A hazard assessment was conducted of contaminants found at inflow and outflow monitoring stations of the Water Conservation Areas (WCAs) in South Florida. WCAs (1, 2A, 2B 3A, 3B) lie north of Everglades National Park (ENP) and southeast of Lake Okeechobee, span almost 1400 mi2, and serve a number of water resource functions which include food control for three major counties, delivering water to ENP, and water storage during dry downs and for recharging groundwater. Measured concentrations of contaminants in sediment and water were evaluated at 13 monitoring stations in the WCAs using a screening benchmark approach. Chemicals of potential ecological concern (COPECs) included herbicides, organochlorine pesticides, organochlorine industrial chemicals, and heavy metals. Of the stations, total cadmium was a COPEC at nine of them. Most sites had maximum detected concentrations of cadmium that exceeded state of Florida (USA) water quality criteria standards. Beryllium, copper, mercury, methylmercury, and zinc (measured as total metal concentration) also exceeded surface water criteria at several sites. Several organochlorine chemicals in sediment were COPECs; chlordane, polychlorinated biphenyls, and p,p′-DDT with its metabolites (p,p′-DDD and p,p′-DDE) had more than 200 sediment benchmark exceedences. Mercury in fish tissue was a COPEC at S5A when compared to a no-effect residue value for survival. Greater potential hazards were observed at northern monitoring sites than southern sites around the WCAs. The hazard assessment approach for screening water quality data described in this article can help focus higher tier risk assessment work, including laboratory, field, and data analysis studies, on contaminants with greater potential for adverse biological effects.

Persistence of legacy soil P and elevated background water P concentrations in Water Conservation Area 2A, a northern Everglades wetland

AbstractUpstream source control and Stormwater Treatment Areas (STAs) have reduced phosphorus (P) loads to Water Conservation Area 2A (WCA‐2A), a northern Everglades wetland, by three quarters since year 2000. Nevertheless, large storages of P remain in enriched peat soils and it is unclear how legacy stores will impact spatial and temporal scales of recovery. We remeasured soil P enrichment along a well‐studied eutrophication gradient in WCA‐2A and applied a profile modeling approach with uncertainty analysis to assess changes in longitudinal soil P gradients 13 years after load reductions. We then analyzed existing internal water P data, using a novel data screening approach, for evidence of lowest possible water P concentrations independent from inflows. We interpret such water P limits as evidence of the strength of internal loading at a location. Results indicate that soil P enrichment persists in the ∼7.5 km long “impacted” zone, with no significant evidence of net advancement or recession, while a large pool of labile P in the flocculent layer consolidated and diminished. There is indeed evidence, both spatial and temporal, that this extensive zone of enriched soil P continues to elevate lowest achievable water P concentrations. The corresponding gradient of elevated water P limits is both receding and diminishing since load reductions, thus providing further evidence toward recovery. However, results also suggest that these “transitory P limits” due to internal loading are likely to persist for decades above water quality targets. These results advance our understanding of recovery in impacted wetlands and are relevant to Everglades restoration.

Distribution, activities, and interactions of methanogens and sulfate-reducing prokaryotes in the Florida Everglades.

To gain insight into the mechanisms controlling methanogenic pathways in the Florida Everglades, the distribution and functional activities of methanogens and sulfate-reducing prokaryotes (SRPs) were investigated in soils (0 to 2 or 0 to 4 cm depth) across the well-documented nutrient gradient in the water conservation areas (WCAs) caused by runoff from the adjacent Everglades Agricultural Area. The methyl coenzyme M reductase gene (mcrA) sequences that were retrieved from WCA-2A, an area with relatively high concentrations of SO4 (2-) (≥39 μM), indicated that methanogens inhabiting this area were broadly distributed within the orders Methanomicrobiales, Methanosarcinales, Methanocellales, Methanobacteriales, and Methanomassiliicoccales. In more than 3 years of monitoring, quantitative PCR (qPCR) using newly designed group-specific primers revealed that the hydrogenotrophic Methanomicrobiales were more numerous than the Methanosaetaceae obligatory acetotrophs in SO4 (2-)-rich areas of WCA-2A, while the Methanosaetaceae were dominant over the Methanomicrobiales in WCA-3A (with relatively low SO4 (2-) concentrations; ≤4 μM). qPCR of dsrB sequences also indicated that SRPs are present at greater numbers than methanogens in the WCAs. In an incubation study with WCA-2A soils, addition of MoO4 (2-) (a specific inhibitor of SRP activity) resulted in increased methane production rates, lower apparent fractionation factors [αapp; defined as (amount of δ(13)CO2 + 1,000)/(amount of δ(13)CH4 + 1,000)], and higher Methanosaetaceae mcrA transcript levels compared to those for the controls without MoO4 (2-). These results indicate that SRPs play crucial roles in controlling methanogenic pathways and in shaping the structures of methanogen assemblages as a function of position along the nutrient gradient.

Механизм экологической компенсации в водоохранной зоне (на примере реки Дунцзян)

Механизм экологической компенсации в водоохранной зоне (на примере реки Дунцзян)

Quantitative Comparison of Plant Community Hydrology Using Large-Extent, Long-Term Data

Large-extent vegetation datasets that co-occur with long-term hydrology data provide new ways to develop biologically meaningful hydrologic variables and to determine plant community responses to hydrology. We analyzed the suitability of different hydrological variables to predict vegetation in two water conservation areas (WCAs) in the Florida Everglades, USA, and developed metrics to define realized hydrologic optima and tolerances. Using vegetation data spatially co-located with long-term hydrological records, we evaluated seven variables describing water depth, hydroperiod length, and number of wet/dry events; each variable was tested for 2-, 4- and 10-year intervals for Julian annual averages and environmentally-defined hydrologic intervals. Maximum length and maximum water depth during the wet period calculated for environmentally-defined hydrologic intervals over a 4-year period were the best predictors of vegetation type. Proportional abundance of vegetation types along hydrological gradients indicated that communities had different realized optima and tolerances across WCAs. Although in both WCAs, the trees/shrubs class was on the drier/shallower end of hydrological gradients, while slough communities occupied the wetter/deeper end, the distribution of Cladium, Typha, wet prairie and Salix communities, which were intermediate for most hydrological variables, varied in proportional abundance along hydrologic gradients between WCAs, indicating that realized optima and tolerances are context-dependent.

Mercury accumulation in largemouth bass (Micropterus salmoides Lacépède) within marsh ecosystems of the Florida Everglades, USA.

This study evaluates factors, particularly water quality related, that may influence mercury (Hg) bioaccumulation in largemouth bass (LMB, Micropterus salmoides Lacépède) within the Everglades marshes of South Florida. The investigation is an empirical analysis of ambient data from both long-term fish monitoring and marsh water quality monitoring sites across the Everglades Protection Area. Previous Hg studies of Everglade's marsh biota have focused on the role that sulfate plays in Hg bioaccumulation. While sulfate can be important under some environmental conditions, this empirical analysis in Everglades marshes showed that sulfate has little association with Hg concentrations in LMB. It is suggested that other water quality variables including water pH, alkalinity and specific conductance may have as much or more influence in the accumulation of Hg in LMB. Furthermore, tissue Hg concentration normalized to body-weight and age-specific growth rates were significantly correlated with Water Conservation Area (WCA)-1, WCA-2 and Everglades National Park (ENP) but not WCA-3. However, body condition was correlated negatively with Hg concentration only within WCA-2, WCA-3 and ENP; the relationship was not significant within WCA-1. This disparity between Hg concentration and body condition could be attributed to ecological effects including water quality and quantity conditions within each compartment of the system that are significant driving forces for biota abundance, trophic structure and distribution within the Everglades ecosystem. While water quality and quantity are important, trophic position of LMB has the potential to influence Hg accumulation dynamics. In spite of documented biogeochemical linkages to Hg accumulation, this empirical analysis did not demonstrate enough quantitative interaction to be useful for Hg management in the Everglades ecosystem.

Soil Phosphorus and Nitrogen Predictions Across Spatial Escalating Scales in an Aquatic Ecosystem Using Remote Sensing Images

The incorporation of remote sensing (RS) data into digital soil models has shown success to improve soil predictions. However, the effects of multiresolution imagery on modeling of biogeochemical soil properties in aquatic ecosystems are still poorly understood. The objectives of this study were the following: 1) to develop prediction models for soil total phosphorus (TP) and total nitrogen (TN) utilizing RS images and environmental ancillary data at three different resolutions; 2) to identify controlling factors of the spatial distribution of soil TP and TN; and 3) to elucidate the effects of different spatial resolutions of RS images on inferential modeling. Soil cores were collected $(n=108)$ from the top 10 cm in a subtropical wetland: Water Conservation Area-2A, the Florida Everglades, USA. The spectral data and derived indices from RS images, which have different spatial resolutions, included the following: MODIS (500 m resampled to 250 m), Landsat ETM+ (30 m), and SPOT (10 m). Block kriging and random forest (RF) were employed to predict soil TP and TN using RS-image-derived spectral input variables, environmental ancillary data, and soil observations. The RF models showed $R^{2}$ between 0.90 and 0.93 and root mean square error between 100.4 and 115.9 $\hbox{mg}\cdot\hbox{kg}^{-1}$ for TP and between 1.45 and 1.52 $\hbox{g}\cdot\hbox{kg}^{-1}$ for TN. Soil TP was mainly predicted from RS-derived spectral indices that infer on biotic/vegetation characteristics, whereas soil TN was predicted using a combination of biotic/vegetation, topographic, and hydrologic variables. Results suggest that the spectral data informed soil models have excellent predictive capabilities in this aquatic ecosystem. Interestingly, there was no noticeable distinction among different spatial resolutions of RS images to develop prediction models for soil TP and TN in terms of error assessment. However, the variability and complexity of soil TP and TN variations were much better expressed with the finer resolution ${\rm RF}_{\rm SPOT}$ model than the coarser resolution ${\rm RF}_{\rm MODIS}$ model as demonstrated using entropy.

Syntrophs dominate sequences associated with the mercury methylation-related gene hgcA in the water conservation areas of the Florida Everglades.

The mechanisms and rates of mercury methylation in the Florida Everglades are of great concern because of potential adverse impacts on human and wildlife health through mercury accumulation in aquatic food webs. We developed a new PCR primer set targeting hgcA, a gene encoding a corrinoid protein essential for Hg methylation across broad phylogenetic boundaries, and used this primer set to study the distribution of hgcA sequences in soils collected from three sites along a gradient in sulfate and nutrient concentrations in the northern Everglades. The sequences obtained were distributed in diverse phyla, including Proteobacteria, Chloroflexi, Firmicutes, and Methanomicrobia; however, hgcA clone libraries from all sites were dominated by sequences clustering within the order Syntrophobacterales of the Deltaproteobacteria (49 to 65% of total sequences). dsrB mRNA sequences, representing active sulfate-reducing prokaryotes at the time of sampling, obtained from these sites were also dominated by Syntrophobacterales (75 to 89%). Laboratory incubations with soils taken from the site low in sulfate concentrations also suggested that Hg methylation activities were primarily mediated by members of the order Syntrophobacterales, with some contribution by methanogens, Chloroflexi, iron-reducing Geobacter, and non-sulfate-reducing Firmicutes inhabiting the sites. This suggests that prokaryotes distributed within clades defined by syntrophs are the predominant group controlling methylation of Hg in low-sulfate areas of the Everglades. Any strategy for managing mercury methylation in the Everglades should consider that net mercury methylation is not limited to the action of sulfate reduction.

An extended riparian buffer strip concept for soil conservation and stream protection in an agricultural riverine area of the La Chevrotière River watershed, Québec, Canada, using remote sensing and GIS techniques

The implementation of riparian buffer strips in agricultural areas is regarded as a means to protect watercourses against runoff water carrying sediments and contaminants. In the field, riparian buffers are usually dimensioned to meet the minimum width required by policies and regulations. In the case of the province of Québec, Canada, regulation stipulates a width of 1–3 m in agricultural watersheds. However, such small riparian strips offer little protection, especially during the spring-snowmelt period when the soil is saturated, infiltration is low, vegetative cover is poor and soil erosion and runoff are the dominant hydrological processes. In this study, high-resolution, remote sensing, raster-based information is used to evaluate an extended riparian buffer strip concept with variable widths of 5–120 m to assess soil erosion and to convert agricultural riverine areas into soil and water conservation areas. For a studied watershed of 108 km2 in Québec, this would enable reducing soil erosion in riverine areas from 361 to 1.0 t year−1 (1.9 to 0.005 t ha−1 year−1), and thereby reducing soil erosion at the watershed scale by 40% (calculated with the Revised Universal Soil Loss Equation, RUSLE). The extended riparian buffer strip concept would require the conversion of 7% of the 29 km2 of agricultural land.

Factors influencing phosphorus levels delivered to Everglades National Park, Florida, USA.

Everglades restoration is dependent on constructed wetlands to treat agricultural phosphorus (P)-enriched runoff prior to delivery to the Everglades. Over the last 5years, P concentrations delivered to the northern boundary of Everglades National Park (Park) have remained higher than the 8μg L(-1)-target identified to be protective of flora and fauna. Historically, Everglades hydrology was driven by rainfall that would then sheetflow through the system. The system is now divided into a number of large impoundments. We use sodium-to-calcium ratios as a water source discriminator to assess the influence of management and environmental conditions to understand why P concentrations in Park inflows remain higher than that of the target. Runoff from Water Conservation Area 3A (Area 3A) and canal water from areas north of Area 3A are two major sources of water to the Park, and both have distinct Na:Ca ratios. The P concentrations of Park inflows have decreased since the 1980s, and from June 1994 through May 2000, concentrations were the lowest when Area 3A water depths were the deepest. Area 3A depths declined following this period and P concentrations subsequently increased. Further, some water sources for the Park are not treated and are impeding concentration reductions. Promoting sheetflow over channelized flow and treating untreated water sources can work in conjunction with constructed wetlands to further reduce nutrient loading to the sensitive Everglades ecosystem.

Global uncertainty and sensitivity analysis of a spatially distributed ecological model

The Florida Everglades are experiencing a shift in vegetation, due to the more invasive Typha domingensis (cattail) occupying areas that were historically dominated by Cladium jamaicense (sawgrass). A computer simulation model is required in order to better understand these vegetation dynamics and to develop best management practices, as the focus of the comprehensive Everglades restoration plan (CERP) shifts more toward ecology. Recently, the coupled regional simulation model (RSM) and transport and reaction simulation engine (TARSE) model were adapted to simulate ecological processes, specifically Typha domingensis (cattail) dynamics in the Everglades, with five levels of increasing complexity being used. These levels ranged from a simple logistic equation to additional functionality through influences from water depth, soil phosphorus concentration and interspecies competition. In order to address the model “relevance trilemma” – balancing complexity, uncertainty and sensitivity, a global uncertainty and sensitivity analysis (GUSA) was conducted on these five levels of algorithm complexity. Spatial uncertainty in the initial data maps was addressed through the use of a sequential indicator simulation (SIS), whereby 250 alternate maps, all obeying observed data and spatial correlation, were produced. Other parameters used in the GUSA include the sawgrass initial density (uniformly distributed across Water Conservation Area 2A), the growth rate for both cattail and sawgrass, a water depth value, and soil phosphorus concentration. The statistic used for the GUSA output was the change in regional mean density (DM) from initial conditions, which signals an increase or decrease in mean density over time. The global uncertainty was determined through a 95% confidence interval on a frequency distribution plot of the DM statistic. Complexity Levels 1 and 4 had the lowest uncertainties. The narrow output distribution of Level 1 (the simple logistic equation) was expected and does not inspire confidence in that algorithm being able to accurately represent the dynamics of the system. The variance-based Sobol method was used to conduct the global sensitivity analysis. Through this analysis it was determined that the most influential parameter was water depth, followed by soil phosphorus concentration and initial distribution. The first order and total order sensitivities were very similar for complexity Levels 3, 4, and 5. This is expected because, aside from Level 5, there are no feed-back or interaction effects in the algorithms. Levels 1 and 2 have different sensitivities due to the low number of variables associated with each algorithm. Therefore it was determined that the Level 4 complexity algorithm was the most relevant, or best suited, to model cattail densities in the region, as it contains the least uncertainty, without increasing sensitivity, and it has less risk of over-parameterisation as is potentially the case with Level 5.

玛曲高寒草甸沙化过程中群落结构与植物多样性研究

Maqu alpine meadow is the important part of the Qinghai-Tibet Plateau and the main water conservation area in the upper reaches of Yellow River. But in recent years,the problems of the sandy desertification and soil erosion have become a serious threat to the ecological safety of the alpine meadow in the Qinghai-Tibet Plateau. To solve these problems,this paper examined the vegetation structure characteristics and the variation of α and β diversity on the potential,slight,moderate and serve desertification meadows in Maqu alpine meadows using sampling survey methods from July to September2008. The results showed that in the desertification processes of Mqu alpine meadows,1) the community coverage droppedgradually( 99. 216%,80. 078%,49. 895% and 36. 398%,respectively),the species number also reduced gradually( 53,32,14,13,respectively),community structure took a trend of simplification( the number of the dominant species were 28,16,10,8,respectively). The typical dominant and companion species of the alpine meadow also withdrew from the communities gradually,and the species adapted to the sandy environment occupied an important position in these plant communities. The typical Maqu alpine meadow ecosystem was gradually changing to the desertification alpine ecosystem,and experienced four stages,i. e.,Carex moorcroftii+Poa alpina communities→Carex moorcroftii +Saposhnikovia divaricata+Kobresia pygmaea communities → Kobresia pygmaea + Saposhnikovia divaricata + Carex moorcroftii communities → Leymus paboanus + Corispermum tibeticum + Carex moorcroftii + Saposhnikovia divaricata communities. 2) The species richness,Shannon-Wiener indexes and Simpson indexes were declining significantly. The Pielou evenness indexes and Alatalo evenness indexes showed a decreasing trend following the first increasing,and it reached the maximum in the slight desertification meadow,but their differences were not significant. The dominant index was increasing significantly,and there was extremely significant difference between the moderate desertification meadow and the slight one. 3) In terms of Whittaker index,there were extremely significant differences between the potential desertification meadow and other three ones,and there was significant difference between the moderate desertification meadow and the severe one,whereas there was no difference between the slight desertification meadow and the moderate one. 4) The community dissimilarity coefficient between the potential desertification meadow and other three ones were greater( the value in the range of 0.705—0. 937),while the community common indexes between them were lower( the value in the range of 0. 034—0. 173),and the trend between the slight desertification meadow and the severe one was similar. However,the community dissimilarity coefficients between the moderate desertification meadow and severe one and the slight desertification meadow and the moderate one were lower( the value in the range of 0. 545—0. 553),and the community common indexes were higher( the value in the range of 0. 293—0. 303). The analysis from all the results revealed that the slight and severe desertification stages were the most important phases in the desertification process of Maqu alpine meadow. So,the potential desertification meadow must be protected and managed scientifically in order to prevent desertification from occurring.Artificial measures,e. g.,enclosure,rotational grazing and tending were applied. However,in the sandy desertification meadows,vegetation restoration measures,such as turf transplantation,reseeding,fertilization as well as sand control measures must be taken to prevent the exacerbating and spreading of desertification.

The Impact of Stormwater Treatment and Best Management Practices on Nutrient Concentration in the Florida Everglades

More than half of the original Everglades system has been lost to drainage and development. What remains is primarily included within the boundaries of the Everglades Protection Area (EPA) comprising three water conservation areas (WCAs) and the Everglades National Park (Park) that receive inflows containing elevated nutrient concentrations. Six large constructed wetlands called stormwater treatment areas (STAs) were constructed to improve water quality. All WCAs and the Park trend analyses indicate that the concentrations of most nutrients in the WCAs and Park are decreasing. In general, nutrient concentrations in all WCAs were higher during the pre-STA period than after the STA became operational. Trend analysis suggests that agricultural best management practices (BMPs) lead to a large initial reduction in nutrient concentrations in the EPA. As STAs were brought online, although still declining, the rate of decline of nutrient concentration in the WCAs was lower than that of the period during initial BMP implementation. Substantially smaller amounts of nutrients from farmland runoff and leaching are being delivered to the STAs for treatment; these results indicate that the STAs may have a limited effect on nutrient concentrations in the WCAs and the Park. However, managers must improve both BMPs and the efficacy of STAs to remove nutrients from water delivered to the EPA if the Everglades ecosystem is to be restored.

The impact of stormwater treatment areas and agricultural best management practices on water quality in the Everglades Protection Area

Half of the original Everglades system has been lost to drainage and development. What remains is included within the boundaries of the Everglades Protection Area (EPA), comprised of three Water Conservation Areas (WCAs) and Everglades National Park (Park). Inflows to the EPA contain elevated nutrient concentrations. Best management practices (BMPs) were implemented and six large wetlands called stormwater treatment areas (STAs) were constructed to improve water quality. We analyzed water quality in the WCAs and Park and performed an economic analysis of the STAs to remove nutrients from EPA inflows. In general, nutrient concentrations in all WCAs were higher during the pre-STA period than after the STAs became operational. In WCA2 and the Park, total phosphorus (TP) trends showed more negative slopes prior, as compared to after, the STAs became operational. These results suggest that BMPs lead to large initial decreases in nutrient export resulting in improved downstream water quality. A preliminary economic analysis shows that operation and management of the STAs are complicated and cost intensive. Comparing the cost of phosphorus (P) removal from water entering the EPA using BMPs and STAs may not currently be viable. BMPs prevent P from being applied to, or leaving from agricultural fields while STAs remove P from stormwater. We expect nutrient concentrations in water flowing into and out of the STAs to decline as both BMPs and STAs become more effective. We suggest an economic analysis of BMPs, STAs, and other potential approaches to determine the most cost-effective methods to reduce nutrient concentrations and related stressors affecting the Everglades.

Mercury hotspot identification in Water Conservation Area 3, Florida, USA

A significant amount of science and effort has been placed on understanding the biogeochemical cycle of mercury within the Florida everglades. The range of resolution for these studies include regional (Everglades Protection Area) and site-specific scales, with very little attention being given to the landscape scale. However, a lot of questions still exist regarding methyl mercury (MeHg) synthesis, bioaccumulation and environmental accumulation. I used the Geti–Ord Gi * spatial clustering statistic to describe and evaluate soil total mercury (THg) and MeHg data collected by U.S. Environmental Protection Agency Regional Environmental Monitoring and Assessment Program between 1995 and 2005. Soil mercury (total and methyl) displayed distinct spatial clustering within Water Conservation Area 3 (WCA3) and was dependent on canal density, water control structure density and hydroperiod. THg hotspots were identified consistently within the southern portion of WCA3A and WCA3B in areas with prolonged hydroperiods (360.9 ± 0.7 days), low canal densities (0.064 ± 0.008 canals/km2) and low structure densities (0.008 ± 0.001 structures/km2). MeHg hotspots consistently occurred within the northern portion of WCA3A and during the last year of sampling in WCA3B. MeHg hotspots occurred in areas with shorter hydroperiods (282.0 ± 8.8 days), lower canal density (0.109 ± 0.013 canals/km2) and higher structure density (0.029 ± 0.005 structures/km2). Results presented in this study provide further understanding to Hg hotspot dependence on hydrological factors and potentially help guide water management decisions.

Wetland Fire Scar Monitoring and Analysis Using Archival Landsat Data for the Everglades

The ability to document the frequency, extent, and severity of fires in wetlands, as well as the dynamics of post-fire wetland land cover, informs fire and wetland science, resource management, and ecosystem protection. Available information on Everglades burn history has been based on field data collection methods that evolved through time and differ by land management unit. Our objectives were to (1) design and test broadly applicable and repeatable metrics of not only fire scar delineation but also post-fire land cover dynamics through exhaustive use of the Landsat satellite data archives, and then (2) explore how those metrics relate to various hydrologic and anthropogenic factors that may influence post-fire land cover dynamics. Visual interpretation of every Landsat scene collected over the study region during the study time frame produced a new, detailed database of burn scars greater than 1.6 ha in size in the Water Conservation Areas and post-fire land cover dynamics for Everglades National Park fires greater than 1.6 ha in area. Median burn areas were compared across several landscape units of the Greater Everglades and found to differ as a function of administrative unit and fire history. Some burned areas transitioned to open water, exhibiting water depths and dynamics that support transition mechanisms proposed in the literature. Classification tree techniques showed that time to green-up and return to pre-burn character were largely explained by fire management practices and hydrology. Broadly applicable as they use data from the global, nearly 30-year-old Landsat archive, these methods for documenting wetland burn extent and post-fire land cover change enable cost-effective collection of new data on wetland fire ecology and independent assessment of fire management practice effectiveness.

GIS modelling for locating the risk zone of soil erosion in a deciduous forest

The maps of altitude, geology, vegetation cover and land use were prepared and classified as the main criteria to locate soil and water conservation programs. Analytical Hierarchy Process (AHP) was used to determine the relative priorities of these criteria by pairwise comparison. All the thematic maps were then integrated using the overlay process in Geographical Information System (GIS) and the final map of soil erosion risk was produced. Results indicated that vegetation cover was given the highest weight (0.494). The geology was assigned the second highest weight (0.313), as the main cause of initiation of the erosion of erodible lands. Land-use change has a local influence on soil erosion, so it was assigned the third weight (0.151). Altitude is a low-impact variable for predicting the water and soil conservation areas.  

Evidence of Recent Phosphorus Enrichment in Surface Soils of Taylor Slough and Northeast Everglades National Park

Everglades National Park (ENP) is the last hydrologic unit in the series of impounded marsh units that make up the present-day Everglades. The ENP receives water from upstream Water Conservation Areas via canals and water control structures that are highly regulated for flood control, water supply, wildlife management, concerns about poor water quality and the potential for downstream ecosystem degradation. Recent surveys of surface soils in ENP, designed for random sampling for spatial analysis of soil nutrients, did not sample proximate to inflow structures and thus did not detect increased soil phosphorus associated with these water conveyances. This study specifically addressed these areas in a focused sampling effort at three key inflow points in northeast ENP which revealed elevated soil TP proximate to inflows. Two transects extending down Shark River Slough and one down Taylor Slough (a natural watershed of particular ecological value) were found to have soil TP levels in excess of 500 mg kg−1—a threshold above which P enrichment is indicated. These findings suggest the negative impact of elevated water (P) from surface flows and support the assertion that significant soil TP enrichment is occurring in Taylor Slough and other areas of northeastern ENP.

Mercury Bio-concentration Factor in Mosquito Fish (Gambusia spp.) in the Florida Everglades

The aim of this study was to evaluate Gambusia spp. (mosquito-fish) mercury bio-concentration factor in relation to marsh surface water sulfate concentration. As part of the everglades regional environmental monitoring and assessment marsh biogeochemical parameters were collected by the US Environmental Protection agency between 1995 and 2005 within the Everglades Protection Area and Everglades National Park (ENP). Surface water sulfate and methyl-mercury concentration data in combination with mosquito-fish total mercury concentration data was used to elucidate the gambusia mercury bio-concentration and surface water sulfate relationship. Previous studies hypothesized that the relationship of biota mercury and surface water sulfate concentrations is unimodal. However this study shows that the relationship of biota mercury and sulfate surface water concentrations in mosquito-fish adheres closely with a log-log relationship. Furthermore mosquito-fish bio-concentration factor were similar for Water Conservation Area (WCA) 1 and WCA2, while WCA3 and ENP were significantly different between all pairs throughout the study period. This difference in hypothesized relationships versus the relationship defined in this study could be the result of life span (extent of exposure) or life history of mosquito-fish.

A spatially distributed, deterministic approach to modeling Typha domingensis (cattail) in an Everglades wetland

Abstract Introduction The emergent wetland species Typha domingensis (cattail) is a native Florida Everglades monocotyledonous macrophyte. It has become invasive due to anthropogenic disturbances and is out-competing other vegetation in the region, especially in areas historically dominated by Cladium jamaicense (sawgrass). There is a need for a quantitative, deterministic model in order to accurately simulate the regional-scale cattail dynamics in the Everglades. Methods The Regional Simulation Model (RSM), combined with the Transport and Reaction Simulation Engine (TARSE), was adapted to simulate ecology. This provides a framework for user-defineable equations and relationships and enables multiple theories with different levels of complexity to be tested simultaneously. Five models, or levels, of increasing complexity were used to simulate cattail dynamics across Water Conservation Area 2A (WCA2A), which is located just south of Lake Okeechobee, in Florida, USA. These levels of complexity were formulated to correspond with five hypotheses regarding the growth and spread of cattail. The first level of complexity assumed a logistic growth pattern to test whether cattail growth is density dependent. The second level of complexity built on the first and included a Habitat Suitability Index (HSI) factor influenced by water depth to test whether this might be an important factor for cattail expansion. The third level of complexity built on the second and included an HSI factor influenced by soil phosphorus concentration to test whether this is a contributing factor for cattail expansion. The fourth level of complexity built on the third and included an HSI factor influenced by (a level 1–simulated) sawgrass density to determine whether sawgrass density impacted the rate of cattail expansion. The fifth level of complexity built on the fourth and included a feedback mechanism whereby the cattail densities influenced the sawgrass densities to determine the impact of inter-species interactions on the cattail dynamics. Results All the simulation results from the different levels of complexity were compared to observed data for the years 1995 and 2003. Their performance was analyzed using a number of different statistics that each represent a different perspective on the ecological dynamics of the system. These statistics include box-plots, abundance-area curves, Moran’s I, and classified difference. The statistics were summarized using the Nash-Sutcliffe coefficient. The results from all of these comparisons indicate that the more complex level 4 and level 5 models were able to simulate the observed data with a reasonable degree of accuracy. Conclusions A user-defineable, quantitative, deterministic modeling framework was introduced and tested against various hypotheses. It was determined that the more complex models (levels 4 and 5) were able to adequately simulate the observed patterns of cattail densities within the WCA2A region. These models require testing for uncertainty and sensitivity of their various parameters in order to better understand them but could eventually be used to provide insight for management decisions concerning the WCA2A region and the Everglades in general.