ABSTRACTS-Hydrology'09: EvergladesHUB

EvergladesHUB Home > Science Literature > Hydrology (1/2)


TEXT	Authors - Year - Title - Journal/Source
	(2009) Cerna, B., Rejmankova, E., Snyder, J.M. and Santruckova, H. Heterotrophic nitrogen fixation in oligotrophic tropical marshes: changes after phosphorus addition. Hydrobiologia 627(1), 55-65
	Abstract In order to determine the impact of nutrient enrichment on phosphorus (P) limited wetlands, we established experimental P additions in marshes throughout northern Belize. P significantly increased macrophyte primary production, which led to the rapid elimination of cyanobacterial mats. The replacement of cyanobacterial mats by macrophytes constrained autotrophic nitrogen (N) fixation, increased the quantity, and changed the quality of organic matter input to the sediments. We predicted that the activity of sediment heterotrophic N fixers will be impacted by these alterations in carbon input. We used the acetylene reduction technique to measure potential (glucose amended) nitrogenase activity (NA) in sediments from controls and treatment plots that have been P enriched for four years and dominated either by Eleocharis cellulosa, or Typha domingensis for two years. NA in P-enriched plots was 2-3 orders of magnitude higher than NA in controls. NA was positively correlated with the soil reactive P, both total organic and microbial carbon, live root biomass, and total phospholipid fatty acids (PLFA) as an indicator of active microbial biomass. It was negatively correlated with the concentration of ammonium-N. Path analysis revealed that the indirect effect of P on NA through the root biomass was more important than the direct effect of P. NA of the upper sediment layer was consistently higher in Eleocharis than in Typha dominated plots, despite the higher litter input by Typha. We feel that the higher levels of lignin and phenolics occurring in Typha litter, relative to Eleocharis, constrained NA in Typha plots.
	(2009) Chang, C.C.Y., McCormick, P.V., Newman, S. and Elliott, E.M. Isotopic indicators of environmental change in a subtropical wetland. Ecological Indicators 9(5), 825-836.
	Abstract The delta N-15 and delta C-13 signatures of major organic matter (OM) pools were measured across chemical and hydrologic gradients in a large (58,800 ha) subtropical wetland to evaluate whether stable isotopes were useful indicators of environmental change. Once a rainfall-driven wetland, the Loxahatchee National Wildlife Refuge in the Florida Everglades now receives agricultural and urban drainage that has increased phosphorus (P) and mineral loads around the wetland perimeter. Additionally, water impoundment at the southern end has produced a latitudinal hydrologic gradient, with extended hydroperiods in the south and overdrained conditions in the north. Detritus (-4.8 parts per thousand to 8.6 parts per thousand), floc (-1.4 parts per thousand to 3.6 parts per thousand), and metaphyton (-6.6 parts per thousand to +7.4 parts per thousand) delta N-15 declined southward with changes in hydrology as indicated by water depth. This pattern was attributed to higher mineralization rates under shorter hydroperiods. These signatures were also strongly correlated with increased nutrient and mineral loading. Rooted macrophyte delta N-15, by contrast, appeared more responsive to soil nutrient pools. Cattail (-8.9 parts per thousand to +7.7 parts per thousand) was restricted to the wetland perimeter and had the widest delta N-15 range, which was positively correlated with soil P. Sawgrass (-5.3 parts per thousand to +7.7 parts per thousand) occurred across most of the wetland, but its ON was not strongly correlated to any gradient. Patterns for delta C-13 were more strongly related to chemical gradients caused by canal intrusion than to latitude or hydrology. Again, metaphyton and detrital signatures were more sensitive to water chemistry changes than macrophytes. This pattern is consistent with their locations at the soil-water (detritus-floc), and air-water (metaphyton) interface. Metaphyton delta C-13 (-36.1 parts per thousand to -21.5 parts per thousand) which had the broadest range, was affected by DIC source and pool size. In contrast, cattail delta C-13 (-28.7 parts per thousand to -26.4 parts per thousand) was more closely related to soil P and sawgrass delta C-13 (-30.1 parts per thousand to -24.5 parts per thousand) was not related to any environmental gradient except latitude. There was no correlation between the two isotopes for any OM pool except cattail. These results indicate that isotopic signatures of microbial (metaphyton and detrital) pools are more responsive to changes in wetland hydrology and water chemistry while those of rooted macrophytes respond only to the extent that soil chemistry is altered. Rooted macrophytes also differ in the sensitivity of their isotopic signatures to environmental change. The selection of OM pools for isotopic analysis will, therefore, affect the sensitivity of the analysis and the resulting patterns. Furthermore, delta N-15 may be more robust and interpretable than delta C-13 as an indicator of ecosystem change in wetlands exposed to multiple or complex anthropogenic gradients.
	(2009) Cohen, M.J., Lamsal, S., Osborne, T.Z., Bonzongo, J.C.J., Newman, S. and Reddy, K.R. Soil Total Mercury Concentrations across the Greater Everglades. Soil Science Society of America Journal 73(2), 675-685.
	Abstract Elevated Hg concentrations in the Everglades pose ecological and human health risks. We mapped soil total Fig concentrations per mass (THgM) and area THgA) across the Everglades, and investigated relationships with soil properties (total P [TP] and organic matter content), community type, and hydrologic compartmentalization. Samples (n = 600) from surface soils (0-10 cm) were selected from a Population of 1405 sites spanning the Everglades. Overall, 168 sites had THgM levels >0.2 mg kg(-1); interpolation suggests that 23% of the Greater Everglades exceeds this threshold. Hot spots (>0.4 mg kg(-1)) were observed in eastern Water Conservation Area (WCA) 1 and west-central WCA3A; parts of WCA2A, WCA3AN, and WCA3B were locally high. Despite significant global differences in THgM among plant Communities, differences evaluated using paired proximate sites were not significant, suggesting that large spatial scale depositional gradients govern ecosystem storage. Median THgA was 1.89 mg m(-2) (range 0.07-12.05 mg m(-2)), representing approximately 100 yr of atmospheric deposition at contemporary rates (similar to 19 mu g m(-2) yr(-1)). Correlation between TP and THgM was positive in unimpacted areas (TP < 500 mg kg(-1), r = 0.69), but negative in impacted areas (TP > 500 mg kg(-1), r = -0.47), probably due to accelerated peat accretion rates in P-enriched areas. Moreover, while reverse correlation with distance from a canal for THgM (0.70) and TP (-0.77) supports Hg enrichment via atmospheric deposition, THgM hotspots in WCA3AS, WCA1, and the Holeyland and Rotenberger tracts are suggestive of local enrichment mechanisms. Finally, despite dramatic regional emissions declines, the estimated mass of Hg in surface soils across the Everglades has increased similar to 20% (11,000 vs. 13,100 kg) since 1996; while the statistical significance of this change is unknown, it provides a useful benchmark for future surveys.
	(2009) Harvey, J.W. and McCormick, P.V. Groundwater's significance to changing hydrology, water chemistry, and biological communities of a floodplain ecosystem, Everglades, South Florida, USA. Hydrogeology Journal 17(1), 185-201
	Abstract The Everglades ( Florida, USA) is one of the world's larger subtropical peatlands with biological communities adapted to waters low in total dissolved solids and nutrients. Detecting how the pre-drainage hydrological system has been altered is crucial to preserving its functional attributes. However, reliable tools for hindcasting historic conditions in the Everglades are limited. A recent synthesis demonstrates that the proportion of surface-water inflows has increased relative to precipitation, accounting for 33% of total inputs compared with 18% historically. The largest new source of water is canal drainage from areas of former wetlands converted to agriculture. Interactions between groundwater and surface water have also increased, due to increasing vertical hydraulic gradients resulting from topographic and water-level alterations on the otherwise extremely flat landscape. Environmental solute tracer data were used to determine groundwater's changing role, from a freshwater storage reservoir that sustained the Everglades ecosystem during dry periods to a reservoir of increasingly degraded water quality. Although some of this degradation is attributable to increased discharge of deep saline groundwater, other mineral sources such as fertilizer additives and peat oxidation have made a greater contribution to water-quality changes that are altering mineral-sensitive biological communities.
	(2009) Harvey, J.W. and McCormick, P.V. Groundwater's significance to changing hydrology, water chemistry, and biological communities of a floodplain ecosystem, Everglades, South Florida, USA. Hydrogeology Journal 17(1), 185-201.
	Abstract The Everglades ( Florida, USA) is one of the world's larger subtropical peatlands with biological communities adapted to waters low in total dissolved solids and nutrients. Detecting how the pre-drainage hydrological system has been altered is crucial to preserving its functional attributes. However, reliable tools for hindcasting historic conditions in the Everglades are limited. A recent synthesis demonstrates that the proportion of surface-water inflows has increased relative to precipitation, accounting for 33% of total inputs compared with 18% historically. The largest new source of water is canal drainage from areas of former wetlands converted to agriculture. Interactions between groundwater and surface water have also increased, due to increasing vertical hydraulic gradients resulting from topographic and water-level alterations on the otherwise extremely flat landscape. Environmental solute tracer data were used to determine groundwater's changing role, from a freshwater storage reservoir that sustained the Everglades ecosystem during dry periods to a reservoir of increasingly degraded water quality. Although some of this degradation is attributable to increased discharge of deep saline groundwater, other mineral sources such as fertilizer additives and peat oxidation have made a greater contribution to water-quality changes that are altering mineral-sensitive biological communities.
	(2009) Harvey, J.W., Schaffranek, R.W., Noe, G.B., Larsen, L.G., Nowacki, D.J. and O'Connor, B.L. Hydroecological factors governing surface water flow on a low-gradient floodplain. Water Resources Research 45, Art.No.W03421.
	Abstract Interrelationships between hydrology and aquatic ecosystems are better understood in streams and rivers compared to their surrounding floodplains. Our goal was to characterize the hydrology of the Everglades ridge and slough floodplain ecosystem, which is valued for the comparatively high biodiversity and connectivity of its parallel-drainage features but which has been degraded over the past century in response to flow reductions associated with flood control. We measured flow velocity, water depth, and wind velocity continuously for 3 years in an area of the Everglades with well-preserved parallel-drainage features (i.e., 200-m wide sloughs interspersed with slightly higher elevation and more densely vegetated ridges). Mean daily flow velocity averaged 0.32 cm s(-1) and ranged between 0.02 and 0.79 cm s(-1). Highest sustained velocities were associated with flow pulses caused by water releases from upstream hydraulic control structures that increased flow velocity by a factor of 2-3 on the floodplain for weeks at a time. The highest instantaneous measurements of flow velocity were associated with the passage of Hurricane Wilma in 2005 when the inverse barometric pressure effect increased flow velocity up to 5 cm s(-1) for several hours. Time-averaged flow velocities were 29% greater in sloughs compared to ridges because of marginally higher vegetative drag in ridges compared to sloughs, which contributed modestly (relative to greater water depth and flow duration in sloughs compared to ridges) to the predominant fraction (86%) of total discharge through the landscape occurring in sloughs. Univariate scaling relationships developed from theory of flow through vegetation, and our field data indicated that flow velocity increases with the square of water surface slope and the fourth power of stem diameter, decreases in direct proportion with increasing frontal area of vegetation, and is unrelated to water depth except for the influence that water depth has in controlling the submergence height of vegetation that varies vertically in its architectural characteristics. In the Everglades the result of interactions among controlling variables was that flow velocity was dominantly controlled by water surface slope variations responding to flow pulses more than spatial variation in vegetation characteristics or fluctuating water depth. Our findings indicate that floodplain managers could, in addition to managing water depth, manipulate the frequency and duration of inflow pulses to manage water surface slope, which would add further control over flow velocities, water residence times, sediment settling, biogeochemical transformations, and other processes that are important to floodplain function.
	(2009) Heithaus, M.R., Delius, B.K., Wirsing, A.J. and Dunphy-Daly, M.M. Physical factors influencing the distribution of a top predator in a subtropical oligotrophic estuary. Limnology and Oceanography 54(2), 472-482.
	Abstract We used longline fishing to determine the effects of distance from the ocean, season, and short-term variation in abiotic conditions on the abundance of juvenile bull sharks (Carcharhinus leucas) in an estuary of the Florida Everglades, U.S.A. Logistic regression revealed that young-of-the-year sharks were concentrated at a protected site 20 km upstream and were present in greater abundance when dissolved oxygen (DO) levels were high. For older juvenile sharks (age 1+), DO levels had the greatest influence on catch probabilities followed by distance from the ocean; they were most likely to be caught at sites with > 3.5 mg L-1 DO and on the main branch of the river 20 km upstream. Salinity had a relatively small effect on catch rates and there were no seasonal shifts in shark distribution. Our results highlight the importance of considering DO as a possible driver of top predator distributions in estuaries, even in the absence of hypoxia. In Everglades estuaries hydrological drivers that affect DO levels (e.g., groundwater discharge, modification of primary productivity through nutrient fluxes) will be important in determining shark distributions, and the effects of planned ecosystem restoration efforts on bull sharks will not simply be mediated by changing salinity regimes and the location of the oligohaline zone. More generally, variation in DO levels could structure the nature and spatiotemporal pattern of top predator effects in the coastal Everglades, and other tropical and subtropical estuaries, because of interspecific variation in reliance on DO within the top predator guild.
	(2009) Herring, G., Gawlik, D.E. and Rumbold, D.G. Feather mercury concentrations and physiological condition of great egret and white ibis nestlings in the Florida Everglades. Science of the Total Environment 407(8), 2641-2649.
	Abstract Mercury contamination in the Florida Everglades has reportedly played a role in the recent decline of wading birds, although no studies have identified a mechanism leading to population-level effects. We assessed feather mercury levels in great egret (Ardea alba; n=91) and white ibis (Eudocimus albus; n=46) nestlings at breeding colonies in the Florida Everglades during a year (2006) with excellent breeding conditions (characterized by hydrology leading to concentrated prey) and a year with below average breeding conditions (2007). We also assessed the physiological condition of those nestlings based on levels of plasma and fecal corticosterone metabolites, and stress proteins 60 and 70. Mercury levels were higher in both species during the good breeding condition year (great egret=6.25 mu g/g +/- 0.81 SE, white ibis = 1.47 mu g/g +/- 0.41 SE) and lower in the below average breeding year (great egret=1.60 mu g/g +/- 0.11 SE, white ibis=0.20 mu g/g +/- 0.03 SE). Nestlings were in better physiological condition in 2006, the year with higher feather mercury levels. These results support the hypothesis that nestlings are protected from the harmful effects of mercury through deposition of mercury in growing feathers. We found evidence to suggest shifts in diets of the two species, as a function of prey availability, thus altering their exposure profiles. However, we found no evidence to suggest they respond differently to mercury exposure.
	(2009) Knickerbocker, C.M., Leitholf, S., Stephens, E.L., Keellings, D.J., Laird, H., Anderson, C.J.R., Fauth, J.E. and Quintana-Ascencio, P.F. Tree Encroachment of A Sawgrass (Cladlum jamaicense) Marsh within an Increasingly Urbanized Ecosystem. Natural Areas Journal 29(1), 15-26.
	Abstract Fire suppression and altered water drainage often change community structure and species composition in human-dominated ecosystems. We describe the decline of sawgrass marshes between 1940 and 2002, and assess the current condition of remnant marshes within the MacKay Tract, an isolated wetland embedded within rapidly developing eastern Orlando, Florida. We tested the correlation between live sawgrass and presence of adult hardwood trees and seedlings (primarily red maple, Acer rubrum) and describe vegetation in plots with different levels of tree encroachment. Total area occupied by open sawgrass in the MacKay Tract has declined dramatically the last 60 years, in 2006, open sawgrass comprised only 12% of the area covered in 1940. Tree basal cover was negatively associated with live sawgrass and positively related to red maple seedling density, but not associated with dead sawgrass tussocks. Sawgrass was positively correlated with the second axis of a non-metric multidimensional scaling ordination on understory plant assemblage, while red maple seedlings and several species associated with disturbed areas were significantly negatively cot-related with this axis. Another nine plant species were positively correlated with the first axis, while Osmunda cinnamomea (cinnamon fern) was negatively associated with it. We suggest that woody species are continuing to colonize what is left of the sawgrass marsh. Without intervention (e.g., restoring hydrologic flow and fire), the sawgrass (Cladium jamaicense Crantz) area within the marsh will continue being replaced by woody and exotic species.
	(2009) Larsen, L.G., Harvey, J.W., Noe, G.B. and Crimaldi, J.P. Predicting organic floc transport dynamics in shallow aquatic ecosystems: Insights from the field, the laboratory, and numerical modeling. Water Resources Research 45, Art.No.W01411.
	Abstract Transport of particulate organic material can impact watershed sediment and nutrient budgets and can alter the geomorphologic evolution of shallow aquatic environments. Prediction of organic aggregate ("floc'') transport in these environments requires knowledge of how hydraulics and biota affect the entrainment, settling, and aggregation of particles. This study evaluated the aggregation and field transport dynamics of organic floc from a low-gradient floodplain wetland with flow-parallel ridges and sloughs in the Florida Everglades. Floc dynamics were evaluated in a rotating annular flume and in situ in the field. Under present managed conditions in the Everglades, floc is not entrained by mean flows but is suspended via biological production in the water column and bioturbation. Aggregation was a significant process affecting Everglades floc at high flume flow velocities (7.0 cm s(-1)) and during recovery from high flow; disaggregation was not significant for the tested flows. During moderate flows when floc dynamics are hydrodynamically controlled, it is possible to model floc transport using a single "operative floc diameter'' that accurately predicts fluxes downstream and to the bed. In contrast, during high flows and recovery from high flows, aggregation dynamics should be simulated. When entrained by flow in open-water sloughs, Everglades floc will be transported downstream in multiple deposition and reentrainment events but will undergo net settling when transported onto ridges of emergent vegetation. We hypothesize that net transport of material from open to vegetated areas during high flows is critical for forming and maintaining distinctive topographic patterning in the Everglades and other low-gradient floodplains.
	(2009) Marshall, F.E., Wingard, G.L. and Pitts, P. A Simulation of Historic Hydrology and Salinity in Everglades National Park: Coupling Paleoecologic Assemblage Data with Regression Models. Estuaries and Coasts 32(1), 37-53.
	Abstract Restoration of Florida's Everglades requires scientifically supportable hydrologic targets. This study establishes a restoration baseline by developing a method to simulate hydrologic and salinity conditions prior to anthropogenic changes. The method couples paleoecologic data on long-term historic ecosystem conditions with statistical models derived from observed meteorologic and hydrologic data that provide seasonal and annual variation. Results indicate that pre-drainage freshwater levels and hydroperiods in major sloughs of the Everglades were about 0.15 m higher and two to four times greater, respectively, on average compared to today's values. Pre-drainage freshwater delivered to the wetlands and estuaries is estimated to be 2.5 to four times greater than the modern-day flow, and the largest deficit is during the dry season. In Florida Bay, salinity has increased between 5.3 and 20.1 with the largest differences in the areas near freshwater outflow points. These results suggest that additional freshwater flows to the Everglades are needed for restoration of the freshwater marshes of the Everglades and estuarine environment of Florida Bay, particularly near the end of the dry season.
	(2009) McCormick, P., Newman, S. and Vilchek, L. Landscape responses to wetland eutrophication: loss of slough habitat in the Florida Everglades, USA. Hydrobiologia 621(105-114.
	Abstract Much of the historical Everglades has been either lost or degraded as a result of human activities. Among the aquatic habitats that comprise the Everglades landscape mosaic, open-water sloughs support critical ecological functions and appear especially sensitive to both hydrologic and water-quality perturbations. We used a combination of remote sensing and on-the-ground sampling to document spatial changes in the extent and vegetative composition of sloughs along a phosphorus (P) gradient in the northern Everglades. Increasing levels of water and soil P were associated with a decline in slough coverage, loss of the abundant native periphyton community, and a shift in dominant macrophyte species. The characteristic slough macrophyte species Eleocharis cellulosa and Nymphaea odorata exhibited different sensitivities to P enrichment, but both species declined with enrichment as slough habitats were invaded by Typha domingensis, a species that is known to expand aggressively in response to enrichment. A limited amount of open-water habitat occurred in highly enriched areas, but these habitats were maintained largely as a result of airboat disturbance and did not contain characteristic slough vegetation. Many changes in slough coverage and composition occurred in areas where water and soil P concentrations were only marginally higher than background levels. Our findings support the need for Everglades hydrologic restoration efforts to adhere to strict water-quality standards for P to avoid further degradation of this key landscape feature.
	(2009) Miao, S.L. and Zou, C.B. Seasonal variation in seed bank composition and its interaction with nutrient enrichment in the Everglades wetlands. Aquatic Botany 90(2), 157-164.
	Abstract In the Florida Everglades, nutrient enrichment from agricultural outflow and the change in hydrology have collectively contributed to the expansion of cattails (Typha spp.). To assess the effectiveness of prescribed fire in controlling cattails and to predict vegetation dynamics after the fire, it is important to understand the seasonal variation of the soil seed bank and how the seed bank is affected by nutrient enrichment and fire. This paper investigates the effects of season, nutrient enrichment, and fire on soil seed bank species composition, richness, and density along a nutrient gradient in Water Conservation Area 2A (WCA 2A) of the Florida Everglades. Species richness was significantly affected by nutrient enrichment and season but not their interaction. Total seed density, however, was significantly affected by the interaction between nutrient enrichment and season. Yet, at species level, the relationship between seed density, nutrient enrichment and season varied. The highest seed density of cattail occurred in summer at highly enriched sites, but that of sawgrass occurred in fall regardless of enrichment; the seed density of water lily was very low regardless of season and nutrient enrichment, and the highest Amarathus seed density occurred at highly enriched sites year round. Moreover, germination timing differed greatly among species. While cattail seeds had a short incubation period and started to germinate 2-3 days after initiation of the germination assay, sawgrass seeds generally started to germinate 4 weeks later. Further, both the prescribed summer fire at the highly enriched site and the natural winter fire at the moderately enriched site reduced the seed density of cattail but not of sawgrass. Our results suggest that fire application for vegetation recovery in WCA 2A would benefit from explicitly considering seasonal dynamics of the seed bank. (C) 2008 Elsevier B.V. All rights reserved.
	(2009) Miao, S.L., Zou, C.B. and Breshears, D.D. Vegetation Responses to Extreme Hydrological Events: Sequence Matters. American Naturalist 173(1), 113-118.
	Abstract Extreme hydrological events such as flood and drought drive vegetation dynamics and are projected to increase in frequency in association with climate change, which could result in sequences of extreme events. However, experimental studies of vegetation responses to climate have largely focused on responses to a trend in climate or to a single extreme event but have largely overlooked the potential for complex responses to specific sequences of extreme events. Here we document, on the basis of an experiment with seedlings of three types of subtropical wetland tree species, that mortality can be amplified and growth can even be stimulated, depending on event sequence. Our findings indicate that the impacts of multiple extreme events cannot be modeled by simply summing the projected effects of individual extreme events but, rather, that models should take into account event sequences.
	(2009) Min, J.H. and Wise, W.R. Simulating short-circuiting flow in a constructed wetland: the implications of bathymetry and vegetation effects. HydrologicalProcesses 23(6), 830-841.
	Abstract Short-circuiting flow, commonly experienced in many constructed wetlands, reduces hydraulic retention times in unit wetland cells and decreases the treatment efficiency. A two-dimensional (2-D), physically based, distributed modelling approach was used to systematically address the effects of bathymetry and vegetation on short-circuiting flow, which previously have been neglected or lumped in one-dimensional wetland flow models. In this study, a 2-D transient hydrodynamics with advection-dispersion model was developed using MIKE 21 and calibrated with bromide tracer data collected at the Orlando Easterly Wetland Cell 7. The estimated topographic difference between short-circuiting flow zone and adjacent area ranged from 0.3 to 0.8 m. A range of the Manning roughness coefficient at the short-circuiting flow zone was estimated (0.022-0.045 s m(-1/3)). Sensitivity analysis of topographical and vegetative heterogeneity deduced during model calibration shows that relic ditches or other ditch-shaped landforms and the associated sparse vegetation along the main flow direction intensify the short-circuiting pattern, considerably affecting 2-D solute transport simulation. In terms of hydraulic efficiency, this study indicates that the bathymetry effect on short-circuiting flow is more important than the vegetation effect.
	(2009) Richardson, T.C., Robison, C.P., Neubauer, C.P. and Hall, G.B. Hydrologic Signature Analysis of Select Organic Hydric Soil Indicators in Northeastern Florida. Soil Science Society of America Journal 73(3), 831-840.
	Abstract The magnitude, duration, and return intervals of surface water flooding and dewatering of the landward extent of the hydric soil indicators muck (LM), histic epipedon (LHE), and Histosol (LH) were quantitatively defined, providing a better understanding of the hydrologic conditions maintaining these hydric soil indicators. Land surface elevations were determined for the LM, LHE, and LH at 16 lakes with long-term (30-60-yr) modeled or gauged hydrologic data. The probability of flooding and dewatering of the elevations of the LM, LHE, and LH were determined from frequency analysis of hydrologic data from each lake. The resulting hydrologic signatures for the LM, LHE, and LH are composed of magnitude and return interval of 1, 30, 90, 183, 274, and 365-d duration flooding and dewatering events. As an example, the LM, LHE, and LH were flooded for 30 continuous days with average annual probabilities of 42, 65, and 77%, respectively. As a second example, the LM, LHE, and LH were dewatered for 365 continuous days with average annual probabilities of 49, 24, and 16%, respectively. Probabilities of flooding and dewatering for the LM, LHE, and LH are presented for 1, 30, 90, 183, 274, and 365-d durations. Mean hydrologic signatures reduce variability and may be considered representative of each soil characteristic. Quantitatively defining the hydrology associated with the presence of the LM, LHE, and LH as well as other soil characteristics is essential for environmental protection, assessment of hydrologic impacts, wetlands restoration, wetlands creation, and other environmental management applications.
	(2009) Saha, A.K., Sternberg, L. and Miralles-Wilhelm, F. Linking water sources with foliar nutrient status in upland plant communities in the Everglades National Park, USA. Ecohydrology 2(1), 42-54.
	Abstract Plant communities within an ecosystem can vary in water source usage and nutrient availabilities, thus permitting community coexistence and diversity. We investigated the differences in water source utilization in two ecologically important upland plant communities: tropical hardwood hammocks and pine rocklands in the predominantly flooded Everglades ecosystem. We then linked these differences with their foliar nutrient levels and photosynthetic performance as measured by delta C-13 abundance. Based on a comparison of delta O-18 of plant stem waters with those of potential water sources (nutrient-poor groundwater and nutrient-rich water in organic litter referred to as soilwater), we observed that during the wet season hammock plants relied on soilwater while in the dry season they relied on groundwater. A similar seasonal shift was observed in pineland plants, however, groundwater constituted the major part of water uptake throughout the year except for late wet season. Consistent with the nutrient concentration of different water sources used in the two communities, hammocks had a greater annual mean foliar nitrogen and phosphorus concentration at the community level over pinelands as well as a higher leaf area index. High foliar N concentration in hammock plants was associated with eventual stomatal limitation of photosynthesis. Hammock species being intolerant of flooded soils are restricted to water uptake in the shallow unsaturated soil layer in the wet season, yet access the lowered groundwater table in the dry season. This dependence on a relatively narrow annual range of water table levels should be considered in South Florida water management and Everglades restoration.
	(2009) Simoneit, B.R.T., Xu, Y.P., Neto, R.R., Cloutier, J.B. and Jaffe, R. Photochemical alteration of 3-oxygenated triterpenoids: Implications for the origin of 3,4-seco-triterpenoids in sediments. Chemosphere 74(4), 543-550.
	Abstract The reactivity of higher plant derived 3-oxy-triterpenoids to sunlight was investigated using a series of pure reference standards both under simulated and real solar exposure. The majority of the exposed compounds showed reactivity to light, particularly to simulated sunlight and among others generated seco-derivatives. While photochemical processes have been suggested for the formation of such compounds, their abundances in some sediments have often been assumed to be the result of diagenetic reworking of parent triterpenoids. Analyses of mangrove leaf waxes, an important known source of taraxerol in coastal ecosystems, showed the presence of the 3,4-seco-derivative dihydrolacunosic acid. which could represent an important biotic source for des-A-triterpenoid precursors to such sediments, and is unrelated to aquatic organic matter diagenesis.
	(2009) Smith, T.J., Anderson, G.H., Balentine, K., Tiling, G., Ward, G.A. and Whelan, K.R.T. Cumulative Impacts of Hurricanes on Florida Mangrove Ecosystems: Sediment Deposition, Storm Surges and Vegetation. Wetlands 29(1), 24-34.
	Abstract Hurricanes have shaped the structure of mangrove forests ill the Everglades via wind damage, storm Surges and sediment deposition. Immediate effects include changes to stern size-frequency distributions and to species relative abundance and density. Long-term impacts to mangroves are poorly Understood at present. We examine impacts of Hurricane Wilma oil mangroves and compare the results to findings from three previous storms (Labor Day, Donna, Andrew). Surges during Wilma destroyed 1,250 ha of mangroves and set back recovery that started following Andrew. Data from permanent plots affected by Andrew and Wilma showed no differences among species or between hurricanes for % stern mortality or % basal area lost. Hurricane damage was related to hydro-geomorphic type of forest. Basin mangroves suffered significantly more damage than riverine or island mangroves. The hurricane by forest type interaction was highly significant. Andrew did slightly more damage to island mangroves. Wilma did significantly more damage to basin forests. This is most likely a result of the larger and more spatially extensive storm surge produced by Wilma. Forest damage was not related to amount. of sediment deposited. Analyses of reports from Donna and the Labor Day storm indicate that sonic sites have recovered following catastrophic disturbance. Other sites have been permanently converted into a different ecosystem, namely intertidal mudflats. Our results indicate that mangroves are not in a steady state as has been recently claimed.
	(2009) Utescher, T., Ivanov, D., Harzhauser, M., Bozukov, V., Ashraf, A.R., Rolf, C., Urbat, M. and Mosbrugger, V. Cyclic climate and vegetation change in the late Miocene of Western Bulgaria. Palaeogeography Palaeoclimatology Palaeoecology 272(1-2), 99-114.
	Abstract A late Miocene paludal to lacustrine sequence from a carbonate basin in NW Bulgaria (Staniantsi Basin) is analysed displaying up to 27 rhythmically bedded sedimentary cycles. In the lower part of the sequence, the cycles consist of alternating autochthonous brown coal and marls containing diverse mollusc assemblages. The upper part of the sequence is characterized by alternating dark to light grey clays and calcareous silts. A palynomorph record comprising 163 samples is analysed by statistical means to reconstruct vegetation changes. The Coexistence Approach is used to calculate quantitative palaeoclimate records for 6 parameters. The studied section displays hierarchical cyclicity patterns. Longer-term cycles possibly related to eccentricity (period similar to 100 kyr) are present in the palynomorph record and show climate changes of warmer/wetter and cooler/drier periods in combination with frequency oscillations of thermophilous elements. Short-term cycles most probably related to precession (period similar to 21.7 kyr) are expressed by alternations of brown coal and marl/shell beds and show cyclic change in peat-forming vegetation related to oscillations of the groundwater level. As a triggering mechanism, wetter/warmer and drier/cooler climate phases related to orbital precession are probable. In addition, sections sampled at high resolution display small scale climate and vegetational variability. As is shown by the analysis ferns were an important component of the peat-forming vegetation, while outside the mire, a wetland vegetation consisting of pioneers and a mixed mesophytic forest with evergreen shrubs existed. An oligo- to mesotrophic slightly alkaline lake became repeatedly established with a diverse mollusc fauna and a dense hydrophytic vegetation with characean meadows. In the upper part of the section, a spreading of herbaceous vegetation is observed, also known from other contemporaneaous palynomorph records in Bulgaria and surrounding areas. The increase of Asteraceae in the upper part of the section, combined with a marked decrease in woody taxa, points to an opening of habitats and a decrease in mean annual precipitation. This trend is paralleled by the mollusc fauna which yields several terrestrial, partly xerophilous taxa.
	(2009) Wang, H.Q., Walclon, M.G., Meselhe, E.A., Arceneaux, J.C., Chen, C.F. and Harwell, M.C. Surface Water Sulfate Dynamics in the Northern Florida Everglades. Journal of Environmental Quality 38(2), 734-741.
	Abstract Sulfate contamination has been identified as a serious environmental issue in the Everglades ecosystem. However, it has received less attention compared to P enrichment. Sulfate enters the Arthur R. Marshall Loxahatchee National Wildlife Refuge (Refuge), a remnant of the historic Everglades, in pumped stormwater discharges with a mean concentration of approximately 50 mg L-1, and marsh interior concentrations at times fall below a detection limit of 0.1 mg L-1. In this research, we developed a sulfate mass balance model to examine the response of surface water sulfate in the Refuge to changes in sulfate loading and hydrological processes. Meanwhile, sulfate removal resulting from microbial sulfate reduction in the underlying sediments of the marsh was estimated from the apparent settling coefficients incorporated in the model. The model has been calibrated and validated using long-term monitoring data (1995-2006). Statistical analysis indicated that our model is capable of capturing the spatial and temporal variations in surface water sulfate concentrations across the Refuge. This modeling work emphasizes the fact that sulfate from canal discharge is impacting even the interior portions of the Refuge, supporting work by other researchers. In addition, model simulations suggest a condition of sulfate in excess of requirement for microbial sulfate reduction in the Refuge.
	(2009) Whelan, K.R.T., Smith, T.J., Anderson, G.H. and Ouellette, M.L. Hurricane Wilma's Impact on Overall Soil Elevation and Zones within the Soil Profile in a Mangrove Forest. Wetlands 29(1), 16-23.
	Abstract Soil elevation affects tidal inundation period, inundation frequency, and overall hydroperiod, all of which are important ecological factors affecting species recruitment composition, and survival in wetlands. Hurricanes can dramatically affect a site's soil elevation. We assessed the impact of Hurricane Wilma (2005) on soil elevation at a mangrove forest location along the Shark River in Everglades National Park, Florida, USA. Using multiple depth surface elevation tables (SETs) and marker horizons we measured soil accretion, erosion, and soil elevation. We partitioned the effect of Hurricane Wilma's storm deposit into four constituent soil zones: surface accretion) zone, shallow zone (0-0.35 m). middle zone (0.35-4 m), and deep zone (4-6 m). We report expansion and contraction of each soil zone. Hurricane Wilma deposited 37.0 (+/- 3.0 SE) mm of material: however, the absolute soil elevation change was + 42.8 mm due to expansion in the shallow soil zone. One year post-hurricane, the soil profile had lost 10.0 mm in soil elevation, with 8.5 mm of the loss due to erosion. The remaining soil elevation loss was due to compaction from shallow subsidence. We found prolific growth of new fine rootlets (209 +/- 34 SE g m(-2)) in the storm deposited material suggesting that deposits may become more stable in the near future (i.e., erosion rate will decrease). Surficial erosion and belowground processes both played an important role ill determining the overall soil elevation. Expansion and contraction ill the shallow soil zone may be due to hydrology. and in the middle and bottom soil zones due 10 shallow subsidence. Findings thus far indicate that soil elevation has made substantial gains compared to site specific relative sea-level rise, but data trends suggest that below-round processes, which differ by soil zone. may come to dominate the long term ecological impact of storm deposit.
	(2008) Baiser, B., Boulton, R.L. and Lockwood, J.L. Influence of water depth on nest success of the endangered Cape Sable seaside sparrow in the Florida Everglades. Animal Conservation 11(3), 190-197.