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Premise: The southern Florida Everglades landscape sustains wetlands of national and international importance. Sawgrass (Cladium jamaicense), the dominant macrophyte in the Everglades, has two phenotypes that vary in size and density between Everglades marl prairies and peat marshes. Marl prairies have recently been hypothesized to be a newly formed habitat developed after European colonization as a result of landscape‐scale hydrologic modifications, implying that sawgrass marl phenotypes developed in response to the marl habitat. We examined whether sawgrass wetland phenotypes are plastic responses to marl and peat soils. Methods: In a common‐mesocosm experiment, seedlings from a single Everglades population were grown outdoors in field‐collected marl or peat soils. Growth and morphology of plants were measured over 14 mo, while soil and leaf total nitrogen, total phosphorus, total carbon, and plant biomass and biomass allocation were determined in a final harvest. Results: Sawgrass plant morphology diverged in marl vs. peat soils, and variations in morphology and density of mesocosm‐grown plants resembled differences seen in sawgrass plants growing in marl and peat habitats in Everglades wetlands. Additionally, sawgrass growing in marl made abundant dauciform roots, while dauciform root production of sawgrass growing in peat was correlated with soil total phosphorus. Conclusions: Sawgrass from a single population grown in marl or peat soils can mimic sawgrass phenotypes associated with marl vs. peat habitats. This plasticity is consistent with the hypothesis that Everglades marl prairies are relatively new habitats that support plant communities assembled after European colonization and subsequent landscape modifications. [ABSTRACT FROM AUTHOR]

Water depth and flow effects on growth and nutrient content of three marsh plants ( Cladium jamaicense Crantz, Eleocharis cellulosa Torr., and Nymphaea odorata Aiton) and on soil-building were estimated in the Loxahatchee Impoundment Landscape Assessment where macrocosms contain habitats distinguished by relative water depth (deep slough, shallow slough, and mid-ridge) but that differ in flow. We hypothesized that optimal growth would vary with water depth and species, paralleling distributions in the natural environment, and that growth and tissue nutrients would be positively affected by flow. In addition, we hypothesized that plant morphology would influence sediment deposition with the dense growth of C. jamaicense supporting greatest accretion. Our hypotheses were partly supported. Cladium jamaicense unexpectedly grew best in deep sloughs at depths greater than previously reported. Eleocharis cellulosa had a wide depth tolerance and grew best in flowing conditions. Nymphaea odorata grew best in slough habitats. Nutrient contents differed among species and plant parts but were not affected by flow. Soil accretion did not vary with biomass but partially varied with depth and flow, both key factors in conceptual models of vegetation and soil dynamics in wetlands, especially in the Everglades ridge-and-slough topography. [ABSTRACT FROM AUTHOR]

Abstract: Growth, morphology and biomass allocation in response to water depth was studied in white water lily, Nymphaea odorata Aiton. Plants were grown for 13months in 30, 60 and 90cm water in outdoor mesocosms in southern Florida. Water lily plant growth was distinctly seasonal with plants at all water levels producing more and larger leaves and more flowers in the warmer months. Plants in 30cm water produced more but smaller and shorter-lived leaves than plants at 60cm and 90cm water levels. Although plants did not differ significantly in total biomass at harvest, plants in deeper water had significantly greater biomass allocated to leaves and roots, while plants in 30cm water had significantly greater biomass allocated to rhizomes. Although lamina area and petiole length increased significantly with water level, lamina specific weight did not differ among water levels. Petiole specific weight increased significantly with increasing water level, implying a greater cost to tethering the larger laminae in deeper water. Lamina length and width scaled similarly at different water levels and modeled lamina area (LA) accurately (LAmodeled =0.98LAmeasured +3.96, R 2 =0.99). Lamina area was highly correlated with lamina weight (LW=8.43LA−66.78, R 2 =0.93), so simple linear measurements can predict water lily lamina area and lamina weight. These relationships were used to calculate monthly lamina surface area in the mesocosms. Plants in 30cm water had lower total photosynthetic surface area than plants in 60cm and 90cm water levels throughout, and in the summer plants in 90cm water showed a great increase in photosynthetic surface area as compared to plants in shallower water. These results support setting Everglades restoration water depth targets for sloughs at depths ≥45cm and suggest that in the summer optimal growth for white water lilies occurs at depths ≥75cm. [Copyright &y& Elsevier]

Abstract: Historically, the Florida Everglades was characterized by a corrugated landscape of shorter hydroperiod, elevated sawgrass (Cladium jamaicense) ridges and longer hydroperiod, deep water slough communities. Drainage and compartmentalization of the Everglades have fundamentally altered this pattern, and sawgrass ridge communities have expanded at the expense of deep water slough communities throughout much of the landscape. In this study we provide a simple isotopic and nutrient characterization of major components of the slough ecosystem to elucidate physiological and nutrient differences among species and to suggest pathways for organic matter decomposition that contribute to peat development in deep water sloughs. We examined carbon (C) and nitrogen (N) isotopes and C, N and phosphorus (P) concentrations of the floating-leaved macrophytes Nymphaea odorata and Nymphoides aquatica, the emergent macrophyte Eleocharis elongata, and the submerged species Utricularia foliosa and Utricularia purpurea, as well as soil and flocculent material from the southern Water Conservation Area 3-A. Flocculent material and soils had the highest N content (4.5±0.2%) and U. foliosa and N. odorata had the highest P content (0.13±0.01% to 0.12±0.01%). The range for δ15N average±SE values was 5.81±0.29‰ (U. foliosa) to −1.84±0.63‰ (N. odorata), while the range for δ13C values was −23.83±0.12‰ (N. odorata) to −29.28±0.34‰ (U. purpurea). Differences of up to 10‰ in C isotopic values of U. foliosa and N. odorata suggest fundamental physiological differences between these species. Along a degradation continuum, enrichment of 13C and 15N and extent of decomposition was negatively related to phosphorus concentrations. A two end-member 13C mixing model suggested that Utricularia species were the primary organic source for flocculent materials, whereas organic matter derived from root decomposition of N. odorata contributed to the progressively enriched δ13C values found with depth in soils. These results illustrate the fundamentally important roles of Nymphaea and Utricularia species in ecosystem dynamics of deep water sloughs. [Copyright &y& Elsevier]

The Florida Everglades is a mosaic of short and long-hydroperiod marshes that differ in the depth, duration, and timing of inundation. Algae are important primary producers in widespread Everglades’ periphyton mats, but relationships of algal production and community structure to hydrologic variability are poorly understood. We quantified differences in algal biomass and community structure between periphyton mats in 5 short and 6 long-hydroperiod marshes in Everglades National Park (ENP) in October 2000. We related differences to water depth and total phosphorus (TP) concentration in the water, periphyton and soils. Long and short-hydroperiod marshes differed in water depth (73 cm vs. 13 cm), periphyton TP concentrations (172 μg g−1 vs. 107 μg g−1, respectively) and soil TP (284 μg g−1 vs. 145 μg g−1). Periphyton was abundant in both marshes, with short-hydroperiod sites having greater biomass than long-hydroperiod sites (2936 vs. 575 grams ash-free dry mass m−2). A total of 156 algal taxa were identified and separated into diatom (68 species from 21 genera) and “soft algae” (88 non-diatom species from 47 genera) categories for further analyses. Although diatom total abundance was greater in long-hydroperiod mats, diatom species richness was significantly greater in short- hydroperiod periphyton mats (62 vs. 47 diatom taxa). Soft algal species richness was greater in long-hydroperiod sites (81 vs. 67 soft algae taxa). Relative abundances of individual taxa were significantly different among the two site types, with soft algal distributions being driven by water depth, and diatom distributions by water depth and TP concentration in the water and periphyton. Periphyton communities differ between short and long-hydroperiod marshes, but because they share many taxa, alterations in hydroperiod could rapidly promote the alternate community. [ABSTRACT FROM AUTHOR]

Sawgrass, Cladium jamaicense, is the dominant macrophyte in the Florida Everglades. We examined sawgrass flowering phenology and compatibility reactions in ex situ and in situ populations over 2 yr. Sawgrass flowers in May in southern Florida. Flower maturation was relatively synchronous within an inflorescence. Along the entire inflorescence, functionally male flowers emerged initially, followed by stigmas, then anthers of hermaphroditic flowers. Flowers of each sex expanded over 2 d with less than 1 d in between, totaling 6-7 d for an inflorescence to complete flowering. Hand pollinations showed that sawgrass was self-compatible and not pollen-limited, because open pollinations produced fruit set similar to self- and cross-pollinations. Fruit set was low in autogamy and manipulation treatments. Manipulation treatments were used to study the effect of exposure to airborne pollen during hand pollinations. This treatment thus provides a useful technique for studies on the in situ compatibility of wind-pollinated graminoids. Sawgrass was able to self- fertilize, but the timing of flower maturation on an inflorescence promoted outcrossing. Actual outcrossing rates in sawgrass thus depend on clonal architecture and the timing of floral maturation on other inflorescences within a clone rather than on inflorescences of other genets in a population. [ABSTRACT FROM AUTHOR]

Sagittaria lancifolia leaf morphology varies in the Everglades of southern Florida, USA, from plants with broadly ovate laminae to plants with linear laminae. To understand the morphological response of S. lancifolia to increased nutrients, we (1) grew S. lancifolia plants in solutions with either 1mM or 10μM P and measured morphological responses, as well as tissue N:P content and (2) grew field-collected plants that had a range of leaf morphologies in the greenhouse and measured morphological and tissue N:P responses. Plants in high P (HP), as compared to low P (LP), were larger (biomass 48.3g HP versus 16.9g LP), produced more leaves (16.9 HP versus 10.7 LP) and inflorescences (2.9 HP versus 0.3 LP), and branched more (shoots 3.8 HP versus1.1 LP). Biomass allocation to leaves and inflorescences was greater in HP as compared to LP plants (leaves 61% HP versus 37% LP; inflorescences 15% HP versus 2% LP), while plants in LP allocated relatively more biomass to roots and rhizomes than plants in HP (roots 8% HP versus 25% LP; rhizomes 15% HP versus 35% LP). Leaf morphology changed with P-addition, so that plants in high P produced leaves with longer leaf bases (352mm HP versus 219mm LP), longer and wider blades (290mm × 49mm HP versus 176mm × 9mm LP), and a larger leaf area (99cm2 HP versus 13cm2 LP) than plants in LP, whereas plants in LP produced leaves with longer petioles (277mm HP versus 346mm LP). Leaf N:P ratios decreased in HP relative to initial ratios (43initial to 17final) and increased in LP (45initial to 86final). The direction of change in lamina width of field-collected plants grown under greenhouse conditions depended on the original leaf morphology—plants with narrow blades in the field produced wider laminae in the greenhouse, while plants with wide blades in the field produced narrower laminae. These plastic changes in leaf morphology mimic the differences in leaf morphology between S. lancifolia subsp. media and S. lancifolia subsp. lancifolia. Our results show that S. lancifolia responds rapidly to changes in environmental nutrient status, especially in lamina morphology. Blade shape thus provides a field indicator of soil/pore water nutrient status: narrow blades indicate nutrient limitation, whereas broader blades indicate nutrient enrichment. [Copyright &y& Elsevier]

Genetic diversity studies of wetland plants are scarce, but estimates of genetic diversity are useful for learning about plant biology or developing appropriate management strategies. We used allozymes to examine patterns of genetic diversity in Cladium jamaicense, the dominant plant species of the Florida Everglades. We sampled 18 populations (a total of 818 plants) in a replicated grid pattern. Because C. jamaicense can reproduce asexually, we compared estimates of genetic diversity calculated using all sampled ramets to those using only genets within populations. Fewer than half of the 13 loci studied were polymorphic (P. = 46.2%), with just under two alleles per locus on average (A. = 1.9). Heterozygosity was also low and was lower for ramet-level estimates (ramets: H[sub es] = 0.069, H[sub ep] = 0.051; genets: H[sub es] = 0.094, H[sub ep] = 0.067). Ramet-level estimates indicated heterozygote excess in eight populations and heterozygote deficiencies in four populations, but genet-level estimates indicated inbreeding in only one population. Ramet-level estimates indicated significant population differentiation (F*[This character cannot be converted to ASCII text] = 0.268), but genet-level estimates did not (F*[This character cannot be converted to ASCII text] = 0.035). Similarly, mean genetic distance between populations was higher based on ramet-level estimates (D = 0.024) than genet-level estimates (D = 0.016), and we found a weak correlation between genetic and geographic distance based on ramet-level estimates (r = 0.15, P = 0.02) but not genet-level estimates (r = 0.04, P = 0.2). Thus, clonal reproduction resulted in effective genetic differentiation among populations. Observed patterns of population differentiation may reflect high levels of gene flow among populations or patterns established during colonization that persist through long-lived clones. Genetic diversity of Everglades C. jamaicense was low compared to other sedges or other species ... [ABSTRACT FROM AUTHOR]

The role of macrophytes in mercury (Hg) cycling in the Florida Everglades ecosystem has not been fully understood. In this study, a stable isotope (199Hg2+) addition technique was used to trace the methylation, uptake, and translocation of Hg by sawgrass (Cladium jamaicense) and quantitatively evaluate the contribution of atmospheric and soil Hg to Hg in sawgrass leaves and below-ground biomass. The results showed that spiked 199Hg2+ could be rapidly methylated to monomethylmercury (Me199Hg) in the soil of the sawgrass pots. Only small portions of total Hg (THg) and monomethylmercury (MeHg) in the soil could be taken up by sawgrass, indicated by the ratios of T199Hg and Me199Hg (tracer) concentrations in the sawgrass below-ground biomass (BGBM) over that in the soil (6.50 ± 1.9% and 12.8 ± 3.6% for THg and MeHg, respectively). Concentrations of T199Hg (tracer) and Me199Hg (tracer) in sawgrass leaves only accounted for 5.50 ± 2.8% and 15.6 ± 4.0%, respectively, of that in the BGBM, implying that the fractions of mercury species transported upward by sawgrass were also small. Statistical analysis (t test) showed that sawgrass preferred MeHg over THg in both uptake and upward translocation. The majority (>90%) of THg in sawgrass leaves were estimated to be obtained from atmospheric Hg, rather than from soil, suggesting that assimilation of atmospheric Hg could increase the overall Hg stock in the Florida Everglades ecosystem. The finding about foliar uptake of Hg is especially important for a better understanding of mercury cycling in the Everglades, given the large amount of sawgrass biomass in this ecosystem. [ABSTRACT FROM AUTHOR]

• Cladium jamaicense (sawgrass) has little to no seed germination in salinities ≥ 5 ppt. • Cladium jamaicense (sawgrass) has reduced and delayed germination in salinity ≥ 5 ppt. • Seed germination in Cladium jamaicense (sawgrass) needs freshwater for ≥ 4 weeks. Sea level rise threatens coastal peatlands globally, as increased salinity can cause peat collapse and formation of brackish ponds, replacing marshes. Sawgrass, Cladium jamaicense Crantz (Cyperaceae), is the charismatic macrophyte that dominates Everglades marshes (Florida, USA). Sawgrass root growth is reduced by salinity pulses of 20 ppt, impacting soil structure and organic input into coastal peats and possibly leading to coastal marsh loss. The potential for regeneration of coastal sawgrass marsh from seeds depends on how salinity affects sawgrass germination. Although adult sawgrass plants can tolerate salinities of 10–20 ppt in the field, the effect of salinity on seed germination is not known. In this study, sawgrass seeds were exposed to salinities of 0, 5, 15, and 25 ppt and observed weekly for germination over seven months (Oct. 2017-Apr. 2018). Twenty-eight percent of seeds in 0 ppt water germinated, while only 4% of seeds in 5 ppt germinated. Seeds in 15 and 25 ppt salt did not germinate. After 3.6 months, four-fifths of the seedling trays at the two higher salinities were transferred to 0 ppt. Beginning 7 weeks after transfer, 6% (15 ppt) and 3% (25 ppt) of transferred seeds germinated, while seeds remaining at the higher salinities did not. These results indicate that sawgrass seeds have greatly reduced or no germination in elevated salinity. If salinities rise in coastal areas, this lack of germination could prevent coastal sawgrass regeneration from seed, negatively affecting coastlines as sea level continues to rise. [ABSTRACT FROM AUTHOR]

This letter to the editor discusses naturally depleted levels of phosphorous (P) in Florida's Everglades wetlands and how water deliveries intended to restore hydrologic conditions are introducing increased levels of phosphorous, resulting in environmental effects that disrupt trophic relationships.

Abstract: Simulating ecological indicator responses to alternate restoration strategies provides decision support tools for resource managers and restoration planners. Our case study provides a methodology for how to utilize hydrologic suitability for native vegetation to evaluate effects of modeled restoration scenarios. We propose that hydrologic suitability of white water lily, Nymphaea odorata, an indicator species of the native Florida Everglades slough vegetation community, be used to evaluate modeled restoration scenarios in the Everglades ridge and slough landscape. Based on experimentally derived mesocosm and field studies and historical evidence, we developed a predictive performance measure to assess hydrologic suitability for N. odorata. We applied the performance measure to predict the hydrologic suitability for slough vegetation in the Everglades ridge and slough landscape using model-simulated hydrology of existing conditions, future conditions with restoration, and the predrainage Everglades. Our results indicate that Everglades restoration will provide the greatest benefits to native slough vegetation in Arthur R. Marshall Loxahatchee National Wildlife National Refuge (LNWR), Water Conservation Area (WCA) 3B, and Everglades National Park, and may degrade slough conditions within portions of WCA 2 and WCA 3A. Our analysis indicates that additional restoration efforts are needed to fully restore native slough vegetation communities throughout the Everglades ridge and slough landscape. Performance measure results for the predrainage scenario in the WCAs conflict with paleoecological data; these results indicate a need to improve the modeled predrainage topography as well as flow and evapotranspiration rates of the Natural System Model version 4.6.2 (hereinafter NSM). [Copyright &y& Elsevier]

Abstract: We have developed a comprehensive ecological indicator for invasive exotic plants, a human-influenced component of the Everglades that could threaten the success of the restoration initiative. Following development of a conceptual ecological model for invasive exotic species, presented as a companion paper in this special issue, we developed criteria to evaluate existing invasive exotic monitoring programs for use in developing invasive exotic performance measures. We then used data from the selected monitoring programs to define specific performance measures, using species presence and abundance as the basis of the indicator for invasive exotic plants. We then developed a series of questions used to evaluate region and/or individual species status with respect to invasion. Finally, we used an expert panel who had answered the questions for invasive exotic plants in the Everglades Lake Okeechobee model to develop a stoplight restoration report card to communicate invasive exotic plant status. The report card system provides a way to effectively evaluate and present indicator data to managers, policy makers, and the public using a uniform format among indicators. Collectively, the model, monitoring assessment, performance measures, and report card enable us to evaluate how invasive plants are impacting the restoration program and how effectively that impact is being managed. Applied through time, our approach also allows us to follow the progress of management actions to control the spread and reduce the impacts of invasive species and can be easily applied and adapted to other large-scale ecosystem projects. [Copyright &y& Elsevier]

Spatial patterns in mercury cycling and bioaccumulation at the landscape level in the Everglades were investigated by collecting and analyzing multimedia samples for mercury species and biogeochemical characteristics from 228 randomly located stations. Higher total mercury (THg) in environmental compartments (surface water, soil, flocculent detrital material (floc), and periphyton) generally occurred in the northern and central Everglades, but higher THg in water and periphyton in the Everglades National Park was an exception. Multiple biogeochemical characteristics, such as surface water dissolved organic matter (DOCSW), pH, chloride, and compositional properties of solid compartments (soil and floc), were identified to be important factors controlling THg distribution. Methylmercury (MeHg) was also higher in the northern Everglades for water, soil, and floc, but not for periphyton. Higher mosquitofish THg and bioaccumulation factor were observed in the central and southern Everglades, partially in accordance with periphyton MeHg distribution, but not in the "hot spot" areas of water, soil, or floc MeHg. The discrepancy in mercury bioaccumulation and mercury distribution in environmental compartments suggests that in addition to MeHg production, biogeochemical controls that make MeHg available to aquatic organisms, such as DOCSW and compositional properties of soil and floc, are important in mercury bioaccumulation. [ABSTRACT FROM AUTHOR]

We estimated the mass budget for mercury (Hg) seasonally deposited into the Florida Everglades and investigated seasonality of Hg cycling by analyzing data obtained for water, soil, flocculent detrital material (floc), periphytón, and mosquitofish collected throughout the Everglades freshwater marshes in the 2005 dry and wet seasons. Higher wet season total Hg (THg) in soil, floc, and periphyton agreed with greater Hg amounts entering these compartments during the wet season, probably owing to substantially greater Hg deposition in the wet season than in the dry season. Seasonal differences were absentfor THg in surface water. Methylmercury (MeHg) showed mixed seasonal patterns, with higher water and soil MeHg and lower periphyton MeHg in the dry season but no seasonality for floc MeHg. Seasonal variations in Hg deposition, MeHg production and transport, and mass of ecosystem compartments could be responsible for the seásonality of MeHg cycling. Higher mosquitofish THg, higher bioaccumulation factors, and higher biomagnification factors from periphyton to mosquitofish were observed inthe wet season than in the dry season, indicating that the wet season is more favorable for Hg bioaccumulation. The mass budget estimation agreed with this result [ABSTRACT FROM AUTHOR]

Saltwater intrusion and salinization of coastal wetlands around the world are becoming a pressing issue due to sea level rise. Here, we assessed how a freshwater coastal wetland ecosystem responds to saltwater intrusion. In wetland mesocosms, we continuously exposed Cladium jamaicense Crantz (sawgrass) plants and their peat soil collected from a freshwater marsh to two factors associated with saltwater intrusion in karstic ecosystems: elevated loading of salinity and phosphorus (P) inputs. We took repeated measures using a 2 × 2 factorial experimental design (n = 6) with treatments composed of elevated salinity (~9 ppt), P loading (14.66 μmol P/d), or a combination of both. We measured changes in water physicochemistry, ecosystem productivity, and plant biomass change over two years to assess monthly and two‐year responses to saltwater intrusion. In the short‐term, plants exhibited positive growth responses with simulated saltwater intrusion (salinity + P), driven by increased P availability. Despite relatively high salinity levels for a freshwater marsh (~9 ppt), gross ecosystem productivity (GEP), net ecosystem productivity (NEP), and aboveground biomass were significantly higher in the elevated salinity + P treated monoliths compared to the freshwater controls. Salinity stress became evident after extended exposure. Although still higher than freshwater controls, GEP and NEP were significantly lower in the elevated salinity + P treatment than the +P treatment after two years. However, elevated salinity decreased live root biomass regardless of whether P was added. Our results suggest that saltwater intrusion into karstic freshwater wetlands may initially act as a subsidy by stimulating aboveground primary productivity of marsh plants. However, chronic exposure to elevated salinity results in plant stress, negatively impacting belowground peat soil structure and stability through a reduction in plant roots. [ABSTRACT FROM AUTHOR]