▪ Abstract We review the evidence of regime shifts in terrestrial and aquatic environments in relation to resilience of complex adaptive ecosystems and the functional roles of biological diversity in this context. The evidence reveals that the likelihood of regime shifts may increase when humans reduce resilience by such actions as removing response diversity, removing whole functional groups of species, or removing whole trophic levels; impacting on ecosystems via emissions of waste and pollutants and climate change; and altering the magnitude, frequency, and duration of disturbance regimes. The combined and often synergistic effects of those pressures can make ecosystems more vulnerable to changes that previously could be absorbed. As a consequence, ecosystems may suddenly shift from desired to less desired states in their capacity to generate ecosystem services. Active adaptive management and governance of resilience will be required to sustain desired ecosystem states and transform degraded ecosystems...

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Regime Shifts, Resilience, and Biodiversity in Ecosystem Management

Wetlands and streams buffer the interactions among uplands and adjacent aquatic systems. Phosphorus (P) is often the key nutrient found to be limiting in both estuarine and freshwater ecosystems. As such, the ability of wetlands and streams to retain P is key to determining downstream water quality. This article reviews the processes and factors regulating P retention in streams and wetlands and evaluates selected methodologies used to estimate P retention in these systems. Phosphorus retention mechanisms reviewed include uptake and release by vegetation, periphyton and microorganisms; sorption and exchange reactions with soils and sediments; chemical precipitation in the water column; and sedimentation and entrainment. These mechanisms exemplify the combined biological, physical, and chemical nature of P retention in wetlands and streams. Methodologies used to estimate P retention include empirical input-output analysis and mass balances, and process kinetics applied at various scales, including micro- a...

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Phosphorus Retention in Streams and Wetlands: A Review

Wetlands seem to be especially vulnerable to invasions. Even though ≤6% of the earth's land mass is wetland, 24% (8 of 33) of the world's most invasive plants are wetland species. Furthermore, many wetland invaders form monotypes, which alter habitat structure, lower biodiversity (both number and “quality” of species), change nutrient cycling and productivity (often increasing it), and modify food webs. Wetlands are landscape sinks, which accumulate debris, sediments, water, and nutrients, all of which facilitate invasions by creating canopy gaps or accelerating the growth of opportunistic plant species. These and other disturbances to wetlands, such as propagule influx, salt influx, and hydroperiod alteration, create opportunities that are well matched by wetland opportunists. No single hypothesis or plant attribute explains all wetland invasions, but the propensity for wetlands to become dominated by invasive monotypes is arguably an effect of the cumulative impacts associated with landscape sinks, incl...

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Causes and Consequences of Invasive Plants in Wetlands: Opportunities, Opportunists, and Outcomes

The potential for constructed wetlands for wastewater treatment and reuse in developing countries: a review

The water quality response to implementation of conservation measures across watersheds has been slower and smaller than expected. This has led many to question the efficacy of these measures and to call for stricter land and nutrient management strategies. In many cases, this limited response has been due to the legacies of past management activities, where sinks and stores of P along the land-freshwater continuum mask the effects of reductions in edge-of-field losses of P. Accounting for legacy P along this continuum is important to correctly apportion sources and to develop successful watershed remediation. In this study, we examined the drivers of legacy P at the watershed scale, specifically in relation to the physical cascades and biogeochemical spirals of P along the continuum from soils to rivers and lakes and via surface and subsurface flow pathways. Terrestrial P legacies encompass prior nutrient and land management activities that have built up soil P to levels that exceed crop requirements and modified the connectivity between terrestrial P sources and fluvial transport. River and lake P legacies encompass a range of processes that control retention and remobilization of P, and these are linked to water and sediment residence times. We provide case studies that highlight the major processes and varying timescales across which legacy P continues to contribute P to receiving waters and undermine restoration efforts, and we discuss how these P legacies could be managed in future conservation programs.

Phosphorus legacy: overcoming the effects of past management practices to mitigate future water quality impairment.

The recent expansion of Typha domingensis (Typha) into areas of the Ev- erglades previously dominated by Cladium jamaicense (Cladium) communities has led to competing hypotheses about the importance of nutrient concentration vs. hydroperiod in controlling the distribution of these species. In this study, experimental mixtures of Typha domingensis, Cladium jamaicense, and Eleocharis interstincta (Eleocharis), a member of the Cladium community, were subjected to two levels of nutrient concentration and three contrasting hydroperiods to determine how these variables might affect Typha's ability to displace the Cladium community. Mixtures of the three species were established in outdoor tanks containing soil from the northern Everglades region where the experiment was con- ducted. Nutrient treatments consisted of nutrient additions to adjust ambient water con- centrations to either 50 ,ug/L phosphorus (P) or 100 pug/L P plus nitrogen (N). The three hydroperiods were achieved by maintaining water depths within ranges observed in the northern Everglades. Maximum water depths of 15, 30, and 60 cm were established through- out the wet season (May-November) followed by lowering to 5 cm during the dry season. Over a 2-yr period, biomass was monitored nondestructively and aboveground material was harvested at the end of the experiment. Analysis of the biomass changes over time showed that differences between the species developed by the end of the first growing season. Typha and Eleocharis had initial growth rates substantially higher than those observed for Cladium. Typha's growth in mixtures responded positively to both elevated nutrients (by as much as 45%) as well as to increased water depth (by as much as 60%), while Cladium and Eleocharis did not increase in response to these variables. Tissue P concentrations were found to be higher for Typha and Eleocharis than for Cladium under nearly all conditions. Net accu- mulation of P in Typha shoots was 2-3 times greater than in the other species. The en- hancement of Typha by elevated nutrients and increased flooding is associated with a syndrome of life history characteristics that includes rapid growth rates, high tissue con- centrations of P, tall leaves, and a greater response to contrasting environmental conditions. Cladium, in contrast, showed a slow growth rate, low tissue concentrations of P, a greater capacity to resist invasion by Typha in shallow waters, and less of a growth response to contrasting environmental conditions, traits that would seem to be well suited to the nutrient- poor, hydrologically unstable conditions natural to the Everglades. Results from this study suggest that attempts to limit the spread of Typha should consider hydrologic restoration as well as reduction in surface water nutrients.

https://www.jstor.org/stable/pdfplus/2269482.pdf

Effects of Nutrients and Hydroperiod on Typha, Cladium, and Eleocharis: Implications for Everglades Restoration

The Florida Everglades developed as a nutrient-poor, rain-fed ecosystem. However, for the past 30 yr, the Everglades have received nutrient-enriched surface water runoff from the adjacent Everglades Agricultural Area (EAA). This study examines the response of a pristine wetland, Water Conservation Area 1 (WCA 1), part of the northern Florida Everglades, to nutrient loading as documented by soil nutrient concentrations. During 1979 to 1988, WCA 1 received 138 t total P (TP) and 4919 t total N (TN), retaining 53% of the TP load and 58% of the TN load. Analyses of the spatial distribution of soil N and P showed steep gradients of TP along the western canal boundary, adjacent to inflow points importing EAA runoff. Surficial soils (0-10 cm depth) at interior marsh sites had a mean TP concentration of 368 mg kg -1 , compared with 1028 mg kg -1 measured at sites adjacent to the western canal. Similar trends were observed for soil Ca and Mg, while C and N did not show the same boundary effects on spatial enrichment. Nutrient-enriched sites also had higher porewater soluble reactive P (SRP; 0.15 mg L -1 ) and NH 4 -N (1.65 mg L -1 ) than unenriched sites (SRP = 0.02 mg L -1 , NH 4 -N = 0.85 mg L -1 ). Of the 90 sites sampled, 66 sites consisted of sloughs and sawgrass (Cladium jamaicense Crantz); the remaining 24 sites were either cattail (Typha spp.) dominated or had a significant cattail presence. These 24 cattail sites were closest to the nutrient inflow areas and had the highest soil nutrient concentrations.

Spatial distribution of soil nutrients in a northern Everglades marsh: water conservation area 1

https://soils.ifas.ufl.edu/wetlands/publications/PDF-articles/231.Factors%20influencing%20cattail%20abundance%20in%20northern%20everglades.pdf

Factors influencing cattail abundance in the northern Everglades

The Florida Everglades have undergone significant ecological change resulting from anthropogenic manipulation of historical regimes of hydrology, nutrient loading, and fire. Water Conservation Area 2A (WCA-2A) in the northern Everglades has been a focal point for the study of ecological effects of nutrient loading, especially phosphorus (P), from the nearby Everglades Agricultural Area (EAA). The overall objective of our study was to evaluate recent (1990 to 1998) changes in the spatial extent and patterns of soil P enrichment in Everglades WCA-2A. Surface soil was sampled to a depth of 10 cm at 62 sites within WCA-2A during 1998 for analysis of total phosphorus (TP) content. Geostatistical methods were used to create an interpolated grid of soil TP values across WCA-2A. Comparison of the results of this study with a similar study performed in 1990 showed that the extent of soil P enrichment in surface soil and sediments increased between 1990 and 1998, as evidenced by increased coverage of highly P-enriched soil near the primary surface inflows and a general increase in the concentration of soil TP in the interior regions of WCA-2A. Approximately 73% (31 777 ha) of the total land area of WCA-2A was considered P-enriched (soil total P > 500 mg kg(-1)) in 1998, compared with 48% of the land area (20,829 ha) in 1990, an average increase of 1,327 ha yr(-1). Study results indicate that the soil P enrichment "front" has advanced further into the relatively unimpacted interior of WCA-2A during the past several years.

Spatio-temporal patterns of soil phosphorus enrichment in Everglades water conservation area 2A.

Phosphorus (P) retention in wetlands is an important function of watershed nutrient cycling, particularly in drainage basins with significant nonpoint nutrient contributions from agriculture and urban sources. Phosphorus storage involves complex interrelated physical, chemical, and biological processes that ultimately retain P in organic and inorganic forms. Both short-term storage of P mediated by assimilation into vegetation, translocation within above- and below-ground plant tissues, microorganisms, periphyton, and detritus, and long-term storage (retention by inorganic and organic soil particles and net accretion of organic matter) need to be considered. Here, we review and synthesize recent studies on P cycling and storage in soils and sediments throughout the Greater Everglades Ecosystem and the influence of biotic and abiotic regulation of P reactivity and mobility as related to restoration activities in south Florida. Total P storage in the floc/detrital layer and surface soils (0–10 cm) is estima...

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S. Newman

Papers

Effects of Nutrients and Hydroperiod on Typha, Cladium, and Eleocharis: Implications for Everglades Restoration

Spatial distribution of soil nutrients in a northern Everglades marsh: water conservation area 1

Factors influencing cattail abundance in the northern Everglades

Spatio-temporal patterns of soil phosphorus enrichment in Everglades water conservation area 2A.

Phosphorous Cycling in the Greater Everglades Ecosystem: Legacy Phosphorous Implications for Management and Restoration