Never before has the resiliency of wetland ecosystems to climatic and anthropogenic stressors been more important or more recognized by those who study these unique ecosystems. The goal of this chapter is to discuss a variety of management and restoration approaches to building resiliency in wetlands that are subjected to changing conditions. We examine wetland responses to changing climatic and hydrologic conditions at multiple spatial (global to microscopic level) and temporal (100-million-year to 1-year) scales which informs our perspective on predicting future wetland responses to both anthropogenic and natural perturbations. Additionally, we introduce the utility of having advanced tools for monitoring changes at the biogeochemical scale, which is likely to be one of the first indicators of change to be detected. The case studies that we present enable us to learn techniques and approaches to address current and future stressors (natural and anthropogenic) on both coastal and inland wetland ecosystems and contain the common thread of carbon sequestration and biogeochemical cycling. We focus on the functional roles of wetlands in providing ecosystem services and how those ecosystem services are best protected, managed, and restored in light of a variety of stressors, such as global climate change, increased water use and demand, and land use changes. Wise-use approaches that enhance wetland biodiversity and resiliency to these changes and impacts are discussed, as are wetland-specific ecosystem services that provide enhanced water quality, water supply, flood protection, storm damage protection, pollution attenuation, and climate change resiliency for adjacent human communities.

Vegetation response to wildfire has been studied extensively in upland ecosystems, but fire effects on temperate wetlands are less understood. We evaluated vegetation response to extensive wildfire in wetlands of Okefenokee National Wildlife Refuge (ONWR), USA, with a spatially explicit Bayesian belief network model informed with data recorded during 1990–2012. We assessed model accuracy and effects of fire frequency on vegetation composition with predictive scenarios of fire absence or a fire return interval (FRI) every 5 or 10 years during 2012–2032. In fire absence, shrubs increased 100%, primarily in the northern half of the Refuge, while the herbaceous class that was widespread in 2012 was eliminated. Areas dominated by forest during the past ~65 years were maintained with the 5- and 10-year FRI. Herbaceous-dominated areas maintained with the 5-year FRI decreased (90%) with the 10-year FRI. Shrub coverage increased with fire (17%, 5-year FRI; 20%, 10-year FRI), while scrub/shrub decreased (12%; 5-year FRI) or increased (6%; 10-year FRI). A 5-year FRI during conditions promoting severe fire may maintain the distribution of herbaceous and forested areas that followed an extensive drought and fires in 2011, and may limit scrub/shrub expansion that previously occurred with longer FRIs in the ONWR.

Summary Anadromous fish populations entering freshwater ecosystems provide organic matter and marine‐derived nutrients during spawning and subsequent mortalities of adults. Dams and other impediments to connectivity in rivers and streams have affected anadromous fish populations in many regions and prevented or reduced this influx of organic materials and nutrients. This study used historical data on the timing of delivery of marine‐derived nutrients; we added a carcass analogue (pellets made from the carcasses of Chinook salmon, Oncorhynchus tschawytcha) to simulate potential effects of restored access of anadromous fish to streams. We used stable isotopes to document the extent of nutrient incorporation of nitrogen and carbon from the carcass analogue by macroinvertebrates and juvenile Atlantic salmon (Salmo salar) in salmon nursery streams. We stocked four headwater streams that historically hosted spawning Atlantic salmon and sea lamprey (Petromyzon marinus) in Maine, U.S.A. with Atlantic salmon fry and simulated timing of nutrient addition by spawning sea lamprey in the early summer and Atlantic salmon in the autumn. Macroinvertebrates and Atlantic salmon assimilated nitrogen (12–57% of total N) and carbon (21–65% of total C) from the added pellets, and the magnitude and duration of enrichment varied temporally and with macroinvertebrate functional feeding group. Assimilation of nutrients from carcass analogues was both direct and indirect, and a nutrient legacy was evident in the second year of sampling. Incorporation of nutrients from the pellets at a range of heights in the food web demonstrated the potential for marine‐derived subsidies to contribute to freshwater ecosystem processes in Atlantic salmon nursery streams.

Our study used historic marine-derived nutrient (MDN) delivery timing to simulate potential effects of restored connectivity on juvenile Atlantic salmon (ATS; Salmo salar) growth and condition. Four headwater streams were stocked with ATS young of the year (YOY) and received carcass analog additions (0.10 kg·m–2wetted area) in treatment reaches to match the timing of sea lamprey (Petromyzon marinus) spawning. Individual ATS mass was 33%–48% greater and standard length was 9%–15% greater in treatment reaches relative to control reaches for 4 months following nutrient additions. Percent total lipids in YOY ATS were twice as great in treatment reaches 1 month following carcass analog additions and remained elevated in treatment fish for 2 more months. Absolute growth rates, based on otolith microstructure analysis, correlated with water temperature fluctuations in all reaches and were elevated by an average of 0.07 mm·day–1in treatment reaches for 1 month following carcass analog additions. Simulated sea lamprey MDNs increased juvenile ATS growth, which, via potential increases in overwinter survival and decreases in smolt age, may contribute to population persistence and ecosystem productivity.

This research examined responses of Atlantic salmon ( Salmo salar) stream communities to experimental simulation of marine-derived nutrient input. Prior to construction of dams beginning in the early 1800s, Atlantic salmon and other anadromous species migrated from the ocean to spawn in Maine's extensive rivers and streams. Spawning fish transported marine-derived nutrients to these systems as carcasses, eggs, and waste products. These contributions may have influenced productivity in otherwise nutrient limited systems, bolstering growth and survival of young Atlantic salmon and other anadromous species and influencing other components of the stream communities. This study involved a reach-scale experiment to explore assimilation of marine-derived nutrients supplied to small streams in Maine. Four headwater streams were stocked with Atlantic salmon fry in May 2009 and 2010, and marine-derived nutrient input was simulated with a carcass analog placed in treatment reaches to match timing of sea lamprey (Petromyzon marinus; July) and Atlantic salmon (October) spawning. Total dissolved nitrogen and phosphorus concentrations were greater in treatment reaches two days following carcass analog additions and returned to background concentrations approximately one month later. Periphyton biomass did not differ between control and treatment reaches for eight weeks following additions. Macroinvertebrate community assemblages differed between control and treatment reaches two and four weeks following additions. Macroinvertebrates and Atlantic salmon assimilated nitrogen (12-57% of total N) and carbon (21-65% of total C) from carcass analogs, and the magnitude and duration of enrichment varied temporally and by functional feeding group. Mass was 33-48% greater and length was 9-15% greater in young-of-the-year Atlantic salmon in treatment reaches for four months following nutrient additions. Percent total lipids in Atlantic salmon were twice as great in treatment reaches one month following carcass analog additions, and lipid levels remained elevated for two more months. Absolute growth rates, based on otolith microstructure analysis, correlated with water temperature fluctuations in all reaches and were elevated in treatment reaches for one month following carcass analog additions. Simulated sea lamprey spawning increased stream water nutrient concentrations, shifted macroinvertebrate community structure, and increased growth potential of juvenile Atlantic salmon, which may contribute to population persistence and ecosystem productivity.