Freshwater Coastal Wetlands Research Articles

Nutrient amendments enrich microbial hydrocarbon degradation metagenomic potential in freshwater coastal wetland microcosm experiments.

The impact of oil spills in a freshwater aquatic environment can pose dire social, economic, and ecological effects on the region. An oil spill in the Laurentian Great Lakes region has the potential to affect the drinking water of more than 30 million people. The light synthetic crude oil used in this experimental microcosm study is transported through an underground pipeline crossing the waterway between two Laurentian Great Lakes. This study collected metagenomic data (experiments in triplicate) and assessed the quantity of BTEX compounds, which connected microbial degradation function to gene potential. The resulting data documented the bioremediation capabilities of native microbes in a freshwater coastal wetland. This study also provided evidence for this region that bioremediation can be a viable remediation strategy instead of invasive physical methods.

Applying portfolio theory to benefit endangered amphibians in coastal wetlands threatened by climate change, high uncertainty, and significant investment risk

The challenge of selecting strategies to adapt to climate change is complicated by the presence of irreducible uncertainties regarding future conditions. Decisions regarding long-term investments in conservation actions contain significant risk of failure due to these inherent uncertainties. To address this challenge, decision makers need an arsenal of sophisticated but practical tools to help guide spatial conservation strategies. Theory asserts that managing risks can be achieved by diversifying an investment portfolio to include assets – such as stocks and bonds – that respond inversely to one another under a given set of conditions. We demonstrate an approach for formalizing the diversification of conservation assets (land parcels) and actions (restoration, species reintroductions) by using correlation structure to quantify the degree of risk for any proposed management investment. We illustrate a framework for identifying future habitat refugia by integrating species distribution modeling, scenarios of climate change and sea level rise, and impacts to critical habitat. Using the plains coqui (Eleutherodactylus juanariveroi), an endangered amphibian known from only three small wetland populations on Puerto Rico’s coastal plains, we evaluate the distribution of potential refugia under two model parameterizations and four future sea-level rise scenarios. We then apply portfolio theory using two distinct objective functions and eight budget levels to inform investment strategies for mitigating risk and increasing species persistence probability. Models project scenario-specific declines in coastal freshwater wetlands from 2% to nearly 30% and concurrent expansions of transitional marsh and estuarine open water. Conditional on the scenario, island-wide species distribution is predicted to contract by 25% to 90%. Optimal portfolios under the first objective function – benefit maximization – emphasizes translocating frogs to existing protected areas rather than investing in the protection of new habitat. Alternatively, optimal strategies using the second objective function – a risk-benefit tradeoff framework – include significant investment to protect parcels for the purpose of reintroduction or establishing new populations. These findings suggest that leveraging existing protected areas for species persistence, while less costly, may contain excessive risk and could result in diminished conservation benefits. Although our modeling includes numerous assumptions and simplifications, we believe this framework provides useful inference for exploring resource dynamics and developing robust adaptation strategies using an approach that is generalizable to other conservation problems which are spatial or portfolio in nature and subject to unresolvable uncertainty.

Physicochemical, Coliform and Agrochemical Analysis to Evaluate the Water Quality of Coastal Freshwater Wetlands in Tonosí in Panama

Physicochemical, Coliform and Agrochemical Analysis to Evaluate the Water Quality of Coastal Freshwater Wetlands in Tonosí in Panama

Rediscovery, systematics and conservation of an enigmatic freshwater crayfish (Parastacidae) from the Australian monsoon tropics

AbstractFreshwater wetlands are among the world's most valuable ecosystems, supporting diverse biota and critical ecological services, yet these habitats have suffered extensive and pervasive anthropogenic disturbance. Northern Australia represents a rare example of a relatively unmodified, vast wetland habitat. The freshwater crayfishes of the region are poorly documented, with one enigmatic species, the nutcracker yabby Cherax nucifraga, described from a single individual sampled opportunistically from the stomach of a predatory fish. Here we report on the rediscovery of C. nucifraga from a relatively limited distribution in semi‐permanent coastal freshwater wetlands. Field studies were conducted to inform natural resource management and conservation. Genome skimming to recover mitogenomes, 18S–28S and histone sequences demonstrated a sister relationship with two congeners from the tropics, and moderate molecular genetic substructure was apparent within C. nucifraga between mainland and Melville Island locations. Cherax nucifraga is characterised by the presence of a strawberry‐coloured soft patch on the outer margin of the claw, uniquely present in both mature males and females. Meristic and multivariate morphometric comparisons are made with the co‐occurring redclaw Cherax quadricarinatus and the allopatric whiteclaw yabby Cherax bicarinatus, with a summary of diagnostic traits developed into a visual guide and key. Programs to further understand ecology, threats and traditional ecological knowledge will help to inform the future conservation management of the species in the face of increasing development and environmental change to northern Australian coastal freshwater wetlands. Specific conservation actions include identifying and protecting refuge habitats and preventing incursions by other Cherax species.

Fish Assemblage Responses to the Exclusion of Invasive Common Carp (Cyprinus carpio) from a Large Freshwater Coastal Wetland, Delta Marsh, Manitoba

Fish Assemblage Responses to the Exclusion of Invasive Common Carp (Cyprinus carpio) from a Large Freshwater Coastal Wetland, Delta Marsh, Manitoba

Contribution of soil seed banks to vegetation resilience in coastal freshwater wetlands of subtropical Australia

AbstractQuestionsWhat role do soil seed banks play in the resilience of coastal freshwater wetland vegetation communities? How might soil seed bank composition and similarity to standing vegetation drive changes in vegetation expression, particularly given projected changes in climate?LocationSixty wooded coastal freshwater wetlands in southeast Queensland, Australia.MethodsWe surveyed standing vegetation and investigated soil seed bank composition through an 8‐month‐long emergence experiment.ResultsSoil seed bank assemblages were dominated by forb and sedge species (23% exotic), but composition varied throughout the study region. Spatial (north–south) and land‐use (urban–rural) gradients explained some variation in soil seed bank composition. Soil moisture and groundwater dependence also influenced species distributions, particularly for freshwater wetland species. The similarity of soil seed banks to standing vegetation was low. Species present in both extant and soil seed bank assemblages were commonly native wetland taxa, including one salt marsh species (Juncus kraussii).ConclusionsProjected climatic changes will likely drive changes in coastal freshwater wetland vegetation communities through increases in the frequency and intensity of disturbances (e.g., storm surge). Our results suggest that regeneration from soil seed banks could promote four potential scenarios: (1) expansion of weed communities, (2) expansion of salt marsh communities, (3) maintenance and expansion of wetland/terrestrial species, and (4) transformation to an unvegetated open water zone because of reduced regeneration success under changing conditions. These diverse vegetation futures highlight the vulnerability of wooded coastal freshwater wetlands and the need for research and management interventions to maintain their biodiversity and ecosystem services.

Restored forested wetland surprisingly resistant to experimental salinization.

Salinization of coastal freshwater wetlands is an increasingly common and widespread phenomenon resulting from climate change. The ecosystem consequences of added salinity are poorly constrained and highly variable across prior observational and experimental studies. We added 1.8 metric tons of marine salts to replicated 200 m2 plots within a restored forested wetland in Eastern North Carolina over the course of four years. Based on prior small-scale experiments at this site, we predicted that salinization would lead to slower tree growth and suppressed soil carbon cycling. Results from this large-scale field experiment were subtle and inconsistent over space and time. By the fourth year of the experiment, we observed the predicted suppression of soil respiration and a reduction of water extractable carbon from soils receiving salt treatments. However, we found no cumulative effects of four years of salinization on total soil carbon stocks, tree growth, or root biomass. We observed substantial variation in soil solution chemistry (notably, pH and base saturation) across replicated treatment blocks; the effective salt levels, ionic composition, and pH varied following treatment depending upon pre-existing differences in edaphic factors. Our multi-year monitoring also revealed an underlying trend of wetland acidification across the entire site, a suspected effect of ecosystem recovery following wetland restoration on former agricultural land. The overwhelming resistance to our salt treatments could be attributed to the vigor of a relatively young, healthy wetland ecosystem. The heterogeneous responses to salt that we observed over space and time merits further investigation into the environmental factors that control carbon cycling in wetlands. This work highlights the importance of multi-year, large-scale field experiments for investigating ecosystem responses to global environmental change.

Letting the plants speak: Law, landscape and conservation.

The Botany Wetlands are the contemporary remnant of a formerly extensive coastal freshwater wetland in the inner-urban suburbs of Sydney (Australia). This site supports a range of ecosystem services, including human physical and mental health benefits, filtration of stormwater runoff from a highly urban and industrial catchment, and accommodation space for floodwater. The wetlands also provide habitat to migratory water birds and act as a connective habitat corridor and refuge for native flora and fauna including endangered ecological communities recognised in state and national legislation. Current management strategies and 'on the ground' practices are informed by a hierarchy of laws and management plans that act to create and reinforce a specific narrative in the material landscape. Here we consider the ecological history of the wetlands, derived from paleoecological data, in the context of this complex network of governance entanglements. We argue that the system bears little resemblance to its long-term character and has been made and continually re-made by a portmanteau of inflexible regulatory structures. We suggest that maintaining ecosystem services in such a complex, hybridized sociolegal-biophysical system requires a critical view of both the power relations and physical processes that shape it.

Biological control of invasive floating fern leads to rapid recovery of ecological functions in coastal fresh water wetlands in Louisiana

Biological control of invasive floating fern leads to rapid recovery of ecological functions in coastal fresh water wetlands in Louisiana

Investigation of the concentration, origin and health effects of PAHs in the Anzali wetland: The most important coastal freshwater wetland of Iran

This study investigated the concentration of PAHs in 19 water samples, 34 sediment samples and 22 fish samples of Anzali Wetland, located in north of Iran. The average concentration of ∑PAHs in the wetland sediment was 89.19 μg/kg (8.28–806.64) and 78.31 ng/L (5.14–253.37) in the wetland water. Also, the average concentration of ∑PAHS in the muscle of the investigated fish in the wetland was 23 μg/kg (56.1 to 7.6). The source apportionment of PAHs in water and sediment considering isomeric ratios and statistical methods reveals the predominance of petrogenic origin of the compounds in water and pyrogenic origin in sediment. Overall, the level of contamination in fish is relatively low to moderate, considering ∑PAHs. The findings present clear evidence of low to moderate level of contamination in the wetland, the PAHs contamination however could cross their ecological thresholds in future unless control measures are taken to protect the wetland.

Assessing the impacts of light synthetic crude oil on microbial communities within Laurentian Great Lakes’ sediment habitats

The ability of microbial communities to respond to and degrade crude oil in marine environments is well understood, yet fewer studies have examined freshwater environments. The Laurentian Great Lakes are one of the world’s largest surface freshwater sources. A pipeline that transports light synthetic crude oil crosses between two of the Great Lakes (the Straits of Mackinac, connecting Lakes Michigan and Huron, U.S.A.), and there is uncertainty on how the various habitats within this region would respond to accidental crude oil exposure. In this study, sediment microbial communities from three distinct habitats (coastal beach, freshwater coastal wetland, and Lake Michigan deep sediments) were used in microcosm experiments to document their community response (16S rRNA gene sequencing) to light synthetic crude oil (headspace gas chromatography). Microbial community structure (beta diversity) was impacted after exposure to crude oil in each of the habitats examined, with each habitat showing a different level of resistance to crude oil. Additionally, within each habitat, beta diversity distinguished sub-communities that increased in abundance in experimental treatments. Specifically, an increase in total abundance of Alphaproteobacteria, Betaproteobacteria, or Gammaproteobacteria was observed in microcosms exposed to crude oil regardless of habitat type. Methane, a potential hydrocarbon degradation byproduct, was observed in the headspace of the microcosms after exposure to crude oil, which may indicate methanogenic hydrocarbon degradation. These data suggest Great Lakes freshwater microbial communities will respond differently to crude oil exposure but may have shared community members involved in resisting and degrading light synthetic crude oil.

Understanding Peat Soil Deformation and Mechanisms of Peat Collapse Across a Salinity Gradient in the Southwestern Everglades

AbstractSaltwater intrusion is a significant threat to the structure and ecology of inland and coastal freshwater wetlands, altering biogeochemical cycling and disrupting important ecosystem services. As sea level rises along the Florida coast, the saltwater interface progressively moves further inland reaching freshwater soils previously unexposed to saltwater. One result of this soil salinization is a phenomenon called peat collapse which is currently observable along the South Florida coastline. While previous studies have proposed conceptual models to explain peat collapse many uncertainties still exist regarding the physical mechanisms that trigger this phenomenon. In this study we use a unique combination of laboratory and field‐based measurements using geophysical methods, deformation rods, gas traps, time‐lapse photography, and hydraulic conductivity measurements to investigate the effects of salinization on the physical properties of peat soils across a salinity gradient in the southwestern Everglades. Our results show that freshwater peat soils have about three times greater degree of pore dilation when compared to peat soils previously exposed to saltwater conditions. Differences in soil surface deformation were also observed and related to differences in the soil matrix physical integrity across the salinity gradient. This work also uses electrical resistivity imaging surveys to image areas of peat collapse and demonstrates: (a) the role of salinity in the development of collapse features; and (b) the apparent lack of evidence to suggest subsurface lithological controls on the development of collapse features. A simplified conceptual framework for better understanding peat collapse and pock formation is presented.

Disentangling direct and indirect effects of extreme events on coastal wetland communities.

One of the primary ways in which climate change will impact coastal freshwater wetlands is through changes in the frequency, intensity, timing and distribution of extreme weather events. Disentangling the direct and indirect mechanisms of population- and community-level responses to extreme events is vital to predicting how species composition of coastal wetlands will change under future conditions. We extended static structural equation modelling approaches to incorporate system dynamics in a multi-year multispecies occupancy model to quantify the effects of extreme weather events on a coastal freshwater wetland system. We used data from an 8-year study (2009-2016) on St. Marks National Wildlife Refuge in Florida, USA, to quantify species-specific and community-level changes in amphibian and fish occupancy associated with two flooding events in 2012 and 2013. We examine how physical changes to the landscape, including potential changes in salinity and increased wetland connectivity, may have contributed to or exacerbated the effects of these extreme weather events on the biota of isolated coastal wetlands. We provide evidence that the primary effects of flooding on the amphibian community were through indirect mechanisms via changes in the composition of the sympatric fish community that may have had lethal (i.e. through direct predation) or non-lethal (i.e. through direct or indirect competitive interactions) effects. In addition, we have shown that amphibian species differed in their sensitivity to direct flooding effects and indirect changes in the fish community and wetland-specific conductance, which led to variable responses across the community. These effects led to the overall decline in amphibian species richness from 2009 to 2016, suggesting that wetland-breeding amphibian communities on St. Marks National Wildlife Refuge may not be resilient to predicted changes in coastal disturbance regimes because of climate change. Understanding both direct and indirect effects, as well as species interactions, is important for predicting the effects of a changing climate on individual species, communities and ecosystems.

Tidal restoration to reduce greenhouse gas emissions from freshwater impounded coastal wetlands

Freshwater impounded wetlands are created by artificially restricting coastal wetlands connection to tides. The decrease in salinity and altered hydrology can significantly increase greenhouse gas (GHG) emissions, specifically methane (CH4). Restoration of freshwater impounded wetlands through tidal reintroduction can potentially reduce GHG emissions; however, studies in tropical regions are scare. This study investigates the potential for tidal restoration of impounded freshwater coastal wetlands by comparing their GHG emissions with tidally connected mangrove and saltmarshes in the Burdekin catchment in Queensland, Australia. We found that freshwater impounded wetlands had significantly higher CH4 emissions (3,633 ± 812 μg CH4 m−2 hour−1) than mangroves (27 ± 8 μg CH4 m−2 hour−1) and saltmarsh (13 ± 8 μg CH4 m−2 hour−1). Soil redox, moisture, carbon, nitrogen, and bulk density were all significantly correlated to methane emissions. Conversely, freshwater impounded wetlands had significantly lower nitrous oxide (N2O) emissions (−0.72 ± 0.18 μg N2O m−2 hour−1) than mangroves and saltmarsh (0.35 ± 0.29 and 1.32 ± 0.52 μg N2O m−2 hour−1 respectively). Nevertheless, when converting to CO2 equivalents (CO2‐eq), freshwater impounded wetlands emitted 91 ± 20 g CO2‐eq m−2 hour−1, compared to the much lower 0.8 ± 0.2 and 0.7 ± 0.2 g CO2‐eq m−2 hour−1 emission rates for mangroves and saltmarsh. In conclusion, restoration of freshwater impounded wetlands through tidal restoration is likely to result in reduced GHG emissions.

A Disappearing BRIS Ecosystem and Coastal Freshwater Wetland on the Coastal Plain of Terengganu, East Coast of Peninsular Malaysia

A Disappearing BRIS Ecosystem and Coastal Freshwater Wetland on the Coastal Plain of Terengganu, East Coast of Peninsular Malaysia

Year-around survey and manipulation experiments reveal differential sensitivities of soil prokaryotic and fungal communities to saltwater intrusion in Florida Everglades wetlands

Global sea-level rise is transforming coastal ecosystems, especially freshwater wetlands, in part due to increased episodic or chronic saltwater exposure, leading to shifts in biogeochemistry, plant- and microbial communities, as well as ecological services. Yet, it is still difficult to predict how soil microbial communities respond to the saltwater exposure because of poorly understood microbial sensitivity within complex wetland soil microbial communities, as well as the high spatial and temporal heterogeneity of wetland soils and saltwater exposure. To address this, we first conducted a two-year survey of microbial community structure and bottom water chemistry in submerged surface soils from 14 wetland sites across the Florida Everglades. We identified ecosystem-specific microbial biomarker taxa primarily associated with variation in salinity. Bacterial, archaeal and fungal community composition differed between freshwater, mangrove, and marine seagrass meadow sites, irrespective of soil type or season. Especially, methanogens, putative denitrifying methanotrophs and sulfate reducers shifted in relative abundance and/or composition between wetland types. Methanogens and putative denitrifying methanotrophs declined in relative abundance from freshwater to marine wetlands, whereas sulfate reducers showed the opposite trend. A four-year experimental simulation of saltwater intrusion in a pristine freshwater site and a previously saltwater-impacted site corroborated the highest sensitivity and relative increase of sulfate reducers, as well as taxon-specific sensitivity of methanogens, in response to continuously pulsing of saltwater treatment. Collectively, these results suggest that besides increased salinity, saltwater-mediated increased sulfate availability leads to displacement of methanogens by sulfate reducers even at low or temporal salt exposure. These changes of microbial composition could affect organic matter degradation pathways in coastal freshwater wetlands exposed to sea-level rise, with potential consequences, such as loss of stored soil organic carbon.

Moderate salinity improves the availability of soil P by regulating P-cycling microbial communities in coastal wetlands.

Accelerated sea-level rise is expected to cause the salinization of freshwater wetlands, but the responses to salinity of the availability of soil phosphorus (P) and of microbial genes involved in the cycling of P remain unexplored. We conducted a field experiment to investigate the effects of salinity on P cycling by soil microbial communities and their regulatory roles on P availability in coastal freshwater and brackish wetlands. Salinity was positively correlated with P availability, with higher concentrations of labile P but lower concentrations of moderately labile P in the brackish wetland. The diversity and richness of microbial communities involved in P cycling were higher in the brackish wetland than the freshwater wetland. Salinity substantially altered the composition of the P-cycling microbial community, in which those of the brackish wetland were separated from those of the freshwater wetland. Metagenomic sequence analysis indicated that functional genes involved in the solubilization of inorganic P and the subsequent transport and regulation of P were more abundant in coastal soils. The relative abundances of most of the target genes differed between the wetlands, with higher abundances of P-solubilization (gcd and ppa) and -mineralization (phoD, phy, and ugpQ) genes and lower abundances of P-transport genes (pstB, ugpA, ugpB, ugpE, and pit) in the brackish wetland. A significant positive correlation between the concentration of labile P and the abundances of the target genes suggested that salinity may, at least in part, improve P availability by regulating the P-cycling microbial community. Our results suggest that the P-cycling microbial community abundance and P availability respond positively to moderate increases in salinity by promoting the microbial solubilization and mineralization of soil P. Changes in microbial communities and microbially mediated P cycling may represent microbial strategies to adapt to moderate salinity levels, which in turn control soil function and nutrient balance.

Improvements in water clarity and submersed aquatic vegetation cover after exclusion of invasive common carp from a large freshwater coastal wetland, Delta Marsh, Manitoba

Once introduced to shallow aquatic ecosystems common carp (Cyprinus carpio) often degrade habitat, negatively impacting the native organisms that rely on these systems. Detrimental effects often observed following the introduction of carp include a reduction in water clarity as bottom sediments become disturbed and resuspended and phytoplankton blooms become more severe and frequent. This results in a reduction of submersed aquatic vegetation (SAV), the effects of which are felt across multiple trophic levels. We sought to limit large carp (>70 mm maximum body width) access to a culturally and biologically significant 18,500 ha freshwater coastal wetland located in Manitoba, Canada to restore pre-carp conditions which were characterized by clear water and abundant SAV. In winter 2012–2013, exclusion structures were built to limit access by large carp to Delta Marsh during the spring and summer. A monitoring program (2009–2018) compared marsh conditions before and after carp exclusion. Water clarity improved following carp exclusion, largely driven by a reduction of inorganic suspended solids (ISS) rather than phytoplankton biomass, indicating that maintaining clear water conditions might be supplemented by reductions in nutrient export from agricultural areas adjacent to the marsh. The decrease in ISS and phytoplankton varied spatially, with the greatest change observed in the westernmost area of the marsh which is more sheltered compared to the large open bays characterizing eastern areas of the marsh. SAV doubled in percent cover through the 6 years of monitoring post-carp exclusion and SAV cover and species richness in the marsh was comparable to what was present in the early 1970s when there was also partial carp exclusion. Similar to water clarity, the increase in SAV cover was most significant in sheltered areas of the marsh. Our results suggest that excluding large carp can improve water clarity, SAV cover, and SAV species richness in large freshwater wetlands, benefiting waterfowl and other species.

Intensity and duration of exposure determine prokaryotic community response to salinization in freshwater wetland soils

The salinization of coastal freshwater wetlands may impact the biogeochemical cycling of critical nutrients by altering soil microbial community structure and function. Nitrate (NO3–) reduction pathways appear particularly sensitive, though the interactive effects of salinization intensity and duration of exposure remain unclear. To address this knowledge gap, we performed a transplant experiment that exposed soil from a freshwater (≤0.1 ppt) wetland to oligohaline (1 ppt) and mesohaline (14 ppt) conditions for two years. In transplanted soils, we found physicochemical changes characteristic of salinization events, including elevated porewater concentrations of ammonium and sulfate and decreased soil organic matter and redox potential. Amplicon sequencing (16S rRNA) revealed that mesohaline levels of salinization caused rapid community restructuring; distinct transition communities were evident by the first sampling event (5 months) and persisted for ∼2 years (19–22 months). In contrast, freshwater communities transplanted to oligohaline conditions were highly resistant to restructuring, and it took nearly 2 years of salinization for differences to manifest. For both transplants, community shifts included changes in the distribution and abundance of taxa capable of NO3– reduction, including several groups also known for sulfur redox metabolism. Nitrate (15NO3-) reduction assays were performed to determine how rates were affected. Dissimilatory nitrate reduction to ammonium (DNRA) increased for all sampling events, but only under mesohaline conditions, whereas denitrification responses depended more on the duration of exposure than salinity level. These findings may be useful for determining when and how the ability of wetlands to remove nitrogen will be impacted by sea-level rise. Further, these results suggest that efforts to synthesize and generalize prior research regarding salinization effects on wetland microbial community structure and function must explicitly consider both salinity intensity and exposure length.

Phosphorus sorption capacity in soils from freshwater restored coastal wetlands increased with restoration age

• P sorption capacity in soils increased with wetland restoration age. • Elevated P sorption related to the improvement of soil properties in restored wetland. • The P loss potential was less affected by the wetland restoration age. • The restored wetland was identified as the P storage hotspot at the landscape scale. Coastal wetlands, located at the intersection of land and sea, are considered to be a phosphorus (P) sink, source, and reactor in the global P cycle. However, the variation in P sorption capacity with wetland age and the related sorption mechanisms are not well understood. In this study, we collected the surface soil samples (0–20 cm) from 10 coastal freshwater wetlands that had been restored for 0–44 years surrounding China’s Bohai Rim. Through a series of batch experiments, we studied the factors controlling P sorption and release in these soils. The results showed that the maximum P sorption capacity (Q max ) in these wetlands was 294–2447 mg kg −1 , with an average of 1472 mg kg −1 . The Q max generally increased with increasing wetland restoration age. The degree of P saturation (DPS) and the P eutrophication risk index (ERI) for coastal wetlands were 0.5–9.5% and 0.9–21.1%, respectively. The DPS and ERI values did not vary significantly with wetland age. These data suggest that freshwater restoration significantly increases P sorption capacity, while not greatly affecting the P release potential in the coastal wetlands surrounding Bohai Rim. These observations may be related to the soil desalination and organic matter and amorphous Fe and/or Al accumulation that occur during the freshwater restoration of degraded wetlands. Coastal wetlands (especially restored wetlands) were suggested as P storage hotspots among upland, wetland, and offshore along the coastal watersheds of Bohai. These findings indicate that the freshwater restoration significantly improved the soil properties in the degraded coastal wetlands, and therefore increased P sorption capacity in the restored wetlands.