Mangroves are one of the most carbon‐dense forests on the Earth and have been highlighted as key ecosystems for climate change mitigation and adaptation. Hundreds of studies have investigated how ...mangroves fix, transform, store, and export carbon. Here, we review and synthesize the previously known and emerging carbon pathways in mangroves, including gains (woody biomass accumulation, deadwood accumulation, soil carbon sequestration, root and litterfall production), transformations (food web transfer through herbivory, decomposition), and losses (respiration as CO2 and CH4, litterfall export, particulate and dissolved carbon export). We then review the technologies available to measure carbon fluxes in mangroves, their potential, and their limitations. We also synthesize and compare mangrove net ecosystem productivity (NEP) with terrestrial forests. Finally, we update global estimates of carbon fluxes with the most current values of fluxes and global mangrove area. We found that the contributions of recently investigated fluxes, such as soil respiration as CH4, are minor (<1 Tg C year−1), while the contributions of deadwood accumulation, herbivory, and lateral export are significant (>35 Tg C year−1). Dissolved inorganic carbon exports are an order of magnitude higher than the other processes investigated and were highly variable, highlighting the need for further studies. Gross primary productivity (GPP) and ecosystem respiration (ER) per area of mangroves were within the same order of magnitude as terrestrial forests. However, ER/GPP was lower in mangroves, explaining their higher carbon sequestration. We estimate the global mean mangrove NEP of 109.1 Tg C year−1 (7.4 Mg C ha−1 year−1) or through a budget balance, accounting for lateral losses, a global mean of 66.6 Tg C year−1 (4.5 Mg C ha−1 year−1). Overall, mangroves are highly productive, and despite losses due to respiration and tidal exchange, they are significant carbon sinks.
Worldwide, human activities have modified hydrology and nutrient loading regimes in coastal wetlands. Understanding the interplay between these drivers and subsequent response of wetland plant ...communities is essential to informing wetland management and restoration efforts. Recent restoration strategies in Louisiana proposes to use sediment diversions from the Mississippi River to build land in adjacent wetlands and reduce the rate of land to open water conversion. In conjunction with sediment delivery, diversions can increase nutrient loads and water levels in the receiving basins. We conducted a greenhouse mesocosm experiment in which we exposed three common tidal freshwater and brackish marsh plants (
Panicum hemitomon, Sagittaria lancifolia,
and
Spartina patens
) to two nitrate loading rates high (35 g N m
2
year
−1
) and low (0.25 g N m
2
year
−1
), and two flooding treatments (with and without diversion pulsing). Experimental units were set at two different elevations within the treatment tanks to simulate both a healthy and degraded marsh. Plant growth metrics and soil physicochemical properties were measured monthly. Final total biomass was determined at the study’s conclusion. Growth responses differed between species but were not significantly influenced by the treatments. Soil redox potential decreased significantly following the increase in flooding associated with the diversion pulse, but recovered to pre-diversion levels after a 3-month recovery period. Our study suggests short flooding pulses with a recovery period may be key for maintaining healthy marshes, however there remains a need for longer-term empirical studies to understand marsh response to pressures associated with river sediment diversions over time.
Plant functional trait frameworks have been increasingly used to understand plant community dynamics, linkages between plants and ecosystem function, and have recently been applied to inform species ...selection for restoration of many ecosystem types. Yet, despite rapid development in this field over the past decade, the use of plant functional trait frameworks in the context of wetland restoration remains limited. Ambitious wetland restoration goals, and previous difficulties to meet them, underscore the need for continued refinement of science-backed restoration approaches for present and future conditions. Plant functional traits are one approach that deserves additional attention and scientific inquiry to inform restoration in wetlands. We conducted a systematic review of the peer-reviewed literature (published 2000 to 2020) addressing plant functional traits in wetland restoration. Here, we summarize that body of literature and identify factors limiting the inclusion of plant functional trait frameworks in wetland restoration. We emphasize the need for consensus on terminology and trait selection in this field, provide definitive guidelines for moving this field forward for both researchers and practitioners, identify key plant functional traits to inform specific restoration goals, and highlight case studies exemplary of this approach in wetland restoration. A plant functional trait framework has the potential to inform and improve restoration of the world’s wetlands by making important linkages between traits, desired ecosystem functions, and restoration trajectories. However, the use of this approach requires further development and that both research and practice reach a consensus on which traits are most critical to measure.
As annual minimum temperatures increase due to climate change, species once constrained by minimum temperatures are expanding poleward.
Avicennia germinans
(black mangrove), a freeze-intolerant tree, ...has been expanding northward into salt marsh-grass-dominated communities. Distribution and colonization dynamics of
A. germinans
are crucial for understanding changes in coastal habitats and ecosystem structure and function along the Gulf of Mexico Coast (USA). We transplanted
A. germinans
seedlings and propagules into salt marsh plots of
S. alterniflora
, half of which had the canopy removed, along a latitudinal gradient that spanned locations within and outside of
A. germinans
’ current range limits (29°7′20″N to 30°23′41″N). Plot microclimate and transplant survival and growth were monitored for 2 years. Canopy removal resulted in lower minimum temperatures and longer cumulative freeze duration. Seedling survival was greatest at the southernmost site; however, seedling growth was reduced in plots with the canopy intact, as hypothesized. Seedling survival at northern sites was limited to plots with the
S. alterniflora
canopy intact. Propagules survived and established at all sites in the second year, although there was no
S. alterniflora
canopy effect on propagule survival and establishment. Our results illustrate the complexity of ecological interactions between herbaceous marsh species and mangroves at the species’ range limit.
There is interest in the direct in situ measurement of protein aggregation and reversible protein–protein interactions at high pressure as a means to assess protein stability. This is currently ...limited by the availability of in-house analytical methods. High-pressure (HP) scattering instrumentation (using either neutrons, X-rays, or light sources) are relatively rare, due to extensive development hurdles and lack of standardization. This report focuses on design, operation, and application of a new HP light scattering apparatus based on commercially available equipment with a view to wider applications. HP static light scattering results were obtained for two monoclonal antibodies (MAbs) that exhibit different extents of unfolding and aggregation at these conditions. Aggregation that was observed during in situ pressure incubations varied by MAb and total ionic strength of solution. This was conducted in tandem with ex situ measurements on MAb solutions that were incubated under pressure, where monomer loss was measured with size exclusion chromatography. Pressure cycling was also used to assess the extent of pressure-induced reversible and irreversible aggregation. Finally, the ability of the HP light scattering apparatus to assess the influence of pressure on reversible protein–protein interactions in the canonical sense of second osmotic virial coefficients was assessed using lysozyme, a relatively well-characterized protein under hydrostatic pressure. The method offers a convenient and reproducible capability that complements current small angle neutron/X-ray instrumentation, providing measurements that can be used to optimize the planning and interpretation of scattering data from synchrotron or neutron research facilities. Our results address a growing demand to characterize protein aggregates and aggregation-prone partially unfolded intermediates.
The effects of high pressure and low temperature on the stability of two different monoclonal antibodies (MAbs) were examined in this work. Fluorescence and small-angle neutron scattering were used ...to monitor the in situ effects of pressure to infer shifts in tertiary structure and characterize aggregation prone intermediates. Partial unfolding was observed for both MAbs, to different extents, under a range of pressure/temperature conditions. Fourier transform infrared spectroscopy was also used to monitor ex situ changes in secondary structure. Preservation of native secondary structure after incubation at elevated pressures and subzero ° C temperatures was independent of the extent of tertiary unfolding and reversibility. Several combinations of pressure and temperature were also used to discern the respective contributions of the isolated Ab fragments (Fab and Fc) to unfolding and aggregation. The fragments for each antibody showed significantly different partial unfolding profiles and reversibility. There was not a simple correlation between stability of the full MAb and either the Fc or Fab fragment stabilities across all cases, demonstrating a complex relationship to full MAb unfolding and aggregation behavior. That notwithstanding, the combined use of spectroscopic and scattering techniques provides insights into MAb conformational stability and hysteresis in high-pressure, low-temperature environments.
We all get stressed. To deal with that stress, some of us may exercise, take a bubble bath, cry, or simply leave the stressful situation. But how can you cope with stress if you are rooted in place? ...Plants that live in estuaries are exposed to many types of stresses from the environment, including flooding, high salt levels, low soil oxygen, and waves. Fortunately, wetland plants have developed ways to survive within these conditions, from excreting salt, to growing faster, to even breaking down cell walls to maximize air flow. Plants can tolerate different levels of stress depending on their age and species. Knowing how plants react to stress is important for our understanding of nature and for managing important environments, like wetlands! This article explores how plant species in the San Francisco Estuary react to stress and how we can use knowledge about plant stress responses to protect wetlands.
Liberty Island, California, is a historical freshwater tidal wetland that was converted to agricultural fields in the early 1900s. Liberty Island functioned as farmland until an accidental levee ...break flooded the area in 1997, inadvertently restoring tidal marsh hydrology. Since then, wetland vegetation has naturally recolonized part of the site. We conducted a seed bank assay at the site and found that despite a lack of germination or seedling recruitment at the site, the seed bank contained a diverse plant community, indicating that the site's continuous flooding was likely suppressing germination. Additionally, the frequency of germinating seeds in the seed bank did not represent the dominant adult plant community. We conducted a cold stratification study to determine if this observed disparity could be explained by seed germination dynamics, and whether germination could be enhanced using a pre-germination cold exposure, particularly for species of concern for wetland restoration. The cold stratification study showed that longer durations of pre-germination cold enhanced germination in Schoenoplectus acutus, but reduced germination in Schoenoplectus californicus, and had no effect on Typha latifolia. Overall, germination of S. californicus and S. acutus was much lower than T. latifolia. Our findings suggest that seeding may not be an effective restoration technique for Schoenoplectus spp., and, to improve restoration techniques, further study is needed to more comprehensively understand the reproduction ecology of important marsh species.
Establishment and survival of plant species in systems with dominant environmental drivers (i.e. factors that exert disproportionate control over species establishment and survival) is often thought ...to be dominated by one master variable. In forested wetlands such as mangroves, hydrology is typically considered the dominant limiting driver. At the same time, light is a major driver of plant community dynamics, with some of the best understood plant life‐history tradeoffs related to fast growth under high‐light conditions versus survival under low‐light conditions. Yet light is given relatively limited consideration in mangrove research compared to other drivers. Understanding the relative importance of abiotic drivers for seedling survival is crucial for effective management and restoration of mangrove ecosystems. Despite increasing global efforts to plant mangrove propagules at elevations appropriate for the hydrologic conditions needed at early life history stages, restoration efforts report low survival of planted propagules. Although many studies have made considerable progress to characterize the abiotic limitations of mangrove propagule establishment, fewer studies have addressed multiple abiotic drivers that limit the survival of the established seedling stage. We characterized the light and inundation conditions of more than 900 naturally established mangrove seedlings and monitored the survival of more than 2,800 seedlings (including 16 species) located on a species‐rich island in tropical Southeast Asia for 1 year. Our findings suggest that light has a stronger effect than hydrology on survival following seedling establishment. We provide a conceptual visualization of shifts in the drivers of mangrove survival/loss throughout ontogeny.
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