scholarly journals Long-term CH<sub>3</sub>Br and CH<sub>3</sub>Cl flux measurements in temperate salt marshes

2010 ◽  
Vol 7 (4) ◽  
pp. 6295-6322 ◽  
Author(s):  
E. Blei ◽  
M. R. Heal ◽  
K. V. Heal
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Scale Up ◽  
Global Scale ◽  
Tropical Rainforests ◽  
Salt Marsh Plant ◽  
Flux Measurements ◽  
Methyl Halide ◽  
Net Fluxes

Abstract. Fluxes of CH3Br and CH3Cl and their relationship with potential drivers such as sunlight, temperature and soil moisture, were monitored at fortnightly to monthly intervals for more than two years at two contrasting temperate salt marsh sites in Scotland. Manipulation experiments were conducted to further investigate possible links between drivers and fluxes. Mean (± 1 sd) annually and diurnally-weighted net emissions from the two sites were found to be 300 ± 44 ng m−2 h−1 for CH3Br and 662 ± 266 ng m−2 h−1 for CH3Cl. A tentative scale-up indicates that salt marshes account for 0.5–3.2% and 0.05–0.33%, respectively, of currently-estimated total global production of these two gases, in line with previous findings from this and other research groups, but consistently lower than past global scale-up estimates from Southern Californian salt marshes. Fluxes followed both seasonal and diurnal trends with highest fluxes during summer days and lowest (negative) fluxes during winter nights. Statistical analysis generally did not demonstrate a strong link between temperature or sunlight levels and methyl halide fluxes, although it is likely that temperatures have a weak direct influence on emissions, and both certainly have indirect influence via the annual and daily cycles of the vegetation. CH3Cl flux magnitudes from different measurement locations depended on the plant species enclosed whereas such dependency was not discernible for CH3Br fluxes. In 14 out of 19 collars CH3Br and CH3Cl net fluxes were significantly correlated. The CH3Cl/CH3Br net-emission mass ratio was 2.2, a magnitude lower than mass ratios of global methyl halide budgets (~22) or emissions from tropical rainforests (~60). This is likely due to preference for CH3Br production by the relatively high bromine content in the salt marsh plant material.

scholarly journals Long-term CH<sub>3</sub>Br and CH<sub>3</sub>Cl flux measurements in temperate salt marshes

2010 ◽  
Vol 7 (11) ◽  
pp. 3657-3668 ◽  
Author(s):  
E. Blei ◽  
M. R. Heal ◽  
K. V. Heal
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Southern California ◽  
Tropical Rainforests ◽  
Salt Marsh Plant ◽  
Daily Cycles ◽  
Flux Measurements ◽  
Methyl Halide ◽  
Net Fluxes

Abstract. Fluxes of CH3Br and CH3Cl and their relationship with potential drivers such as sunlight, temperature and soil moisture, were monitored at fortnightly to monthly intervals for more than two years at two contrasting temperate salt marsh sites in Scotland. Manipulation experiments were conducted to further investigate possible links between drivers and fluxes. Fluxes followed both seasonal and diurnal trends with highest fluxes during summer days and lowest (negative) fluxes during winter nights. Mean (± 1 sd) annually and diurnally-weighted net emissions from the two sites were found to be 300 ± 44 ng m−2 h−1 for CH3Br and 662 ± 266 ng m−2 h−1 for CH3Cl. The fluxes from this work are similar to findings from this and other research groups for salt marshes in cooler, higher latitude climates, but lower than values from salt marshes in the Mediterranean climate of southern California. Statistical analysis generally did not demonstrate a strong link between temperature or sunlight levels and methyl halide fluxes, although it is likely that temperatures have a weak direct influence on emissions, and both certainly have indirect influence via the annual and daily cycles of the vegetation. CH3Cl flux magnitudes from different measurement locations depended on the plant species enclosed whereas such dependency was not discernible for CH3Br fluxes. In 14 out of 18 collars with vegetation CH3Br and CH3Cl net fluxes were significantly positively correlated. The CH3Cl/CH3Br net-emission mass ratio was 2.2, a magnitude lower than mass ratios of global methyl halide budgets (~22) or emissions from tropical rainforests (~60). This is likely due to preference for CH3Br production by the relatively high bromine content in the salt marsh plant material. Extrapolation based solely on data from this study yields salt marsh contributions of 0.5–3.2% and 0.05–0.33%, respectively, of currently-estimated total global production of CH3Br and CH3Cl, but actual global contributions likely lie between these values and those derived from southern California.

Effect of nitrate supply on the facilitation between two salt-marsh plants (Suaeda salsa and Scirpus planiculmis)

2020 ◽  
Vol 13 (2) ◽  
pp. 204-212
Author(s):  
Hua Ma ◽  
Li-Juan Cui ◽  
Xu Pan ◽  
Wei Li ◽  
Yu Ning ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Plant Species ◽  
Salt Marshes ◽  
Interspecific Interactions ◽  
Stress Gradient ◽  
Interactive Effects ◽  
Suaeda Salsa ◽  
Environmental Drivers ◽  
Salt Marsh Plant ◽  
Nitrate Supply

Abstract Aims In estuarine salt-marshes, nitrate supply and soil salinity, which are known as two main environmental drivers, simultaneously affect the interspecific interactions between plant species. However, to date, their interactive effects on interspecific interactions have not been closely examined for salt-marsh plant species. Methods Juvenile plants of Suaeda salsa L. (Chenopodiaceae) and Scirpus planiculmis Fr. (Cyperaceae) were grown in rinsed river sand to conduct a greenhouse experiment with three treatment categories: interspecific interaction (mixed culture or monoculture), three salinity levels (1, 50 and 100 mmol L−1) and three nitrate levels (0.5, 5 and 10 mmol L−1). First, height and biomass of all plants were measured. Then, the growth data, relative interaction index and competitive important index of the two species were analyzed. Important Findings The interspecific interactions between S. salsa and S. planiculmis were facilitation across the salinity gradients. The promotion of S. salsa growth with high nitrate supply did not enhance the facilitative effect of the species, especially at low salinity. However, high nitrate supply significantly shifted the interspecific interactions of S. planiculmis from facilitation to competition at high salinity. Our results suggest that excessive nitrate application changes the prediction of the stress-gradient hypothesis along a salinity gradient, leading to collapse of the two species coexistence in the salt-marshes. These findings make a contribution to the understanding of how S. salsa and S. planiculmis, as well as salt-marsh communities, respond to the human modification of estuarine nutritional levels.

scholarly journals Changes in salt-marsh vegetation weakly affect top consumers of aquatic food webs

2020 ◽  
Author(s):  
Lafage Denis ◽  
Carpentier Alexandre ◽  
Sylvain Duhamel ◽  
Christine Dupuy ◽  
Eric Feunteun ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Salt Marsh ◽  
Salt Marshes ◽  
Vegetation Type ◽  
Site Effect ◽  
Salt Marsh Vegetation ◽  
Gut Content ◽  
Marsh Vegetation ◽  
Nitrogen Inputs

AbstractSalt marshes are under high, and increasing, anthropogenic pressures that have notably been reported to affect the diet of several fish species, probably resulting in nursery function alterations. Most of the previous studies in Europe were yet based on gut content analysis of fish, which can be considered a snapshot of immediate impacts of salt-marsh changes, and hardly of long-term effects of disturbances. In this study, we investigated the impact of vegetation type (resulting from both plant invasion and sheep grazing) by assessing trophic network (and especially fish diet and position) of different salt-marsh conditions. Replicated samples of basic sources (particular organic matter and microphytobenthos), dominant vegetation, potential aquatic and terrestrial prey and fish of 3 main species were taken during summer 2010 in two bays from Western France (Mont -Saint-Michel Bay and Seine Estuary) and analysed using C and N stable isotope compositions. All response variables tested (overall trophic organization, trophic niche and trophic position) provided consistent results, i.e. a dominant site effect and a weaker effect of vegetation type. Site effect was attributed to differences in anthropogenic Nitrogen inputs and tidal regime between the two bays, with more marine signatures associated with a higher frequency of flooding events. A second hypothesis is that E. acuta, which has recently totally replaced typical salt-marsh vegetation in Mont Saint-Michel Bay strongly impacted the nursery function. The trophic status of dominant fish species was unchanged by local salt-marsh vegetation, and considered consistent with their diet, i.e. high for predatory species (the sea bass Dicentrarchus labrax and the common goby Pomatoschistus microps) and lower for biofilm grazing species (the thinlip mullet Chelon ramada). This study finally highlights the relevance of stable isotopes analyses for assessing long-term and integrative effects of changes in vegetation resulting from human disturbances in salt marshes.HighlightsCross-ecosystem subsidies are of high functional importance, notably in salt marshesFish are vectors of exchanges, most European studies being based on their gut contentUsing stable isotopes we analysed the effect of surrounding vegetation on food websSurprisingly we found weak vegetation and strong site effects on all metricsNitrogen inputs, site accessibility and loss of nursery function can explain this factAbstract Figure

scholarly journals Minimal net loss of vegetation via interior pond dynamics in an extensive unditched salt marsh

2020 ◽  
Author(s):  
Joseph Smith ◽  
Michael Pellew
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Dynamic Equilibrium ◽  
Long Term Stability ◽  
Cyclical Process ◽  
Marsh Pools ◽  
Nuanced Understanding ◽  
Condition Assessments ◽  
Pool Formation

AbstractPonds in salt marshes are often interpreted as a symptom of degradation, yet ponds can also be part of a cyclical process of pool formation, expansion, tidal breaching and vegetation recovery. Pond dynamics may be altered by accelerated sea level rise, with consequences for the long-term stability of ecosystems. We test the prediction that ponds are in dynamic equilibrium across one the largest expanses of unditched salt marsh in the Northeast USA by (1) examining change in pond and marsh area between 1970 and present and (2) by tracking individual pool dynamics across an 87-year time series. We found that net pond area has remained unchanged since 1970 because the amount of marsh conversion to ponds is equivalent to the amount pond recovery to marsh. The ratio of tidally-connected ponds is increasing relative to non-tidal ponds which suggests that some rates of change may be decoupling, which may be related to a decline in the rate of pond formation. A nuanced understanding of marsh pools needs to be incorporated into marsh condition assessments and establishment of restoration priorities so that ponds are not interpreted as evidence of degradation when they are exhibiting a recovery cycle. Unditched marshes around the world are a rare resource that remains essential for advancing scientific understanding and serving as reference sites for restoration of marshes altered by past management.

scholarly journals Long-term invasion dynamics of Spartina increase vegetation diversity and geomorphological resistance of salt marshes against sea level rise

2020 ◽  
Author(s):  
Dirk Granse ◽  
Sigrid Suchrow ◽  
Kai Jensen
Keyword(s):  
Salt Marsh ◽  
Species Diversity ◽  
Sea Level Rise ◽  
Sea Level ◽  
Salt Marshes ◽  
High Marsh ◽  
Marsh Vegetation ◽  
Vegetation Diversity ◽  
The Impact

AbstractThe cordgrass Spartina anglica C.E. Hubbard (Poaceae) is an invasive transformer in many salt marsh ecosystems worldwide. Relatively little is known about the capacity of Spartina to accelerate salt marsh succession and to protect salt marshes against sea level rise. We analyzed long-term changes in vegetation and elevation in mainland salt marshes of the European Wadden Sea in Schleswig-Holstein, Germany, to estimate the impact of non-native Spartina on the geomorphological resistance of salt marshes to sea level rise and on changes in species diversity. From 1989 to 2019, the Spartina-zone shifted and expanded upwards to elevations of the high marsh zone and Spartina increased in frequency in several salt marsh vegetation communities. At sites where Spartina dominated the vegetation already three decades ago, elevation and species diversity increased with a higher rate compared to sites lacking Spartina. The median change rates reached for elevation MHT +8.6 versus +1.5 mm per year, for species richness +3 versus $$\pm$$ ± 0 species per three decades, and for evenness +0.04 versus −0.08 per three decades, regarding plots with versus without former Spartina dominance, respectively. Invasion of salt marshes by Spartina and its continued, long-term presence were associated with increased elevation and species diversity in the face of sea level rise.

Establishing the value of a salt marsh as a potential benchmark: vegetation surveys and paleoecological analyses as assessment tools

Botany ◽  
2013 ◽  
Vol 91 (11) ◽  
pp. 774-785 ◽  
Author(s):  
Myosotis Bourgon Desroches ◽  
Martin Lavoie ◽  
Claude Lavoie
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
River Estuary ◽  
Assessment Tools ◽  
Vegetation Surveys ◽  
Plant Assemblages ◽  
A Site ◽  
Very High ◽  
St Lawrence River

Identifying tidal salt marshes as priority sites for conservation or restoration remains a challenge, as several sites are so severely degraded that allocating financial resources for their protection would be questionable. The decision-making process could nevertheless be facilitated by comparing species assemblages and the dynamics and (or) ecological functions of a site with an ecological benchmark, i.e., a tidal marsh that remains free from anthropogenic disturbances. We used plant surveys and plant macrofossil and pollen analyses for evaluating the benchmark potential of the Pointe-aux-Épinettes marsh, a protected salt marsh of the St. Lawrence River estuary (Canada) and one of the last salt marshes that could potentially be a benchmark along the estuary. Historical evidence indicated that the forests surrounding the marsh were converted into agricultural lands circa 1850. Nevertheless, this land-use change had little impact on the marsh. The long-term impacts of trampling and grazing by livestock on the vegetation were negligible. Macrofossil analyses indicated that the plant assemblages were dynamic, but past and current vegetation assemblages are representative of those characterizing an undisturbed salt marsh, with a very high proportion of native wetland species. In a context where truly undisturbed salt marshes are extremely rare ecosystems, our study indicates that the Pointe-aux-Épinettes plant assemblages could be used as benchmarks against which the condition of the vegetation of other salt marshes in northeastern North America could be evaluated.

scholarly journals Buying Time with Runnels: a Climate Adaptation Tool for Salt Marshes

2022 ◽  
Author(s):  
Alice F. Besterman ◽  
Rachel W. Jakuba ◽  
Wenley Ferguson ◽  
Diana Brennan ◽  
Joseph E. Costa ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Sea Level Rise ◽  
Sea Level ◽  
Salt Marshes ◽  
Climate Adaptation ◽  
Open Water ◽  
Tidal Range ◽  
Management Interventions

AbstractA prominent form of salt marsh loss is interior conversion to open water, driven by sea level rise in interaction with human activity and other stressors. Persistent inundation drowns vegetation and contributes to open water conversion in salt marsh interiors. Runnels are shallow channels originally developed in Australia to control mosquitoes by draining standing water, but recently used to restore marsh vegetation in the USA. Documentation on runnel efficacy is not widely available; yet over the past 10 years dozens of coastal adaptation projects in the northeastern USA have incorporated runnels. To better understand the efficacy of runnels used for restoration, we organized a workshop of 70 experts and stakeholders in coastal resource management. Through the workshop we developed a collective understanding of how runnels might be used to slow or reverse open water conversion, and identified unresolved questions. In this paper we present a synthesis of workshop discussions and results from a promising case study in which vegetation was restored at a degraded marsh within a few years of runnel construction. Despite case study outcomes, key questions remain on long-term runnel efficacy in marshes differing in elevation, tidal range, and management history. Runnel construction is unlikely to improve long-term marsh resilience alone, as it cannot address underlying causes of open water conversion. As a part of holistic climate planning that includes other management interventions, runnels may “buy time” for salt marshes to respond to management action, or adapt to sea level rise.

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