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.

Salt marsh width positively affects the occurrence of Least and Pectoral Sandpipers in the St. Lawrence River Estuary during fall migration

2021 ◽  
Vol 135 (2) ◽  
pp. 192-202
Author(s):  
Yves Turcotte ◽  
Jean-François Lamarre ◽  
Éliane Duchesne ◽  
Joël Bêty
Keyword(s):  
Climate Change ◽  
Salt Marsh ◽  
Salt Marshes ◽  
Generalized Estimating Equations ◽  
River Estuary ◽  
Effective Management ◽  
Vegetation Zone ◽  
Vegetation Zones ◽  
Coastal Squeeze ◽  
St Lawrence River

Salt marshes are vulnerable to climate change-associated sea-level rise and storm-induced surges. Their degradation will likely affect shorebirds relying on this ecosystem. Least Sandpiper (Calidris minutilla) and Pectoral Sandpiper (Calidris melanotos) migrating along coastline habitats typically use salt marshes to rest and replenish their body reserves. Our objective was to test if width of the different vegetation zones within salt marshes affects the occurrence of Least and Pectoral Sandpipers stopping along the St. Lawrence River Estuary, Quebec, Canada, during fall migration. We established 26 survey sites, each 600 m in length, along the shoreline. Shorebird surveys were conducted in 2011 and 2012. We characterized salt marshes by measuring the width of each vegetation zone (lower marsh and upper marsh). We analyzed shorebird presence/not detected data with generalized estimating equations to test the predictions that occurrence of Least Sandpipers and Pectoral Sandpipers increases with width of both the lower and upper marsh. Upper marsh width was positively associated with probability of occurrence in each species. Our results highlight the importance of protecting the integrity of salt marshes for these two species. In the St. Lawrence River Estuary, where landward migration of salt marshes is no longer possible (coastal squeeze), effective management of shorelines is much needed. Otherwise, salt marshes and these two species could be locally jeopardized.

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.

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.

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.

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.

Long-Term Effects of an Oil Spill on Populations of the Salt-Marsh Crab Uca pugnax

1978 ◽  
Vol 35 (5) ◽  
pp. 648-649 ◽  
Author(s):  
C. T. Krebs ◽  
K. A. Burns
Keyword(s):  
Salt Marsh ◽  
Oil Spill ◽  
Salt Marshes ◽  
Surface Sediments ◽  
Fuel Oil ◽  
Long Term Effects ◽  
Uca Pugnax ◽  
Crab Population ◽  
Body Tissues

A spill of fuel oil at West Falmouth, Massachusetts, in 1969 contaminated contiguous salt marshes with up to 6000 μg oil/g (ppm) of wet mud and affected local populations of the salt-marsh crab Uca pugnax. Directly related to high sediment oil content were reduced crab density, reduced ratio of females to males, reduced juvenile settlement, heavy overwinter mortality, incorporation of oil into body tissues, behavioral disorders such as locomotor impairment, and abnormal burrow construction. Concentrations of weathered fuel oil > 1000 ppm were directly toxic to adults, while those of 100–200 ppm were toxic to juveniles. Cumulative effects occurred at lower concentrations. Recovery of the marsh from this relatively small oil spill is still incomplete after 7 yr. Interpretation of the crab population data upon the basis of detailed analysis of the aromatic fraction of the fuel oil provided by Dr J. Teal, Woods Hole Oceanographic Institution, showed that recovery of the crab populations was highly correlated with the disappearance of the naphthalene fraction of the aromatics. There had been a decrease in the aromatics from 42% in 1970 to approximately 18% in 1976 in Station I surface sediments, while preliminary analyses show aromatics still high at other stations where little recovery has been observed. By 1970–71 all parent naphthalene compounds were gone in Station I surface sediments, but substituted naphthalenes were still in high concentrations. By 1972–73 dimethyl naphthalenes and C3 and C4 substituted naphthalenes remained at about 25% of original values. By 1976–77 only C3 and C4 substituted naphthalenes remained at less than one tenth of their 1973 levels. In 1972–73 the substituted naphthalenes were at high enough concentrations to prevent recruitment, as large juvenile crab settlements in 1970–73 produced no recruitment into the crab populations. By 1976–77 these toxic compounds were at low enough levels that recovery of the crab population was occurring with recruitment, and increasing density was observed in both years. High aromatic concentrations at other stations may still be inhibiting recovery at these stations. The long-term inhibition of recruitment and low population densities may have resulted from exposure to oil in the interstitial waters during the sensitive molt period and/or during the long periods of time while the crabs were overwintering in the substrate. Key words: petroleum, Uca pugnax, crab, salt-marsh, population, pollution

scholarly journals Anthropogenic effects and salt marsh loss in the Mondego and Mira estuaries (Portugal)

Web Ecology ◽  
2006 ◽  
Vol 6 (1) ◽  
pp. 59-66 ◽  
Author(s):  
P. Castro ◽  
H. Freitas
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Anthropogenic Activities ◽  
Aerial Photographs ◽  
Anthropogenic Pressure ◽  
Marsh Area ◽  
Mondego Estuary ◽  
Natural Dynamics ◽  
Salt Marsh Area

Abstract. Recent decades have witnessed marked losses of coastal wetlands worldwide, but consistent data on salt marsh area are not available. The main goal of this study was to provide information on two Portuguese estuarine habitats (Mondego and Mira) over a period of four to six decades, and to assess how anthropogenic activities have altered the salt marsh ecosystem. Chronological sequences of aerial photographs covering a period of 54 yr (1947–1998) and 38 yr (1958–1995) for the Mondego and Mira estuaries, respectively, were considered for this study. Long-term changes in the Mondego estuary revealed a clear decline in the salt marsh area during the past six decades due to urban and industrial expansion. In contrast, the Mira estuary salt marshes remained almost unchanged since 1958. This ecosystem is relatively undisturbed by anthropogenic activities, and marsh variation seems to follow natural dynamics rather than being vulnerable to anthropogenic pressure. The sustainable management of salt marshes must be a priority concern to ensure the long-term viability of their ecological, economic and social capital.

scholarly journals Site Characteristics More Than Vegetation Type Influence Food Web Structure of Intertidal Salt Marshes

2021 ◽  
Vol 8 ◽  
Author(s):  
Denis Lafage ◽  
Alexandre Carpentier ◽  
Sylvain Duhamel ◽  
Christine Dupuy ◽  
Eric Feunteun ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Trophic Position ◽  
Vegetation Type ◽  
Sea Bass ◽  
Site Effect ◽  
Salt Marsh Vegetation ◽  
Seine Estuary ◽  
Marsh Vegetation

Salt marshes are under increasing anthropogenic pressures that have been reported to affect the diet of fish (e.g., change in prey composition and availability), eventually resulting in alterations in their nursery function. Most studies in Europe are based on fish gut content analysis, which only reflect a small proportion of pressures to salt marshes, and do not necessarily reflect long-term disturbances. In this study, we investigated the impact of salt-marsh vegetation type on trophic network structures (i.e., fish diet and trophic position). Primary producers (particulate organic matter, microphytobenthos, and dominant terrestrial plants), potential aquatic and terrestrial prey, and fish of two dominant species (sea bass and thinlip mullet) were sampled during the summer of 2010 in four creeks from two sites from Western France (the Mont-Saint-Michel Bay and the Seine Estuary). Analysis was undertaken using C and N stable-isotope compositions. Tested response variables (diet and trophic position) suggested a dominant site effect and a weaker effect of surrounding vegetation type. Site effect was attributed to differences in anthropogenic nitrogen inputs (with a steep increase in the Mont-Saint-Michel Bay) and tidal regime between the two bays, with more marine signatures associated with a higher frequency and duration of tidal flooding events in the Seine Estuary. A second hypothesis is that invasive Elytrigia acuta, which has recently replaced typical salt-marsh vegetation in Mont-Saint-Michel Bay, negatively impacted the native salt-marshes nursery function by modifying the access to terrestrial prey on this site. The trophic position of the sea bass and the thinlip mullet was unchanged by local salt-marsh vegetation, and considered consistent with their diet. This study 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.

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