Multiple stressors and the potential for synergistic loss of New England salt marshes

Crotty, Sinéad M.; Angelini, Christine; Bertness, Mark D.

doi:10.1371/journal.pone.0183058

Cited by 32 publications

(19 citation statements)

References 50 publications

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“…Sea-level rise has already been linked to an intra-marsh Uca range expansion ( Luk & Zajac, 2013 ), and it can directly cause creekbank vegetation loss in the absence of crab impacts ( Schultz, Anisfeld & Hill, 2016 ). These multiple lines of evidence agree with recent findings across southern New England ( Schultz, Anisfeld & Hill, 2016 ; Crotty, Angelini & Bertness, 2017 ) and identify sea-level rise as a potential driver of creekbank vegetation loss in RI, either directly through inundation stress or indirectly via enhanced crab abundance and impacts.…”

Section: Discussionsupporting

confidence: 88%

Top-down and bottom-up controls on southern New England salt marsh crab populations

Raposa

McKinney

Wigand

et al. 2018

PeerJ

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Southern New England salt marsh vegetation and habitats are changing rapidly in response to sea-level rise. At the same time, fiddler crab (Uca spp.) distributions have expanded and purple marsh crab (Sesarma reticulatum) grazing on creekbank vegetation has increased. Sea-level rise and reduced predation pressure drive these changing crab populations but most studies focus on one species; there is a need for community-level assessments of impacts from multiple crab species. There is also a need to identify additional factors that can affect crab populations. We sampled crabs and environmental parameters in four Rhode Island salt marshes in 2014 and compiled existing data to quantify trends in crab abundance and multiple factors that potentially affect crabs. Crab communities were dominated by fiddler and green crabs (Carcinus maenas); S. reticulatum was much less abundant. Burrow sizes suggest that Uca is responsible for most burrows. On the marsh platform, burrows and Carcinus abundance were negatively correlated with elevation, soil moisture, and soil percent organic matter and positively correlated with soil bulk density. Uca abundance was negatively correlated with Spartina patens cover and height and positively correlated with Spartina alterniflora cover and soil shear strength. Creekbank burrow density increased dramatically between 1998 and 2016. During the same time, fishing effort and the abundance of birds that prey on crabs decreased, and water levels increased. Unlike in other southern New England marshes where recreational overfishing is hypothesized to drive increasing marsh crab abundance, we propose that changes in crab abundance were likely unrelated to recreational finfish over-harvest; instead, they better track sea-level rise and changing abundances of alternate predators, such as birds. We predict that marsh crab abundance will continue to expand with ongoing sea-level rise, at least until inundation thresholds for crab survival are exceeded.

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Section: Discussionsupporting

confidence: 88%

Top-down and bottom-up controls on southern New England salt marsh crab populations

Raposa

McKinney

Wigand

et al. 2018

PeerJ

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“…Luk and Zajac (2013) suggested that landward expansion of low marsh vegetation species may facilitate increased distribution of fiddler crabs. Likewise, Crotty et al (2017) indicated the potential interaction between future SLR and Sesarma reticulatum impacts on marshes, as did Raposa et al (2018b) based on increases in crab burrows during recent periods of higher water levels. Likewise, Crotty et al (2017) indicated the potential interaction between future SLR and Sesarma reticulatum impacts on marshes, as did Raposa et al (2018b) based on increases in crab burrows during recent periods of higher water levels.…”

Section: Crabs and Sea-level Risementioning

confidence: 97%

“…Szura et al (2017) found stronger effects of Sesarma reticulatum with increased inundation. Likewise, Crotty et al (2017) indicated the potential interaction between future SLR and Sesarma reticulatum impacts on marshes, as did Raposa et al (2018b) based on increases in crab burrows during recent periods of higher water levels. Vu and Pennings (2017) noted that crab burrowing that increases creek size may actually have a positive effect on marsh integrity in the face of SLR, by increasing drainage.…”

Section: Crabs and Sea-level Risementioning

confidence: 97%

Pattern and scale: evaluating generalities in crab distributions and marsh dynamics from small plots to a national scale

Wasson

Raposa

Almeida

et al. 2019

Ecology

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The generality of ecological patterns depends inextricably on the scale at which they are examined. We investigated patterns of crab distribution and the relationship between crabs and vegetation in salt marshes at multiple scales. By using consistent monitoring protocols across 15 U.S. National Estuarine Research Reserves, we were able to synthesize patterns from the scale of quadrats to the entire marsh landscape to regional and national scales. Some generalities emerged across marshes from our overall models, and these are useful for informing broad coastal management policy. We found that crab burrow distribution within a marsh could be predicted by marsh elevation, distance to creek and soil compressibility. While these physical factors also affected marsh vegetation cover, we did not find a strong or consistent overall effect of crabs at a broad scale in our multivariate model, though regressions conducted separately for each site revealed that crab burrows were negatively correlated with vegetation cover at 4 out of 15 sites. This contrasts with recent smaller-scale studies and meta-analyses synthesizing such studies that detected strong negative effects of crabs on marshes, likely because we sampled across the entire marsh landscape, while targeted studies are typically limited to low-lying areas near creeks, where crab burrow densities are highest. Our results suggest that sea-level rise generally poses a bigger threat to marshes than crabs, but there will likely be interactions between these physical and biological factors. Beyond these generalities across marshes, we detected some regional differences in crab community composition, richness, and abundance. However, we found striking differences among sites within regions, and within sites, in terms of crab abundance and relationships to marsh integrity. Although generalities are broadly useful, our findings indicate that local managers cannot rely on data from other nearby systems, but rather need local information for developing salt marsh management strategies.

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“…There is debate about how salt marshes will change in the Anthropocene; site-level research offers conflicting insight into the relationship of SLR to salt marsh loss such as multiple stressors leading to rapid loss [68] or only extreme SLR scenarios (30 cm) resulting in drowning [69]. Modeling studies suggest migration could lead to relative salt marsh stability [16].…”

Section: Salt Marsh Changementioning

confidence: 99%

Salt marsh monitoring along the mid-Atlantic coast by Google Earth Engine enabled time series

Campbell

Wang

2020

PLoS ONE

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Salt marshes provide a bulwark against sea-level rise (SLR), an interface between aquatic and terrestrial habitats, important nursery grounds for many species, a buffer against extreme storm impacts, and vast blue carbon repositories. However, salt marshes are at risk of loss from a variety of stressors such as SLR, nutrient enrichment, sediment deficits, herbivory, and anthropogenic disturbances. Determining the dynamics of salt marsh change with remote sensing requires high temporal resolution due to the spectral variability caused by disturbance, tides, and seasonality. Time series analysis of salt marshes can broaden our understanding of these changing environments. This study analyzed aboveground green biomass (AGB) in seven mid-Atlantic Hydrological Unit Code 8 (HUC-8) watersheds. The study revealed that the Eastern Lower Delmarva watershed had the highest average loss and the largest net reduction in salt marsh AGB from 1999-2018. The study developed a method that used Google Earth Engine (GEE) enabled time series of the Landsat archive for regional analysis of salt marsh change and identified at-risk watersheds and salt marshes providing insight into the resilience and management of these ecosystems. The time series were filtered by cloud cover and the Tidal Marsh Inundation Index (TMII). The combination of GEE enabled Landsat time series, and TMII filtering demonstrated a promising method for historic assessment and continued monitoring of salt marsh dynamics.

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Multiple stressors and the potential for synergistic loss of New England salt marshes

Cited by 32 publications

References 50 publications

Top-down and bottom-up controls on southern New England salt marsh crab populations

Top-down and bottom-up controls on southern New England salt marsh crab populations

Pattern and scale: evaluating generalities in crab distributions and marsh dynamics from small plots to a national scale

Salt marsh monitoring along the mid-Atlantic coast by Google Earth Engine enabled time series

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