Burrowing and foraging activity of marsh crabs under different inundation regimes

Szura, Katelyn; McKinney, Richard A.; Wigand, Cathleen; Oczkowski, Autumn; Hanson, Alana; Gurak, John A.; Gárate, Melanie

doi:10.1016/j.jembe.2016.10.029

Cited by 15 publications

(7 citation statements)

References 51 publications

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“…Luk and Zajac (2013) suggested that landward expansion of low marsh vegetation species may facilitate increased distribution of fiddler crabs. 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.…”

Section: Crabs and Sea-level Risementioning

confidence: 89%

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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Section: Crabs and Sea-level Risementioning

confidence: 89%

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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“…Because burrowing crabs could impact belowground biomass (Szura et al 2017), we also extracted sediment cores from the middle of each plot (~3,980 cm 3 ). Cores were frozen until processed.…”

Section: Methodsmentioning

confidence: 99%

“…For example, excluding folivorous prairie dogs increased vegetation cover (primarily by increasing the abundance of grasses), but excluding granivorous kangaroo rats had no effect (Davidson and Lightfoot 2008). Likewise, herbivorous crabs ( Sesarma reticulatum ) reduced cordgrass biomass in mesocosm studies (Szura et al 2017), but detritivorous fiddler crabs ( Uca spp.) stimulated cordgrass production at intermediate elevations (i.e., the tall zone of Spartina alterniflora , Bertness 1985).…”

Section: Introductionmentioning

confidence: 97%

Local and regional variation in effects of burrowing crabs on plant community structure

Walker

Rinehart

White

et al. 2020

Ecology

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Burrowing animals can profoundly influence the structure of surrounding communities, as well as the performance of individual species. Changes in the community structure of burrowing animals or plants together with changing abiotic parameters could shift the influence of burrowers on surrounding habitats. For example, prior studies in salt marshes suggest that fiddler crabs stimulate cordgrass production, but leaf‐grazing crabs suppress cordgrass production. Unfortunately, testing this prediction and others are impeded because few studies have examined crab impacts on the plant community and across multiple sites, multiple years, or both. This challenges our ability to predict how burrowing animals will influence plant community structure, and when and where these impacts will occur. We manipulated the densities of the dominant burrowing crabs in plant assemblages dominated by Pacific cordgrass (Spartina foliosa) and perennial pickleweed (Sarcocornia pacifica) at three sites in southern California for three years (2016, 2017, 2018). Crab impacts on plant community structure differed among each of our three sites. In contrast to our predictions, (1) leaf‐grazing crabs (Pachygrapsus crassipes) had positive effects on cordgrass cover at one site and no effect on cordgrass production at a nearby site in the same marsh and (2) fiddler crabs (Uca crenulata) did not stimulate cordgrass production at another marsh. Because crabs affected traits of cordgrass, but not pickleweed, in the direction consistent with changes in cordgrass cover, we propose that marsh‐specific crab effects on community structure were largely mediated through changes in cordgrass, as opposed to pickleweed. Importantly, crabs facilitated cordgrass during marsh‐wide cordgrass loss, suggesting that crabs may mitigate environmental stress for this ecologically important plant. Because cordgrass abundance can be a critical measure of marsh functioning and is often a restoration target, we suggest that managing cordgrass populations would benefit from additional information about crab populations and their impacts among years, and among and within marshes.

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“…This gradually causes cordgrass to shift belowground allocation from dense mats of fine roots to aerenchymatous rhizomes that better oxygenate the soil [ 25 ] and increase pore space, processes that work together to soften the high marsh substrate. Importantly, this loss in the structural rigidity of marsh substrates can facilitate the burrowing and bioturbating activities of marsh infauna, such as crabs [ 26 ][ 27 ]. At the same time, cordgrass at the lowest elevations experiences increased inundation and physical stress regimes, leading to marsh drowning if rates of accretion cannot keep up with the rising seas [ 24 ].…”

Section: Introductionmentioning

confidence: 99%

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

2017

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Climate change and other anthropogenic stressors are converging on coastal ecosystems worldwide. Understanding how these stressors interact to affect ecosystem structure and function has immediate implications for coastal planning, however few studies quantify stressor interactions. We examined past and potential future interactions between two leading stressors on New England salt marshes: sea-level rise and marsh crab (Sesarma reticulatum) grazing driven low marsh die-off. Geospatial analyses reveal that crab-driven die-off has led to an order of magnitude more marsh loss than sea-level rise between 2005 and 2013. However, field transplant experimental results suggest that sea-level rise will facilitate crab expansion into higher elevation marsh platforms by inundating and gradually softening now-tough high marsh peat, exposing large areas to crab-driven die-off. Taking interactive effects of marsh softening and concomitant overgrazing into account, we estimate that even modest levels of sea-level rise will lead to levels of salt marsh habitat loss that are 3x greater than the additive effects of sea-level rise and crab-driven die-off would predict. These findings highlight the importance of multiple stressor studies in enhancing mechanistic understanding of ecosystem vulnerabilities to future stress scenarios and encourage managers to focus on ameliorating local stressors to break detrimental synergisms, reduce future ecosystem loss, and enhance ecosystem resilience to global change.

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Burrowing and foraging activity of marsh crabs under different inundation regimes

Cited by 15 publications

References 51 publications

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

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

Local and regional variation in effects of burrowing crabs on plant community structure

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

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