Feral hog disturbance alters carbon dynamics in southeastern US salt marshes

Coastal saltmarshes are an important and highly diverse ecosystem, shielding the mainland from erosion and flooding. Along the US East Coast these valuable wetlands are endangered due to climate change, sea-level rise, and reduced fluvial sediment fluxes. Although hurricanes are commonly an erosional agent, they may be responsible for delivering significant volumes of sediment to the marsh surface, which could aid resiliency by increasing vertical accretion. This study analyzes marsh sediment cores collected during December 2017 within the Georgia Bight, targeting deposits associated with Hurricane Irma, which caused significant wave energy and storm surge along the coast from Florida to South Carolina in September 2017.We have focused our initial research on samples from Sapelo Island (Georgia), where Hurricane Irma produced maximum wind velocities of 17.5 m/s and a 1.3 m storm surge, inundating the marsh for 14.8 hrs. We find that Irma-related layers are between 2 and 7 cm thick and well-oxidized. These deposits typically consist of laminated mud with low organic content (LOI: 10-25%) and low bulk density (0.3-0.8 g/cm3). On average, Irma event sediment thickness is 4 times the historical average annual accretion, which in Georgia salt marshes is 1.55 mm.A direct comparison of Irma-affiliated marsh accretion and historical rates is complicated due to differences in consolidation, rooting and vegetation, and the sedimentation history of the marsh. Nonetheless, the storm layer represents a significant addition of sediment to the marsh surface. Thus, future increases in event sedimentation, associated with increased frequency or severity of storms, could help compensate for sea-level rise and lessen the likelihood or extent of marsh loss due to submergence.

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Impacts of Age and Expansion Direction of Invasive Spartina alterniflora on Soil Organic Carbon Dynamics in Coastal Salt Marshes Along Eastern China

Estuaries and Coasts ◽

10.1007/s12237-019-00611-4 ◽

2019 ◽

Vol 42 (7) ◽

pp. 1858-1867

Author(s):

Qi Xiangzhen ◽

Liu Huiyu ◽

Lin Zhenshan ◽

Liu Xiang ◽

Gong Haibo

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Spartina Alterniflora ◽

Salt Marshes ◽

Eastern China ◽

Carbon Dynamics ◽

Coastal Salt Marshes ◽

Soil Organic Carbon Dynamics

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Sea-level rise and the emergence of a keystone grazer alter the geomorphic evolution and ecology of southeast US salt marshes

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1917869117 ◽

2020 ◽

Vol 117 (30) ◽

pp. 17891-17902 ◽

Cited By ~ 3

Author(s):

Sinéad M. Crotty ◽

Collin Ortals ◽

Thomas M. Pettengill ◽

Luming Shi ◽

Maitane Olabarrieta ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Salt Marshes ◽

Species Interactions ◽

Spatial Organization ◽

Field Experiments ◽

Keystone Species ◽

Aerial Image ◽

Geomorphic Evolution ◽

Southeastern Us

Keystone species have large ecological effects relative to their abundance and have been identified in many ecosystems. However, global change is pervasively altering environmental conditions, potentially elevating new species to keystone roles. Here, we reveal that a historically innocuous grazer—the marsh crabSesarma reticulatum—is rapidly reshaping the geomorphic evolution and ecological organization of southeastern US salt marshes now burdened by rising sea levels. Our analyses indicate that sea-level rise in recent decades has widely outpaced marsh vertical accretion, increasing tidal submergence of marsh surfaces, particularly where creeks exhibit morphologies that are unable to efficiently drain adjacent marsh platforms. In these increasingly submerged areas, cordgrass decreases belowground root:rhizome ratios, causing substrate hardness to decrease to within the optimal range forSesarmaburrowing. Together, these bio-physical changes provokeSesarmato aggregate in high-density grazing and burrowing fronts at the heads of tidal creeks (hereafter, creekheads). Aerial-image analyses reveal that resulting “Sesarma-grazed” creekheads increased in prevalence from 10 ± 2% to 29 ± 5% over the past <25 y and, by tripling creek-incision rates relative to nongrazed creekheads, have increased marsh-landscape drainage density by 8 to 35% across the region. Field experiments further demonstrate thatSesarma-grazed creekheads, through their removal of vegetation that otherwise obstructs predator access, enhance the vulnerability of macrobenthic invertebrates to predation and strongly reduce secondary production across adjacent marsh platforms. Thus, sea-level rise is creating conditions within whichSesarmafunctions as a keystone species that is driving dynamic, landscape-scale changes in salt-marsh geomorphic evolution, spatial organization, and species interactions.

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A large invasive consumer reduces coastal ecosystem resilience by disabling positive species interactions

Nature Communications ◽

10.1038/s41467-021-26504-4 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Marc J. S. Hensel ◽

Brian R. Silliman ◽

Johan van de Koppel ◽

Enie Hensel ◽

Sean J. Sharp ◽

...

Keyword(s):

Salt Marshes ◽

Species Interactions ◽

Large Scale ◽

Plant Biomass ◽

Ecosystem Resilience ◽

Native Communities ◽

Southeastern Us ◽

Recovery Models ◽

Feral Hogs ◽

Climatic Disturbances

AbstractInvasive consumers can cause extensive ecological damage to native communities but effects on ecosystem resilience are less understood. Here, we use drone surveys, manipulative experiments, and mathematical models to show how feral hogs reduce resilience in southeastern US salt marshes by dismantling an essential marsh cordgrass-ribbed mussel mutualism. Mussels usually double plant growth and enhance marsh resilience to extreme drought but, when hogs invade, switch from being essential for plant survival to a liability; hogs selectively forage in mussel-rich areas leading to a 50% reduction in plant biomass and slower post-drought recovery rate. Hogs increase habitat fragmentation across landscapes by maintaining large, disturbed areas through trampling of cordgrass during targeted mussel consumption. Experiments and climate-disturbance recovery models show trampling alone slows marsh recovery by 3x while focused mussel predation creates marshes that may never recover from large-scale disturbances without hog eradication. Our work highlights that an invasive consumer can reshape ecosystems not just via competition and predation, but by disrupting key, positive species interactions that underlie resilience to climatic disturbances.

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Unpacking Tornado Disasters: Illustrating Southeastern US Tornado Mobile and Manufactured Housing Problem Using March 3, 2019 Beauregard-Smith Station, Alabama, Tornado Event

Natural Hazards Review ◽

10.1061/(asce)nh.1527-6996.0000436 ◽

2021 ◽

Vol 22 (1) ◽

pp. 04020060

Author(s):

Stephen M. Strader ◽

David B. Roueche ◽

Brett M. Davis

Keyword(s):

Manufactured Housing ◽

Housing Problem ◽

Southeastern Us ◽

Tornado Event

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Urbanization impacts on production and recruitment of Fundulus heteroclitus in salt marsh creeks

Marine Ecology Progress Series ◽

10.3354/meps13378 ◽

2020 ◽

Vol 645 ◽

pp. 187-204

Author(s):

PJ Rudershausen ◽

JA Buckel

Keyword(s):

Salt Marsh ◽

Salt Marshes ◽

Fundulus Heteroclitus ◽

Multiple Factor Analysis ◽

Southeastern Usa ◽

Density Dependent ◽

Dependent Relationship ◽

Juvenile Abundance ◽

The Relationship ◽

Throw Trap

It is unclear how urbanization affects secondary biological production in estuaries in the southeastern USA. We estimated production of larval/juvenile Fundulus heteroclitus in salt marsh areas of North Carolina tidal creeks and tested for factors influencing production. F. heteroclitus were collected with a throw trap in salt marshes of 5 creeks subjected to a range of urbanization intensities. Multiple factor analysis (MFA) was used to reduce dimensionality of habitat and urbanization effects in the creeks and their watersheds. Production was then related to the first 2 dimensions of the MFA, month, and year. Lastly, we determined the relationship between creek-wide larval/juvenile production and abundance from spring and abundance of adults from autumn of the same year. Production in marsh (g m-2 d-1) varied between years and was negatively related to the MFA dimension that indexed salt marsh; higher rates of production were related to creeks with higher percentages of marsh. An asymptotic relationship was found between abundance of adults and creek-wide production of larvae/juveniles and an even stronger density-dependent relationship was found between abundance of adults and creek-wide larval/juvenile abundance. Results demonstrate (1) the ability of F. heteroclitus to maintain production within salt marsh in creeks with a lesser percentage of marsh as long as this habitat is not removed altogether and (2) a density-dependent link between age-0 production/abundance and subsequent adult recruitment. Given the relationship between production and marsh area, natural resource agencies should consider impacts of development on production when permitting construction in the southeastern USA.

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