Salt marshes, mangroves and seagrass are examples of vegetated coastal ecosystems that are vulnerable to sea level rise due to their limited elevation range and important functions in shoreline stabilisation, wave attenuation, nutrient filtration, habitat provision and carbon sequestration. The historical and current vertical and horizontal siltation and erosion rates have been quantified. Field data and models have been used to project their size, stability and geographic distribution.

The study focuses on 750,000 acres of sprawling salt marsh systems in the United States around the South Atlantic Bight, an area stretching 150 miles from Cape Fear, North Carolina, to Cape Canaveral, Florida. They looked at research on different species, such as crabs, lugworms and ghost shrimp. The study’s fieldwork includes measurements of mussel cover in the South Atlantic Bight, just published in Nature Communications. More extensive field data was conducted on Sapelo Island, a barrier island off the coast of central Georgia.

According to the results of the study, mussels (Geukensia demise) act as “ecosystem engineers” — creatures that direct or indirectly drive habitat creation and manage resource availability for other organisms. Mussels are considered water quality indicators because they absorb heavy metals and filter toxic sludge and particles. At the same time, they feed and breathe in aquatic habitats. Insects, small fish and plants use their shells as habitats and breeding grounds. In addition to these valuable properties, mussels deposit enormous amounts of material on marsh surfaces during their feeding activity. This material contributes to the growth of marshes through a process known as accretion, the natural activity of sand, soil or silt that washes onto land from the coast.

Faunal animals such as the humble clam play an underappreciated but essential role in protecting and creating coastal ecosystems, according to recent research led by the Carbon Containment Lab at the Yale School of the Environment.

Sinéad Crotty, associate director of science at the CC Lab and lead author of the study, said: “As sea levels rise, coastal ecosystems must adapt and evolve to changing conditions. This study demonstrates that small and harmless animals living in an ecosystem can play a critical role in helping coastal systems sustain in the face of climate change.”

He also said, “This study shows that small and harmless animals living in an ecosystem can play a critical role in helping coastal systems sustain in the face of climate change.”

researcher said. “We found that the effects of mussels are actually much larger than predicted by the models and occur at large landscape scales,”

He added, “This study can help us think about how we prioritize certain wetlands for protection. Given that mussels are disproportionately important in promoting fouling and other ecosystem functions, we should prioritize their protection, or replanting, as a means of promoting all of their associated benefits.

The researchers used three studies to assess the influence of mussels on fouling, ranging from small, local scales to entire landscape sizes, in addition to observations conducted across seasons and tidal phases. The largest experiment over three years involved transporting more than 200,000 mussels from one landscape to another by hand and observing changes in marsh height.

The author emphasizes that similar trends are expected to occur in other faunal engineers, such as bioturbating crabs or worms. According to the study authors, involving ecosystem engineers in future modeling and ecosystem management will be critical as sea levels continue to rise.

According to co-author and senior scientist Tjeerd J. Bouma of the Royal Netherlands Institute for Sea Research, the research provides crucial information about salt marshes and climate change.

He said, “The current study provides new insight into the mechanisms by which coastal ecosystems highly valuable for flood defenses, such as salt marshes, can cope with sea level rise.”

Researchers from the Faculty of Civil and Coastal Engineering at the University of Florida School for Sustainable Infrastructure and Environment, the Royal Netherlands Institute for Sea Research and the Department of Physical Geography at Utrecht University all contributed to the study.

The result shows that mussels filter sediment from the water column and serve as an important, spatially distributed epicenter for sediment uptake in this vegetated coastal environment. They show that these fauna engineers make an important contribution to the salt marsh sediment budgets, as a result of which the deposition locally increases by an order of magnitude.

Magazine reference:

  1. Pinton, D., Canestrelli, et al. Fauna engineering boosts landscape-scale accretion in salt marshes in the US southeastern region. Nature Communication. DOI: 10.1038/s41467-023-36444-w