Animal ecosystem engineers much stronger driver of salt marsh accretion than expected

The fate of coastal ecosystems depends on their ability to keep pace with sea-level rise-yet projections of accretion, the process by which marshes build up vertically, have widely ignored effects of animal ecosystem engineers. Researchers at the University of Florida (UF), the Royal Netherlands Institute for Sea Research (NIOZ) and Utrecht University combined observational, experimental, digital mapping and modelling work to show that ecosystem engineering by mussels in Southeastern US salt marshes is a much stronger driver of accretion rates than expected, as shown in a new study recently published in Nature Communications.  

"This result suggests that animals may have a far greater role in helping coastal systems adapt to climate change than previously thought," said lead author Sinéad M. Crotty, associate director of science of the Carbon Containment Lab at Yale University. "Up to now, there’s been no study showing this connection." 

Relocating 200,000 mussels by hand

Using fieldwork data and a model, the researchers aimed to predict the effect of mussels on marsh accretion. They then conducted a large-scale mussel experiment, which involved removing over 200,000 mussels by hand, and moving them to a new location. "We found that, in reality, the effects of mussels are far greater than predicted by the models, and occur at large, landscape scales," said Crotty.

The present study provides new insight into the mechanisms by which coastal ecosystems that are highly valuable for flood defense, such as salt marshes, can cope with sea-level rise.

Tjeerd Bouma


The findings suggest that initiatives to protect and restore coastal areas, specifically efforts to support these systems in adapting to climate change, should consider a larger suite of organisms. In the case of salt marshes, mussels may be the key differentiator.

"The present study provides new insight into the mechanisms by which coastal ecosystems that are highly valuable for flood defense, such as salt marshes, can cope with sea-level rise," said co-author Tjeerd J. Bouma , professor at Utrecht University and senior scientist at NIOZ.  

Ecosystem services

In addition to coastal defense, salt marshes, which stretch over one million acres of the southeastern US Atlantic coast, supply many other ecosystem services.

"Salt marshes are vital to the cultural identity, economic security and health of the millions of residents that live along the coast in this region," said Christine Angelini, Ph.D., oeuf associate professor and project lead. "These wetlands sustain valuable recreational and commercial fisheries, such as blue crabs, oysters and shrimp, and they store large quantities of carbon, thereby helping offset the impacts of climate change."  

Going forward, models of marsh accretion should incorporate the direct and indirect effects of animals, the researchers say.

Publication

Crotty, S.M., Pinton, D., Canestrelli, A. et al. Faunal engineering stimulates landscape-scale accretion in southeastern US salt marshes. Nat Commun  14 , 881 (2023). https://doi.org/10.1038/s41467­’023 -36444-w