A Nor'Easter storm passed through New England in January of 2018 leaving in its wake a series of 'marsh bergs', or ice-rafted sediment deposits. These deposits add, on average, 7cm of sediment to the surface of the marsh and act as a critical form of secondary sediment deposition that can aid marsh vertical accretion. Despite smothering plants, infauna, and epifauna initially, we saw full recovery of the marsh within 18 months, showcasing how resilient these systems can be to natural disturbances. (Wittyngham et al. 2021)
Ice-Rafting in New England
Periwinkle snails are generalists
While wandering through a brackish marsh along the York River, a William & Mary undergraduate, Caroline Failon, noticed something interesting. We know that the marsh periwinkle, Littoraria irrorata, is an herbivore of the smooth cordgrass, Spartina alterniflora, and in extraordinarly high densities, it can lead to marsh die-back. However, in this brackish marsh, Caroline noticed that periwinkles also covered stems and leaves of the big cordgrass, Spartina cynosuroides, a phenomenon never documented before. We sought to answer whether big cordgrass provided ecologically equivalent habitat for periwinkles. It turns out, it does! Despite differences in environmental conditions, predation pressure, and plant palatability, periwinkles appear to use both cordgrass species as habitat and refuge. (Failon et al. 2020)
Caroline at Taskinas Creek Marsh surrounded by Spartina alterniflora (right) and Spartina cynosuroides (left)
Serina (left) and Caroline (right) after a muddy field day.
A periwinkle snail climbing on Spartina cynosuroides.
An ice-rafted sediment deposit in The Great Marsh, MA.
An ice-rafted sediment deposit with a quadrat for counting plant stems.
Revisiting contributions to sediment volume in salt marshes
Sometimes science happens because of who you meet! Erin and I met at the AGU conference in December of 2022 and began chatting about our previous work in salt marshes. It turned out that Erin had hundreds of CT scans of salt marsh sediment cores, but hadn't measured plant belowground biomass. One thing led to another, and this project emerged! Using machine learning and statistical analyses, we've found that standard loss on ignition techniques (LOI) commonly used in the estimation of carbon stocks and models of vertical accretion and saltmarsh resilience are most likely overestimating sediment organic matter (SOM) contribution, as some percentage of this is actually dissolved organic matter (DOM) and lost to tidal flushing and compaction. By creating correction factors that account for DOM, we can more accurately assess carbon storage and predict saltmarsh stability under climate change.(Peck & Wittyngham, in prep)
An example of a machine-learning trained CT scan of a saltmarsh sediment core. Cores were separated into sediment, roots, and rhizomes.