Historical changes in mollusc communities from a temperate chenier ridge system (Mont-Saint-Michel Bay, France)

A decline in grazing and carnivorous species, along with a shift towards suspensivore-dominated mollusc communities, has been documented in Mont-Saint-Michel Bay, France. This change reflects the loss of macrophytobenthic habitats such as seagrass beds and macroalgal belts, likely due to environmental factors including rising water temperatures. The study compared present-day active chenier ridges with fossil ridges dated to the Early Medieval Period, revealing that while shellfish farming and invasive species have had minimal impact on mollusc death assemblages so far, taphonomic inertia delays the detection of recent ecological changes. Water temperature emerges as a key driver of these shifts, with warm-water species becoming more prevalent in modern ridge systems. The research highlights the value of shelly chenier ridges as long-term records of coastal ecosystem changes, offering insights that extend far beyond conventional monitoring timelines.

Poirier, C., Caline, B., Fournier, J., & Tessier, B. (2022). Historical changes in mollusc communities from a temperate chenier ridge system (Mont-Saint-Michel Bay, France). Geological Society, London, Special Publications, 529(1), 263–279. https://doi.org/10.1144/sp529-2022-73