Mark and Diane Littler and their colleague Ned Smith are reporting on mysterious pancake-like patterns, resembling flattened circular nests of drifting seagrass blades, from Florida Bay, USA. The 2,072-km2 bay, with its vast mangrove, seagrass and coral-reef habitats, interacts importantly with the entire Florida Keys and Coral Reef Tract. The drifting fragments, consisting mostly of the shoal grass Halodule wrightii (Cymodoceaceae), are exceptional because they can maintain viability for up to 4 weeks. Interestingly, such extraordinary mosaic patterns of pancake-seagrass rafts are previously unreported, but consistently originate in the western region of Florida Bay under light wind and wave conditions.
To date, the Littlers have no evidence identifying the mechanisms responsible for the circular patterns, but the patterns do appear to be analogous to cold-water pancake-ice formations, in respect to how they take shape. As in pancake-ice, the patterns are posited to be sculpted by the bumping action of adjacent clumps, in conjunction with the nature of the curved crescent-shaped individual blades. The initial stages of formation seem to develop from a tendency for the buoyant blades to be shuffled inward to coalesce as overlapping/interlocking concentric rings, with the mean pancake diameter being 18 cm ±4 SD. The possibility that the pancakes are rolled into shape by tidal-current shear has also been suggested.