Ulva carsoniae, Dibner & Gabrielson & Freshwater, 2025

4.9 Ulva sp. NC 9 – Ulva carsoniae sp. nov

This species was represented by a single specimen in this study that was collected at Carrot Island, near Beaufort, NC. Other specimens of this species have been collected from Virginia, Maryland, Delaware and Rhode Island along the United States east coast, and a single specimen is known from Japan ’ s west coast ( Guidone et al. 2013; Melton and Lopez-Bautista 2021; Ogawa et al. 2013). It is resolved in the rbc L and tufA trees within a large clade that includes the types of U. australis , U. expansa , U. fenestrata , U. rigida , and other undetermined species. The single North Carolina collection was a cluster of unbranched blades with fused bases that were growing attached to a small shell. Specimens from Virginia, Maryland and Delaware were reported as having blades with tubular bases that became distromatic with tubular margins, and polygonal cells in surface view with a single pyrenoid ( Melton and Lopez-Bautista 2021). The North Carolina specimens were similar in having polygonal shaped cells in surface view, and pyrenoid numbers that were mostly one, but cells in the North Carolina specimens also sometimes had two or three pyrenoids and the blades lacked hollow bases and margins. The central region interior to the surface cells, extending from the terete base of the stipe immediately above the holdfast through the compressed and then flatten base of the blade was filled with a solid mass of rhizoidal extensions of the cell walls. The large size of the Virginia specimen illustrated by Melton and Lopez-Bautista (2021) suggests that the North Carolina specimens were likely young.