Ulva sp.

4.5 Ulva sp. NC 5 - Ulva tepida

Using only ITS sequences, this sample was confirmed as U. tepida . The ITS sequence of the U. tepida holotype was an exact match to one of the ITS sequences found in North Carolina specimens and was only 1 bp (0.004 %) different from the other North Carolina ITS sequence for this species. Phylogenetically, this species groups with samples from the Mediterranean, East Pacific and Indian Ocean, as well as from the Northwest Atlantic ( Melton and Lopez-Bautista 2021).

Krupnik et al. (2018) found U. tepida samples that were all tubular, narrow, and hair-like. The original description of the species states that thalli are up to 11.5 cm in length and up to 8 mm in diameter, with cells containing 1 – 5 pyrenoids ( Masakiyo and Shimada 2014). The North Carolina samples fall within this size description, and their pyrenoid counts fell into the categories of 1 – 3 or greater than 3 per cell, which matches the original description. However, this description is very broad and overlaps that of many other Ulva species.

Ulva tepida was described as a species subsequent to Kapraun (1984), but when specimens of this species are identified using that dichotomous key, they identify as U. ‘ flexuosa subsp. paradoxa ’ or U. ‘ torta ’. Our sequence data indicates that the name U. ‘ torta ’ is more applicable to Ulva

sp. NC 4, but the description of U. ‘ torta ’ in North Carolina is also applicable to U. tepida .