Common Green Seaweed Tubes

What Green, Tubular Seaweeds are in Maine?

Three of Maine’s green seaweed genera include species with a tubular morphology, but the number of tubular species within each is unclear. Recent molecular work has uncovered tremendous cryptic diversity and undescribed species. All three genera are undergoing taxonomic revision, and many previously-used macrocharacters are no longer accurate for identification.

The following five groups represent common green tubes that can sometimes be field-identified; however, because they are morphologically variable, molecular data is necessary for a positive determination:

• Ulva intestinalis
• Ulva prolifera
• Ulva compressa
• Capsosiphon spp.
• Blidingia spp.

Two additional species of tubular seaweeds have been reported in Maine but are not yet molecularly confirmed: Ulva paradoxa and Ulva flexuosa. U. paradoxa is a branched tube with uncertain taxonomic status in the Northwest Atlantic. U. flexuosa is likely present and merely overlooked, as DNA evidence supports its presence both south and north of Maine. This species may be branched or unbranched and cannot be distinguished from U. prolifera or U. compressa without molecular data.