Occurrence of the Introduced Red Alga Antithamnion pectinatum (Ceramiaceae) in New Hampshire, U.S.A.

In the present note we describe the recent occurrence of the introduced Australasian red alga Antithamnion pectinatum (Montagne) Brauner from southern New Hampshire. The alga was initially collected during May 2018 from the Outer Sunken Rocks area of Hampton, New Hampshire (42°53.657′N, 70°47.177′W) by divers from Normandeau Associates, Inc. who were conducting destructive biomass studies of attached seaweeds at a depth of ca. 12.2 m (40 ft). The location represents one of their long-term study sites (Station B19) utilized during environmental monitoring of the Seabrook Power Station and the contiguous Hampton-Seabrook area (Normandeau Associates, Inc. 2007). The station also represents a study site (i.e., HB4) previously evaluated by Mathieson and Fralick (1972) in their detailed floristic studies of algal vegetation of the Hampton-Seabrook Estuary and the open coast of Hampton, New Hampshire, where the alga was not previously found. Recently (2020), Normandeau divers also found A. pectinatum at two other Hampton-Seabrook study sites (i.e., B31 and B35) during multiple sampling periods.