Distribution and ecology of Colpomenia peregrina (Phaeophyceae) within the Northwest Atlantic

• Published in: Rhodora 2016-07, Vol.118 (975), p.276-305
• Main Authors: Mathieson, Arthur C, Dawes, Clinton J, Green, Lindsay A, Traggis, Hannah
• Format: Article
• Language: English
• Subjects: ecology; epiphyte; introduced brown alga; northwest Atlantic; reproduction; sea potato; seasonality
• ISSN: 0035-4902; 1938-3401
• DOI: 10.3119/15-24

The saccate Asiatic brown seaweed Colpomenia peregrina was first recorded within the NW Atlantic in 1960 at Atkins Point, Nova Scotia. By 2014 it was recorded from 57 sites ranging from the Grand Barachois Lagoon, Newfoundland to South Wellfleet, MA. We first found extensive populations in New England at Fort Foster, Kittery, Maine where we subsequently conducted floristic and ecological studies of the alga. Colpomenia peregrina is superficially similar to another saccate brown alga, Leathesia marina, although they have differences in morphology, anatomy, and reproduction. The species is a common epiphyte on at least 33 seaweeds within the NW Atlantic, with Corallina officinalis being its most common host. It also grows on the seagrass Zostera marina and on at least two common invertebrates, Mytilus edulis and Semibalanus balanoides. Colpomenia peregrina is an annual somewhat like Petalonia fascia, with some specimens bearing plurilocular gametangia year-round. Based upon collection of samples from 57 sites, its convoluted hollow thalli had mean diameters and heights of less than 7.5 cm and damp dried weights of less than 10.0 g. Subtidal transects studies within the shallow subtidal zone at the Isles of Shoals, NH/ME, showed a wide range of densities (15–2721 m−2) and mean diameters of 0.47–1.72 cm. The demography of 663 drift, 442 attached, and 903 epiphytic thalli were documented from Fort Foster, ME during 31 monthly visits. Drift thalli had their largest diameter and height in winter (6.9×4.7 cm), whereas those from low intertidal ledge quadrats were largest in summer (3.4×2.5 cm), and random mid-intertidal pool samples were largest in the fall (2.9×1.6 cm). The mean number of epiphytic thalli on apical parts of three fucoid algae within a mid-intertidal pool ranged from 0.09 cm−1 on Ascophyllum nodosum, to 0.23 cm−1 on Fucus vesiculosus, and 0.43 cm−1 on F. distichus subsp. evanescens. The alga's southward expansion and colonization of low intertidal and shallow subtidal habitats in the NW Atlantic indicate that it is already competing for space and resources with native vegetation as well as causing removal of attached hosts.