Multiple assessments of introduced seaweeds in the Northwest Atlantic

Abstract

Historical and recent floristic studies, rapid assessment surveys, and molecular investigations were used to evaluate the occurrence of 20 seaweeds introduced to the Northwest Atlantic, including 2 green, 4 brown, and 14 red algae. Based on floristic comparisons of Mount Desert Island and Casco Bay, ME, from the late 1800s to the early 1900s, some initial records of seaweed introductions were documented, as well as increased numbers of non-indigenous taxa. Detailed floristic studies in southern ME and NH from the mid-1960s to 2007 have revealed expansive patterns for two Asiatic taxa (Codium fragile subsp. tomentosoides and Neosiphonia harveyi). Rapid assessment surveys conducted between the Bay of Fundy and Long Island, NY, during four summers (2002, 2004, 2005, and 2007) revealed seven introduced species and a recent expansion of the Asiatic red alga Grateloupia turuturu into the Gulf of Maine. Molecular evaluations confirmed the presence of several cryptic introduced species of Porphyra from Asia. A synopsis of the dates of introduction, probable vectors, and sources of these 20 introduced taxa in the Northwest Atlantic is given, as well as comparisons of numbers of non-indigenous taxa from other geographies. © 2008 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved.