An historical comparison of seaweed populations from Casco Bay, Maine

• Published in: Rhodora
• Main Authors: Mathieson, Arthur C., Hehre, Edward J., Dawes, Clinton J., Neefus, Christopher D.
• Format: Text
• Language: unknown
• Published: University of New Hampshire Scholars' Repository 2008
• Subjects: Scientific Contribution Number 2323; Plant Sciences; Northwest Atlantic
• Online Access: https://scholars.unh.edu/nhaes/189; https://doi.org/10.3119/06-23.1

Based on recent and historical collections dating back to the early 1900s, the seaweed flora in Casco Bay, Maine consists of 206 taxa: 55 Chlorophyta, 70 Phaeophyta, and 81 Rhodophyta. In 1911, Frank Shipley Collins recorded 173 taxa from Casco Bay, while 164 taxa were found during recent sampling since 1994. A comparison of the two time periods shows a 77.7% similarity; some plants have apparently disappeared (or are very rare) and others are newly recorded. Eight newly collected seaweeds represent species that are most common in estuarine and shallow embayments and have southern warm-water affinities (e.g., Hummia onusta, Striaria attenuata, Callithamnion corymbosum, Ceramium cimbricum, Chondria baileyana, Polysiphonia denudata, P. elongata, and Spyridia filamentosa); six others represent introduced taxa, including Codium fragile subsp. tomentosoides, Ulonema rhizophorum, Bonnemaisonia hamifera and its "Trailliella intricata" stage, plus Dumontia contorta, Lomentaria clavellosa, and "Porphyra yezoensis f. yezoensis. The Asiatic red alga Neosiphonia harveyi, which represents another introduced taxon (i.e., 7th), was reported by Collins during the early 1900s. Comparisons of historical and present-day floras at two sites in Harpswell, Maine showed that the percent similarity values were lower and ranged from 41.5% at Basin Cove to 48.9% at Potts Point. At Basin Cove enhanced water motion and the loss of a tidal dam caused increased and altered species composition, while anthropogenic impacts due to a lobster pound diminished the flora at Potts Point. Historical floristic comparisons of seven other areas (Helgoland, Germany; the North Adriatic Sea; Denmark; Mount Desert Island, Maine; Penikese Island, Massachusetts; southern California; and the Florida Keys) are used to evaluate the stability of Casco Bay's flora and the impact of oil pollution. A comparison of Casco Bay's "composite" flora of 206 taxa with several other Northwest Atlantic sites shows that its species richness is approximately the same as that ...