Refugial Laminaria Abundance and Reduction in Urchin Grazing in Communities in the North-West Atlantic

• Published in: Journal of the Marine Biological Association of the United Kingdom
• Main Author: Keats, Derek W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1991
• Subjects: Aquatic Science; Newfoundland; North West Atlantic
• Online Access: http://dx.doi.org/10.1017/s0025315400053510; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0025315400053510

A literature review and new data are used to clarify geographical patterns of community response to release from heavy grazing by green sea urchins, Strongylocentrotus droebachiensis (O.F. Müller) within the north-west Atlantic region. Large geographical areas identified where urchin-removal experiments have not been conducted are the Passamaquoddy Bay area of the northern Bay of Fundy, the south and west coasts of Newfoundland, and southern Labrador. Within the north-west Atlantic region, there has been variation in the degree of domination by Laminaria species of post-urchin-removal communities. This is probably due, at least in part, to variation in the availability of Laminaria populations in refugia from urchin grazing. The following hypothesis is developed and given a preliminary test: in eastern Newfoundland, the absence of refugial Laminaria longicruris populations is due to periodic ice-scour. Despite the absence of significant Laminaria populations following short-term (<5 years) urchin-removal experiments in some areas, it is suggested that Laminaria spp. may be the natural, long-term community dominants in the absence of significant urchin grazing throughout the region. In view of the logistic problems involved in conducting long-term (6–15 years) urchin-removal experiments, it is suggested that urchin-removal/Laminaria-seeding experiments should be conducted within this region.