Effects of Grazers and Algal Competitors on Fucoid Colonization in Tide Pools1

In New England, fucoids are conspicuously absent from midlittoral sheltered tide pools, though abundant on adjacent emergent rocks. Experimental removal of either herbivores or potential algal competitors from mid littoral tide pools failed to result in the establishment of fucoids. However, removal of both groups together resulted in the establishment of Fucus vesiculosus L. Once established, some individuals persisted for up to three years. These grew well, were of normal, healthy appearance and reproduced. The herbivores removed were Littorina littorea, L. obtusata and Acmaea testudinalis. Algae removed were Chondrus crispus Stackhouse, Ulva lactuca L., Rhizoclonium tortuosum Kützing, Spongomorpha spinescens Kützing, Polysiphonia sp., Dumontia incrassata (O.F. Muller) O. Kuntze and Scytosiphon lomentaria (Lyngbye) Link. It is concluded that absence of fucoids from mid littoral, protected pools is due to the joint action of herbivores and algal competitors and not to possible deleterious factors associated with constant submersion.