and remote video devices has extended our knowledge of depth 

 maxima of algal communities significantly (summarized in Table 

 1 ) . These include discoveries of record extinction depths for 

 the tropical Atlantic (Littler et al . , 1985, 1986) and tropical 

 Pacific oceans (Agegian and Abbott, 1985) and the unique deep 

 water kelp communities of the Mediterranean Sea (Mojo and Buto, 

 1970; Drew et al . , 1982). Overall, however, patterns of 

 extinction depth distribution of algae are rare, or spuriously 

 collected, depending on the availability of deep diving 

 submersibles or manned underwater habitats (Earle, 1972; Sears 

 and Cooper, 1978; Littler et al . , 1986). Although other deep 

 water collections have been reported, we have not listed them 

 because they represent dredged specimens, (e.g., Laminaria 

 brasiliensis is reported from depths greater than 70 m; Joly and 

 Oliveira Filho, 1967; Oliveira Filho, 1976). 



Light is often considered to be the most important element 

 influencing patterns of algal depth distributions. This was 

 recently reviewed by Hiscock (1986, p. 294) who stated: 



"Several studies, including those published by Boulter et 

 al. (1974), Norton et al . (1977) and Luning and Dring 

 (1979), have indicated that the critical depth below which 

 kelp fail to grow is where about 1% of surface illumination 

 is reached. For the foliose red algae, the critical depth 

 is that at which c. 0.1% of surface illumination 

 penetrates. " 



Hiscock 's (1986) review indicated that algal extinction depths 

 are constant for kelp and foliose algae when considered as a 

 function of the percentage of surface irradiance. This 

 suggestion has not been tested in the western North Atlantic 

 which contains a different subtidal algal flora. 



What little is known of algal depth patterns in the western 

 North Atlantic Ocean has been described largely from nearshore 

 scuba observations (Lamb and Zimmerman, 1964; Edelstein et al . , 

 1969; Adey, 1973; Sears and Wilce, 1975; Steneck, 1978; 

 Mathieson, 1979; Himmelman, 1980; Mathieson et al . , 1981). 

 Relatively few direct observations have been made subtidally on 

 offshore islands or submerged ledges (but see Sears and Cooper, 

 1978). These offshore habitats are important to study, however, 

 because their geographic isolation and oceanic character make 

 them unique. Additionally they may provide insight into 

 processes such as recruitment, productivity, herbivory and 

 evolutionary relationships which are important to more broadly 

 distributed nearshore communities. 



Here we describe the algal assemblage of a submerged 

 pinnacle that lies well offshore in the Gulf of Maine and has a 

 relatively shallow (24m) summit. We report several new depth 

 records for the North Atlantic, the existence of a deep water 

 Laminaria "park" ( sensu Kitching, 1941) and a three zone depth 

 pattern of algal dominance which we believe may be a worldwide 



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