period of 2 to 3 years. The structure of the holdfast also 

 appears to support this interpretation, which usually shows two to 

 three (occasionally seven) distinct whorls of haptera. Locally, 

 we observed a striking pattern of broad clear areas surrounding 

 many of the Laminaria plants. These halos presumably were due to 

 whiplash effects from the long sweeping fronds. Agarum cribrosum 

 was the deepest recorded kelp (40m), although small non-digitate 

 plants resembling the genus Laminaria were also observed in the 

 same zone (35-40m) but could not be collected. Laminaria 

 longicruris was extremely rare and interspersed with Laminaria sp. 

 at the shallower depths. 



Foliose red algae were dispersed among kelp and on ridges 

 between dense stands of anemones where they formed narrow dense 

 patches. They also occurred singly or as tiny, inconspicuous 

 tufts. Dominant in this assemblage was Ptilota serrata and 

 Phycodrys rubens (about equally abundant). We also found 

 Callophyllis cristata , Membranoptera alata and Phyllophora 

 truncata (Table 2). 



Both calcified and noncalcified crusts were found in all 

 zones. Fleshy crusts are found slightly shallower (to 55m) than 

 are coralline crusts (to 63 m) (Table 2). Coralline abundance was 

 considerable at depths over 50 meters and was observed to cover up 

 to 80% of the rock substrate in places. The dominant fleshy crust 

 was Peyssonnelia and the dominant coralline crusts were 

 Lithophyllum orbiculatum at 30 m and Leptophytum laeve at 55-63 m. 



Underwater light readings revealed marked differences between 

 Ammen Rock Pinnacle and the coast of Maine due to the turbidity of 

 the water (Fig. 3). Both profiles approximate a linear function 

 when natural log-transformed and show that light penetration at 

 Ammen Rock is significantly greater. When expressed as percent of 

 surface irradiance the light levels corresponding to the 

 extinction depths of the three major functional-form groups are: 

 0.44% for kelps, 0.11% for foliose red algae and 0.02% for 

 coralline crusts. 



DISCUSSION 



We found three distinct algal assemblages zoned with depth at 

 the Ammen Rock Pinnacle. This pattern is not unlike those found 

 in shallower nearshore regions throughout the Gulf of Maine and 

 elsewhere. The patterns are recognizable as assemblages of 

 morphologically similar species which represent distinct 

 functional groups ( sensu Littler and Littler, 1980; Steneck and 

 Watling, 1982). Three of these groups; leathery macrophytes, 

 foliose algae and crustose algae dominate the three depth zones 

 respectively (Fig. 2). 



The maximum depth for each of the three algal zones exceeds 

 that known for the Gulf of Maine and for any boreal-subarctic 

 environment (Table 1 and Fig. 4). This is probably due to the 



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