phenomenon. An interesting and important feature of the Ammen 

 Rock site is the lack of large herbivores, especially sea urchins, 

 which may contribute to the establishment and persistence of these 

 macroalgal assemblages at record depths. 



MATERIALS AND METHODS 



During the summers of 1984 and 1985 we made a series of dives 

 with the 2-man submersible, Mermaid II , 4-man submersible Johnson 

 Sea-Link and an unmanned reconnaissance vehicle, Recon IV , as a 

 part of NOAA's National Undersea Research Program. We report here 

 on the results of two Recon IV surveys and four Mermaid II and 

 Johnson Sea-Link dives on a shallow pinnacle ( ca 24 m) near Ammen 

 Rock which is part of Cashes Ledge approximately 104 km east of 

 Boothbay Harbor, Maine (Fig. 1). 



Our study site, called "Ammen Rock Pinnacle" is located in 

 the center of the Gulf of Maine and is influenced by strong 

 currents and oceanic water masses of low turbidity (we observed up 

 to 30 m lateral visibility, see also light data below) and high 

 salinity. Water temperatures from June to August are typical for 

 Maine Intermediate Water (Hopkins and Garfield, 1979) and ranged 

 from 5°C to 9°C at the summit of the pinnacle and from 5°C to 

 6.5°C at 75 m. Typically however, benthic temperatures ranged 

 from 5 . 5°C to 7 . 5°C in the photic zone. The Ammen Rock Pinnacle 

 consists of a steeply sloping granitic outcrop. The walls descend 

 sharply from the summit to about 30 m and then at a lesser angle 

 to 43 m. Large boulders lie at the base of the pinnacle forming a 

 talus slope. Below 43 m, boulders and ledge outcrops form most of 

 the available hard substrata, gradually being replaced by cobbles 

 rocks, sand and small outcrops of ledge. Sediment accumulations 

 increase with depth and increasingly reduce the amount of primary 

 substratum on horizontal surfaces below 50 m. 



Visual (recorded with cassette tape), photographic and video 

 observations were made on the submersible dives. The submersibles 

 were equipped for limited collecting with a suction sampler and a 

 manipulator arm. Neither collection technique was satisfactory 

 but between them provided voucher specimens or fragments of 

 several algae. Rocks encrusted with coralline algae up to 30 x 30 

 cm in size were collected with the manipulator arm. During 1985 

 limited scuba diving was permitted to 30 m to collect algae. 

 Underwater light readings were made in 1985 by Dr. James Sears 

 with a Licor Underwater Photometer Model Li 185B with a cosine 

 corrected sensor. The unit measures PAR in the 400-700 nm 

 waveband and the unit of measurement is u. A series of 5 tests 

 were run over a two day period at midday during calm clear weather 

 conditions. For comparison a similar test was run with a Licor 

 Model 188b integrating quantum meter with a Li 905B spherical 

 sensor during calm conditions on the coast at Pemaquid, Maine. 



Data records of algal observations were pooled from our 



11 



