observations and those made by J. Sears, K. Sebens and J. Witman. 



RESULTS 



Seventeen algal species were recorded from Ammen Rock Pinnacle 

 including three kelps, five foliose reds, two small filamentous 

 forms, three fleshy red crusts, three crustose corallines and one 

 erect articulated calcareous alga (Table 2). Surprisingly, large 

 filamentous and thin sheet-like algae were not observed on the 

 pinnacle. All of the specimens observed or collected at these 

 depths appeared healthy and several were reproductive. 

 Interestingly, the thallus sizes of kelps were sharply truncated at 

 the deepest depths. Typically the maximum size of thalli for each 

 taxon decreases with depth. Kelps, for example, ranged in size 

 from 100-200 cm near the summit to 10-20 cm at the lowermost 

 limits. 



A striking zonation pattern exists on the pinnacle (Fig. 2). 

 The summit of one of the shallower peaks (observed in 1984 but not 

 located in 1985) was not examined in detail but the upper walls (ca 

 23m) were covered by dense carpets of sea anemones, Metridium 

 senile . Kelps began at 24m and co-occurred with sea anemones over 

 much of their range to a depth of 40m. Foliose red algae grew in 

 the kelp zone and extended to a depth of 50m. Corallina 

 officinalis was observed at 24 to 30m whereas calcified (coralline) 

 and non-calcified (fleshy) algal crusts were observed at all zones 

 having algae. Peyssonnelia was the deepest occurring fleshy crust 

 (55 m) whereas Leptophytum laeve was the deepest coralline crust 

 and alga observed on the pinnacle (63m). 



Invertebrate populations were also zoned with depth. Below 

 the shallow band of M_^ senile from 50-90m were patchy assemblages 

 of sponges ( Haliclona , Suberitechinus , Polymastia, and Phakellia) , 

 ascidians ( Aplidium , Ascidia , and Botyrilloites ) , and two other 

 anemones ( Tealia and Bolocera ) . Also invertebrates such as Modiolus 

 and Myxicola were abundant in places at this depth range. Most 

 conspicious in their absence within the zones of algae were sea 

 urchins. All other herbivores were rare. We collected a few small 

 limpets and chitons but these would have little impact on benthic 

 algae. 



The kelp zone was occasionally sandwiched in places between 

 dense beds of Metridium . The dominant kelp was a Laminaria species 

 of uncertain taxonomic affinity but which resembles L^ digitato . 

 The great depths to which this species grows, aspects of its 

 morphology (described below) and anatomy (presence of mucilage 

 ducts in the frond and stipe) suggest that this may be a new taxon. 

 This Laminaria formed an open or park-like canopy ( sensu Kitching, 

 1941; Luning and Dring, 1979) mainly between 25-30m. Individual 

 stipes were spaced 0.2 to 0.5 m apart. Fronds of this species were 

 up to 2m in length with wide, sparsely digitate lamina with one or 

 two conspicuous vertical constrictions. The latter apparently 

 occur annually suggesting that the larger fronds survive for a 



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