pul ligo was more abundant in deeper areas 

 (-11 m), There was little overlap in 

 their distribution. The third species, T. 

 montereyi , was the least abundant of the 

 three turban snails, and tended to be most 

 common at ^ 6 m depth. In addition to 

 living and feeding on large brown algae, 

 these species can be found at densities of 

 ^ 40/m 2 on the substratum (Watanabe 

 1984a). Here, they may also graze small 

 plants and spores. 



Many other grazing gastropods are 

 present in Macrocystis forests; their 

 habits and effects are largely unknown. 

 Several species of Cal liostoma (Plate IF) 

 can be found on kelp plants. They are 

 omnivores eating sessile animals as well 

 as kelp (Morris et al . 1980), but their 

 effects on kelp tissue are probably 

 minimal. Mitre 11 a carinata and Lacuna 

 unifasciata are both small species, and 

 can be the most abundant gastropods found 

 on Macrocystis plants (Leighton 1971, 

 Morris et al . 1980). Their grazing 

 effects are also probably minimal. 

 Norrisia norrisi (Figure 20) and species 

 of Astraea can be abundant in kelp 

 forests, particularly on the fronds of 

 Macrocystis and Eisenia (Schmitt et al . 

 1983). NT" norrisi feed on sporophylls, 

 stipes and young fronds, and Leighton 

 (1971) reported that stipe breakage may 

 result from this grazing. The giant 

 keyhole limpet ( Megathura crenulata ) and 

 several species of chitons may graze algal 

 spores from the substratum, but no 

 significant effects on kelp have been 

 reported. Ton ice! la lineata (Plate 2A) is 

 often abundant on encrusting corallines in 

 central California kelp forests, and may 

 be responsible for keeping areas free of 

 other algae. 



The California brown sea hare, 

 Aplysia californica , may be locally common 

 in kelp forest and grazes on a variety of 

 algae (Morris et al. 1980). We have seen 

 mating aggregations of this species in 

 kelp forests in Carmel Bay. During 

 periods of calm water, individuals can 

 occasionally be found in the tops of 

 Pterygophora cal ifornica , grazing on the 

 blades. A. vaccaria , the California black 

 sea hare is most common in southern 

 California and Baja California, Mexico. 

 This species may be the world's largest 

 gastropod, with individuals over 0.5 m 



long and weighing nearly 16 kg. Egregia 

 is reported as its primary food (Morris et 

 al. 1980). 



Several species of abalone live in 

 kelp forests, and all consume many species 

 of algae. The red abalone ( Hal iotis 

 rufescens ; Figure 20), the green abalone 

 ~{IL fulgens ) , and the pink abalone (H_. 

 corrugata ) were important species in sport 

 and commercial fisheries but, recently, 

 the harvest of the primarily intertidal 

 black abalone (_H. cracherodii ) has 

 increased, probably because of the impacts 

 of commercial and sport fishing on the 

 former species (see Section 6.2.2.2). 

 Hines and Pearse (1982) report that 

 abalone populations within a kelp forest 

 foraged by sea otters exhibit high 

 recruitment, growth rates, and turnover 

 rates. Abalone feed extensively on 

 Macrocystis (Leighton 1971, Tegner and 

 Levin 1982). This is almost entirely 

 drift material, however, captured by the 

 animals with their powerful feet. Species 

 of Hal iotis have little effect on attached 

 plants. 



4.4.3.3 Crustaceans (Arthropoda, 

 Crustacea) . The kelp isopod Idotea (= 

 Pentidotea ) resecata (Figure 20) dwells on 

 the upper fronds and blades of Macro - 

 cystis , and can heavily graze the blades 

 (Jones 1971). North (1966) reported that 

 this feeding activity once extensively 

 damaged the canopy of Macrocystis in a 

 wide area of the Point Loma kelp forest. 

 The holes in blades resulting from their 

 grazing may also be sites for fungal and 

 bacterial infections. Another isopod, the 

 pillbug Paracerceis cordata , probably 

 causes little damage to kelp plants. 



The gribble Limnoria (= Phyco - 

 limnoria ) algarum may occasionally cause 

 adult Macrocystis to be detached from the 

 substratum. This isopod can be abundant 

 in Macrocystis holdfasts (Andrews 1945). 

 It burrows into the haptera, forming 

 tunnels which may severely weaken the 

 holdfasts (Jones 1971). Increased water 

 motion may then dislodge these plants. A 

 related isopod can cause considerable 

 weakening of giant kelp holdfasts in 

 Argentina (see Section 3.3.3). 



The kelp curling amphipods Ampithoe 

 humeralis , A. rubricata , and Cymadusa 



65 



