californianus is from a subtidal reef 

 (Chan 1973). This suggests that perhaps 

 predation, and not the abiotic environment 

 or food availability, limits the abundance 

 of this genus in kelp forests. The 

 purple-ringed rock scallop Hinnites 

 giganteus (= H. mul tirugosus ) is common in 

 kelp forests, occurring attached by one 

 valve to rock walls and inside crevices. 

 This species is taken for food by sport 

 divers, and is being investigated as a 

 possible candidate for mariculture 

 (Leighton and Phleger 1977). Two other 

 locally abundant bivalves that attach by 

 one valve are the jingle, Pododesmus 

 cepio , and Chama arcana (= C. pel lucida ). 

 The latter can occur stacked up at 

 densities of near 300/0.1 m 2 on subtidal 

 reefs (Pequegnat 1964). The small scallop 

 Leptopecten latiauratus occasionally 

 settles in large numbers on giant kelp 

 fronds in southern California, and may 

 cause the fronds to sink (Carter pers. 

 comm.). Bernstein and Jung (1979) 

 suggested that this animal, like the 

 oceanic barnacle, is normally excluded 

 from kelp forests by predatory fishes. 



In addition to the filter feeding 

 molluscs mentioned above, there are a few 

 that capture particles in mucous nets. 

 The vermetid Petaloconchus montereyensis 

 grows in masses of intertwined calcareous 

 tubes, each tube about 2 mm in diameter, 

 at densities of up to 100,000 snails/ m 2 

 (Morris et al . 1980). The larger sessile 

 snail Serpulorbis squamigerus occurs 

 singly or in masses. Both species are 

 preyed upon by the sea star Pisaster 

 giganteus (Foster 1975b, Harrold 1981), 

 and the former is a major item in the diet 

 of this sea star in one central California 

 kelp forest (Harrold 1981). 



Although only occasionally common, 

 the nudibranch Mel ibe leonina is of 

 interest because, unlike most of its 

 predatory relatives, this large nudibranch 

 commonly sits on giant kelp fronds, and 

 captures food from the passing water in 

 its expanded oral hood (Morris et al . 

 1980). 



4.4.2.6 Polychaete worms (Annelida, 

 Polychaeta) . Polychaetes are probably 

 second only to crustaceans in diversity 

 and abundance in giant kelp forests. 



Polychaetes occur in almost all subhabi- 

 tats within a kelp forest. Normally 

 hidden, they are rarely seen except when 

 when samples are being sorted in the 

 laboratory. Abundances are particularly 

 high in kelp holdfasts (Andrews 1945, 

 Ghelardi 1971). Many are probably preda- 

 tors on other small animals. 



Polychaetes that are commonly visible 

 underwater generally capture particles in 

 the water with modified head parts or 

 gills that project out from tubes, cracks, 

 etc. on or in the substratum. The most 

 common are spirorbids, whose tiny, coiled, 

 calcareous tubes dot the surfaces of giant 

 kelp blades and understory algae 

 (particularly Rhodymenia spp.). Bernstein 

 and Jung (1979) found Spirorbis spirillum 

 most abundant in the troughs of 

 corrugations on older Macrocystis blades 

 (up to 3/cm 2 ). Chemicals from the algae 

 apparently stimulate spirorbid larvae to 

 settle on particular species, and even 

 parts of plants (Morris et al. 1980). The 

 sabellid (feather duster worm) Eudistylia 

 polymorpha is common on the bottom, where 

 its colorful feeding and respiratory plume 

 projects out of holes and crevices. 



Perhaps the most abundant large 

 polychaete in kelp forests is Diopatra 

 ornata , whose parchment-like tubes, 

 decorated with rubble and algal fragments, 

 project above unconsolidated substrata. 

 Densities can be so high that the worms 

 can completely cover the bottom. 



4.4.2.7 Sipunculans (Sipuncula) . 

 Peanut worms are often common in kelp 

 forests, but like the brittle stars 

 discussed above, are rarely seen because 

 of their cryptic habits. They feed by 

 eating sediment and ingesting organic 

 matter, or by capturing small particles. 

 Phascolosoma agassizii is probably most 

 common, and Andrews (1945) found over 80 

 individuals of this species per square 

 meter (projected holdfast area) in giant 

 kelp holdfasts from central California. 

 Foster (pers. obs.) found similar 

 densities in recent collections from this 

 area. Morris et al. (1980) indicate that 

 sipunculans are preyed upon by gastropods. 



4.4.2.8 Crustaceans (Arthropoda, 

 Crustacea) . Crustaceans are certainly the 

 numerically dominant animals in kelp 



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