there is such overlap, we have put the 

 animal in what appears to be the most 

 common or notorious feeding type. 



4.4.2 Filter, Suspension, and Detritus 

 Feeders 



4.4.2.1 Sponges (Porifera) . 

 Sponges, along with tunicates and 

 bryozoans, are probably the most common 

 sessile animals in kelp forests, 

 particularly on steeply sloping walls and 

 in deeper water (Plate 2C). North (1971b) 

 listed 41 species of sponges in southern 

 California-Baja California kelp forests, 

 with encrusting Haliclona spp. , vase-like 

 Leucil la (= Rhabdodermel la ) nuttingi , and 

 the large, spherical, orange Tethya 

 aurantia (Figure 19) the most common. In 

 central California, Pearse and Lowry 

 (1974) mentioned 22 species from the Point 

 Cabrillo kelp forest near Monterey, and 

 McLean (1962) 11 species from Granite 

 Creek south of Carmel , California. 

 Species are generally similar in both 

 central and southern California. The 

 cobalt sponge Hymenamphiastra cyanocrypta 

 (Plate 2B) is particularly abundant as 

 encrusting sheets on vertical walls and 

 under ledges from Monterey south in 

 central California kelp forests. The deep 

 blue color is derived from a symbiotic 



Pachycenathis iimbnaius 



Figure 19. Invertebrate filter, suspen- 

 sion, and detritus feeders common in kelp 

 forests. 



blue-green alga living in its tissue 

 (Morris et al. 1980). Many sponges are 

 important in the diets of nudibranchs, and 

 the top shell Cal 1 iostoma annulatum feeds 

 on T. aurantTa (Gotshall and Laurent 

 1979J. 



4.4.2.2 Cnidarians (Cnidaria) . Hy- 

 droids, sea anemones, solitary (cup) cor- 

 als, hydrocorals, and gorgonians are ubi- 

 quitous members of the kelp forest sessile 

 animal assemblage. The hydroids Abietin - 

 aria sp. and Aglaophenia spp. are common, 

 and along with other species, are often 

 early colonists of new substrata. Many 

 hydroids are preyed upon by nudibranchs 

 (Morris et al . 1980). 



Six genera of sea anemones commonly 

 occur in kelp forests, with the large, 

 solitary Tealia spp. (Figure 19), 

 Anthopleura xanthogrammica , and especially 

 in deeper water, Metridium senile , locally 

 abundant. The most conspicuous and 

 abundant species is the strawberry 

 "anemone" (not a true anemone) Corynactis 

 californica . Colonies of this animal may 

 completely cover vertical walls, and the 

 orange to red bodies with white, club- 

 shaped tentacles, are visually striking 

 (Plate 2E). In addition to the above 

 species, the tube-dwelling Pachycerianthus 

 fimbriatus (Figure 19) is frequent in sand 

 patches within and along ^e outer edge of 

 kelp forests. All of these anemones feed 

 on almost any animal tissue or detritus of 

 appropriate size that comes within reach 

 of thei r tentacles. 



Anemones, like other cnidarians, have 

 stinging structures (nematocysts) , and 

 when the animals are aggregated (e.g., 

 Corynactis cal ifornica ) , may constitute a 

 barrier to mobile benthic animals such as 

 sea stars. Sea star prey such as 

 gastropods may thus have a refuge from 

 predators when surrounded by anemones or 

 corals (Herri inger 1983). However, the 

 leather star Dermasterias imbricata feeds 

 on C. cal ifornica (Rosenthal and Chess 

 19727. 



Three species of cup corals, 

 Balanophyllia elegans (Plate 2B), Para - 

 cyathus stearnsii , and Astrangia 

 lajol laensis occur in giant kelp forests. 

 The bright orange EL elegans is most 

 common, often growing with Corynactis 



56 



