It remains unclear whether sites which 

 naturally feature dense stands of kelp are 

 simply environmentally favorable, while 

 sites with fewer plants reflect less 

 favorable conditions. The alternative is 

 that the density of the plants themselves 

 modifies the site. Of course, both of 

 these are possibilities in particular 

 circumstances, but they are relevant to 

 attempts at establishing kelp in areas 

 where it is now absent. 



4.3.2.2 Other species that form 

 surface canopies in California and Mexico . 



Nereocystis luetkeana (Figure 3) may occur 

 in both pure and mixed stands with 

 Macrocystis in that area of California 

 where their ranges overlap (Yellin et al. 

 1977). Most of the work on this species, 

 however, has been done north of Santa 

 Cruz, California, where it is the dominant 

 kelp which forms a surface canopy. This 

 species is an annual, and may form dense 

 stands to a depth of % 12 m in central 

 California (Foster 1982a). Nereocystis 

 usually occurs in more turbulent water 

 than Macrocystis , and Foster (1982a) and 

 Van Blaricom [Tn press) suggested from 

 their observations that bull kelp 

 populations may also be less affected by 

 sea urchin grazing. 



Duggins (1980) found that when dense 

 aggregations of sea urchins were removed 

 in Torch Bay, Alaska, a dense stand of 

 Nereocystis quickly recruited. This 

 species is an annual, however, and was 

 eventually replaced by perennial 

 laminarians. Nevertheless, dense stands 

 of Nereocystis occur year after year in 

 large areas of inshore waters, indicating 

 its ability to maintain space through 

 reseeding areas occupied by adult plants 

 (Duggins 1980, Foster 1982a). 



Inshore areas from the low intertidal 

 to a few meters depth are often inhabited 

 by dense stands of Egregia menziesii 

 (Figure 3), a species that can overlap in 

 depth distribution with Macrocystis 

 integrifol ia , but does not usually extend 

 into deep enough waters to affect the 

 abundance or distribution of M. pyrifera . 

 Black (1974) did a demographic study of E. 

 menziesi i in the intertidal zone near 

 Santa Barbara, from recruitment to 

 senescence. He found that the grazing 

 activities and the scars formed by the 



limpet Notoacmea insessa were a major 

 cause of frond breakage, and that the life 

 histories of these two species were 

 intimately associated (Black 1974). 



The outer edges of some kelp forests 

 in southern California are inhabited by 

 the elk kelp Pelagophycus porra (Figure 3, 

 Plate ID). Because it occurs in deep 

 water (18+ m) and is not generally 

 abundant, there is little known of its 

 biology. In a recent study, Hart (1982) 

 found that stipe elongation was density- 

 dependent. Plants in a 10 m 2 area at 

 1.4/m 2 grew significantly faster than 

 those in a 10 m 2 area at 0.25 plants/m 2 . 

 Plant blades were significantly larger, 

 however, in the less dense stand. Studies 

 by Parker and Bleck (1966) and Coyer and 

 Zaugg-Haglund (1982) indicate that this 

 species is an annual . 



Pelagophycus may be found at depths 

 to 30 m. Haptera are usually attached to 

 rock, but may spread to sand and gravel. 

 A population at Big Fisherman's Cove, 

 Catalina Island grows entirely on a sand 

 substratum. Stipes may reach lengths of 

 27 m, while the blades of mature 

 sporophytes may be up to 20 m long and a 

 meter broad (Abbott and Hollenberg 1976). 

 This species may have been more abundant 

 in the past; drifting plants were commonly 

 used as a navigational aid to Spanish and 

 Portugese mariners in the 1600' s, 

 signalling a change in a ship's course 

 before land was sighted (Dawson and Foster 

 1982). 



Cystoseira osmundacea (Figure 1) is a 

 perennial species in the Fucales that 

 cohabits inshore areas with Macrocystis 

 plants. A study in the Point Cabrillo, 

 Monterey kelp forest (Schiel in press a) 

 showed that single plants 6-9 m deep could 

 have 30+ fronds extending to the surface. 

 Although the plants are perennial, the 

 reproductive tissues and vegetative 

 structures which accompany them are highly 

 seasonal, appearing at the surface of the 

 sea between June and September. After 

 reproduction, these structures deteriorate 

 and break away, leaving the holdfast and 

 larger basal blades. In mid-summer 

 densities of 9 plants/m 2 may produce an 

 estimated 20% of the surface canopy in a 

 forest shared with Macrocystis . 

 Cystoseira osmundacea is depth-restricted, 



48 



