m depth (Velimirov et al. 1977, Dieckmann 

 1980). Ecklonia maxima can create bare 

 substrata by the sweeping motion of blades 

 on a long and flexible stipe (Velimirov 

 and Griffiths 1979). Dieckmann (1980) 

 found that the growth rate of L. pal 1 ida 

 followed a seasonal cycle, with the 

 highest rate in early summer and the 

 lowest in winter. He also found that 

 plants at a deeper station (14 m) had 

 lower growth rates than those at 8-m 

 depth. He estimated that this species may 

 1 ive 9+ years. 



Some of the longer-bladed 

 Laminariales from Japan can form surface 

 canopies in shallow water. Species of 

 Laminaria and Undaria are also extensively 

 cultivated (Hasegawa and Sanbonsuga 1972). 

 The biology of these species is well known 

 (Saito 1972), but there is little 

 information on field populations. 



4.3.4 Bottom Canopy Species 



4.3.4.1 Fleshy and filamentous 

 species . There are hundreds of species of 

 fleshy and filamentous algae found in kelp 

 forests, but only the more common species 

 for which we have some ecological 

 information will be discussed and 

 illustrated. Dawson et al. (1960) 

 described many species; North (1971a) 

 provided a list of those most common in 

 southern and Baja California, Mexico, 

 while Devinny and Kirkwood (1974), Pearse 

 and Lowry (1974), Foster et al . (1979a), 

 and Abbott and Hollenberg (1976) listed 

 species from central California. 



There are several studies from 

 California that show some of the effects 

 of overstory plants on bottom canopy 

 species, and also the effect of these 

 bottom canopy species on the recruitment 

 of other species. Kastendiek (1982) found 

 at Santa Catalina Island that the red alga 

 Pterocladia capil lacea was abundant under 

 a canopy of Eisenia . If this canopy was 

 removed, the fucoid Halidrys dioica was 

 able to spread adventitiously and exclude 

 Pterocladia . Pterocladia could flourish 

 outside of canopies if Hal idrys was 

 prevented from preempting space. 

 Pterocladia capillacea appeared in this 

 case to act as a refuge species, occupying 

 substrata under canopies of Eisenia where 

 Hal idrys could not flourish. 



Several studies by Foster and his 

 co-workers in California have paid 

 particular attention to bottom canopy 

 species as important members of kelp 

 communities (Foster 1982a). Foster 

 (1975a) placed these species into three 

 groups for a study at Santa Cruz Island 

 (Figure 16). Ephemerals included species 

 such as the brown alga Colpomenia that 

 rapidly colonized free space, but were 

 seasonal in their appearance and 

 disappearance. Perennials with rapid 

 growth included the reds Pterosiphonia 

 dendroidea and Rhodymenia cal ifornica 

 (Figure 17), which were seasonal in their 

 colonization of space, but could persist 

 through time. Perennials with slow growth 

 included Gi gar tin a spp. (Figure 17), and 

 the corallines (Plate IF), which were very 

 slow to colonize space, but could persist 

 for several years. Colonization by these 

 species varied with season, with most 

 having either a spring-summer or autumn- 

 winter period of maximum reproduction 

 (Figure 16). Foster (1975b) found that 

 the presence of an overstory could reduce 

 algal diversity and the percentage cover 

 of species below. 



Following the removal of Macrocystis 

 canopies near Santa Cruz, the annual brown 

 alga Desmarestia 1 igulata var. 1 igulata 

 (Figure 17) became locally abundant during 

 spring and summer (Cowen et al . 1982; 

 Foster 1982a). Reed and Foster (1984) 

 also found that this species became 

 abundant when Macrocystis and Pterygophora 

 canopies were removed. It was 

 particularly abundant, however, in 

 treatments where the branches of 

 articulated coralline algae were also 

 removed. Desmarestia spp. may reach a few 

 meters in length, but do not have erect 

 stipes to hold fronds above the 

 substratum. During the summer months, the 

 canopy of this species may completely 

 cover the bottom in some local sites, 

 particularly in areas where winter storms 

 have removed Macrocystis and Nereocystis 

 (Foster 1982a, Cowen et al. 1982, Reed and 

 Foster 1984). 



Other species may also have an annual 

 cycle. The fleshy red algae Polyneura 

 latissima , Plocamium cartilagineum , 

 Botryoglossum farlowianum (Figure 17, 

 Plate 2D) , and Phycodrys setchelli i are 

 particularly abundant during summer in 



52 



