Loma. A succession of programs developed 

 to study southern California kelp forest 

 communities and to restore Macrocystis in 

 areas where it was formerly abundant. The 

 Institute of Marine Resources sponsored 

 programs from 1956 to 1963; the Kelp 

 Habitat Improvement Project investigated a 

 number of problems from 1964 to 1976; and 

 recently, the California Department of 

 Fish and Game assumed responsibility for 

 restoring coastal habitats (see Chapter 

 6). In addition, this work became partic- 

 ularly concerned with the interactions of 

 sea urchins and kelp (North 1983a). Dense 

 aggregations of sea urchins dislodged 

 Macrocystis plants that subsequently 

 drifted away (Leighton 1971). The major 

 problem is that once plants have been 

 removed by any cause, drift material de- 

 clines, sea urchins apparently begin to 

 forage actively for food, and this 

 intensive grazing may prevent the re- 

 establishment of kelp populations for some 

 time (see Chapter 5). This has resulted 

 in many programs to destroy sea urchins 

 (Wilson and McPeak 1983). 



The problems of controlling and 

 managing what was seen as a resource 

 eventually highlighted the need for work 

 to assess the importance of other factors. 

 In addition, recent work on giant kelp 

 forests in central California (Pearse and 

 Hines 1979, Cowen et al. 1982, Foster 

 1982a), South America (Barrales and Lobban 

 1975, Santelices and Ojeda 1984a, b), and 

 southern California (Dean and Deysher 

 1983, Dayton et al. 1984) has begun to 

 provide a broader perspective on the 

 ecology of these communities. Table 1 

 presents a summary of factors which have 

 been suggested or observed to affect the 

 presence and abundance of kelp plants (see 

 Chapters 2, 3, and 4 for details). The 

 effects of most of these are not known, 

 except in broad outline. The basic 

 resources of space, light, and nutrients 

 may be altered by differing biotic and 

 abiotic conditions. Moreover, we have 

 little idea of how different levels or 

 combinations of these factors affect plant 

 recruitment, growth, reproduction, and 

 survival. These issues are discussed in 

 detail in the following chapters. 



Table 1. Factors influencing giant kelp forest algal populations with emphasis on 

 Macrocystis pyrifera in California. 



Factor 



Influence 



Substratum 



Sedimentation and 

 sand movement 



Required for attachment 



Hardness related to mortality due to water motion 

 Topographic heterogeneity correlated with distribution and 

 diversity 



Attachment and survivorship, especially of microscopic life stages 



Burial of all or portions of organisms 



Scour 



Light: 

 Amount 

 Quality 



Water motion 



Temperature 

 Nutrients 



Survival and growth of plants, at least 1% of surface for kelps 

 Gametogenesis in kelps 



Plant and animal loss in surge and currents 

 Distribution of food (plankton and detritus) 

 Nutrient availability and uptake 



Growth and fertility of plants and animals 



Growth of benthic plants (and phytoplankton) 



(continued) 



7 



