condition of particular forests will 

 probably be confused, and correlations 

 with one event or the other could be 

 misleading. Good descriptive studies at a 

 variety of sites, combined with experi- 

 mental tests of hypotheses and demographic 

 analyses that include monitoring of 

 environmental variables, appear most 

 appropriate for unravelling the complexi- 

 ties of kelp forest ecology. However, 

 even this approach can be confounded by 

 historical events, making the interpre- 

 tation of present patterns difficult 

 (Dayton and Tegner 1984a). 



Listed below are generalizations 

 about the ecology of giant kelp forests 

 that have emerged from our review of the 

 literature, along with suggestions for 

 future studies. For reasons discussed at 

 length in Chapter 5, these generalizations 

 should be considered working hypotheses. 

 They are made in the context of within the 

 geographic range of Macrocystis pyrifera 

 and within the limits of temperature, 

 salinity, nutrients, and light necessary 

 for giant kelp to persist. They apply to 

 the entire life histories of the species 

 involved. 



1. The primary requirement for the 

 existence of a kelp forest is hard sub- 

 strata (Chapter 2). Lack of hard 

 substrata commonly accounts for the 

 absence of the community within depths, 

 and often determines the deeper, offshore 

 boundary of the community. More studies 

 are needed on the effects of sedimentation 

 and burial on community structure and 

 dynamics. 



2. Extreme water motion associated 

 with storms is very important to community 

 structure in central California, and 

 occasionally important in southern 

 California (Chapters 2 and 3). Storms 

 commonly remove canopies and entire 

 plants, can directly or indirectly lead to 

 the invasion and proliferation of species 

 other than Macrocystis , and may determine 

 the shallow, inshore boundary of giant 

 kelp distribution. Water motion also has 

 important effects on the abundance and 

 behavior of other species. Studies are 

 needed to determine the relationship of 

 holdfast structure, frond abundance, and 

 frond size to mortality of Macrocystis 

 during periods of extreme water motion. 



3. Local differences in light, 

 caused by changes in abiotic conditions 

 and, more especially, by various canopy 

 layers, have a profound effect on algal 

 growth and recruitment and probably the 

 deeper, offshore boundary of giant kelp 

 distribution (Chapters 2 and 3). Coordi- 

 nated laboratory and field studies of the 

 light requirements for species other than 

 Macrocysitis are needed, as are studies of 

 the relationship between variations in 

 light characteristics and the distribution 

 of plant species within a kelp forest. 



4. Variability in temperature and 

 nutrients affects community structure, 

 particularly in southern California 

 (Chapter 2). The effects of these abiotic 

 factors on organisms other than Macro - 

 cystis need further study. 



5. Spore and larval dispersal are 

 important to population and community 

 structure (Chapters 3, 4 and 5). Studies 

 of dispersal and its effects on community 

 structure and dynamics are few and 

 difficult to do, but essential to our 

 understanding of kelp forest ecology. 



6. Some grazers, particularly sea 

 urchins, have large, local effects on the 

 community by removing algae and preventing 

 recruitment (Chapters 3 and 4). Grazers 

 may alter species assemblages, allowing 

 invasion and dominance of species differ- 

 ent from those consumed. More information 

 is needed on the distribution and abun- 

 dance of sea urchins within areas and 

 among broader areas of coastline to 

 provide a context for their effects. 

 Information is also needed on the effects 

 of grazers other than sea urchins (e.g., 

 small crustaceans, Patiria miniata ). 



7. Sea otters cause reductions in 

 invertebrate densities, particularly those 

 of sea urchins and abalone (Chapters 4 and 

 5); reductions in the numbers of sea 

 urchins can cause an increase in kelp and 

 other foliose algae. The spatial scale of 

 these increases will vary depending on the 

 distribution, abundance, and behavior of 

 sea urchins prior to their reduction. The 

 relationship between sea otter foraging in 

 California and the "health" and "stabil- 

 ity" of kelp communities needs to be 

 examined in both the general and local 

 contexts of grazer effects without otters, 



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