CHAPTER 4 



NATURAL HISTORY AND ECOLOGY OF 

 KELP FOREST ORGANISMS 



The number of living creatures of all Orders whose existence 

 intimately depends on the kelp is wonderful. Darwin (1860). 



4.1 INTRODUCTION 



This chapter discusses most of the 

 common species of algae, invertebrates, 

 fish, birds, and mammals that frequent 

 Macrocystis forests or are an integral 

 part of them along the west coast of North 

 America. Where relevant, we also include 

 comparisons with other regions of the 

 world. This chapter is not meant to 

 provide comprehensive species checklists 

 of the organisms which may occur in kelp 

 forests; these may be obtained from other 

 sources referred to in the appropriate 

 sections below. Rather, we discuss the 

 natural history of many species and 

 they may function in, or contribute 

 the structure of kelp forests 

 particular localities. We divide 

 ubiquitous and diverse benthic inverte- 

 brates and seaweeds into functional 

 categories, grouping species which we 

 subjectively judge to have similar effects 

 on the other species present. These 

 categories are then 

 taxonomic groups, 

 decomposers and diseases 

 separate sections, as are 

 mammals. 



how 



to, 



in 



the 



separated into 

 Plankton and 

 are treated in 



fish, birds, and 



4.2 PLANKTON AND DECOMPOSERS 



As might be expected given the 

 diversity of large plants and animals in 

 giant kelp forests, attention has focused 

 on these, and relatively little is known 

 about the small plants and animals that 



constitute the planktonic assemblage in 

 the water. Clendenning (1971a) gave a 

 brief list of phytoplankton from the La 

 Jolla kelp forest, and Miller and Geibel 

 (1973) discussed the seasonal abundance of 

 various plankton groups (especially 

 zooplankton) in the kelp forest at Point 

 Cabrillo near Monterey, California. 

 Additional studies have examined 

 zooplankton in relation to fish feeding 

 (Hobson and Chess 1976, Bray 1981, Bray et 

 al. 1981) or migratory behavior (Hobson 

 and Chess 1976, Hammer and Zimmerman 1979, 

 Hammer 1981). There are no complete 

 identification guides. Cupp (1943) is 

 still the best available guide to the 

 diatoms, and the text by Newell and Newell 

 (1963) is useful for identifying the more 

 common phyto- and zooplankton. Parsons et 

 al. (1977) reviewed planktonic organisms 

 and the oceanographic processes that 

 affect them, and provide an excellent 

 bibliography. 



As shown in Figure 11, plankton may 

 be produced in the kelp forest or imported 

 (primarily from offshore). With the 

 exception of some mysids (discussed 

 below), few entirely planktonic organisms 

 (holoplankton) appear to be residents of 

 kelp forests; most are probably imported. 

 The kelp forest community produces 

 plankton in three general categories: 

 meroplankton--the spores, larvae, or 

 detached individuals (e.g., benthic 

 diatoms) of benthic organisms; demersal 

 zooplankton -- primarily small crustaceans 



43 



