THE INVERTEBRATE ASSEMBLAGE ASSOCIATED WITH THE 



GIANT KELP, MACROCYSTIS PYRIFERA, AT SANTA CATALINA 



ISLAND, CALIFORNIA: A GENERAL DESCRIPTION WITH 



EMPHASIS ON AMPHIPODS, COPEPODS, MYSIDS, AND SHRIMPS 1 



James A. Coyer 2 

 ABSTRACT 



The motile invertebrate assemblage associated with the giant kelp, Macrocystis pyrifera, fronds was 

 examined monthly from June 1975 through December 1976, at Santa Catalina Island, California. Replicate 

 samples were collected from each of three vertical zones (canopy |C|, middle [M|, bottom [B]). 



The number of species collected from all zones was 114 and ranged from 51 to 75 for any given month. 

 Amphipods, copepods, mysids, and shrimps comprised the majority of invertebrate abundance (86 [C], 92 

 [M], 93 f ; |B|) and biomass (90 [C|, 89 [M|, 86 f i [B]). Gammarid amphipods dominated the assemblage in 

 numbers (34 [C|, 60 [M], 519? |B]), biomass (34 [C|, 68 [M], 67% [B]), and number of species (20). 



The assemblage displayed three patterns of vertical stratification within the Macrocystis forest: 1) The 

 mean number of species progressively decreased from the bottom to the canopy (several species displayed 

 zone preferences); 2) more individuals and a greater total biomass were present in the lower zones than in the 

 canopy; and 3) the mean lengths of gammarids, mysids, and shrimps were significantly larger and propor- 

 tionately greater numbers of large individuals were present in the canopy than in either of the lower 

 zones. 



Subtidal forests of giant kelp have long attracted the 

 interest of biologists, beginning with Darwin's (1860: 

 240) description of the organisms associated with the 

 giant kelp forests off Tierra del Fuego. Since the 

 advent of scuba techniques in the mid-1950's, 

 several studies have examined in detail the attached 

 and/or motile species of invertebrates associated 

 with surfaces of the giant kelp, Macrocystis pyrifera 

 (Limbaugh 1955; Clarke 1971; Ghelardi 1971; Jones 

 1971; Wing and Clendenning 1971; Miller and 

 Geibel 1973; Lowry et al. 1974; Bernstein and Jung 

 1979; Yoshioka 1982 a, b). Few, however, have 

 attempted a long-term and comprehensive examina- 

 tion of the entire assemblage of small and motile 

 invertebrates found with the giant kelp. The as- 

 semblage is important for several reasons, notably as 

 the major source of food for most fishes residing 

 within the kelp forests (see fish diet studies by Quast 

 1968; Hobson 197 1; Bray and Ebeling 1975; Hobson 

 and Chess 1976). 



The present report examines the composition, pat- 

 terns of vertical stratification, and seasonal dynamics 

 of the small and motile invertebrate assemblage 



'Contribution No. 37, from the Catalina Marine Science Center. 



: Catalina Marine Science Center (University of Southern Califor- 

 nia), Avalon, Calif.; present address: Division of Science and 

 Mathematics, Marymount Palos Yerdes College, Rancho Palos Ver- 

 des, CA 90274. 



associated with the fronds of M. pyrifera. A general 

 overview of the assemblage and a detailed examina- 

 tion of the amphipods, copepods, mysids, and 

 shrimps are presented. 



STUDY AREA 



The study area was Habitat Reef, located in Big 

 Fisherman Cove, Santa Catalina Island, Calif, (lat. 

 33°28'N, long. 118°29'W). Habitat Reef is a 

 fingerlike extension of bedrock ranging in depth from 

 2 to 18 m and is bounded on the three outer margins 

 by an expansive area of shelly debris substrate. The 

 western and northern sides of the reef slope sharply 

 to a depth of 20-25 m, whereas the eastern edge 

 slopes gradually to a shallower area ranging from 8 to 

 19 m. Water temperatures at Habitat Reef ranged 

 from 13.6° to 21.2°C during the study, warmest dur- 

 ing July through September and coolest from 

 December to February. 



The algal community of the shoreward portion (<3 

 m depth) of Habitat Reef was dominated by Phyllo- 

 spadix torreyi, Eisenia arborea, Cystoseira neglecta, 

 and Sargassum muticum (seasonally) . The outermost 

 portion (>3 m depth) was dominated by Macrocystis 

 and the understory algae in this area was sparse, 

 although small patches of Dictyopteris zonarioides 

 and C. neglecta were present in some areas. 



Manuscript accepted August 1983. 

 FISHERY BULLETIN: VOL. 82, NO. 1, 1984. 



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