Sea Otters, Sea Urchins, and Kelp Beds: Some Questions of Scale

Estes, J.A.; Harrold, Christopher

doi:10.1007/978-3-642-72845-7_6

Cited by 13 publications

(8 citation statements)

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“…In the Northeast Pacific, the emphasis has been on a particular predator, the sea otter. This interaction has been generalized as 'extremely' or 'most' important in organizing kelp assemblages in this region (Estes & Palmisano, 1974;Dayton, 1975b;Duggins, 1980), and appears to have achieved the status of a paradigm (Estes & Harrold, 1988;Levin, 1988). As such, it has been incorporated into the popular literature, ecology texts, ecological reviews (e.g.…”

Section: Algal Abundance In Subtidal Kelp Assemblagesmentioning

confidence: 99%

Organization of macroalgal assemblages in the Northeast Pacific: the assumption of homogeneity and the illusion of generality

1990

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Evidence for the geographic generality of the causes of intertidal zonation and the indirect effects of a 'keystone' predator, the sea otter, on subtidal kelp assemblages was examined. Most research on intertidal algal assemblages has been done at a few protected sites where zonation is distinct. Surveys of wave-exposed intertidal sites in central and northern California show that assemblage structure is highly variable. This indicates that our present understanding of assemblage organization, including the effects of mussel-algal interactions, may not be widely applicable. Surveys of kelp forest habitat along the entire coast of California suggest that deforestation by sea urchins is uncommon in the absence of sea otters. These examples indicate that the generality of commonly accepted causes of algal assemblage structure in the Northeast Pacific may be an illusion based on assumptions of environmental homogeneity.

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Section: Algal Abundance In Subtidal Kelp Assemblagesmentioning

confidence: 99%

Organization of macroalgal assemblages in the Northeast Pacific: the assumption of homogeneity and the illusion of generality

1990

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“…Although predation by sea otters in central California and elsewhere is highly influential (Estes & Palmisano 1974, Estes et al 1978, Duggins 1980, Breen et al 1982, VanBlaricom 1984, Estes & Harrold 1988, it is unlikely that sea otters were responsible for the decline of Strongylocentrotus purpuratus on the Outer Pinnacles. The sea otter population of the Carmel Bay area did not change substantially during this period (R. Jameson, US Fish & Wildlife Service unpubl.).…”

Section: Sea Urchin Population Dynamicsmentioning

confidence: 99%

“…Forests of giant kelp Macrocystis pynfera are productive, dynamic comunities in which physical factors such as storms and biological factors such as predation and competition play important roles (see Foster & Schiel 1985, Dayton 1985, Schiel & Foster 1986, Estes & Harrold 1988 for recent reviews).…”

Section: Introductionmentioning

confidence: 99%

Destructive grazing by sea urchins Strongylocentrotus spp. in a central California kelp forest: potential roles of recruitment, depth, and predation

Watanabe¹,

Harrold²

1991

Mar. Ecol. Prog. Ser.

105

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In January 1986, a sea-urchm mediated deforestation began in C a m e l Bay, California. USA, near the center of the California sea otter's range. The deforestation occurred on a n offshore rocky reef where depths range from l ? to > 30 m. Both purple (Strongylocentrotus purpuratus) and red (S. franciscanus) sea urchins were abundant and probably belonged to a cohort that settled in 1984. By October 1986, nearly all non-crustose algae had been removed, as were most sessile invertebrates (excluding the cnidarians Balanophyllia elegans and Corynactis californica). Concurrent samples taken from 2 nearby forested sites at comparable depths showed no evidence of overgrazing by urchins. Populations of red sea urchins at the deforested site remained fairly stable, but purple sea urchins declined to zero by July 1989. Algal spores were available during the deforestation, but recruitment of seaweeds d d not occur until after sea urchln abundance had decllned Reasons for the decline of the purple sea urchin population are not clear, although predation by sea otters 1s unlikely. Circumstances surrounding these events indicate kelp forest deforestations may b e controlled not only by mortality of adult sea urchins (from predation or disease) and fluctuation of their food supply, but also by factors affecting recruitment such a s larval abundance and early post-settlement sunrival.

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“…For example, in the species-rich kelp forests off California, sea urchins may overgraze kelp in some areas (Lawrence, 1975;Harrold & Pearse, 1987) while extensive parts of the coastline suffer no large-scale effects (Foster & Schiel, 1988). 'Stabilizing predatory relationships' (Dayton, 1985) by sea otters (Estes etal., 1978;Estes & Harrold, 1988), fishes (Bernstein etal., 1981;Tegner & Dayton, 1981;Cowen, 1983), crabs and lobsters (Breen & Mann, 1976a;Bernstein et al, 1981;Wharton & Mann, 1981;Tegner & Levin, 1983) may diminish the effects of sea urchins by reducing their abundance. In the kelp forests of Chile, where only a few kelp species are present, sea urchins do not seem to graze extensively on attached plants (Moreno & Sutherland, 1982;Dayton, 1985) and algal interactions may strongly influence the structure of algal stands (Santelices & Ojeda, 1984).…”

Section: Introductionmentioning

confidence: 99%

Macroalgal assemblages in New Zealand: structure, interactions and demography

Schiel¹

1990

Hydrobiologia

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Quantitative descriptions of macroalgal distributions from low intertidal regions to a sublittoral depth of 20 m are presented for rocky reefs from several localities ranging over 16°latitude in New Zealand. These include the northern and southern main islands as well as the Chatham Islands and the sub-antarctic Auckland Islands. Fucalean algae are dominant in the shallow sublittoral regions throughout NZ. Laminarian species are rare and generally reach their greatest abundances at 7-17 m depth. The colder waters in central and southern NZ tend to have different dominant species from those in northern NZ. Sea urchins form a characteristic zone devoid of kelp at 5-8 m in the north, but tend to occur only in patches on reefs in southern localities. Summaries of experiments in the north show that strong interspecific effects occur among algal species, particularly due to canopy shading, and between sea urchins and algae. Much of the patchiness in algal assemblages, however, is not accounted for by these effects. A knowledge of the demographic processes of individual species is necessary to understand assemblage organization; life histories, phenology and biogeography significantly affect distributions and interactions.

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Sea Otters, Sea Urchins, and Kelp Beds: Some Questions of Scale

Cited by 13 publications

References 0 publications

Organization of macroalgal assemblages in the Northeast Pacific: the assumption of homogeneity and the illusion of generality

Organization of macroalgal assemblages in the Northeast Pacific: the assumption of homogeneity and the illusion of generality

Destructive grazing by sea urchins Strongylocentrotus spp. in a central California kelp forest: potential roles of recruitment, depth, and predation

Macroalgal assemblages in New Zealand: structure, interactions and demography

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