Biological Accommodation in the Benthic Community at McMurdo Sound, Antarctica

Studies of the benthos between 30 and 60 m at Cape Armitage, McMurdo Sound. Antarctica, reveal an epifaunal community in which sponges and their asteroid and nudibranch predators predominate. Field experiments demonstrated that, with the exception of Mycale accrata, the growth rates of the sponges are too slow to measure in one year. Mycale, however, was observed to increase its mass as much as 67%. Because of its more rapid growth rate, Mycale appears to be the potential dominant in competition for substratum space, the resource potentially limiting to the sessile species. This conclusion is supported by observations of Mycale growing over and, in some cases, apparently having smothered many other sessile species representing at least three phyla. The densities and size frequency distributions of all the predators were measured; numerous feeding observations allowed an accurate appraisal of dietary compositions. Because of the predators' very slow consumption rates, however, direct measures of ingestion and its impact on prey populations were not possible. Estimates of the ingestion rates were derived from measurements of predator respiration rates, growth rates, and gonad growth. Data from the field surveys and the energetics studies suggest that Mycale is prevented from dominating the space resource by the predation of two asteroids. Perknaster fuscus antarcticus and Acodontaster conspicuus. Adult Perknaster specialize on Mycale, and the sponge provides a small proportion of the diet of A. conspicuus. Acodontaster conspicuus and the dorid nudibranch Austrodoris memurdensis are the most important predators on three species of rossellid sponges (Rossella racovitzae, R. nuda, and Scolymastra joubini). Despite this relatively heavy consumption and despite the fact that none of these sponges has a refuge in growth from potential mortality from A. conspicuus, very large standing crops of the rossellid sponges have accumulated. This accumulation appears to result from predation on larval and young A. conspicuus and Austrodoris by Odontaster validus, which is primarily a detrital feeder and apparently acts as a filter against the settlement and survival of the A. conspicuus and Austrodoris larvae. In addition, predation upon adult A. conspicuus by O. validus and the actinian urticinopsis antarcticus annually kills approximately 3.5% of the A. conspicuus population. This mortality exceeds the apparent rate at which A. conspicuus escape the larval filter.

[1]  R. Paine.  A Short‐Term Experimental Investigation of Resource Partitioning in a New Zealand Rocky Intertidal Habitat , 1971 .

[2]  R. Paine.  Food Web Complexity and Species Diversity , 1966, The American Naturalist.

[3]  B. Maguire.  Phytotelmata: Biota and Community Structure Determination in Plant-Held Waters , 1971 .

[4]  P. Dayton,et al.  Role of biological disturbance in maintaining diversity in the deep sea , 1972 .

[5]  H. Welch.  Relationships between Assimiliation Efficiencies and Growth Efficiencies for Aquatic Consumers , 1968 .

[6]  R. Whittaker,et al.  Allelochemics: chemical interactions between species. , 1971, Science.

[7]  John L. Harper.  A DARWINIAN APPROACH TO PLANT ECOLOGY , 1967 .

[8]  P. Dayton.  Competition, Disturbance, and Community Organization: The Provision and Subsequent Utilization of Space in a Rocky Intertidal Community , 1971 .

[9]  D. J. Hall,et al.  AN EXPERIMENTAL APPROACH TO THE PRODUCTION DYNAMICS AND STRUCTURE OF FRESHWATER ANIMAL COMMUNITIES1 , 1970 .

[10]  P. Dayton,et al.  Feeding Behavior of Asteroids and Escape Responses of their Prey in the Puget Sound Region , 1968 .

[11]  C. Hubbs,et al.  The elementary chemical composition of marine organisms , 1955 .

[12]  S. Dodson.  COMPLEMENTARY FEEDING NICHES SUSTAINED BY SIZE‐SELECTIVE PREDATION1 , 1970 .

[13]  Frank A. Brown,et al.  Comparative Animal Physiology , 1951 .

[14]  P. Dayton,et al.  Anchor Ice Formation in McMurdo Sound, Antarctica, and Its Biological Effects , 1969, Science.

[15]  H. L. Sanders,et al.  Marine Benthic Diversity: A Comparative Study , 1968, The American Naturalist.

[16]  D. Culver,et al.  Diversity in Terrestrial Cave Communities , 1969 .

[17]  E. Zeuthen.  Oxygen Uptake as Related to Body Size in Organisms , 1953, The Quarterly Review of Biology.

[18]  Joseph H. Connell,et al.  A Predator‐Prey System in the Marine Intertidal Region. I. Balanus glandula and Several Predatory Species of Thais , 1970 .

[19]  T. Zaret.  Predator‐Prey Interaction in a Tropical Lacustrine Ecosystem , 1972 .

[20]  R. Paine.  Ash and Calorie Determinations of Sponge and Opisthobranch Tissues , 1964 .

[21]  Joseph H. Connell,et al.  Effects of Competition, Predation by Thais lapillus, and Other Factors on Natural Populations of the Barnacle Balanus balanoides , 1961 .

[22]  J. Caperon,et al.  Coral-Eating Sea Stars Acanthaster planci in Hawaii , 1971, Science.

[23]  D. Janzen.  Herbivores and the Number of Tree Species in Tropical Forests , 1970, The American Naturalist.

[24]  A. C. Giese,et al.  Annual reproductive cycles in four species of West Coast starfishes , 1958 .

[25]  S. Hemmingsen,et al.  Energy metabolism as related to body size and respiratory surfaces, and its evolution , 1960 .

[26]  J. Porter.  Predation by Acanthaster and Its Effect on Coral Species Diversity , 1972, The American Naturalist.