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Blankenship, LE, Yayanos AA, Cadien DB, Levin LA.  2006.  Vertical zonation patterns of scavenging amphipods from the Hadal zone of the Tonga and Kermadec Trenches. Deep-Sea Research Part I-Oceanographic Research Papers. 53:48-61.   10.1016/j.dsr.2005.09.006   AbstractWebsite

Deep-sea trenches present an ideal system in which to study vertical zonation, though the difficulties inherent in studying these great depths have thus far deterred such research. Here, we present the first account of the structure and vertical zonation of the scavenging guild residing in the hadal habitat of the Tonga and Kermadec Trenches (SW Pacific Ocean). Four species of scavenging amphipod (Eurythenes gryllus, Scopelocheirus schellenbergi, Hirondellea dubia, and Uristes sp. nov.) were captured with baited free-vehicle traps set 1 m above the seafloor and deployed to bottom depths between 5155 and 10,787 m. Each species occupied a distinct vertical zone of 3.5 km or less, and the scavenging amphipod assemblage vertically partitioned the hadal zone. Scavenging amphipod diversity and evenness sharply declined below 9 km. For S. schellenbergi and H. dubia, population structure was stratified ontogenetically. Early instars appeared to reside exclusively in the shallower depths of each species' vertical zone, and were functionally missing from the median and deeper regions. We captured brooding Uristes sp. nov. females, documenting the first bait-attendance event of brooding amphipods in the hadal zone. Separation of habitat in conjunction with deviations in reproductive traits, behaviors, and nutritional strategies may facilitate the coexistence of these four related species in this harsh and confining habitat. (c) 2005 Elsevier Ltd. All rights reserved.

Smith, CR, Levin LA, Mullineaux LS.  1998.  Deep-sea biodiversity: a tribute to Robert R. Hessler. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 45:1-11.   10.1016/s0967-0645(97)00088-x   AbstractWebsite

Through extraordinary research and training of graduate students, Robert R. Hessler has profoundly influenced our knowledge of biodiversity in the deep sea. This special volume honors his contributions and presents recent advances in the study of deep-sea biodiversity on a broad range of topics. (C) 1998 Elsevier Science Ltd. All rights reserved.

Levin, LA, Childers SE, Smith CR.  1991.  Epibenthic, agglutinating foraminiferans in the Santa Catalina Basin and their response to disturbance. Deep-Sea Research Part a-Oceanographic Research Papers. 38:465-483.   10.1016/0198-0149(91)90047-j   AbstractWebsite

There are five common species of large (0.5-6 cm long) epibenthic, agglutinating foraminiferans in the Santa Catalina Basin (1200-1350 m). This paper describes their basic ecology and response to mound disturbance. Combined, the five species attain mean densities of 200-300 individuals per m2 and their protoplasm has an average biomass of 199.5 mg m-2. Individual species occur at densities ranging from 7 to 100 m-2, and each species has a different population size structure. Protoplasm comprises < 2% of test volumes. Analysis of excess Th-234 revealed no indication of particle sequestering within tests, and acridine orange direct counts of bacteria provided no evidence of microbial gardening or enhancement associated with tests. Twenty-five per cent of tests examined had metazoan associates; approximately half of these were polychaetes. Experiments were carried out to investigate the response of the epibenthic foraminiferal assemblage to disturbance from large, biogenic mounds, a common feature on the Santa Catalina Basin floor. Three branched forms, Pelosina cf. arborescens, P. cf. cylindrica and a mud-walled astrorhizinid, were most abundant on background sediments, less common on natural mounds and absent from artificially-created mounds exposed for 10.5 months. Two spherical species, Oryctoderma sp. and a different mud-walled astrorhizinid, were present at similar densities on artificial mounds (9.5-10.5 months old), natural mounds and undisturbed sediments, but Oryctoderma sp. attained largest sizes on mounds. These two species appear to be opportunistic taxa that can colonize and grow rapidly on mound sediments. This study suggests that disturbance, in this case that by sediment mound builders, is an important source of spatial heterogeneity in deep-water foraminiferal communities. Where sediment mounds occur, foraminiferal assemblages will experience disequilibrium dynamics.

Levin, LA.  1991.  Interactions between metazoans and large, agglutinating protozoans: implications for the community structure of deep-sea benthos. American Zoologist. 31:886-900. AbstractWebsite

Large, agglutinating protozoans belonging to the Foraminiferida (suborder Astrorhizina) and the Xenophyophorea are conspicuous, often dominant faunal elements in the deep sea. A review of known and suspected interactions between these forms and metazoans reveals a potentially significant role for the protozoans in structuring deep-sea metazoan assemblages. Direct interactions include provision to metazoans of (a) hard or stable substratum, (b) refuge from predators or physical disturbance, and (c) access to enhanced dietary resources. In some instances, rhizopod tests may provide a nursery function. Xenophyophore modification of flow regimes, particle flux, bottom skin friction and sediment characteristics appear likely and are believed to account for altered composition and abundance of meiofauna and macrofauna in the vicinity of rhizopod tests. Some analogous interactions are observed between metazoans and biogenic sediment structures in shallow water. However, metazoan-rhizopod associations are hypothesized to be more highly developed and complex in the deep sea than are comparable shallow-water associations, due to rhizopod abilities to enhance scarce food resources and to low rates of disturbance in much of the deep sea. Agglutinating rhizopods appear to be a significant source of heterogeneity on the deep-sea floor and large tests often represent 'hotspots' of metazoan activity. As such, they are hypothesized to have contributed to the origin and maintenance of metazoan diversity in the deep sea by providing distinct microenvironments in which species can specialize.