Comparison of pelagic and nepheloid layer marine snow: implications for carbon cycling期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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Comparison of pelagic and nepheloid layer marine snow: implications for carbon cycling

Authors:	Barbara Ransom Kevin F Shea Patti Jo Burkett Richard H Bennett Roy Baerwald

Institution:	^a Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0220, USA ^b Naval Research Laboratory, Stennis Space Center, MS 39529, USA ^c SEAPROBE Inc., 01 Pine Street, Picayune, MS 39566, USA ^d Department of Biology, University of New Orleans, New Orleans, LO 70148, USA

Abstract:	Marine snow from upper and mid-water (i.e., pelagic) depths on the California margin is texturally and compositionally different from that traveling in the nepheloid layer. Transmission electron microscopy shows that pelagic marine snow consists primarily of bioclasts (e.g., diatom frustules, foram tests), organic matter, and microbes. These components are entrained as discrete particles or small aggregates μm in diameter) in a loose network of exocellular, muco-polysaccharide material. Clays are infrequent but, when present, are constituents of comparatively compact organic-rich microaggregates. Microbes are abundant and appear to decrease in number with increasing water depth. In contrast, marine snow aggregates collected from just above the sea floor in the nepheloid layer are assemblages of clay particles, clay flocs, and relatively dense clay–organic-rich microaggregates in an exocellular organic matrix. Bioclasts and microorganisms occur only rarely. The prevalence of clay–organic-rich aggregates in the nepheloid layer suggests that, prior to final deposition and burial, marine snow from the pelagic zone is subject to disaggregation and recombination with terrigenous detrital material near or at the sea floor. Results have significant implications for the accumulation and burial rates of organic carbon on continental margins and the aging and bioavailability of sedimentary organic matter. Samples examined were collected offshore of northern and central California.

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