Diel variations of marine snow concentration in surface waters and implications for particle flux in the sea |
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| Institution: | 1. Marine Environmental Sciences Consortium, Dauphin Island Sea Lab., 101 Bienville Blvd., Dauphin Island, Alabama 36528, USA;2. Marine Science Institute, University of California, Santa Barbara, CA 93106, USA;3. Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106, USA;1. Faculty of Science and Engineering, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan;2. Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan;3. Graduate School of Environmental Science, Hokkaido University, N10W5 Sapporo, Hokkaido 060-0810, Japan;4. National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan;5. Research and Development Center for Global Change, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 3173-25, Showa-machi, Kanazawa, Yokohama, Kanagawa 236-0001, Japan;6. Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan;7. National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan;8. Graduate School of Environment and Information Science, Yokohama National University, 79-7, Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan;1. Key Laboratory of Freshwater Aquatic Genetic Resources, Ministry of Agriculture, Shanghai 201306, China;2. Shaoxing University, Shaoxing 312000, China;3. National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai 201306, China;4. Shanghai Engineering Research Center of Aquaculture, Shanghai 201306, China;1. Department of Ocean Sciences, Tokyo University of Marine Science and Technology, Minato-ku, Tokyo 108-8477, Japan;2. Public Health Foundation of India, Delhi NCR 44, Gurgaon 122002, India;3. Marine Ecosystem Dynamics Research Group, Research and Development Centre for Global Change, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi, Kanazawa-ku, Yokohama 236-0001, Japan;4. Department of Mathematics, Institute of Science, Banaras Hindu University, Varanasi 221005 India;1. Fisheries and Quantitative Sciences Branch, Australian Bureau of Agricultural and Resource Economics and Sciences, 18 Marcus Clarke Street, Canberra, ACT 2601, Australia;2. School of Physical, Environmental and Mathematical Sciences, UNSW Canberra, PO Box 7916, Canberra BC, ACT 2610, Australia |
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| Abstract: | Successive measurements of the size distribution and abundance of marine snow in the upper 100 m of the Santa Barbara Channel, California, with an in situ still camera system following 11 tagged water masses revealed a consistent pattern of nighttime decreases in the abundance of large particles. A net nocturnal reduction in particulate flux from the upper 100 m as calculated from camera profiles occurred in 75% of the day–night comparisons, and nighttime aggregate carbon losses resulted in a 38% average reduction in camera-derived aggregate flux. Intensive investigation of three stations for 24–48 h each indicated that nighttime decreases in aggregate concentrations and derived aggregate flux could be registered throughout the observed water column. Nocturnal decreases in marine snow concentration are unlikely to result from diel variations in the production of marine snow either as feeding webs of zooplankton or through variations in aggregation rates of smaller particles. Moreover, measured diel variations in the intensity of surface mixing and convective overturn during one of the 24 h deployments were not intense enough to produce aggregate fragmentation and reduced aggregate flux. Nighttime increases in large crustacean zooplankton (i.e., euphausiids and the large copepod Calanus pacificus) could explain some or all of the reduction in aggregate abundance at most stations. Fragmentation and consumption of marine snow by migrating macrozooplankton could produce our observed synchronous diel cycles in marine snow concentration. This is the first empirical evidence of a diel pattern in the concentration and calculated particulate flux of large sinking particles in near-surface waters. The data presented here are consistent with the only other existing diel study, which also reported decreases in marine snow abundance at night at 270 m depths in the oceanic north Atlantic. Diel variations in the sizes and concentrations of marine snow may impact water column processes dependent upon particle availability and size, such as grazing and remineralization, and may generate a diel cycle of food availability to the benthos. |
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