Section outline

    • Download sedimentation rate calculation sheet (Excel) Folder

      　The formula for Stokes sedimentation is now available in an excel sheet. Entering seawater and particle density, and temperature (viscosity depends on temperature), the sedimentation rate for each particle size can be calculated. It can also be output as a double-logarithmic graph. The yellow cells indicate where to enter numerical values in Excel, and the orange cells indicate where to output them.

      　Each person should enter the size of the phytoplankton, the size of the phytoplankton community, the number of attached mineral particles, and the density, and calculate how fast the particles will sediment. Incidentally, the size of mineral particles deposited from the atmosphere to the ocean generally falls in the range of 1 to 5 μm in radius (the most common is about 2 μm).

    • Download ocean density data (Reference) Folder
      　To calculate the sedimentation rate of the particles, we need to be given density data for the ocean. If you want to use actual density data, you can download it here. The results were observed at the 155°E line in the Northwestern Ocean during the Oshoro Maru oceanographic training (2016).

      　Chlorophyll concentration is also available. We can estimate how much phytoplankton was actually distributed and at what depth. If the chlorophyll concentration is below 0.05 μg/L, it should be considered almost zero. (This is below the lower limit of quantitation for chlorophyll analysis.)

      　All of the observation sites were at depths of about 5000 m. Some stations made CTD observations only down to 1000 m or 3000 m.


    • Theme: Please set up some theme and use the Stokes sedimentation equation to calculate and discuss particles sedimenting in the ocean (phytoplankton, zooplankton, zooplankton fecal particles, mineral particles deposited from the sky) and floating particles (e.g., TEP).

      Example of a theme: Phytoplankton floating in the ocean surface layer (either as individual particles or as aggregates) are exposed to mineral particles falling from the sky (in the North Pacific, Asian dust particles), which accelerate the sedimentation of phytoplankton particles, known as the "ballast effect". This is explained quantitatively using the Stokes sedimentation equation. The density of the seawater and the size and density of the phytoplankton and mineral particles should be set by the user. The average size of Asian dust particles is about 2 μm in radius. For the annual deposition of Asian dust particles and the number of its events, you should obtain information from the website of the Japan Meteorological Agency or other organizations and assume a certain amount.

      ※The "ballast effect" of Asian dust particles and their downward transport of organic matter is a puzzle even at the research level. There is no single correct answer.

      Example of a theme: Assume that the TEP produced by phytoplankton in the surface layer is floating in the surface layer as the same as the seawater density. If phytoplankton particles attach to it, can they drift through the surface mixed layer to the sub-surface layer immediately below? We look for that condition. If so, it will become food for eels migrating in the sub-surface layer.

      Example of a theme:       In carbon transport to the deep ocean, the effect of zooplankton predation on phytoplankton and their sedimentation and transport as fecal particles has attracted much attention. What types of phytoplankton are preyed upon by what types of zooplankton, and what types of fecal particles are transported to the deeper layers? Estimate and discuss using the Stokes sedimentation equation.
      　
      　Each of these themes is difficult to research level if you try to tackle them seriously. Each of you should summarize as much as you can within the limited time available.
    • Asian dust Aerosolpedia (from the Japan Association of Aerosol Science and Technology) URL

      The Japan Association of Aerosol Science and Technology has sent out information on Aerosolpedia. The annual deposition of Asian dust in western Japan is reported to be 10 g m-2. This is quite a large amount because of its proximity to the Chinese continent. In the open ocean area of the Pacific Ocean, the amount may be about one-tenth of that. Also note that this is an annual deposition amount.

    • Download "Mechanisms of Vertical Transport of Organic Matter in the Ocean : The Role of Fecal Grains in Vertical Transport (MATSUEDA & HANDA, 1984)" URL

      The shape and composition of organic particles collected in a sediment trap placed in the deep ocean were investigated, and they were assumed to be the feces of the large zooplankton, Salpa. Hydrocarbon composition was explored as an indicator substance for the fecal particles. This is a scatology paper.

    • Download "Sedimentation Fluxes of Diatoms and Silicoflagellates in the Western North Pacific, Bering Sea, and Arctic Ocean ~ (Ocean Research: ONODERA, 2012)" URL
      This is a commemorative paper for the Okada Prize of the Oceanographic Society of Japan. Since it is a commemorative paper, it is written about this and that. The paper also uses the results of a sediment trap moored at St. KNOT in the Northwest Pacific Ocean (where the Oshoro Maru goes for oceanographic training).

      There may be some hints for you to consider in your report assignment.


    • Download "~Time Series Variation of Diatom Shell Fluxes, ONODERA, Diatom (2014)" URL

      Here is another paper by Mr.ONODERA (JAMSTEC): JAMSTEC continues to observe moored systems at Station K2 in the Northwest Pacific subarctic region. The data are analyzed.

    • Download PDF file of "Marine Environment and Plankton (TANIGUCHI Asahi)" URL

      This is an article by Prof. TANIGUCHI (now at Tokyo University of Agriculture and Technology), an alumna of the Faculty of Fisheries, Hokkaido University. The article includes a chapter titled "Plankton that want to sink".


    • How to find Japanese-language literature 【J-stage】 Enter the [J-stage] website on the Internet.

      In the "Search Articles" search window, type, for example, "plankton sedimentation."

      You will get a lot of hits, but leave the search result display set to "Hit rate" and limit the display to "Journal" and "Peer-reviewed" from the tabs on the left side. You can then browse the titles in order from the top, or use the tabs on the left to further limit the search results by "field" or "name of material".

      For English-language papers, "Nature communications" and "Scientific Reports" are short, high-impact, open access journals published by Nature. A keyword search in the "Search" window of Nature's website will return results from all of Nature's journals. The articles marked "Open" are articles that can be downloaded by anyone.

      When you have time, search around and expand your interests.