Water column

About: Water column is a research topic. Over the lifetime, 13706 publications have been published within this topic receiving 496626 citations.

Paleoenvironmental Changes in the Japan Sea During the Last 85,000 Years

Abstract: Five distinct changes in the paleoenvironment of the Japan Sea within the last 85,000 years are revealed from the sedimentary record of a piston core recovered from the Oki Ridge. Changes in both surface and deepwater conditions are registered by changes in lithology, calcium carbonate content, organic carbon content, oxygen and carbon isotope ratios, and microfossil assemblages including calcareous nannoplankton, diatoms, radiolaria, and foraminifera. Between 85 and 27 ka the warm Tsushima Current did not flow into the Japan Sea, and cold surface water conditions prevailed. Environments at the seafloor fluctuated between dysaerobic to weakly oxic conditions. Between 27 and 20 ka, freshwater input to the Japan Sea, probably from the Huang Ho River in China, stratified the water column, and the severe anoxic conditions eliminated most benthic fauna. Between 20 and 10 ka the cold Oyashio Current flowed into the Japan Sea through the Tsugaru Strait, reestablishing deepwater ventilation. Shallow water benthic assemblages of the North Pacific Ocean subsequently colonized the Japan Sea and occupied the vacant niches of the deep basins. Between 10 and 8 ka the foraminifer compensation level (FCL) gradually rose to a depth shallower than 1000 m, and bottom conditions changed from dysaerobic to oxic. At 10 ka the warm Tsushima Current started to flow into the Japan Sea through the Tsushima Strait to establish the modern oceanographic regime which has existed since 8 ka. The eustatic sea level during the last glacial maximum was above the sill depths (130 m) of the Tsushima and Tsugaru straits, assuming that tectonic movements at these straits were negligible for the last 20 ka.

The phytoplankton population as a compound photosynthetic system

Abstract: The ecological significance of the photosynthetic characteristics of planktonic algae has long been recognized. A simple application of these to the behaviour of natural populations is not possible, however, since the latter is normally governed by the average behaviour of cells continuously circulating within the strong vertical gradient of light intensity characteristic of natural waters. In this situation the unit of ecological significance can often be interpreted as the total population present below unit area of surface. The photosynthesis of this unit constitutes the total or integral photosynthesis in the water column concerned. Its properties are of direct ecological interest. Their relation to the photosynthetic characteristics of the algae present is discussed in this paper, and the influence of various environmental factors is considered. Here an analysis of the variation of photosynthetic rate with depth in the water column is first discussed in relation to an experimental study of the photosynthesis of a freshwater plankton diatom, Asterionella formosa Hass. A mathematical model (of which a preliminary account was given by Talling, 1955), describing the general case of integral photosynthesis in the water column, is attempted. Its application to ecological situations is illustrated by examples relating to the growth of Asterionella in Lake Windermere.