Quarterdeck Volume 5, Number 1, Spring 1997
Particles in the water column
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1. Phytoplankton are microscopic marine
plants. They use chlorophyll to absorb light, which supplies the energy
they need to create living tissue out of carbon (C) and raw nutrients such
as nitrogen (N) and phosphorus (P). Phytoplankton are abundant near the
ocean surface, where there is plenty of sun. In these upper layers of the
water column phytoplankton are responsible for most of the light absorption
and scattering. When plankton die, their skeletons sink very slowly.
2. Tiny, slowly sinking particles sometimes stick together to form aggregates, and these larger clumps sink through the water more quickly.
3. When marine creatures feed on phytoplankton, they remove the tiny living particles from the water. In return they excrete waste products, including fecal pellets that sink quickly. The waste contains some of the same nutrients that the plankton initially incorporated. Waste particles sink to seafloor where the nutrients from suface waters are released in ocean sediments.
4. Instead of using photosynthesis to survive zooplankton eat phytoplankton near the sea surface. They repackage material into fecal pellets or transport it to deeper waters as they migrate throughout the water column.
5. Turbulence caused by currents and storms stirs up sediment from the ocean floor making the water cloudy. In this way buried nutrients re-enter the deepest layer of the water column. Resuspended sediments cause most of the light scattering in the deep ocean.
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