Quarterdeck Volume 5, Number 2, Summer 1997
Phytoplankton in the water column
Sunlight and nutrient concentrations determine where phytoplankton
can survive. In a hypothetical scenario, nutrients might be equally available
at any depth. If this were true, phytoplankon might live near the ocean
surface where light is brightest.
In
reality strong sun at the surface slows the growth of some tiny plants,
and they actually live deeper in the water.
Phytoplankton use nutrients as they become available, keeping concentrations low at the depths where they reside. Plankton and other organic particles also sink, taking their nutrients to deeper waters. When phytoplankton exhaust available nutrients, the populations stop growing.
Light diminishes and disappears with increasing depth, and so do the tiny marine plants. Nutrient concentrations are greater in deep water where there are no phytoplankton to use them.
Individual species in various locations respond differently
to their environments, but in the Gulf of Mexico the water column generally
exhibits the nutrient concentrations, light levels, and phytoplankton abundance
illustrated here.
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