standardization of environmental data and information - International ...

phosphorus. In the oceanic environment, phytoplankton directly
assimilates dissolved inorganic phosphorus for use in the energy cycle of
the cell. Organic forms, particulate and dissolved, result from growth,
decomposition, and various excretions and secretions of living cells.
Phosphorus in tropical and subtropical surface waters, like nitrogen, is
present in relatively low concentrations, and dissolved inorganic and
organic phosphorus forms are assimilated as rapidly as they become
available. Roels et al. 56 comprehensively reviewed information on
phosphorus concentrations in the eastern tropical Pacific. Westward from
California along the North Equatorial Current, equivalent nutrient levels of
phosphate occur at increasing depths along and perpendicular to the axis of
the current. The nutrient maximum is larger and shallower in the east. The
phosphate maximum generally coincides with the oxygen minimum,
implicating regeneration of biological material as the nutrient source.
Phosphate concentrations in the area generally decline from the maximum
of 3-3.5 µm at 300-1200 m to a level of 2.25-2.5 µm at the bottom. Typical
concentrations in the DOMES data were about 0.32 µm in the mixed layer,
increasing to a maximum of about 3.0 µm between 800-1000 m and
decreasing slowly to about two-thirds of the maximum at the bottom 57 .
Trace compounds, or micronutrients, include metals and organic
substances such as vitamins and their precursors that are necessary for
algal growth. Values from a station to the north of the DOMES area (32 o 41'
N, 145 o 00' W) 58 show maxima in manganese concentrations at the surface
(0.62 nanogram-atom per kilogram) and in the oxygen minimum (0.71
nanogram-atom per kilogram). Copper and nickel concentrations increased
with depth.
Suspended particulate matter (SPM) includes living and non-living,
organic and inorganic particles. The non-living portion is called detritus.
However, even inorganic detritus has bacteria and other microorganisms
associated with it, and the term "organic aggregate" is sometimes applied.
SPM is an important component of the planktonic food web because it is
present in sizes commonly ingested by zooplankton. DOMES results 59
showed mixed layer concentrations of SPM of about 47 microns per litre
and maxima (to 110 µg/l) just above the thermocline. Concentrations
below 200 m were uniform at about 10 µg/l with a slight increase (to about
12 µg/l) within 400 m of the bottom. The inorganic fraction of the SPM
increased near the bottom, suggesting sediment resuspension by bottom
currents.
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