Geology Reference
In-Depth Information
Figure 11 The depth distribution of nitrate (
K
), phosphate (
'
), and silicate (
m
) in the
North Pacific Ocean
(Data from Bruland, 1980.
13
)
regenerated and their concentrations in deepwaters are much greater than
those observed in the surface waters, thereby accounting for the fertilising
effect of upwelling. It should be noted that the siliceous remains behave
differently than the calcareous shells discussed previously. The oceans
everywhere are under-saturated with respect to silica. Its solubility exhib-
its no pronounced variation with depth and there is no horizon analogous
to the CCD (see Section 4.2.2.3). Silica is preserved to any great extent
only in deep-sea sediments associated with the highly productive upwell-
ing zones in the ocean.
4.2.4 Trace Elements
Trace elements in seawater are taken to be those that are present in
quantities less than 1 mg L
1
, excluding the nutrient constituents. The
distribution and behaviour of minor elements have been reviewed in the
light of data that conform to an oceanographically consistent manner.
1,8
