Environmental Engineering Reference
In-Depth Information
a few meters below the surface (near the top of the shallow pycnocline); this
phenomenon was more pronounced at M8 that had a thicker surface mixed layer.
The other notable difference between the two stations was that the chlorophyll
a
concentration declined rapidly below the oxycline at M8 but not at M1A. This
could be attributed to the preservation of chlorophyll in anoxic waters. In spite of
the prevalence of anoxic conditions at very shallow depths, column-integrated
primary production at M1A (1.47 g C m
−
2
d
−
1
) was comparable with that at
M8 (2.15 g C m
−
2
d
−
1
).
Figure 7.
Vertical profiles of temperature, salinity, O
2
,NO
3
−
,NH
4
+
,H
2
S, primary productivity
and chlorophyll
a
at Sta. M1A located over the inner shelf off Mangalore (13
o
08'N, 74
o
38'E;
water depth 27 m; date of sampling 19/9/2001).
Since an observable suboxic layer did not exist above the anoxic bottom
water, as a possible consequence of the thin oxygenated surface layer containing
negligible amounts of NO
3
−
and NO
2
−
at Sta. M1A, PP at this station should
have been fuelled entirely by NH
4
+
. This represents an unusual situation since,
