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productivity and bore consequences for aquatic health issues. One
possibility might be to monitor the water being pumped in order to predict
potential impacts on the water column.
For the protection of human health, metals were the main issue, not
anthropogenic toxins such as DDT or PCBs, whose concentrations in surface
layers at the bottom was sufficiently small that their remobilisation would
probably be insignificant. The release of metals could be great enough to
induce public concern about possible bioaccumulation. As there were
already advisories about mercury in tuna, if the public heard that lead was
being released into the water and getting into the fish, they might be quite
concerned. Thus, monitoring for metals would be important, not that he
expected dangerous concentrations but simply out of a desire to protect
public health.
The monitoring scheme Dr. Matisoff favoured, as laid out in Craig
Smith’s background paper (chapter 3 above), called for four moorings
spaced 50-100 km apart. One of the moorings would rise to within about
50 m from the surface, while the others, equipped also with current meters
for physical oceanographic monitoring, could be at depths of 1-3, 5, 15, 50
and 200 metres off the bottom and at 1.2-2 times the highest topographic
feature. Monitoring should occur in the oxygen-minimum zone as well.
Among the parameters to be monitored should be oxygen and total
organic carbon. He was not sure whether oxygen demand should be
examined, as it was not often studied in the marine world though it was
measured in the terrestrial environment all the time. Monitoring oxygen
demand would give a predictive capability by providing evidence of how
much organic matter or reduced components could be put into the water
column before driving the oxygen level down.
Frequency of sampling had to address seasonality problems. For
that reason he recommended a minimum of twice a year, though others
preferred four times.
Regarding sediment-water flux across the sediment/water interface,
the idea was to measure the components coming out of the bottom and
those resident in pore water. A Fickian diffusion calculation could be
employed to gauge the outward flux; though not very accurate, it was easy
to perform. Oxygen, nutrients and metals in the pore water should also be
monitored.
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