Minerals Report - International Seabed Authority

Upwelling that occurs on the shelf, and highly rich marine life. Yet
another participant wanted to find out whether De Beers Marine had
conducted fish counts before mining started and then monitored the fish
to study migration patterns at the mines and in proximity to them.
In response to the question about the links with oceanographers
and meteorologists to assist in predicting windows of operation, Dr.
Corbett said that De Beers has a very wide network of links with the
scientific community. He said that De Beers Marine works extensively
with oceanographic units and that it considered this a fundamental
requirement in the establishment of a baseline for environmental work. He
pointed out that outside the military, De Beers Marine is probably the
highest resolution survey and mapping organization in the world. He said
that there is therefore a lot of interest in De Beers Marine to collaborate
with university research departments and to engage in activities such as
sonar development high-resolution Chirp development. He also said the
MARIDAN project was borne of that kind of sort of alliance and
collaborative interaction.
With regard to the question on how far down the water column to
dispose of tailings, Dr. Corbett said it is quite a complicated thing to
dispose of the tailings far down the water column. Additionally, he said
that it is uncertain whether there would be significant benefits from
disposing of the tailings close to the seabed. He said that this was an issue
to be investigated along with a few others on the effects of the plumes
generated during mining. He pointed out however that the material that
formed the tailings was rather coarse, resulting in a rapid settling time.
As concerns the impact of plumes on marine life, Dr. Corbett
explained that there are two very active aspects to the dynamic Benguela
system. One is the upwelling and the other, the swells that are generated
in the southern ocean. He said that these cause turbulence and mixing in
the water column. He said that both factors were examined in detail. He
said that there is evidence to show that the turbidity increases in the water
column for a period but that one of the things that came through as well
was that the overall size range of the material in the plume is quite coarse,
so settling is quite quick. He said that the measurements show that the
overall effect on the water column is limited to less than a kilometre away
from any one vessel at any one time. He described this as a very smallscale
effect, and not a dramatic effect on the water column.
INTERNATIONAL SEABED AUTHORITY 663