MARINE PHOSPHATE MINING – WHAT THE ASSESSMENT REPORT SAYS (II)
WINDHOEK, October 27 – One of the biggest questions in most people’s minds
regarding marine phosphate mining off the coast of Namibia is whether or not it
will damage the resources.
In recent days since the environment commissioner Teofelus Nghitila’s
clearance certificate granted on September 5 this year was made public,
there has been so much talk about marine phosphate mining.
Although there are three companies with marine phosphate mining licences in
Namibia, only one – the Namibia Marine Phosphate – has been the talk of the
A joint venture between Omani company Mawarid Mining LLC (85), and Namibian
company Havana Investments (15), Namibia Marine Phosphate wants to operate
Sandpiper Mine that is about 120 kilometres off Walvis Bay.
They are targeting a 700-kilometer stretch of the Atlantic Ocean.
To understand whether marine phosphate mining is harmful to fish resources
or not, Namibia Daily News has access to a March 2012 report compiled by Jeremy
Midgley of J. Midgley & Associates in conjunction with Enviro Dynamics on
behalf of Namibia Marine Phosphate.
This report can be found on www.namphos.com. The report contains comments
made by concerned citizens and organisations among them the Confederation
of Namibia Fishing Associations.
We are running the second part of the assessment report verbatim.
*The effects of redeposition of suspended material*
Release of nutrients by dredging and its direct/indirect effect on benthic
communities, and release of hydrogen sulfide from sediments during dredging.
Other specific concerns voiced during the Public Participation Process and
summarised in the Scoping Report are:
The removal of mats of large sulphur oxidising bacteria and associated
recovery rates; and
The possible proliferation of bacteria in an anaerobic environment,
specifically the botulism causing bacterium Clostridium botulinum , and its
subsequent contamination of fish and other wildlife (and possibly humans).
*Overview of affected environment*
Typical of coastal upwelling systems, the central Namibian shelf is
characterised by the occurrence of natural shelf hypoxia, which is referred
to as the oxygen minimum zone (OMZ).
On the Walvis Bay margin, there are two shelf breaks at about 150 m and 300
– 400 m depths, which effectively divide the shelf into an inner and outer
A significant feature of the central Namibian inner shelf is an extensive
mud belt comprising organically rich diatomaceous oozes originating from
planktonic detritus, which extends over 700 km in an NS direction in
approximately 50-150 water depth.
The mud belt is characterised by severe hypoxic and often anoxic conditions
and high toxic hydrogen sulphide (HS) concentrations in the upper sediment
layers that support extensive mats of large sulphur oxidising bacteria that
reduce the flux of HS into the water column by oxidising sulphide to
sulphur with nitrate to obtain energy.
Occasional HS eruptions from gas pockets contained in the thickest parts of
the mud belt (>8 m) can spread over large areas with disastrous effects on
fish and other marine life.
Put into a regional context, ML170 and specifically the two target mine
areas, are located in a generally sandy environment on the outer shelf
beyond the inner shelf break, and thus offshore of the diatomaceous mud
belt and south of a mid-shelf belt high in organic matter.
As ascertained from the available literature, organic matter as well as
nutrient concentrations in the sediments of the target areas are likely to
be relatively low, which is a result of relatively strong bottom
currents in this region, preventing the deposition of fine material. The
target phosphorite deposits in the licence area are pelletal phosphate
sands of Miocene age that are geographically distinct and have a different
origin than the concretionary phosphorite that presently forms in the
diatomaceous mud belt.
Furthermore, the licence area lies at the southern offshore fringe of the
OMZ, with perennial low dissolved oxygen levels (<0.5 ml/ℓ) at the bottom
but typically not anoxic conditions. Hydrogen sulphide pore water
concentrations, HS fluxes from the sediments and HS bottom water
concentrations are likely to be very low, but it cannot be excluded that HS
concentrations in deeper sediments (>50 cm) may be higher.
Despite oxygen depletion, specialised benthic assemblages can thrive in
OMZs and many organisms have adapted to low oxygen conditions by developing
highly efficient ways to extract oxygen from depleted water.
Within OMZs, benthic foraminiferans, meiofauna (animals between 0.11 mm),
and macrofauna (>1 mm) typically exhibit high dominance and relatively low
Macrofauna and megafauna (>10 cm) often have depressed densities and low
diversity in the OMZ core, where oxygen concentration is lowest, but they
can form dense aggregations at OMZ edges.
Body size seems to be very important as small organisms are best able to
cover their metabolic demands in the OMZ, and besides adaptation to low
oxygen often have a capability to conduct anaerobic metabolism.
Meiofauna may thus increase in dominance in relation to macro-and
megafauna. Nonetheless, although small organisms prevail, the species
inventory of OMZs comprises the whole range between micro-(>0.1 mm such as
bacteria) and megafauna. Very little is known about the benthic fauna
specific to the Namibian OMZ. Data from a macrofauna baseline survey in SP-
1 have shown that overall species richness of the benthic macrofauna
assemblages was relatively low and strongly dominated by polychaetes
particularly the spionid polychaete Paraprionospio pinnata, which is the
dominant species found worldwide in oxygen – constrained environments.
Crustaceans, on the other hand, were both in terms of abundance
and biomass very poorly represented. The phyla distribution is generally in
common with other OMZs around the world. Most species found in the study
area have a larger geographical distribution and/or have been recorded
elsewhere from the Namibian and/or South African west coast. No data exist
on meioor microfauna (bacteria) composition in the target areas , but
evidence from published data strongly suggests that concentrations of large
sulphur-oxidizing bacteria in the target areas are likely to be very low,
if present at all.
An assessment of the risks associated with the dredging activity identified
nine potential negative impacts on the benthic biota in the two target
areas or beyond. Of these, two impacts are considered to be of medium
significance, six of low significance, and one is assessed as having no