Deep Sea Mining

Question 1

What is the DISCOL experiment?

Answer 1

DISturbance and reCOLonization experiment (DISCOL) took place in 1989 in the Peru Basin

Question 2

What are the impacts of the DISCOL experiment? Longevity?

Answer 2

Effect on Peru Basin megabenthos evident after 26 years:
* Suspension-feeder presence remained reduced in disturbed areas
* deposit-feeders showed no diminished presence
* lower heterogeneity/diversity in disturbed areas and markedly
distinct faunal compositions
Historical Impacts Study:
* Plough tracks were still visible
* Microbial activity was reduced up to fourfold in the affected areas.
* Cell numbers were reduced by ~50% in fresh “tracks” and by <30% in the old tracks.
* Growth estimates suggest that microbially mediated biogeochemical functions need over 50 years to return to undisturbed levels.

Question 3

What are the general impacts of deep sea mining?

Answer 3

• Ambient noise & light
• Reinjection of deep seawater
  into the water column
• Removal of hard nodule surface
• Sediment plume suspension
  and redeposition
• UNKNOWNS: How will this
  affect biodiversity?

Question 4

What are the advantages of mining on land vs. the seabed? Disadvantages?

Answer 4

Issues with land sources:
Land intensive
* Deforestation
* Depletion of biodiversity
* Disruption of carbon sequestration
Inefficient
* .006% yield of metal from metal ore
* 64,000 kg material à 25,000 kg ore à 155 kg metal
* Lots of solid waste
* Tailings dams –> FOREVER cost
Toxicity
* Tailings dam malfunction
* Water pollution
* Air pollution
Humanitarian Issues
* Labor Issues (illness, death, child labor, exploitation)
* Geopolitics
* Cultural displacement

Advantages of using Polymetallic nodules
–>EFFICIENCY
* No tailings, residues or toxic wastes
* Stable high grade ores
* 75% less total material needed to process the
SAME amount of metal as land-based ore
Ambient noise & light

Disadvantages of using them
* Reinjection of deep seawater
into the water column
* Removal of hard nodule surface
* Sediment plume suspension
and redeposition
* UNKNOWNS: How will this
affect biodiversity?

ADVANTAGES
High grades
Little social displacement
Little impact on freshwater
Neutral strip ratio (for now)
Logistics
Opportunity for developing economies
71%; most states coastal; strategic source
Exploring underexplored environments

DISADVANTAGES
Challenging setting
No precedent, oil closest example
Site access, engineering, difficult monitoring
Environment not definitively characterized
Restoration?
Processing
Mining = $$ => difficult to evaluate all impacts empirically
without committing to the process

Question 5

What are the 1st resource of the big 3 of deep sea mining? And where might you find them?

Answer 5

• Polymetallic (aka manganese, ferromanganese) nodules
  > Most often associated with abyssal plain far from
  continents and near/below the CCD
  > NEED TO HAVE LOW SEDIMENTATION RATE
  > CCZ, PEN, PB, Cook Islands EEZ

Question 6

What are the 2nd resource of the big 3 of deep sea mining? And where might you find them?

Answer 6

• Crusts (cobalt-rich crusts)
  > Major focus in western Pacific
  > On seamounts (Indian Ocean Ridge)

Question 7

What are the 3rd resource of the big 3 of deep sea mining? And where might you find them?

Answer 7

• Sulfides (aka seafloor massive sulfides & including
  epithermal)
  > Temp and depth impact formation, metal endowment [arc volcanism or crust divergence (or mantle plumes)]
  > Smokers are interesting and ephemeral
  > Chimneys can grow fast
  > SMS = youngest, fastest growing of ‘big 3’
  > Active tectonic/volcanism
  > Indian Ocean Ridge, Bismarck Sea, Mid-Atlantic Ridge