(The recent approval for Trans Tasman Resources Ltd to mine for iron off the south Taranaki coastline is a huge environmental issue. Retired New Plymouth resident, Murray Crombie, was formerly the city’s DoC Area Manager, so his professional background lies in the protection and management of natural areas. In the article below he analyses the likely impact of this industrial venture.)

Iron sand extraction at what cost?

By Murray Crombie

The Environmental Protection Authority (EPA) has approved with conditions, an application by Trans Tasman Resources Ltd. (TTR) to mine iron sand off the coast of Patea. (Their earlier application in 2014 was rejected.)

The mining licence covers an area of 65 square kilometres. The process will suction a huge quantity of sand and mud off the ocean bottom.

After iron ore is extracted, the residue is returned to the sea. This fine debris will, as depicted in the application, create a plume of sediment spreading east some 15 kilometres wide and 60 kilometres long, tailing out along the foreshore at Wanganui.

Marine ecosystems and species will be damaged and displaced by this work, as will people’s use of the worked area.

What is most important? 

Natural places, contribute materially as well as aesthetically and spiritually to our needs and to the life of other creatures we share space with. We assess and value things as individuals.

We need to decide if the benefits of the sand mining balance its negative environmental effects:

• 

  the jobs

• the income from services and supplies to the dredge
• the royalties promised by the TTR application.

It is important to remember that the approval and economic success of TTRs’ mining will no doubt lead on to other sand mining proposals.

Where is the mining zone?

Sited some 22kms offshore from Patea, at 25 to 65 metres water depth, the mining area is located primarily in the circalitteral zone in the marine environment.

This zone is a broad deposit of mud and sand with patches of hard ground. It begins at where light reaching the sea bed is reduced by water depth and turbidity, extending out to the continental shelf at 100 – 200 metres deep.

It is a settlement area for many minerals including, phosphorus, potassium, sulphur, calcium, magnesium and of course iron ore (titano-magnetite). These minerals are the macro-nutrients required by plants to grow.

The circalitteral zone is not “a featureless wasteland” as described in the mining application.  

A myriad of marine life

While macroalgae (large seaweed) is limited by low light penetration, unusual sponges and corraline algae proliferate.

The seafloor of the circalitteral zone is inhabited by a myriad of adapted creatures.

Per square metre, there are countless tiny microbenthos species (diatoms, bacteria, copepods, amphipods) living in the bottom substrate or on its surface.

Larger animals, nematodes, worms, snails, clams, scallop and oyster species, sea urchins, shrimps, crabs and so on burrow into the mud and sand feeding on other inhabitants or organic residues raining down from above.

The sea bed of this zone is a prime feeding ground for many commercial fish species, snapper, tarakihi, flat fish, school shark, red cod, to name a few, which roam over its surface.

A zone crucial for algae proliferation

This zone is hugely important for phytoplankton (algae) production. These tiny plants and bacteria using sun energy, and photosynthesis convert nutrients and carbon dioxide into organic tissues to make their bodies.

Massive blooms of these one-celled organisms occur when sea currents sweep nutrients from the sea floor along with the cysts or spores of phytoplankton and zooplankton, up into the sunlit surface waters where rapid reproduction can occur.

Phytoplankton are the primary producers of organic carbon. They begin the marine food web which all other ocean animals rely on to survive.

Phytoplankton along with a smaller contribution from coastal sea weeds, also produce more than half of the atmospheric oxygen that life in this world needs.

A critical element in the ocean food chain

Phytoplankton drift everywhere, sustaining filter feeders like pipi and mussels on the foreshore to anchoring the food supply in the open ocean.

• At sea, plankton blooms trigger and feed an exploding population, first of tiny herbivores, zooplankton.
• These are hunted by small carnivores like krill and larval fish. In turn these are food for pilchards, anchovy, mackerel and such.
• These are fed on by kahawai, tuna, kingfish, marlin, shark, dolphin/whale, squid and seal species.
• Diving seabirds are much attracted to the “boil ups” of hunted and feeding fish.
• The baleen whales like the blue and humpbacked, are adapted to feed on the abundant krill and small fish occurring in the blooms.
• The spring/summer abundance of planktonic foods likely encourages surface and mid-water spawning fish species to spawn. Plankton feeds their hatchling larvae.

The circalitteral zone is an important ocean ecosystem sustaining a great many interactive organisms.

Concerns over the application proposal

I have followed with interest the debate about the TTR application to mine iron sand from the sea bed area out off the coast of Patea.

An issue that has worried me much, has been how little information (either omitted or avoided) about the natural ecological values of the ocean mining area, is given in the mining application or in discussion about the proposal.