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Not long ago, the vast expanses of the oceans, which cover some two-thirds
of the Earth’s surface, were seen as ecological deserts with a very low
biological productivity and only few life forms on the seabed. Within the
past 15 years our knowledge of this environment has increased dramatically.
The picture of dark desolation has given way to striking images of some
of the most productive square metres on Earth. Plans to exploit this abundance
are already under way. But treating the deep sea as a resource brings particular
problems. How do we harvest these riches? To whom do they belong? How should
the world regulate the use of this as yet unspoilt environment?

These questions and more were on the agenda earlier this year at a Dahlem
Workshop held in Berlin. This week-long discussion meeting for researchers
had as its theme ‘Use and Misuse of the Sea floor’. Discussion centred on
the potential of the sea floor and the ecological, moral and legal problems
that its exploitation will bring.

The transformation in our understanding of the deep-sea floor came from
pioneering work with the US deep sea submersible Alvin and others. Alvin
gave researchers their first glimpse of the oases of life in this underwater
desert – small areas with thriving communities of many species, some unknown
elsewhere. Such communities form around hydro-thermal vents – which produce
warm water in zones of tectonic activity such as the mid-ocean ridges –
as well as around cold jets of unusually salty water and at places where
hydrocarbons seep from the sea floor. The basis of life in these ecosystems
is not photosynthesis but the activity of bacteria that use the substances
coming out of the sea floor – sulphides in the hot water, for example –
to produce organic compounds and energy. Some of these bacteria are symbionts
living in the tissues of much larger invertebrates.

These autotrophic bacteria are the first links in food chains of considerable
length. According to Myriam Sibuet from the IFREMER centre for research
into oceanography and ocean technology in Brest, France, a total of 223
invertebrate species living in such oases have already been described. Most
of them are molluscs, annelids, arthropods or members of the new phylum
of Vestimentifera, the tube worms. The peracarides and echinoderms that
dominate ‘normal’ seabed communities are only weakly represented. Most of
the hydrothermal species are endemic, differing considerably between vents
in separate geographical zones.

Some of the hot vent organisms can tolerate temperatures up to 250 °C,
a property unusual enough to make these bacteria valuable. Joe Cann of the
University of Leeds told the Dahlem Workshop that such species are already
used in biotechnology to produce heat-resistant enzymes. But most life around
the hot vents exists where hot and cold water mix, at a temperature of between
30 and 40 °C.

These oases can spread over a few hundred square metres, in vent ‘fields’
consisting of several closely spaced hot fountains. Their biomass concentration
is very high, ranging between about 10 and 100 kilograms wet weight per
square metre. Growth rates and rates of oxygen consumption are also high,
comparable to those found in the thriving communities on the floors of shelf
seas. The life span of a hydrothermal vent is assumed to be less than 50
years. So far, nobody knows how the species populating such an oasis can
survive when the vent (or vent field) ceases to be active. Nor do we know
how new vents – opening dozens or even hundreds of kilometres away – are
colonised.

It is obvious that the communities populating these different kinds
of oases are unique and that there are good reasons to protect them; a more
robust scientific activity like geological research, let alone mining the
sea floor or dumping waste, might easily destroy them. The Dahlem discussion
group chaired by Cann recommended regulation of access and use through some
appropriate international authority.

But who could establish such an authority? Who could decide to create
reserves, national parks or even international ones, on the sea floor in
international waters? International law concerning the open sea has developed
considerably within the past few decades. While the notion of territorial
waters and of exclusive economic zones available to only one country remains
intact, the general idea that the open seas are a common heritage belonging
to the whole of humankind is growing.

The question of who controls the sea floor initially arose 30 years
ago, when some highly industrialised countries, including the US, were interested
in mining manganese nodules – lumps of manganese minerals that formed in
sea floor sediments and are now scattered densely across some of the deep
ocean floor. With these plans in mind, legal and other experts started to
work on what has now become the United Nations Convention on the Law of
the Sea (UNCLOS). In the intervening years, metal prices have dropped and
full-scale mining of manganese nodules seems unlikely within the next 20
years. When it does happen, methods and capabilities will be very different
from those envisaged in the 1960s. In consequence, some of the technical
provisions of UNCLOS might be obsolete before they become valid. Nevertheless,
this convention, in the form eventually adopted after long and protracted
discussions, is an important breakthrough in international law.

According to Elizabeth Mann Borgese of Dalhousie University in Halifax,
Canada, UNCLOS is the ‘most advanced system for international cooperation
in technology develop-ment . . . the beginning of a new form of ocean governance
and indeed world governance’. She sees it as a model for controlling the
exploitation of the seas into the 21st century.

So far, the convention has been ratified by 45 countries and needs to
be ratified by another 15 before it can come into force. One of its basic
statements designates the world oceans as a ‘common heritage of mankind’
that cannot be appropriated by any individual, institution or country; must
be managed by and for the benefit of humankind as a whole; must be conserved
for future generations; and must be reserved for exclusively peaceful purposes.

Freedom of the seas

By using this concept of ‘non-property’, Borgese points out, the convention
transcends both the free-market system and the centrally planned system.
It might even provide a point of convergence between them.

The basic idea of UNCLOS is to establish an international authority
that can give exclusive mining rights in a specified area of the sea floor
to a ‘pioneer investor’, such as an interested country or a consortium of
private enterprises. In return for this privilege the pioneer investor has
to make payments to the authority. This money will be used for the benefit
of developing countries. Moreover, the investor has to operate the mining
project as a joint venture with a developing country, training people of
that country to apply the technology used. The developing country then becomes
a joint owner of any new technology arising in the course of the work.

Mining manganese nodules is still at the experimental stage. But other
ores found in the deep sea are also arousing considerable interest. Hydrothermal
vents are also known as ‘black smokers’, because the water they spout brings
many metals from the rocks beneath the sea floor, mostly dissolved as sulphides.
When they enter the cool deep sea, the minerals precipitate as fine particles
that blacken the water so that it resembles black smoke, and as crusts containing
copper, zinc, lead, silver, gold and other metals. According to Steven Scott,
a geologist at the University of Toronto, similar deposits on land are rich
enough in these metals to be exploited as ores.

The technology to mine such crusts does not yet exist. Pumping the fluid
to the surface as it spurts from the sea floor is not a realistic option.
The changes in pressure and temperature from several kilometres under the
sea to the surface would speed precipitation of the ore minerals so much
that the pipes would soon clog up. Moreover, the hot fluid does not itself
have a high enough metal content for efficient recovery. So there seems
to be no immediate threat from this approach to the oases around active
vents.

Precipitation is the essential step that concentrates the elements into
potential ores; once vents are no longer active, their unique fauna disappears
but the valuable crusts remain. Developing an appropriate technology for
recovering such polymetallic crusts would not be too difficult. One likely
idea is to produce a concentrate suitable for further transport on a ship
simply by grinding the rocks to a powder, then separating out the valuable
metals magnetically, without the need to add reagents. With this method,
the tailings returned to the seabed would not contain anything that was
not already there, so there would be no resulting chemical pollution.

Most of the polymetallic deposits are rather small, perhaps a few tens
of square metres across, but this need not affect the economics of the operation.
Equipment could easily be transported from one dead vent field to the next.
If such a method were adopted, UNCLOS provisions designed for nodule mining
would have to be adapted to the different conditions prevailing in mining
polymetallic sulphides.

So far, none of the crust deposits around vents have been sampled in
a systematic way to give an accurate estimate of their bulk composition.
But Scott told the workshop that there is a suspicion within the academic
community that some recent expeditions in international waters, purportedly
for academic research, have in fact been involved in mineral exploration
and resource evaluation.

Scott thinks it unlikely that such deposits could be mined economically
within the next 20 years. Nevertheless some nations are already interested.
The Japanese government is funding a five-year project costing $24 million
to evaluate manganese nodule and polymetallic sulphide resources within
the exclusive economic zones of some Pacific island countries.

Wher there’s sludge

There is an even better chance of using dense hot brines containing
metal sulphides, a feature of some basins at the bottom of the Red Sea.
The German company Preussag has carried out a pilot project there in cooperation
with Saudi Arabia and Sudan, with the help of a heavy subsidy from the German
government. On the basis of its results, Hjalmar Thiel, a marine biologist
at the University of Hamburg, told the Dahlem Workshop that only a very
large enterprise would be economically viable. At least 100 000 cubic metres
of sludge would have to be pumped and processed every day over a period
of 10 to 15 years. The metal compounds, held in 2 to 3 per cent of the sludge,
would have to be separated and transported to the smelter. The rest, most
of the sludge pumped up, in fact, would have to be returned to another part
of the sea floor, where it will not interfere with the sulphide-rich sludge.

This is just one attempt to investigate the problems of harvesting these
resources. One of the discussion groups at the workshop, chaired by Kenneth
Hsu, a geologist at the Swiss Federal Institute of Technology in Zurich,
suggested the establishment of a new regulatory group. An interdisciplinary
working group under an appropriate independent umbrella, perhaps like GESAMP,
the Group of Experts on Scientific Aspects of Marine Pollution, would investigate
all aspects of mining poly-metallic sulphides from the sea floor. Such a
group could also assess independently the environmental impact of such activities
and compare it to the effects of mining on land. Researchers at the workshop
suggested the group should do this through a test mining project on a small
deposit preceded by a detailed biological, geological and geochemical inventory.

The metals formed at vents are not the only asset of the deep sea. Another
is the stable environment. All sorts of dirt and noxious and toxic materials
are carried into the sea by rivers, from the atmosphere, by sewage systems
of coastal towns and holiday resorts, from the cooling water of nuclear
installations, and as a consequence of oil transport and offshore oil drilling.
Some countries even deliberately dump their noxious wastes in the open sea.
As a result, coastal waters and marginal seas in many parts of the world
are polluted. Swimming in such waters is unpleasant and possibly unhealthy.
Oysters and other animals harvested from these waters for human consumption
sometimes contain dangerous levels of toxic substances. There is wide agreement
that this sort of pollution ought to be restricted. Some countries have
enacted pertinent national legislation and the London Dumping Convention
bans dumping some substances in the sea, and requires a special licensing
procedure for others.

Charles Hollister, vice president of the Woods Hole Oceanographic Institution
in Massachusetts, looked at the other side of the coin in his background
paper for the Dahlem Workshop. Put bluntly, the problem is that human society
produces waste. Even if we try as hard as we can to minimise its amount
and to recycle and reuse whatever we can, we are still left with considerable
quantities to be disposed of somewhere. Nobody likes it, but we all produce
it. The problem will not be solved by merely crying ‘NIMBY’ – not in my
back yard.

The quest for dumps gets ever more difficult and expensive and any waste
disposal on land is fraught with environmental risks, especially for underground
water. There is good reason to have another look at the two-thirds of the
Earth covered by oceans and to investigate disposal methods that may pose
reduced environmental risks.

For highly toxic or highly radioactive waste, Hollister and Ross Heath,
of the University of Washington, suggest dumping in the central North Pacific
basin. This part of the sea floor has been geologically quiet for the last
65 million years, while the Alps and the Himalayas rose, the isthmus of
Panama closed and ice ages came and went. The configuration of the continents
suggests that little major geological activity is likely in the area in
the next few thousands or even millions of years.

As in many ocean basins, the bottom of the Pacific is covered by a layer
of creamy clay mud that is hundreds, or even thousands, of metres thick
in places. One way to deal with waste, suggested the workshop, would be
to pack it into a container with a heavy pointed nose cone, and drop it
into the sea. The drum would speed through the water column, sink into the
sediments on the sea floor and most likely be buried by the mud. Any heavy
metals that escape when the container eventually corrodes would be chemically
bound by the clay, slowing or stopping their release. This should reduce
the chance of substances escaping into the water column, but the researchers
stressed that this idea ought to be tested. Many of the participants at
the Dahlem Workshop felt that this idea was worth further exploration; deep-sea
dumping may be ‘the most responsible way to get rid of some waste’, as
the discussion group chaired by Hsu stated in its report.

Monitoring the disposal of sewage sludge in New York Bay has shown what
damage can be done by dumping close to the shore: serious effects such as
a complete loss of oxygen in the water and ‘red tides’ – extensive growth
of algae – as well as sewage particles washing up on the beaches of Long
Island. This is obviously not a good solution to the waste problem, but
the dumping continues. Dumping need not stop altogether, according to the
participants at the Dahlem workshop, but more care is needed in deciding
where to put such waste. They felt that dumping sludge farther away from
the coast may even be feasible.

Jurgen Mientert of the University of Kiel has suggested dumping mildly
toxic materials in areas with strong deep-sea currents that would speedily
disperse it, making the waste essentially harmless. But there are doubts
that even the enormous water masses of the open oceans have the capacity
to act in this way, as ‘infinite diluters’. Nick McCave of the University
of Cambridge told the workshop that dumping sewage sludge from all major
North Atlantic coastal regions into the deep waters of the ocean to be dispersed
could cause problems. According to ‘back of the envelope’ calculations,
this amount of sewage would use up about 10 per cent of the oxygen dissolved
in the ocean water – with patches taking up considerably more. Such a drop
in available oxygen could be ecologically significant.

As an alternative, a group of European investors has suggested a large-scale
dumping experiment lasting 10 years, aimed at containment rather than dispersal
of waste. In this proposal, discussed at a meeting in Woods Hole in January
1991 and developed further at the Dahlem Workshop, about one million tons
of sewage sludge and fly ash would be dumped each year into an appropriate
enclosed basin on the flanks of the Mid-Atlantic Ridge. The material would
have to be transported down in drums or by an enclosed elevator system so
that it did not contaminate the water above the chosen site.

The dump would have to be closely monitored throughout the experiment
by an independent international group of marine scientists to see whether
any environmental impact reached beyond the site. If so, the experiment
might have to be interrupted or even stopped prematurely. If necessary,
the waste would have to be covered by a layer of an impermeable inert material.
Coordination of such monitoring could be handled by one of the ‘Regional
Centres for the Advancement of Marine Sciences and Technology’ to be established
within the framework of UNCLOS.

So far, we have only scratched the surface of the exploration to be
done in the deep oceans. That researchers are already discussing how best
to use these untouched environments is to their credit. Humans will need
the resources offered by the sea floor, so the sooner we understand the
processes that govern this ecosystem, the better we will be able to control
its exploitation. After all, just imagine an international agreement on
mining on land might have done to protect the environment.

Georg Breuer is a freelance scientific writer living in Vienna, Austria.
The Dahlem Workshop report, Use and Misuse of the Seafloor, edited by KJ
Hsu and J. Thiede, will be published by J. Wiley and Sons, Chichester.