452
Hjalmar THIEL
higher water levels, where the particulate matter could
interfere with many organisms. Primary production
and larval development could be affected. Generally,
other interests in the use of the sea, like fisheries and
recreation, would need to be evaluated in advance to
avoid adverse interactions.
Past and future research
Evaluation of the environmental impact of mining
in the deep sea is a major challenge to ecological
research. The potential large-scale intrusions demand
answers on acceptability. Ecological knowledge is not
sufficient (Thiel, 1992), and precautionary research
must specifically consider the scale of impact.
Since polymetallic nodules have been seriously
considered as a mining resource, the environment has
been taken into account. Already in 1970, the first prepilot mining test on the Blake Plateau of the Atlantic
Ocean was monitored to evaluate the consequences of
potential commercial mining (Amos et al., 1972, 1973;
Roels et al., 1972, 1973; Roels, 1974; Amos and Roels,
1977).
Two extensive environmental programs were conducted in the seventies in conjunction with pre-pilot
mining tests. The first accompanied the pre-pilot
mining tests of Ocean Management, Inc. (Burns et al.,
1980) and Ocean Mining Associates (Ozturgut et al.,
1980, 1981b) in a programme named DOMES (Deep
Ocean Mining Environmental Study) conducted in the
Clarion–Clipperton Fracture Zone of the northeastern
Pacific Ocean. This broad oceanographic programme
concluded that mining would not result in harmful
effects on the environment, but some of the authors
(Lavelle et al., 1981; Lavelle and Ozturgut, 1981;
Jumars, 1981; Ozturgut et al., 1981a) expressed
concern about the discrepancy of scale between the
test and commercial mining [see also Thiel (1991)].
A second large study was conducted in the years
1977–1981, and included some monitoring of the
1979 pre-pilot mining test for testing the equipment
for mining of metalliferous mud in the Red Sea.
The total programme, including commercial, technical
and environmental assessment, was termed MESEDA
(Metalliferous Sediments Atlantis II Deep). Plankton
and benthos were studied, as well as primary production, toxicity of tailings, water chemistry, physical
oceanography including the determination of water
transport at great depths, and sedimentology (Thiel,
1979; Weikert, 1980, 1982, 1987; Karbe et al., 1981;
Abu Gideiri, 1984; Beckmann, 1984; Thiel et al.,
1986). The successful mining was completed with a
small discharge test (see above, p. 450), and a tracer
(radioactive iridium) was added to the mud released.
The plume was investigated with an echo-sounder;
two different types of models predicted the short-term
spread of the plume, and sediment samples showed the
distribution of the iridium on the seafloor (Fanger and
Pepelnik, 1979).
The general approaches of DOMES and MESEDA
applied standard methods of oceanography and obtained valuable sets of data on the Pacific Ocean and
the Red Sea, respectively, but the main result of these
studies was the realization that the data sets did not
allow predictions of impact. The studies conducted and
the results achieved are not appropriate to the largescale intrusions anticipated by the mining industry
(Thiel, 1991).
A new approach had to be developed to predict
large-scale impacts of mining. This new step was
successfully commenced when, in the years 1986–
1988, the German Bundesministerium f¨ ur Bildung und
Wissenschaft agreed upon a long-term and large-scale
in situ experimental study close to a national claim
for the mining of polymetallic nodules in the South
Pacific (Thiel, 1991). This project, known under the
acronym DISCOL (DISturbance and reCOLonization
of a manganese nodule area in the South Pacific), was
launched in 1988 and had its first cruise from January
to March 1989 (Thiel and Schriever, 1990). A largescale disturbance of nearly 11 km
2 was achieved by
ploughing the nodules into the sediment and turning its upper layer upside down. A programme for
sampling before and after impact and for video/photo
observations provided a basis for comparisons after
0.5, 3 and 7 years. After three years sedimentologists,
geochemists and modellers joined the project (Thiel
and Forschungsverbund Tiefsee-Umweltschutz, 1995),
which terminated at the end of 1998. Early results indicate that after seven years the ploughing tracks are still
visible, marked by the grey sediment ploughed up from
deeper layers and resting on the surface alongside the
dark brown upper sediment. The upper sediment layer
became a three-dimensional mosaic of very soft, watery
fillings between hard lumps of various sizes. This
situation is expected after the passage of the collector
system in the mining process, but the disturbance may
reach deeper into the sediment. The relatively food-rich
surface layer is mixed with deeper food-poor sediment,
and the oxygen distribution may be changed [compare
K¨ onig et al. (1997)]. In addition to the disturbance
Hjalmar THIEL
higher water levels, where the particulate matter could
interfere with many organisms. Primary production
and larval development could be affected. Generally,
other interests in the use of the sea, like fisheries and
recreation, would need to be evaluated in advance to
avoid adverse interactions.
Past and future research
Evaluation of the environmental impact of mining
in the deep sea is a major challenge to ecological
research. The potential large-scale intrusions demand
answers on acceptability. Ecological knowledge is not
sufficient (Thiel, 1992), and precautionary research
must specifically consider the scale of impact.
Since polymetallic nodules have been seriously
considered as a mining resource, the environment has
been taken into account. Already in 1970, the first prepilot mining test on the Blake Plateau of the Atlantic
Ocean was monitored to evaluate the consequences of
potential commercial mining (Amos et al., 1972, 1973;
Roels et al., 1972, 1973; Roels, 1974; Amos and Roels,
1977).
Two extensive environmental programs were conducted in the seventies in conjunction with pre-pilot
mining tests. The first accompanied the pre-pilot
mining tests of Ocean Management, Inc. (Burns et al.,
1980) and Ocean Mining Associates (Ozturgut et al.,
1980, 1981b) in a programme named DOMES (Deep
Ocean Mining Environmental Study) conducted in the
Clarion–Clipperton Fracture Zone of the northeastern
Pacific Ocean. This broad oceanographic programme
concluded that mining would not result in harmful
effects on the environment, but some of the authors
(Lavelle et al., 1981; Lavelle and Ozturgut, 1981;
Jumars, 1981; Ozturgut et al., 1981a) expressed
concern about the discrepancy of scale between the
test and commercial mining [see also Thiel (1991)].
A second large study was conducted in the years
1977–1981, and included some monitoring of the
1979 pre-pilot mining test for testing the equipment
for mining of metalliferous mud in the Red Sea.
The total programme, including commercial, technical
and environmental assessment, was termed MESEDA
(Metalliferous Sediments Atlantis II Deep). Plankton
and benthos were studied, as well as primary production, toxicity of tailings, water chemistry, physical
oceanography including the determination of water
transport at great depths, and sedimentology (Thiel,
1979; Weikert, 1980, 1982, 1987; Karbe et al., 1981;
Abu Gideiri, 1984; Beckmann, 1984; Thiel et al.,
1986). The successful mining was completed with a
small discharge test (see above, p. 450), and a tracer
(radioactive iridium) was added to the mud released.
The plume was investigated with an echo-sounder;
two different types of models predicted the short-term
spread of the plume, and sediment samples showed the
distribution of the iridium on the seafloor (Fanger and
Pepelnik, 1979).
The general approaches of DOMES and MESEDA
applied standard methods of oceanography and obtained valuable sets of data on the Pacific Ocean and
the Red Sea, respectively, but the main result of these
studies was the realization that the data sets did not
allow predictions of impact. The studies conducted and
the results achieved are not appropriate to the largescale intrusions anticipated by the mining industry
(Thiel, 1991).
A new approach had to be developed to predict
large-scale impacts of mining. This new step was
successfully commenced when, in the years 1986–
1988, the German Bundesministerium f¨ ur Bildung und
Wissenschaft agreed upon a long-term and large-scale
in situ experimental study close to a national claim
for the mining of polymetallic nodules in the South
Pacific (Thiel, 1991). This project, known under the
acronym DISCOL (DISturbance and reCOLonization
of a manganese nodule area in the South Pacific), was
launched in 1988 and had its first cruise from January
to March 1989 (Thiel and Schriever, 1990). A largescale disturbance of nearly 11 km
2 was achieved by
ploughing the nodules into the sediment and turning its upper layer upside down. A programme for
sampling before and after impact and for video/photo
observations provided a basis for comparisons after
0.5, 3 and 7 years. After three years sedimentologists,
geochemists and modellers joined the project (Thiel
and Forschungsverbund Tiefsee-Umweltschutz, 1995),
which terminated at the end of 1998. Early results indicate that after seven years the ploughing tracks are still
visible, marked by the grey sediment ploughed up from
deeper layers and resting on the surface alongside the
dark brown upper sediment. The upper sediment layer
became a three-dimensional mosaic of very soft, watery
fillings between hard lumps of various sizes. This
situation is expected after the passage of the collector
system in the mining process, but the disturbance may
reach deeper into the sediment. The relatively food-rich
surface layer is mixed with deeper food-poor sediment,
and the oxygen distribution may be changed [compare
K¨ onig et al. (1997)]. In addition to the disturbance