Marine Pollution Bulletin, Volume 26, No.3, pp. 128-134, 1993. Contamination of Coastal versus Open Ocean Surface Waters A brief meta-analysis W.JACKSON DAVIS Department of Biology, University of California and The Environmental Studies Institute,

1. Marine Pollution Bulletin
Marine Pollution Bulletin, Volume 26, No.3, pp. 128-134, 1993.
Printed
0025-326X/93 $6.00+0.00
© 1993 Pergamon Press Ltd
in Great Britain.
Contamination of Coastal versus Open
Ocean Surface Waters
A brief meta-analysis
W. JACKSON DAVIS
Department of Biology, University of California, Santa Cruz,
2309 Empire Grade, Santa Cruz, CA 95060, USA
The relative contamination of coastal and open ocean
surface waters by several classes of marine pollutants is
compared by re-analysis of data published by GESAMP
(1990) on the state of the oceans. This re-evaluation,
together with analysis of recent IAEA data, suggests that
marine pollutants can be divided into three broad
categories: 1. those that are more concentrated in the
open ocean environment than in coastal waters, including PCBs and (arguably) radioactive wastes; 2. those
that are equally concentrated in open ocean and coastal
waters, including DDT and its metabolites; and 3. those
that are somewhat more concentrated in coastal waters
than the open ocean, including chlorinated hydrocarbons and the heavy metals. The data do not support
the conclusion drawn by GESAMP that although
coastal waters are contaminated, "the open sea is still
relatively clean". Instead the data support the general
conclusion that, with respect to the contaminants
examined here, open ocean waters are approximately as
contaminated as coastal waters.
C4.
95064; and The Environmental Studies Institute, *
agencies and issued by the United Nations Environmental Program (UNEP). This report notes that coastal
regions are deteriorating seriously world-wide: "destruction of beaches, coral reefs and wetlands, including
mangrove forests, as well as increasing erosion of the
shore, are evident all over the world:' In contrast, the
GESAMP report concluded, in summary, that "the open
sea is still relatively clean".
The purpose of this brief communication is to present
a partial re-evaluation of the database on which the
GESAMP summary conclusions are founded. This reanalysis does not support the 'dirty coast clean seas'
hypothesis. Instead it suggests, for the several contaminants examined, that the surface waters of the
open seas are approximately as contaminated as coastal
waters. This conclusion has implications for both
scientific and policy decisions in the area of marine
pollution.
Methods
There is widespread perception that coastal waters may
suffer point sources of significant pollution, but "the
open sea is still relatively clean" (GESAMP, 1990). Such
a perception reduces the motivation for global action
to preserve the marine environment. Moreover, this
"dirty coasts clean seas" hypothesis is self-perpetuating,
because it inhibits the research and monitoring of the
open ocean that could test the accuracy of the perception. The perception that the open ocean is still
relatively clean therefore has both policy and scientific
ramifications.
The 'dirty coast clean seas' hypothesis originates in
part from a recent analysis of the health of the marine
environment by GESAMP-the authoritative Group of
Experts on the Scientific Aspects of Marine Pollution
(GESAMP), sponsored by several United Nations
*A California Non-Profit Corporation founded in 1981 for purposes
of research and public education on scientific issues related to environmental policy.
128
The data on which the GESAMP conclusions are
based are contained in technical annexes to the
GESAMP report (UNEP, 1990). The present analysis
is confined to data on the concentration of marine
contaminants in coastal and open ocean surface waters,
contained in the excellent review by Fowler (1990). Data
published in the literature, and therefore in Fowler's
review, are generally based on random or pseudorandom sampling, rather than systematic sampling
techniques, especially in regard to the open oceans.
Moreover, means of several measurements from a single
locale are typically presented, without reference to the
population variance. It was impossible, therefore, to test
hypotheses about means using t-tests or their nonparametric equivalents. Instead, means of means are
reported here, and compared across the two categories
of coastal surface waters and open ocean surface waters.
Such procedures do not enable statistically valid conclusions, but rather provide a broad qualitative
impression of the state of the oceans.

2. Volume 26/Number 3/March1993
It is to be emphasized, however, that the database
employed here is identical to that employed by
GESAMP. Therefore, although the procedures used
here cannot satisfy normal standards of scientific confidence, they nonetheless permit a critical evaluation of
GESAMP's conclusions. Data are summarized in the
form of histograms comparing the mean concentration
of specific contaminants in coastal and open ocean
surface waters, in various regions of the world (Figs 19).
Results
Polychlorinated biphenyls (PCBs) are more generally
concentrated in open ocean waters than in coastal
waters (Fig. 1). Average concentrations range from less
than one-tenth of a nanogram per litre of sea water water
(Kanechlor in the Antarctic) to more than 75 nanograms
per litre (Aroclor 1254 in the Atlantic and Pacific). The
higher concentrations in the open ocean presumably
reflect the atmospheric input of PCBs to ocean water
(GESAMP, 1989).
Radioactive wastes may likewise be more concentrated in the open ocean environment, although these
are not covered in the GESAMP report. This conclusion
is based on the historical fact that the deliberate
dumping of radioactive wastes at sea (IAEA, 1990),
combined with the loss of several naval nuclear reactors
at sea, have deposited far more radioactivity in the open
ocean than has entered coastal waters (Davis, 1990;
Davis and Van Dyke, 1990). Radioactive wastes, however, to the extent that they have escaped containment,
have relatively high sediment binding (distribution)
coefficients, which restricts their concentration in ocean
surface water.
The global distribution of DDT and its metabolites
follows a slightly different pattern from that of PCBs.
Where comparisons are possible between concentrations in coastal and open ocean waters, the values are
approximately equal (Fig. 2). In approximately half the
comparisons, concentrations are greater in the open
oceans than in coastal waters. By far the greatest levels
are found in the northeast Atlantic, where concentrations of about 500 nanograms per litre are substantially
greater than concentrations in comparable coastal
Phenoclcr D-P5
10
Aroclor
zones. As a generality, concentrations are larger in the
open ocean in regions of the world where terrestrial
use of DDT's has been curtailed (e.g. the northern
hemisphere), while coastal concentrations are greater in
regions where terrestrial use continues (e.g. the southern
hemisphere). This distribution pattern presumably
reflects the input of this contaminant to the ocean from
riverine sources. Remote regions, where terrestrial DDT
use has never occurred (e.g. the Antarctic), also show
higher concentration in open oceans, though generally
not as high as in industrialized regions, suggesting
incomplete ocean mixing. Assuming a relatively long
residence time for DDT in comparison with mixing
rates, existing concentrations in these remote regions
may be expected to increase over time as mixing
becomes more complete.
A similar analysis for chlorinated hydrocarbons illustrates that concentrations in sea water are generally
slightly (less than a factor of two; north Pacific, northwest Atlantic) to substantially (approximately an order
of magnitude; Mediterranean Sea) higher in coastal
waters (Fig. 3). Only in remote regions, such as the
Antarctic, are concentrations of chlorinated hydrocarbons higher in open ocean waters.
The final class of pollutants examined here, namely
the heavy metals, includes cadmium, lead and mercury.
Cadmium is generally moderately to substantially more
concentrated in coastal zones than the open ocean (Fig.
4). Quantitative analysis shows, however, that over the
entire globe the concentration is only about 2.3 times
higher in coastal waters than in the open ocean.
Inspection of the sources of cadmium contamination
(Fig. 5) suggests that much of it originates from local
coastal "hot spots" such as the New York Bight in the
Atlantic, and various North Sea point sources. When
these local hot-spots (defined, for this analysis, as
regions in which the concentration exceeds twice the
mean value) are eliminated from the means, the concentration ratio (coast/ocean) drops to 1.6. In other words,
the concentration of cadmium in coastal waters is less
than twice as great as in the open ocean waters. These
data are consistent with a dynamic source model in
which cadmium originates largely from land based
sources and is introduced into coastal regions, largely by
run-off but also (potentially) atmospheric input. Considering that the open ocean surface waters represent a
Aroelor
1260
1254
18
8
15
75
6
12
60
9
45
6
30
3
15
Kanechlor
0.10
4
2
0
0
O/G
Med./France
0.08
0.06
0.04
O/G
A/A.P
0
0.02
0.00
O/G
Fig. 1 Mean concentrations of PCBs in ocean (0) and coastal (C) surface waters
litre). Abbreviations:
Med., Mediterranean
Sea; A, Atlantic; P, Pacific;
Data are means of means presented in tables in Fowler (1990). Numbers
represent the 'sample' size (where individual samples are, in some cases,
several measurements).
O/G
AntlAnt
AP/AP
(nanograms per
Ant, Antarctic.
above each bar
mean values of
129

3. Marine Pollution Bulletin
vastly greater volume than coastal surface waters, these
data demonstrate that the bulk of cadmium has found its
way to the open seas.
Lead exhibits a similar pattern to cadmium. Lead
concentrations are generally higher in coastal waters,
although occasional comparisons reveal greater concentration in the open ocean (Fig. 6). The global ratio of
coastal to open ocean concentration is approximately
2.4, but when localized hot-spots are eliminated (Fig. 7),
the ratio drops to 1.6.
Finally, mercury concentrations present a similar
pattern to cadmium and lead. Concentrations are generally, but not always, higher in coastal waters, but the
difference is generally moderate (Fig. 8). Elimination of
local hot-spots again yields roughly equivalent concentrations in coastal and open ocean waters (Fig. 9).
North
A,N
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Fig. 2 Mean concentrations
of DDT and its metabolites (nanograms per litre) in open ocean (0)
and coastal (C) surface waters. Abbreviations: 0, concentration in ocean surface waters;
C, concentrations
in coastal surface waters. Histograms are positioned in the approximate
regions where measurements
were made. Further abbreviations: N, north; Chin, China
Sea; NW, northwest; S. south; otherwise as in Fig. 1. Data are means of means presented in
tables of Fowler (1990).
Baltic
~'~JjP'N
~
0
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a
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Fig. 3 Mean concentrations of chlorinated hydrocarbons (nanograms
and coastal (C) surface waters. Otherwise as in Fig. 2.
130
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per litre) in open ocean (0)
o
a
o

4. Volume 26/Number
3/March
1993
Discussion
Re-analysis here of the admittedly incomplete data
based employed by GESAMP in its recent report on the
state of the oceans suggests that ocean contaminants
can be divided into three broad categories. The first
category, including PCBs and arguably radioactive
wastes (IAEA, 1990), is more concentrated in the open
~[i
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0
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Fig.4
Mean concentration
of cadmium (nanograms
surface waters. Otherwise as in Fig. 2.
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Coastal Surface Waters
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Fig. 5 Histograms showing concentrations
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concentrations
(point sources or 'hot spots). Lower graphs are of the same data in the
upper graphs but on an expanded scale. Data are means of means presented in tables of
Fowler (1990).
131

5. Marine Pollution
ocean than in coastal regions, reflecting their input from
atmospheric sources (PCBs) or past dumping at sea
(radioative wastes). The second category of contaminants, including DDT and its metabolites, is approxi-
Bulletin
mately equally concentrated in the open ocean and
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that have reduced over time. And the third class of
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6. Volume 26/Number
3/March
1993
the heavy metals, is generally somewhat more concentrated in coastal waters, although elimination of
especially large point sources of contamination Chot
spots') in coastal waters nearly eliminates the difference
with the open oceans. The distribution pattern of the
third class of contaminants presumably originates from
continuing coastal inputs.
Although the data reviewed here do not enable statisArc
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Histograms showing concentrations
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panels) and coastal (right panels) surface waters, by region, illustrating locally high
concentrations
(point sources or 'hot spots'). Otherwise as in Fig. 5.
133

7. Marine Pollution
ticallyvalid conclusions, the data are identical to those
on which GESAMP based its summary conclusions. The
data do not support the unqualified 'dirty coast clean
seas' hypothesis. Instead, they indicate that the open
oceans are approximately as contaminated as coastal
waters. Therefore, if coastal waters are considered to be
seriously impacted, as stated by GESAMP, then so also
are open ocean waters. Coastal zones suffer greater
pollution from erosion, turbidity, direct sewage discharge and riverine inputs; but by the same token, the
open oceans may suffer more from deliberate dumping,
which, with the exception of dredged materials, is
generally not undertaken in coastal waters; and from
atmospheric inputs, if ony because the receptive surface
area of the open ocean is far greater.
The levels of contamination in open ocean surface
waters revealed by the available data merit more
detailed attention for several interacting reasons: 1. 90%
of biological productivity occurs there, and this productivity is concentrated in surface waters; 2. The concentrations and biological impacts of literally hundreds of
ocean contaminants are unknown; 3. Concentrations
recorded in the open ocean (as high as hundreds of
nanograms per litre) appear greater than those known,
for some pollutants (e.g., tributyl tin), to produce significant biological defects (1-2 nanograms per litre; Smith,
198]; Goldberg, 1990); 4. The additive, or interactive,
effects of ocean stressors, such as the combination of
increased ultraviolet radiation from ozone depletion
with existing levels of contamination, are largely
unknown; 5. The surface micro layer is lipophilic owing
to the concentrations of biological membrane, and
hence concentrates organic contaminants such as PCBs;
6. Concentration factors in living unicellular organisms
can be as high as I00 000 times above the ambient water
concentration; 7. Developmental events crucial to most
ocean life forms occur within the surface micro layer; 8.
Approximately one-third of ocean pollution is transmitted to ocean waters through this surface microlayer
from the atmosphere (GESAMP, 1989, 1990); 9.
134
Bulletin
Concentrations of contaminants in the surface microlayer have generally not been measured; and 10.
Potential damage from these contaminants may occur in
a binary or discontinuous (threshold) mode and be
irreversible owing to long time lags.
The GESAMP report on the state of the oceans
acknowledges the general inadequacy of the available
database, and especially the paucity of data available
for the open ocean. The GESAMP report also warns
of the need for concerted international action within
the next decade if serious and potentially irreversible
degradation of the oceans is to be averted. The present
re-examination of available data supports that recommendation, but suggests further that the oceanic ecosystem may presently be more vulnerable than suggested
by GESAMP's summary conclusions.
Davis, W. J. (1990). Global aspects of marine pollution policy: The need
for a new international convention. Mar. Po!. 14, 191-197.
Davis, W. J. & Van Dyke, J. M. (1990). Dumping of decommissioned
nuclear submarines at sea. A technical and legal analysis. Mar. Pol. 14,
467-476.
Fowler, S. W. (1990). Concentration
of selected contaminants in water,
sediments and living organisms. In UNEP: Technical annexes to the
report on the state of the marine environment. UNEP Regional Sea
Reports and Studies No. 11412. UNEP, 1990, pp. 209-230.
Goldberg,
E. D. (1990). Selected contaminants:
Tributyltin
and
chlorinated hydrocarbon biocides.ln UNEP. Technical annexes to the
report on the state of the marine environment. UNEP Regional Seas
Reports and Studies No. 11412. UNEP, 1990, pp. 209-230.
GESAMP (1989). The Atmospheric Input of Trace Species to the World
Ocean, 1989, Rep. Stud. GESAMP (38).
GESAMP (1990). The state of the marine environment. Rep. Stud.
GESAMP (39).
International Atomic Energy Agency. Inventory of Radioactive Material
Entering the Marine Environment. Part I: Sea Disposal of Packaged
Low Radioactive
Waste. Issued in draft form in Sept. 1990 as
document LDC/3/INF.23
by the London Dumping Convention.
Vienna: IAEA, and London: International
Maritime Organization
(1M 0).
Smith, B. S. (1981). Male characteristics in female snails caused by antifouling bottom paints. 1. Appl. Toxicol. 1,22-25.
UNEP (1990). Technical annexes to the report on the state of the marine
environment. UNEP Regional Seas Reports and Studies No. 11412.
UNEP, 1990 (Volumes 1 and 2).