The Mediterranean Crises
François Doumenge
Director, Institut océanographique,
Musée océanographique, Monaco,
and Secretary General, International Commission for
the Scientific Exploration of the Mediterranean Sea (CIESM), Monaco
Presentation Made at the UNU Headquarters
on 15 July 1996, Tokyo, Japan.
Preface
This report contains two environmental lectures given at the United Nations University
(UNU) by two internationally renowned scientists. They are presented between the same
covers as the topics, albeit very different, have much in common. Both of the lectures deal
with global scale, long-term environmental change, with implications on water resources.
Both of the authors have their background in the Mediterranean basin, a fact that becomes
evident from their focus on that region. Both also take a broad view linking natural
environmental change with the development of human civilizations.
Dr. François Doumenge, Director of the Oceanographic Institute in Monaco and Secretary
General of the International Commission for the Scientific Exploration of the
Mediterranean Sea (CIESM), gave a seminar at the UNU headquarters on 15 July 1996. His
presentation, entitled "The Mediterranean Crises", takes a long-term historical look at a
series of environmental crises that have affected the Mediterranean Sea. He then utilizes
this perspective to paint a picture of the human-induced environmental changes
experienced in recent decades in the Mediterranean basin and the Black Sea, which have
now reached a point where a new crisis is in the making unless we make a concerted effort
to act to prevent it.
Professor Arie S. Issar of the Water Resources Center at the Jacob Blaustein Institute for
Desert Research, Ben Gurion University of the Negev, Israel, was the first lecturer to
deliver a speech at the newly opened Global Environment Information Centre (GEIC) on
14 November 1996. GEIC is a joint endeavour of the UNU and the Environment Agency of
Japan founded on the recommendations of the UN Agenda 21 to act as a centre for global
projects, networking and information on issues and activities related to the environment. As
evident from the title, "Climate Change: Is It a Positive or Negative Process?", Professor
Issar presented a provocative view of global climate change, its natural and anthropogenic
causes in a historical perspective, and the need for mankind to act in a proactive way to
adjust to the effects of global warming.
It is our pleasure to be able to offer this report to a wider audience of those who did not
have the chance to participate in these lectures. We hope that the report will provide
interesting and thought-provoking reading, and that it will contribute to the realization that
we all must take responsibility for our common future.
Dr. Juha I. Uitto
Academic Officer
The United Nations University
The Mediterranean Crises
Dr. François Doumenge
I. Introduction: CIESM and Mediterranean Science
Upon the retirement of Jacques Cousteau, I had the privilege to be selected as his successor
as Director at the Musèe ocèanographique in Monaco and also as Secretary General at the
International Commission for the Scientific Exploration of the Mediterranean Sea
(CIESM).
CIESM is a purely scientific international organization, founded by Prince Albert I in 1914,
and as such, one of the oldest international scientific bodies. During his oceanographic
studies, Albert I and his team of scientists found that the Mediterranean Sea is a small-scale
model where we can study most of the large phenomena of the oceans. At that time, Prince
Albert was a supporter of the international cooperation movement and a founder of the
polar scientific organization as well as that concerned with the Mediterranean. He
organized the first meeting of CIESM in Rome in 1914, where he made arrangements with
the different Mediterranean governments to cooperate in scientific research, but WWI
started some months afterwards and the first plenary assembly of the organization itself was
held in Madrid (1920). From 1920 until now, except for a break between 1939 and 1950
due to WWII and its aftermath, CIESM has convened every two years in a congress
covering all aspects of marine research developed in the Mediterranean basin. This research
ranges from marine geology and geophysics to physical oceanography, marine biology,
fisheries, chemical pollution and so on. So, in summary, CIESM is a large organization
supporting and initiating multidisciplinary scientific research in the Mediterranean proper
and also in the adjacent seas (Adriatic and Black Sea).
The founder's membership right applies to all the states which are a part of the
Mediterranean fringe. Every coastal state has only to pay an annual fee in order to belong to
the organization, and there is no vote required on a coastal state's entry. But from the
foundation, scientists and governments working on the Mediterranean were very
international, coming not only from adjacent states, but also from other countries. So it was
necessary to make a separate rule for admission of a non-coastal state working for the
advancement of science in the Mediterranean Sea. In such cases, after an application is
submitted, a two-thirds majority of the Mediterranean states is required for admission.
Currently, the membership comprises all the Mediterranean states, except Libya and
Albania, as well as Romania and Ukraine for the Black Sea. As countries actively engaged
in the Mediterranean, Switzerland, Germany and the Netherlands were elected to join the
organization. The present total is 23 states.
CIESM is also a privileged forum, removed from political tensions. For example, during
the conflict years between Israel and the Arab states, Israel could sit with other Arab
members. More recently, during the Yugoslav crisis, Slovenia, Serbia-Montenegro and
Croatia, notwithstanding their conflicts, were working together and in 1995 it was a
consensus to hold the next CIESM congress in 1998 (these are hosted on a rotating basis) in
Dubrovnik, Croatia. Looking over many years, CIESM has been the only place where
scientific communications and sometimes joint research projects could take place between
Israel and the Arab states without any problem. Other international organizations ask us to
play the role of an intermediary. Thus CIESM has many connections with FAO, UNEP,
UNESCO, as it is asked to host workshop meetings with the participation of different,
conflicting states.
The main duties of CIESM are twofold. First, the organization is accountable to all the
governments with respect to the main scientific problems of the area. Each member state
receives by official channel expert advice, conclusions or observations about the present
status and trends of the Mediterranean basin. This is an official duty, and every year a
meeting is held to inform the states' representatives of current developments and
recommendations. Second, CIESM groups about 220 laboratories and 2,800 scientists who
are active members of scientific committees. These scientists are working in separate
groups on different projects that we support financially. Consequently, CIESM has two
different orientations, one political, the other scientific.
CIESM also circulates information. Since 1922, it has published more than 100 books on
Mediterranean problems, official records and special treaties about some important
questions on physical oceanography, geology and geophysics, marine biology, etc. (Note:
the official language is French, and while English is often used, most publications are
available only in French.)
My presentation will focus on the Mediterranean crises - geophysical, geological and
biological - during different time scales - millions of years, hundred thousands of years,
thousands of years, and decades. So, I must use a very broad multidisciplinary approach.
What are the main problems and the main crises of the Mediterranean Sea? II. Beginning
of Its History - Messinian: State 0 To start, we must look at a state zero, when the
Mediterranean Sea was dry and life disappeared during the Messinian (end of the Miocene)
5 million years ago (figure 1). At that time, there was a blockage at the Strait of Gibraltar
and after some 100,000-200,000 years the basin had evaporated quite completely. Prior to
that, during a period of one million years, between 6 and 5 million years ago, the opening
of the Mediterranean was sometimes from the east and sometimes from the west, so during
those one million years there was a balance. The Mediterranean basin was like the Sahara,
but with a basic level at minus 3,000 m. As a consequence, on the bottom of the basin, there
are giant rock salt deposits with a total volume of 1 to 1.5 million km3. The thickness of
these strata is between 800 m in the Baleares basin to 1,800 m in the Levantine basin with
sometimes 2,000-2,500 m. In another view these deposits could be seen as the most
important reserve of oil and gas of all the world, but under 3,000 m of water!!
This endoreic salt deposit takes away 6% from the dissolved salts of the whole world
ocean: consequently the polar water freezing point goes down as a consequence of 2%
decrease of total oceanic salinity.
In the shallower areas of the Tyrrhenian basin, proto-Adriatic, Aegean basin, the
sedimentation is gypsum and anhydride.
The basin was a pure desert, but on the fringe big "wadi" were running from the mountain
borders to minus 3,000 m. They dug very deep canyons fringing the Gulf of Lions platform
between Provence and Costa Brava, sinking from 200 m to 2,500 m. During the Messinian,
the Mediterranean was functioning exactly like the present Sahara system, with large
central salty chotts and sebkhas and wadi running from the mountains at the peripheries.
So, 5 million years ago, at first we have state 0 for the Mediterranean sea life, because the
basin dried; even though recently the possibility was considered that, based on research of
Israeli scientists, perhaps some 5 or 6 fish species could have survived at the periphery even
under those conditions, taking refuge in some sebkhas in the vicinity of the wadi detritic
deltas.
The present problem stems from the developments that occurred after the Messinian crisis,
when, with the opening of the Strait of Gibraltar, the basin was filled again only by the
Atlantic and not by the Red Sea. The present paradox and the explanation of the permanent
disequilibrium of life in the Mediterranean come from the fact that the Mediterranean Sea is
a subtropical remain of the Thetys which was repopulated by cold water species. That is the
explanation of the present situation.
With the subsequent opening of the Suez Canal and with the upgrading of the temperature,
tropical species can return and colonize the East Mediterranean basin, and they flush out
the cold species which settled there but are not in their adapted habitat.
It is important to remember that from 5 million years ago the Mediterranean Sea has been a
tropical area settled by cold-water origin species, and this is the paradox explaining the
fragility and the incapacity of the present Mediterranean Sea to have a stable population.
III. The Last Glacial Episode and the Three Mediterranean Seas
A more recent major crisis was at 18,000 years before the present (BP) at the end of the last
glaciation (Wurm). What was the state of the Mediterranean Sea at that time (figure 2)?
First, the general oceanic level was about 120 m less than the present level 0. At the end of
the Wurm time, the world oceanic level was down at minus 120 m because the continental
boreal and Antarctic inland seas kept a huge volume of oceanic water locked up. The black
colour marks what was between 0 and minus 120, i.e. what is now sea and used to be
continental. You can see that the northern and central Adriatic Sea was emerged, the Black
Sea, as a freshwater lake, was quite small, and there was a smaller passage at the Strait of
Gibraltar, with only about 30% of the present capacity. So the water exchange between
incoming water from the Atlantic and evaporation was reduced, and consequently
Mediterranean water was not exchanging at the same rate as it is now. This exchange
controls the potential life in the basin.
Looking at the average temperatures in winter and summer [February (figure 2A) and
August (figure 2B)], it is very important to notice that at that time there was not one
Mediterranean Sea but three: on the east side there is a subtropical area where the
temperature was from no less than 15¡C up to 21oC during winter, and between 21oC and
up to 25oC during summer. So this Levantine basin in the east remained tropical and the
warmer species were able to survive in that small area. Then there is a wall of cool and
desalinate water tongue running from the Black Sea, cutting off the Levantine basin from
the Central basin like a thermic and chemical wall. The Black Sea water extended as far as
the coast of Libya. The Central basin is like the present Mediterranean. During the winter,
the temperature is up to 11oC and in the summer between 19oC and 24oC. The Wesotern
basin was like the North Sea or the Sea of Norway with a temperature of 5oC to 9oC during
winter and a very mild 12oC-16oC during summer. That is why there were subarctic fauna
(whales, penguins, and seals), which explains why even today there remains in the Western
basin a huge population of more than 3,000 blue whales.
IV. Sapropels - Abrupt Changes and Massive Mortalities within a Millennium
The last Mediterranean crisis was 8,000 years ago. The big problem that befell the
Mediterranean Sea at that time was what we call a "sapropel" phenomenon. That is a
general mortality of all marine organisms in a very short time with a changing of the
hydrologic condition. That time was 6,000 years before Christ, which was just at the
passage of Egyptian civilization from pastoralism to the Pharaoh state. The time of
changing climate and changing hydrologic condition was also a time of changing history.
The crisis of that time is strictly associated with the story of the deluge as well told by the
Holy Scripture. We must note such a record and description of what happened in the
Middle East and in the Mediterranean basin - the deluge and, as a consequence of the
deluge, the general mortality of life in the seabed area. Why ?
Because heavy rain falling in the Middle East and in the Nile basins and on East African
Rift Valley lake basins increased the capacity of the Nile to a level of running water as for
the present Amazon. Because of this gigantic increased runoff, the eastern part of the
Mediterranean Sea was covered by a superficial freshwater layer in no more time than 40 to
60 years - this surface layer 15 to 20 m deep caused a general mortality because of a
stratification phenomenon: the freshwater lenses floating at the surface cut the
communication between the atmosphere and the sea water, and so under the freshwater
layer, life died from lack of oxygen. Sapropel formation was discovered in 1952, some 20
cm of black organic matter at the bottom of the Mediterranean Sea that caused quite a
surprise. It was studied through thousands of drillings and it was discovered that in a very
short time all the life in the Mediterranean Sea had died.
For the Mediterranean, that crisis happened 8,000 years ago, but for the Black Sea a similar
crisis is of more recent origin (figure 3). Until 7,450 plus or minus 130 years ago, the Black
Sea remained a freshwater lake. But at that time it started changing. The sea level rose and
Mediterranean Sea water entered the Black Sea basin. After a transition phase with the
deposition of aragonites, there were thousands of years of a period of general death. Such a
layer, from 7,450 to 2,720 years ago, can be correlated with some very straight data like the
explosion of Santorin Island and the subsequent general coverage with and deposition of
volcanic ash in the Mediterranean Sea that killed everything. Also shown are the
percentages of CaCO3 and of organic matter. From 1,600 years ago until now, the present
status is an adjustment period. So, the Black Sea is like a laboratory giving us the
possibility of observation, of learning what happened in one general crisis.
During the Holocene, 450,000 years, the Mediterranean suffered 12 sapropel crises
(Herman, 1989). All during the palaeolithic and neolithic times, great meteorological
perturbations caused periodic collapse of Mediterranean marine life. These crises are very
important to understand because they give an explanation of what could happen if we have
a changed climate.
Figure 4 is a general synopsis and explanation of the different crises and changing
hydrological conditions: 18,000 years ago when the level was at the lowest, 12,000 years
ago, and during the sapropel crisis. This illustrates that hydrology, sedimentology and
biology interact together, which demonstrates that without a multidisciplinary approach you
cannot understand anything in the Mediterranean basin.
Some years ago after the Gulf war between March 1991 and October 1991 we saw a presapropel situation coming very close to a disaster. During the Gulf war there were burning
oil wells in Kuwait. These fires caused a lot of smoke and the smoke created a cloud
running about 10,000 m and covering the Arabian Peninsula, the Persian Gulf, and reaching
to East Africa. From March to June and July 1991, this cloud was causing a decrease in
temperature due to very low solar insulation, and the temperature of the Gulf was
decreasing to less than 15¡C. At the same time, there was heavy rain, monsoon rain, in
eastern Africa. The monsoon front was just balancing and was established in eastern Africa
and didn't move.
At a meeting of the Open Partial Agreement on Major Ecological Disasters in Ankara in
July 1991, it was reported to the Mediterranean governments that if the oil fires weren't cut
off, we would enter a pre-sapropelic situation with a strong potential for disaster: a very
cold winter in the Middle East, no more rain in India, excess torrential rain in East Africa,
the Nile rising up from the present low level to an Amazon-like level, keeping out the
Aswan Dam and keeping out Egypt at the same time, causing a general mortality in the
eastern basin. This situation showed that humanity can create a sapropel situation just by
changing the local climate with an excess of some chemical product, in this case burning
crude oil. Prior to the conference, the appeal to put out the fires came only to America, but
after the July meeting more than 30 international bodies called for it and in November the
fires were extinguished. Little by little, things returned to their original state, but during the
1991/1992 winter it was snowing and freezing more than usual, causing problems in the
whole Middle East area. So beware, the sapropel is not just theory, the sapropel can return.
V. The Lessepsian Story - A Century of Man-Made Changes
We now leave the sapropel scale of 1-2,000 years (even though the mechanism can switch
on/switch off in 50-60 years, no more) and look at another present crisis. The
Mediterranean Sea is a warm sea populated by cold species. The present level of the Red
Sea is about 1.2 m higher than the Mediterranean Sea, so the physical pressure pushes the
sea water from the Red Sea to the Mediterranean basin. Now, the Suez Canal is like a
Mississippi running from the Red Sea to the Mediterranean Sea with an open gate. The
former high salinity barrier of Lake Ammer was changing after 50 years of desalinization
of the bottom. From 1970 to 1980, when Lake Ammer bottom water was of the same
salinity level as the Gulf of Suez (43-48%), the chemical barrier disappeared. Second, the
Nile did not act anymore as a freshwater tap at the entrance of the Suez Canal because the
Aswan Dam cut the Nile freshwater flow, to less than 10% of the previous level. So, the
Suez Canal is an open gate (14.5 m deep and 325 m large) running a huge volume of water
from the Red Sea to the Mediterranean. The result is Red Sea fauna entering more and
more in the eastern Mediterranean - first discussed by Por (1978) because along the Israeli
coast there was a change in fisheries, the fishermen catching more Red Sea fishes and
crustacean species than those of the Mediterranean.
This transfer phenomenon was named Lessepsian migration, from the name of the famous
constructor of the Suez Canal, Ferdinand de Lesseps. The Lessepsian province resulting
from this migration is shown in figure 5. You can see that we are returning to the preMessinian situation. With the entrance of plenty of new fishes and invertebrates in a very
short time (25-30 years), the biological balance of the eastern Mediterranean has been
changing very fast. Every year are discovered five to ten new species from the Red Sea and
from the Indian Ocean. You can see that mankind was able to return to a geological
situation. This is very interesting and a test of the fragility and the capacity for change of
the Mediterranean Sea.
VI. Black Sea Disasters
The fastest changing part is the Black Sea. It is a model of what happens in a crisis. We are
scientifically fortunate, but as part of mankind we are unfortunate to have that example.
What happened in the Black Sea in recent years? The economic development of big
industries and intensive agriculture in the eastern European area, Soviet Russia and the
Danubian states caused a drastic reduction of the inflow of fresh water with the increase of
fresh water used for irrigation and industries. So the present Black Sea is returning to a preglacial state with a low inflow of fresh water and the entrance of too much salt water,
changing the balance. At the same time, the remaining fresh water is heavily polluted with
phosphates and nitrates and also heavy metals.
As a consequence a general mortality has affected not only fish and shellfish but also
seaweed. As an example, the Black Sea was very famous for a large meadow of more than
11,000 km2 of five kinds of red algae (Phyllophora sp.), but from 1950 to 1980 there was a
general regression until a quasi-total disappearance occurred.
So the Black Sea was completely disturbed by the chemical and physical intervention of
man. The result was that only a few remaining organisms survived. And such surviving
capacity was giving them the possibility to bloom and make a general invasion of all
biotopes, i.e., when 90% of the organisms died, the remaining 10% of the organisms
exploded and colonized the whole water body.
In the Black Sea it was a local jellyfish, Aurelia aurita, that exploded between 1987 and
1989 (see figure 6; unit: billion tons of jellyfish), but in 1988 something new happened. It
was another jellyfish which competed making another bloom. This jellyfish, Mnemiopsis, is
an American jellyfish of the Nantucket area which was accidentally introduced into the
Black Sea: perhaps American ships visiting Odessa and the Sebastopol harbours
transported the jellyfish in the ballast tank and released them during the exchange of water.
Mnemiopsis reached complete saturation. The fisheries of the Black Sea collapsed by more
than 90% from 1 million tons to 100,000 tons. In only a few years everything can change, a
first crisis with a local species and the second with an exotic one. Figure 7 shows the
changes in the general balance of the basic trophic population. From 1978 to 1988, the
balance was the peak of jellyfish but the phytoplankton remained. In 1991-1992 the amount
of phytoplankton came down, Aurelia also went down but Mnemiopsis went up. This shows
the general components of trophic change in the Black Sea and is proof that in a very few
years everything can change.
VIII. Mediterranean Bottom Life in Question?
Another conclusion on a more general topic: we study now what happens in the deep seas,
we study the balance between the surface and the bottom. And we note that the next
eutrophication process, the next sapropel process can be predicted in a very few years. The
remainder of life in the depths depend on the balance between the oxygen content and the
oxidation coming from the surface by way of minerals or organic carbon.
Winter oxygenation with the prospect of keeping life in the depth of the Mediterranean
basin is quite simple. In winter, the cool air from the north decreases the temperature of the
surface. The high density winter water sinks and goes down and brings down the oxygen of
the surface and this gives the depths the capacity for life. If there are no more cool winters,
there is no more life. It is the cool winters of the northern Mediterranean that give the
depths life. If you have climate warming - and right now we have quite creditable data for a
warming - you don't have the currents resulting in the downward transport of oxygen nor
the upward transport of minerals to the surface. Now you have a cycle of oxygenation and
fertilization - winter cooling gives oxygen to the depths and summer returning the water
from the depths to the surface without oxygen but with minerals (potassium, phosphate)
and organic matter - and with that cycle of oxygenation and fertilization you have life. But
if the cycle is cut, life is interrupted and there is death.
Another question is that if the surface water has not only oxygen but an excess of mineral
salts the oxygen reduction cannot work. Figure 9 shows the critical level of the remaining
life in the depths. If the present trend of excess salt at the surface and the present trend in
warming remains there will be no more oxygen in the western basin around the year 2045
and in the eastern basin around 2055. The present trend is completely changing the capacity
of oxygenation of the deep bottom and so we predict that if we don't change in 50-60 years
we will have a general death.
Another fact: With a 3% rate of organic matter increase in the Mediterranean Sea,
saturation of the surface water will be reached from the continents in the eastern
Mediterranean around 2020-2025 (figure 10), so if the present trend continues, we must
face the next large-scale biological crisis in 25 years' time. If the inflow of organic matter is
controlled to maintain present levels, the crisis could be postponed until 50 years from now,
and, of course, by reducing the inflow we can buy even more time.
In conclusion, you can see that the crises are not only scientific curiosities or something
academic. Mankind has shown that it can change the environment and create crisis
conditions in a very short period of time, as compared with the geological time scale. To
save the Mediterranean Sea, we need to act quickly, and this requires political will more
than anything.
_________
References
Arthur (M.A.), Dean (W.E.), Neff (E.D.), Hay (B.J.), King (J.) and Jones (G.). 1994. Varve calibrated records
of carbonate and organic carbon accumulation over the last 2000 years in the Black Sea. Global
Biogeochemical Cycles, vol. 8, no. 2, pp. 195-217.
Bethoux (J.P.). 1989. Oxygen consumption, new production, vertical advection and environmental evolution
in the Mediterranean Sea. Deep-Sea Research A, vol. 36, no. 5, pp. 769-781.
Fairbanks (R.G.). 1989. A 17,000-year glacio-eustatic sea level record: influence of glacial melting rates on
the Younger Dryas event and deep-ocean circulation. Nature, vol. 342, no. 6250, pp. 637-642.
Howel (M.W.) and Thunell (R.). 1992. Organic carbon accumulation in Bannock Basin: Evaluating the role
of productivity in the formation of eastern Mediterranean sapropels. Marine Geology, vol. 103, no. 1/3, pp.
461-471.
Jones (G.A.) and Gagnon (A.R.). 1994. Radiocarbon chronology of Black Sea sediments. Deep-Sea Research
I, vol. 41, no. 3, pp. 531-557.
Lebedeva (L.P.) and Shushkina (E.A.). 1994. Modelling the effect of Mnemiopsis on the Black Sea plankton
community. Oceanology, vol. 34, no. 1, pp. 72-80.
Por (F.D.). 1978. Lessepsian Migration: The influx of Red Sea biota into the Mediterranean by way of the
Suez Canal. Springer-Verlag, Berlin, Ecological Studies, vol. 23, 230 p.
Por (F.D.). 1990. Lessepsian migration. An appraisal and new data. In: Godeaux (J.) ed., A propos des
migrations lessepsiennes. Bull. Inst. océanogr. Monaco, no. spécial 7, pp. 1-10.
Shushkina (E.A.) and Vinogradov (M.Ye.). 1991. Long-term changes in the biomass of plankton in open
areas of the Black Sea. Oceanology, vol. 31, no. 6, pp. 716-721.
Sonnenfeld (P.). 1985. Models of upper Miocene evaporite genesis in the Mediterranean region. In: Stanley
(D.J.) and Wezel (F.-C.), Geological evolution of the Mediterranean basin, pp. 323-353.
Stanley (D.J.) and Blanpied (C.). 1980. Late Quaternary water exchange between the eastern Mediterranean
and the Black Sea. Nature, no. 285, pp. 537-541.
Tang (C.M.) and Stott (L.D.). 1993. Seasonal salinity changes during Mediterranean sapropel deposition 9000
years B.P.: Evidence from isotopic analyses of individual planktonic Foraminifera. Paleoceanography, vol. 8,
no. 4, pp. 473-493.
Thiede (J.). 1978. A glacial Mediterranean. Nature, vol. 276, no. 5689, pp. 680-683.
Zaitsev (Y.P.). 1993. Impact of eutrophication on the Black Sea fauna. CGPM/FAO: Studies and Reviews,
no. 64, pp. 63-86.