the Institute's FACT SHEETS
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True to its missions, the Oceanographic Institute has been providing its audiences with summaries since 2011 to promote knowledge and protection of the Ocean.
These sheets are written by members of the Institute’s Scientific Council as well as by some of the world’s leading ocean experts. They are offered to help you better understand what is at stake today in terms of the functioning of the Ocean, marine biodiversity and the relationship between Man and the Ocean.
They are classified by publication number (1 to 103 as of September 2020) and colour-coded according to the theme of the sheet and related sub-themes.
How the ocean works
- Seawater chemistry
- Climate, Ocean/Atmosphere interactions, ocean dynamics
- Biodiversity studies
- Biological diversity, the appearance of Life
- Current threats to marine biodiversity
- Protection of biodiversity
Man and the Ocean
- Marine resources
- Environmental risk
- Ocean pollution
- Law of the sea, maritime law, conventions around the sea and international organizations
- Participatory science, mediation
- Scientific innovations and new technologies
- Art and science
Microalgae are a virtually unknown world of biodiversity, which presents
unsuspected promise of value-added in the fields of energy, nutrition, health and the environment.
pharmacology, cosmetics and nutraceuticals. However, for these opportunities to be
economically viable, research still faces many challenges, including
improve production processes.
Plastics undergo degradation processes in the ocean, resulting in the formation of microplastics that pollute 80% of the ocean surface (small particles can also enter directly). The major ecological risk is their ingestion by marine organisms and a possible transfer in the food chain that can lead to humans.
Another threat is that some of the plastics may spread invasive or toxic species. Their total clearance of the oceans is simply impossible. The solutions involve regulatory measures, changing consumer behaviour, increasing recycling, promoting the circular economy.
Walter “Zarh” Howlison Pritchard (1866-1956) was the first painter to don a diving helmet, weight his easel with lead, and produce oil paintings under the surface of the sea.
At the beginning of the 20th century, he turned to painting underwater scenes, from the warm waters of Tahiti to the icy seas of western Scotland. Today, his paintings take on a poignant quality as a record of once thriving marine environments.
Scattered throughout the decor of the Oceanographic Museum of Monaco, the jellyfish remind us that it was by collecting Pelagia noctiluca that Prince Albert I of Monaco began his career as an oceanographer. Then, in the bathypelagic fauna, the violet-purple colour of the Atolla intrigued him. This is what justifies their presence in the Museum’s decor.
By the time Prince Albert I of Monaco began his campaigns in 1885, the controversy over the famous azoic zone below 500 m had died down. And this is thanks to observations that the Prince considers to be the highlights of the history of biological oceanography, and whose emblematic animals he stages in the mosaics of his Museum.
Diatoms are unicellular microalgae present in all aquatic environments, particularly abundant in coastal regions and high latitudes. Their photosynthetic activity is equivalent to that of all tropical forests, making them a key component of aquatic food chains. Diatoms also contribute to the Earth’s biogeochemical cycles, and our oil and gas reserves are largely derived from diatoms. Scientists are keen to learn how they build their glass cell walls, so that the knowledge can be used for nanotechnology.
In 2014 and 2015, during his round-the-world trip on a sports catamaran, Yvan Bourgnon noticed that the sea was littered with plastic waste in certain places. With the creation of his association, The Sea Cleaners, dedicated to the fight against ocean pollution, he embarked on the design of a revolutionary vessel, a giant quadrimaran, the MANTA, a collector of plastic macro-waste. Presented at the COP22 in Marrakech in November 2016, it received a very positive reception and entered, at the beginning of 2017, its first study phases, with a view to the construction of the vessel.
The word “algae” refers to organisms that belong to lineages of the living world that are sometimes very distant from each other. Until the 1960s, the classification of living organisms included a plant kingdom subdivided into Cormophytes and Thallophytes (algae, fungi and lichens). But what do a porcini and a kelp have in common? The very notion of the “Plant Kingdom” is impossible to define clearly. The definition of algae is not simple and is more a matter of practical necessity than a natural group. For a systematist, algae do not exist.
The theory of endosymbiosis has now been solidly demonstrated: the mitochondrion is thought to be derived from a purple bacterium that has provided its host with the metabolic chains of respiration; the plastid originates from a cyanobacterium that has provided oxygen-producing photosynthesis. The most complex associations found in algae result from successive nesting of several prokaryotic and eukaryotic partners. The cells of eukaryotes, including our own, would therefore be chimeras resulting from the association and coevolution of several types of organisms.
Some of the decorations in the side panels of the ceiling of the conference room of the Oceanographic Museum in Monaco represent marine animals selected from illustrations in the book Kunst-Formen der Natur published in 1904 by Ernst Haeckel, professor of zoology in Jena (Germany). In the centre of this ceiling, six paintings are allegories of important moments in the career of Prince Albert I of Monaco, the Prince Savant.
An endocrine disruptor is a substance or mixture of substances that alters the functions of the endocrine system. They can be of natural or anthropogenic origin. These compounds will eventually be found in all ecosystems, and ultimately in the marine environment. Their harmful effects in the marine environment are now well established: these compounds can induce developmental and/or reproductive disorders in exposed organisms. They have become a global concern and are considered one of the most serious threats to biodiversity and ecosystem health.
As early as 1959, the Antarctic Treaty, of indefinite duration, reserved the southern region for peaceful and scientific activities only. A territorial “freeze” has been retained. Activities relating to mineral resources other than those carried out for scientific purposes are prohibited. The legal framework for human activities has been strengthened by the adoption of new decisions by States on tourism. Together with the conventions that have entered into force, they form what is known as the “Antarctic Treaty System”. States shall ensure that the cooperation they have successfully established in the Antarctic is sustainable.
Long considered as fatty substances serving as energy reserves, lipids have been recognized as essential constituents of cell membranes, and various advances now give them the status of biochemically active compounds in the cell. Certain lipids contribute to the maintenance of good health and are of interest in the prevention and treatment of pathologies. The extraordinary molecular diversity of marine organisms, often without terrestrial equivalent, constitutes the most original, vast and promising source of biologically active lipids.
Photosynthesis ensures the production of living matter from solar energy. Light energy is captured by the chlorophyll. Other pigments act as light-collecting antennae, giving the organisms various hues. Research has made it possible to trace the origin and evolution of photosynthesis in living beings. Photosynthesis, invented by bacteria, has been acquired several times by various lineages of eukaryotic organisms without direct kinship. These results explain why all organisms capable of photosynthesis are no longer grouped into a single set in modern classifications.
Squid include about 290 species. The largest marine invertebrates belong to this group. These molluscs have been increasingly exploited by fishermen since the second half of the 20th century. Most of the 40 species caught complete their life cycle in one year. Their survival in the wild is not well known because their rapid growth means that they cannot be caught for long by the same type of gear. The classic approach, by modelling in order to allocate them to fishing quotas for each fleet, in fisheries biology is not always transposable to these molluscs.
Stained glass windows are located in the library of the Maison des Océans, the Parisian establishment of the Oceanographic Institute, Foundation Albert I, Prince of Monaco. The painting of these stained glass windows was the subject of a study of the technique of their realization. The theme is based on illustrations from the illustrated plates of the German naturalist Ernst Haeckel.
The Maison des Océans in Paris, founded by Albert I, Prince of Monaco, is decorated with a stained-glass window representing eighteen marine animals, reproduced from the plates of Ernst Haeckel’s book Kunstformen der Natur. The selection seems to have been dictated by the Prince’s favourite themes: origin of life, emergence from the water to the earth, symmetry planes, viviparity, protection of the young. At the beginning of the 20th century, these themes were still arguments in support of the theory of evolution.
The OceanoScientific Programme, which was established in 2005, is in line with the global science policy on climate change. The OceanoScientific Campaign consists of a series of expeditions around Antarctica, on a specially designed sailboat, equipped with sensors for about ten parameters. This sailboat evolves at the ocean-atmosphere interface without polluting its environment, nor diverting the wind, nor distorting the temperature readings of the surface sea water. It is also able to move on the ocean, in total energy autonomy. The inaugural expedition left Monaco on November 17, 2016, led by Yvan Griboval solo.
DORIS is a participative website from the French Federation of Underwater Studies and Sports. From its conception, it was also intended to become an educational tool, as a source of information and photographs, at the service of FFESSM executives. The idea of an illustrated file of underwater species as exhaustive as possible was born from an observation: the vast majority of current fauna guides present 80% of the same species. It is often difficult to find information to help determine a less common species that nevertheless arouses curiosity!
Born in 1882 in Lamballe, Mathurin Méheut enrolled at the age of 20 at the School of Decorative Arts in Paris and at the Normal School for Teaching Drawing. He began to approach the marine environment in 1910. In 1913, he participated in the first animal painters’ exhibition and acquired the title of animal painter. Méheut’s art was largely inspired by the reality of the marine world and its biodiversity. As a craftsman and naturalist observer, Méheut was able to combine scientific truth with an aesthetic form of harmony.
Large, highly protected marine reserves are an essential tool for addressing several issues that affect the health of the ocean. These reserves protect ocean areas from destructive human activities, such as industrial fishing, illegal fishing or natural resource extraction. They also help preserve species, habitats and the functional diversity of ecosystems. Yet to date, only about 2% of the world’s oceans have been designated as highly protected marine reserves.
The Pew Charitable Trusts and several partners launched the Global Oceans Legacy Project in 2006. The goal is to help create marine reserves of at least 200,000 square kilometres. World Ocean Heritage works with communities, governments and scientists around the world to safeguard some of the world’s most important and best preserved ocean environments. To monitor and enforce nature reserves, Pew has partnered with Satellite Applications Catapult, a UK government initiative, to launch the Eyes on the Seas project and its virtual monitoring centre.
In 1925, “bacteria” in the sense of the time (called prokaryotes) were considered fundamentally different from all other living things (called eukaryotes).
The strong resemblance of the plastids and mitochondria to bacteria, as well as observations followed by numerous studies, showed that they would be prokaryotes that settled in eukaryotic cells and co-evolved with them. Advances in genomics now tend to show that a massive transfer of bacterial genes into an archaea preceded these installations. Eukaryotic cells would therefore be chimeras containing genetic material of multiple origins.
Used since ancient times, natural sponges belong to the group of Sponges, whose animal or vegetable nature has long been debated. They would represent the oldest multi-cellular animals. These filter-feeders have a major impact on water quality. In the abyss, some sponges have become carnivorous. They are found from the coast to the deepest depths, and there are freshwater species. Easily accessible to predators, they defend themselves by producing an exceptional variety of more or less toxic molecules, which are of great interest in pharmacology.
The living marine world can be considered as a natural deposit rich in a wide variety of compounds and biologically active molecules, often without terrestrial equivalents. Marine organisms live in very different conditions and can sometimes be exposed to extreme conditions. They produce a wide variety of substances with specific activity, in particular lipids, major sources of metabolic energy and essential materials for the formation of cell and tissue membranes. This synthesis presents the main classes of marine lipids, of interest in human nutrition and health, and their sources.
The development of fisheries has resulted in a massive impact on the living resources of the sea and a sharp decline in the abundance of target species. The challenge is to limit the impact of fishing on resources and ecosystems. It is up to policy makers to choose a management objective that is considered desirable and sustainable.
Stock assessments are carried out by groups of experts, who meet annually at the initiative of international organizations that are gradually being set up in all the world’s oceans.
Aggregates are the second most consumed natural resource in the world, and include mainly sand and gravel. They form on geological time scales. The exploitable resources of sand and aggregates are limited and non-renewable. The world consumption of aggregates is growing and reaching colossal values. Siliceous aggregates are mainly used for construction, beach nourishment and coastal protection, land reclamation, roads and railways, and drainage. The limestone aggregates are used for the amendment of agricultural land.
Atlantic bluefin tuna migrate extensively between the cold regions where they feed and the warmer regions where they spawn. A very fertile species, it can live up to 40 years. In the Mediterranean basin, it has been exploited since the Neolithic period. Atlantic bluefin tuna is exploited by more than 20 countries. The boom in the sashimi market has led to overexploitation. The International Commission for the Conservation of Atlantic Tunas adopted a recovery plan for eastern Atlantic and Mediterranean bluefin tuna in 2007, which has led to an improvement in the situation.
Marine litter is defined as any persistent solid material that is manufactured or processed and left or abandoned in the marine environment. This is a complex problem with important consequences for the marine and coastal environments and the human activities that take place there. This waste comes from many sources and generates a wide range of environmental, economic, health and socio-cultural impacts, as well as on safety at sea.
The climate of northern Africa underwent a rapid change about 10,000 years ago. The Sahara was then a region covered with vegetation, whereas today we only see dry, bare soil. This oscillation, between a humid climate and aridification, is revisited using powerful geochemical tools. This work, covering the last 20,000 years, makes it possible to establish a link between paleo-environmental variations and the phases of human evolution and/or occupation along the Nile watershed.
Rogue waves are isolated waves that are abnormally high compared to the surrounding wave field. They are dangerous because they are unexpected, in a given wave field to which the sailors have spontaneously adapted, and they escape their vigilance. In some cases, they can reach 30 m in height. Seafarers are paying more and more attention to them as they are more frequently reported by sailors nowadays. Recently, they have become the subject of more scientific approaches.
A tsunami is a wave generated by a sudden movement of the sea floor. Characterized by a long wavelength, a tsunami loses very little of its mechanical energy as it travels and can cross an entire ocean: distant tsunamis can be just as devastating as local tsunamis. Their sometimes very high speed of propagation increases the constraints of remote tsunami warning systems and makes it necessary to educate the population, when dealing with local tsunamis. Coastal morphology can enhance or mitigate tsunami amplification processes.
In the Arctic, the warming of the surface and the retreat of the sea ice are exceptional compared to the previous 1,400 years. Dramatic changes are occurring in the cryosphere. On a large scale, human influence is currently the dominant factor in Arctic warming.
On the other hand, Greenland’s is 1/3 due to human influence, and 2/3 to the configuration of the atmospheric circulation. The melting of the Arctic ice will continue, even in the most optimistic scenarios for controlling greenhouse gas emissions.
Invasive species are generally known to proliferate and compete with native species or those exploited by humans. Eradicating them or controlling their biomass is a very expensive and long-term challenge. However, the biomass of certain species, such as grateloupe and crepidula, which is available in large quantities and renewable, could be of great economic interest and become a source to exploit.
The contribution of coastal zones to sustaining the ecosystems that enable the development of most of the human societies that live there is important. Since 1993, the Land-Ocean Interactions in the Coastal Zone (LOICZ) programme has evolved from a project originally based on biogeochemical fluxes to include the challenge of sustainability of socio-ecological systems in the coastal zone. Renamed the Land of the Future – Coasts project, it is entering a new era of research to provide knowledge and support for transformations towards a sustainable world.
The first sailing story is the famous journey of Ulysses in the Mediterranean, a journey so wonderfully recounted by Homer almost three millennia ago. Recognized as the first literary masterpiece, the Odyssey features the mythical hero grappling with the vicissitudes of a sea voyage, which, while adding an epic note, is above all an extraordinary description of the sea.
Tropical coral reefs must be exposed to sunlight to allow photosynthesis of their endosymbiotic algae. Corals therefore receive high doses of UV from the sun. Strong UV radiation causes damage to biomolecules such as DNA and proteins. To avoid the damage of solar radiation, the coral tissues contain anti-UV solar filters, called mycosporin-type amino acids, molecules produced jointly by the host coral and the symbiotic algae, which intercept and neutralize UV rays.
The Southern Ocean is bounded by the Circumpolar Current, which forms an ecological barrier. Its benthic invertebrate fauna is rich, diverse and abundant. It has many characteristics: strong endemism, gigantism, important proportion of “incubating” species. Many species live in wide depth ranges.
This fauna, whose biodiversity is underestimated and which is adapted to an extreme environment, is unique and fragile, and will not be able to resist the impact of global change.
Four key factors differentiate the high seas from coastal waters and must be taken into account in management approaches: depth and three-dimensionality, wide species ranges, habitat stability, and links between the seabed, water column and surface waters.
Human activities on the high seas are damaging essential vertical and horizontal linkages. To mitigate these effects, the high seas must be managed in an integrated manner, explicitly taking these linkages into account.
Until 2008, it was believed that two billion years ago, the Earth was populated only by micro-organisms. But the Gabonese fossils, biota called the Gabonionta group, prove that something radically new happened at this time: cells began to cooperate to form larger, more complex units. From that moment on, the way was open for new evolutionary experiments, which would transform the biosphere by enriching it with multi-cellular organisms.
Cold fluid outflows from the seafloor, particularly within continental margins, are still poorly understood and are likely to be more abundant than those from hydrothermalism. These fluids can be emitted, depending on their depth of origin, at temperatures of several tens of degrees. The importance of these fluids is relatively recent. Locally, these fluids released on the seabed can have a significant impact on the deep environment and the establishment of specific ecosystems.
When the Mediterranean was part of the ancient Tethys, it had many reef formations, which became extinct during the Messinian salinity crisis. When the Strait of Gibraltar was opened, new species of coral reappeared, and the Mediterranean currently has more than 200 of them, which have colonised all environments, from the surface to more than 1 000 m deep. Hard corals in the Mediterranean can give rise to quite significant bioconstructions. Deep cold coral reefs have taken hundreds of years to form, but are under inexorable threat.
The existence of these gigantic, aggressive sea creatures with huge tentacles, capable of sinking ships, has captured the imagination of humans since ancient times. The first encounter with a real giant squid took place on November 30, 1861 off Tenerife. The knowledge of these giants living in an environment relatively close to man, populating all the oceans between about 250 and 1,300 m deep, was a challenge for scientists in the mid-20th century. In 2004, Japanese researchers took the first photos of a giant squid in its natural habitat.
The proportion of marine fish stocks considered to be fished at biologically sustainable levels has declined from 90% in 1974 to 71.2% in 2011. The decline of large predators in coastal areas has spread throughout the ocean, with potentially serious consequences for ecosystems. Among fish, concerns include selachians, sturgeon and the European eel, as well as groupers and tuna.
The sensitive and protected habitats damaged by illegal fishing are mainly Posidonia meadows, coralligenous bioconcretions, calcareous red algae beds and deep white corals.
One of the major consequences of climate change is the rise in sea levels, caused mainly by the thermal expansion of the oceans, the melting of polar ice caps and mountain glaciers. Over the next few decades, climate scenarios indicate that this process will continue and accelerate.
Rising sea levels pose a threat to low-lying and densely populated coastal areas, which will then be at greater risk of erosion, flooding and saline intrusion into aquifers. It also raises the question of the future of the low-lying islands, especially the atolls.
Sometimes during the spring and summer, the sea gets colored and cloudy. Some beaches are covered with whitish, foul-smelling moss deposits, dead fish or green algae deposits… These nuisances are the various symptoms of a malfunctioning marine coastal ecosystem subjected to increasing inputs of nutrients of human origin: the sea is suffering from an excess of nutrients. The phenomenon is called anthropogenic or cultural eutrophication.
The international community’s concern for the conservation and sustainable use of marine biodiversity in areas beyond national jurisdiction (ABNJ) is growing with the increase in threats, as well as with the difficulties in reaching international agreements. The NLFAs include the high seas and the Area. They represent about 50% of the Earth’s surface, host a significant percentage of its biodiversity and are in urgent need of governance and protection measures. Seamounts, deep coral reefs and hydrothermal spring habitats are considered priority candidates for new MPAs.
Sharks have a very particular skin covering, made up of thousands of denticles whose tips are oriented towards the back of the body. These elements, also known as odontodes or placoid scales, differentiated more than 420 million years ago, cover the bodies of the majority of the approximately 1,150 species of sharks and rays currently recorded.
Skin denticles owe their name to their dermal-epidermal structure, similar to that of a tooth. Replaced continuously throughout the life of the animal, they present a great polymorphism.
Seas and oceans represent more than 90% of the volume available to life. Out of just over 2 million species, less than 250,000 live in the ocean. Life appeared in the ocean about 3,900 million years ago (Ma) and only emerged from the ocean about 450 Ma ago in the case of elaborate forms of metazoans. Then from 130-115 Ma, speciation exploded on the continents. So why doesn’t the ocean have as many species? Connectivity and stability explain this apparent paradox. The ocean, however, is home to many more groups and phyla.
The protection of coastal and marine areas is generally intended for practical purposes, although generally the main focus is on the protection of biodiversity. The sustainable use of marine resources requires that certain areas be maintained in their natural state. Safeguarding habitats critical to fish production, preserving genetic resources, protecting scenic sites and benefiting from natural heritage all require protection management, as well as appropriate regulations and legislation. The main tool is the establishment of marine protected areas, with different degrees of restrictions and types of management.
During the tsunami of March 11, 2011, 50-foot waves hit the Fukushima-Daiichi nuclear power plant, causing major damage to the entire power grid. The uncooled fuel rods overheated, producing hydrogen gas. Hydrogen explosions resulted in fuel melting. Radioactivity was released, prompting an extensive evacuation operation. The liquid discharges have caused ongoing contamination of the marine environment, and ocean currents have carried radionuclides into the Pacific Basin. Contaminated groundwater near the nuclear plant has been a major concern.
The Mediterranean owes much of its richness to two coastal habitats, including the coralligenous. Its upper boundary is marked by the presence of photophilic algae, while at its deeper boundary the last macrophytes disappear. Two types of populations can be distinguished: wall coralligenous (the cover is mainly made up of sciaphilous algae and invertebrates), and coralligenous bioconcretion (the main structure is built by calcified coralline algae and secondarily by other less calcified algae and invertebrates with a mineralized skeleton). The coralligenous is a jewel of the Mediterranean’s underwater heritage, but it is fragile.
Scientific research in recent decades has changed our perception of sharks, which are still enigmatic in many ways. They are creatures perfectly adapted to their environment and to their function as predators. Sharks have a long evolutionary history: more than 3,000 fossil species are known, and today 530. Once abundant, many shark populations are in decline due to overexploitation. There are a few dozen shark attacks on humans per year worldwide.
Plate kinematics is the study of the past and present movements of the tectonic plates that make up the most superficial envelope of the solid earth called the lithosphere. It is simply the quantitative extension of the theory of plate tectonics, which Wegener first predicted as “continental drift” at the beginning of the last century, but whose concepts were definitively established in the mid-1960s.
Ocean ridges are the site of intense tectonic, volcanic and hydrothermal activity. The sea water infiltrates and percolates through the permeable zones thus created. It heats up by several hundred degrees per kilometre, reacts strongly with the rocks it passes through and becomes loaded with many chemical elements, as well as dissolved metals. Warmer, it rises and spurts out onto the sea floor. Its sudden cooling, by mixing with water at 2°C, leads to the crystallization of the dissolved elements which then form metallic sulphides.
The United Nations consists of a central core around which specialized agencies and affiliated organizations revolve. UNCLOS is the major legal instrument for addressing ocean governance. The IMO deals with issues relating to maritime transport. FAO is the competent international authority for setting technical standards for fisheries, UNEP plays a similar role in environmental protection and regional coordination of the seas, and UNESCO’s IOC deals with oceanography and marine technology. Other UN organizations have an interest in the oceans.
The marine environment contains almost all living phyla. This legacy of a long evolutionary history makes the marine environment a gigantic genomic repertoire. To date, marine genetic resources are only partially covered by existing conventions and protocols. Research and development of marine biotechnology is essential, but there is also a need to establish a governance framework that restores ethics, equity and consistency in its exploitation. In the situation of accelerated degradation of marine ecosystems, this solution, on which our capacity to protect them also depends, is urgent.
The physical oceanography of the Mediterranean Sea depends mainly on the exchange of water between the sea and the atmosphere, but also on the Coriolis effect, due to the rotation of the Earth.
The Mediterranean climate is relatively dry. The losses of the sea by evaporation are not compensated by the contributions of precipitations and rivers, and, if it did not communicate with the Atlantic Ocean, its level would drop by about one meter per year!
The “Mediterranean machine” transforms oceanic waters with relatively variable characteristics into a series of colder and saltier waters with relatively specific characteristics.
Since April 14, 2006, French marine nature parks aim to protect the sea while promoting the sustainable development of local maritime uses. The first natural marine park was created in 2007 in Iroise. After a phase of consultation with local stakeholders, every marine nature park is created by an interministerial decree. The parks depend on the Marine Protected Areas Agency (now integrated into the French Agency for Biodiversity), under the supervision of the Ministry of Ecology. Some parks and study missions have a cross-border identity by nature.
Sustainable use of the ocean requires understanding it before using it. It is vital to acquire reliable data at selected points in the world ocean to identify changes related to natural phenomena or those related to human activities. This need for time series made it necessary to launch the challenge of multidisciplinary underwater observatories. ESONET aims to prepare the implementation of seabed observatories at 12 sites in Europe. The next step is to federate these multidisciplinary underwater observatories and build new ones; this is the role of EMSO.
Operational oceanography now provides information on the “ocean as it was”, “ocean as it is” and “ocean as it will be” tomorrow. Technological advances in satellite observation, autonomous at-sea measurements and scientific computing, combined with the development of complex mathematical models and assimilation techniques, gave rise to this new component of oceanography some 15 years ago. The fields of application of operational oceanography naturally respond to major climatic, ecological and socio-economic issues.
The IPCC was created in 1988 with the mission of taking stock of knowledge on climate change. Under the supervision of WMO and UNEP, the experts, divided into three groups, regularly produce a general report. Group I’s contribution to the 5th report was approved at the end of September 2013. For the first time, an entire chapter is devoted to sea level rise. The ocean slows global warming, but absorbs about a quarter of the CO2 released. It will continue to warm in the 21st century, adding to the damage from acidification.
The ocean is made up of a set of ecosystems that are separated by invisible boundaries. In 1998, Alan Longhurst described 56 biogeochemical provinces, bounded by boundaries that are easily identifiable as convergence, divergence or other types of oceanic frontal zones. The increasing availability of observations of the marine environment has allowed the development of so-called ‘robust’ or ‘correlative’ biogeographic approaches, as compared to the so-called ‘descriptive’ historical approaches. In a context of global ecosystem change, the establishment of regional and global ecosystem divisions is a necessary prerequisite.
In the sea, chemical communication systems are an indispensable element in the establishment of intra- and interspecific relationships. Moreover, the vector function of water favours chemical communication phenomena. Marine biodiversity and the resulting chemical diversity are mobilizing a growing number of research teams, and major pharmaceutical companies are looking into this pool of molecules. The persistence of chronic or acute forms of certain diseases and the emergence of resistance phenomena mean that the need for new-generation drugs is topical. The oceans are a resource that is still under-exploited.
Silicon is abundant on the planet Earth, mainly in the form of silica, which is a component of many minerals. Si is one of the key elements involved in the biosphere. The leaching of siliceous minerals by rainwater produces soluble silicic acid (Dsi). Many living organisms are capable of absorbing Dsi: diatoms, silicoflagellates, radiolarians, several species of choanoflagellates and some sponges. As the first link in the food web, diatoms contribute nearly 50% of the primary production of the world’s oceans, and through photosynthesis produce about a quarter of the oxygen we breathe.
Sea level rise is a global issue because half of the world’s population lives within 200 km of a coastline, and 1 in 10 people live less than 10 metres above sea level. Various compilations confirm an acceleration of the rise in sea level with an average rate of less than 1.5 mm/year before the 1950s, up to more than 3 mm/year today. Altimetry data confirmed the rise in sea level. Current trends are expected to continue due to global warming.
Every day, the oceans absorb a quarter of the carbon dioxide produced by humans. The result? The acidification of the oceans is not without consequences for certain species of marine plants and animals. Ocean acidification is sometimes called “the other CO2 problem”. The dissolution of CO2 in seawater leads to chemical changes: a decrease in pH and in the amount of carbonate ions, one of the building blocks needed by marine plants and animals to make their skeletons, shells and other calcareous structures.
The Commission on the Limits of the Continental Shelf is one of the three organisations explicitly created by the United Nations Convention on the Law of the Sea of 10 December 1982. The needs that led to its establishment are related to the evolution of the continental shelf as a legal concept and the need to establish the outer limits of coastal States in this maritime area, separating the seabed and its subsoil that are to be considered under national jurisdiction (continental shelf) from those that are beyond national jurisdiction and are therefore included in the Area.
The development of new tools has allowed demonstrating that microbes dominate both in terms of abundance and biomass the world oceans. They are of size ranging from 0.02 to a few micrometres and include a wide diversity of viruses, prokaryotes and eukaryotes. They play crucially important functions and control the global biogeochemical cycles. We now know that viruses are the most abundant biological entities of the biosphere. This huge numerical abundance suggests that viruses can account also for the vast majority of the genetic diversity of the Earth. They can infect all the known life forms of the oceans.
Near-shore macro-algae blooms are the most widely known cases of marine eutrophication. Eutrophication can be summarized as the production and accumulation, following a significant nutrient enrichment of the environment, of a plant biomass that is excessive in relation to the biological consumption or physical evacuation capacities of the ecosystem. These blooms are widespread throughout the world. The stagnation of high algal biomasses leads to their death and bacterial degradation. A life-threatening health hazard is created by rotting algae deposits.
Sea turtles have been roaming the oceans for over 100 million years. These animals are perfectly adapted to aquatic life. They have a very complex life cycle. Depending on their ontogenetic stage, they occupy different habitats: terrestrial for nesting, pelagic during migration, and neritic for feeding. The turtles travel several thousand kilometres each year to reach them. They are in danger of disappearing from the planet because of human activities.
The term “model organism” is reserved for a few species used by a large number of researchers. However, a host of marine organisms have contributed to important discoveries. Their initial importance has diminished over time as reference models have become more and more prevalent in research and teaching programs. Developing models in all branches of the tree of life is necessary because we never know if the knowledge established in model species applies to all organisms.
The United Nations Convention on the Law of the Sea divides the ocean into six major maritime zones. Four of these areas are under the jurisdiction of the coastal State. The other two correspond to maritime areas beyond national jurisdiction: the high seas and the area of the seabed beyond the continental shelf, known as the Area. The Area has the status of a common heritage of humanity. The International Seabed Authority is an autonomous international organization through which States Parties to UNCLOS organize and control activities in the Area.
Coral reefs are underwater formations made up of a tangle of limestone skeletons belonging to the organisms that build them. Reef-building corals form colonies composed of a large number of entities called polyps. There are two categories of coral reefs: cold-water reefs and tropical reefs.
The main forms of reefs are fringing, barrier and atoll.
Prey is the only food for cold-water corals. In contrast, tropical corals harbour microscopic algae inside their digestive cells. This mutually beneficial association is a symbiosis.
New chemical molecules are constantly being synthesized and are potential sources of harm to the environment, particularly the marine environment. Solid waste can physically reach organisms. They degrade slowly in the ocean into very small particles that, when ingested, contribute to chemical contamination. A more insidious threat comes from repeated exposure to low doses of pollutants. The action of these pollutants may be immediate or may only become apparent in the long term.
The role of scientific mediation does not only involve the popularization of knowledge. Today, knowledge alone is no longer sufficient to deal with the complex problems facing our societies. Behavioural changes are essential for the preservation of the oceans. Contemporary mediation develops a more dynamic educational policy, based on awareness, dialogue and action. Its mission becomes broader, it becomes the interface between the scientific world, the public, civil society, political and economic decision-makers and the media.
In the absence of oxygen in the atmosphere and ocean, iron is soluble. With the development of photosynthesis, iron is only transiently present in the oceanic water column. Microparticles carried by the wind enter the food chain very quickly. The atmosphere of the ice ages was much richer in dust than that of the warm periods, and scientists have speculated that a more abundant supply of iron to the ocean may account in part for the lower carbon dioxide content of the atmosphere.
Hydrothermal” springs are outlets of fluids on the seabed, whose temperature is higher than that of the surrounding water. These emissions reflect the circulation of seawater through fractured rocks under the influence of a heat source. Although the geochemical composition of hydrothermal fluids is highly variable, with a few exceptions they share common characteristics: acidity, “reducing” properties, characterized by the absence of oxygen, and above all high concentrations of sulphide and metals.
The ocean remains largely unexplored. An ambitious programme, Census of Marine Life (CoML), was conducted from 2000 to 2010. He initiated and established the first documented global inventory, stimulated exploration and gave new impetus to species recognition. This Alfred P. Sloan Foundation program has stimulated the contribution of hundreds of institutions and donors from more than 80 countries on all continents. 2,700 scientists contributed to the first baseline of the diversity, distribution and abundance of life in the ocean.
Posidonia oceanica is an endemic species of the Mediterranean. This “engineer” species forms vast meadows which play a major role at the ecological, sedimentary and economic levels. They also provide information on the general state of the water. Posidonia meadows are able to act as a “shock absorber” in the event of extreme weather events. Their major role lies in their capacity to store carbon. The sensitivity of Posidonia meadows to high temperatures may result in their weakening or replacement by other marine magnoliophytes with a warmer affinity
Launched in 2000 by the Intergovernmental Oceanographic Commission and the World Meteorological Organization, the Argo program aims to develop a global network of 3,000 autonomous profiling floats that measure the temperature and salinity of the upper 2,000 meters of the ocean in real time every 10 days. Argo is the first global real-time in-situ ocean observation network. This is a real revolution in global ocean observation. In just a few years, Argo has become the most important source of data for researchers interested in studying the ocean and its role in climate.
Marine ecosystems derive their robustness from the diversity generated by evolution. This diversity, which gives planktonic ecosystems an adaptive capacity, is probably due to the speed with which these organisms reproduce, while being transported by the currents. The goal of TARA OCEANS has been to capture a snapshot of these processes by sampling ecosystems from viruses to zooplankton across the oceans, and then to develop a method to analyze the complexity of these ecosystems. The idea is to define a strategy to characterize the “life domain” of planktonic ecosystems.
Of the solar energy that enters the Earth system, 56% is absorbed by the ocean, which in turn gives some of it back to the atmosphere. This coupling between the ocean and the atmosphere means that the oceanic surface circulation is an imitation of the atmospheric circulation. The thermohaline circulation corresponds to currents produced not by wind but by differences in density between oceanic water masses. A complete turn of the oceanic general circulation takes about a thousand years. This is the so-called “conveyor belt”, which plays an important role in climate dynamics.
The plankton encompasses an incredibly diverse group of organisms, ranging from viruses to large jellyfish, united only by the fact they are all weak swimmers. As the plants of the seas are microscopic, it is not surprising that the herbivores, or grazers of the sea, are also microscopic. The microzooplankton are the organisms which feed on the phytoplankton. They are organisms of a size between 20 and 200 microns. They are what is known as a ‘functional group’, rather than being a group formed of organisms of close heredity.
In ancient times, the nuisance caused by jellyfish prompted Aristotle to give them the name “cnid” (Greek for “stinging”), and as a tribute to them, scientists created the group of Cnidaria to designate all the animals with this function: jellyfish, siphonophores, corals, sea anemones, gorgonians, etc.
Jellyfish are in the news because of envenomations. Because of their pullulations, the general gelification of the oceans due to human activity reflects a dangerous deviation for the economy of the seas because the jellyfish do not have a great food value. This sheet also demonstrates the interest and above all the place of these lower animals in biology, as models both for studies on the marine environment and for studies on the mechanisms that ensure the maintenance of life.
The influence of the environment on marine ecosystems was established in 1887 by a German oceanographer and biologist, Victor Hensen. A century later, an American ecologist, Robert Paine, noted that when a given trophic level was abundant, the lower levels had sparser populations. He introduced the notion of a “trophic cascade”, which was later applied to many marine ecosystem dynamics: when the population of predatory fishes decreases, prey fishes proliferate. The depletion of large predatory fish is profoundly changing the way marine ecosystems function.
In the 1970s, around 50% of the traditional fishing stocks in continental shelves were considered at their maximum sustainable level, or fully exploited. This led to the migration of the fleets to exploit deeper waters in the 1980s and 1990s. The use of intensive trawl technology in deep-sea fisheries was also found to be associated with incidental catch of benthic organisms and habitat disturbance. These fisheries lead to habitat degradation with effects on the local biodiversity and the biomass of the benthic species.
The ocean is the main regulator of the global climate. Its interaction with the atmosphere and its consequences are central to the climate system. First of all, it is the great thermal inertia of the ocean, compared to the atmosphere, which allows it to store solar radiation in summer and to release this thermal energy to the atmosphere in winter…
The ocean is the main regulator of the global climate. Its interaction with the atmosphere and its consequences are central to the climate system. The great thermal inertia of the ocean, compared to the atmosphere, allows it to store solar radiation in summer and to release this thermal energy to the atmosphere in winter. The ocean has been warming in recent decades. 90% of the excess heat accumulated in the climate system over the past 50 years due to anthropogenic warming is stored in the ocean.
We expect 9 billion people in 2050! Until now, almost all of the energy and mineral resources that humanity has needed have come from the exploitation of land. These resources have been largely exhausted. If we want to keep our lifestyle, our only alternative is to go elsewhere! The easiest way is to go and find the energy we will be dependent on for a long time, as well as metals and rare earths, under the surface of the oceans. In addition to technological and environmental challenges, there is also the problem of appropriate international legislation.
Ice floating on the sea surface occurs throughout the Arctic Ocean and near the Antarctic continent. A distinction must be made between the tabular ice sheets formed on the continents, which are the origin of icebergs, and the ice floes that form when sea water freezes during the meteorological winter. This solid ice substrate is home to a complex population that is very active even though the temperature is very low…
In the past geological and physical changes were the main responsible of the most dramatic changes in biodiversity in the Mediterranean sea. Nowadays human activities are essential elements to be considered. The most important threats are habitat loss, degradation and pollution, overexploitation of resources, invasion of alien species and climate change…
Molecular biology is a recent science. The discovery in 1969 of an enzyme will allow its exponential development by allowing the cloning and sequencing of genes. 17 years later, genomics is a revolution: it has changed our vision of the organization of living organisms, and also shows that an organism constitutes an ecosystem in itself. Marine life is much older and more varied than terrestrial life. By using DNA sequences, it is possible to inventory biodiversity much more easily than by conventional methods and to show that marine biodiversity is largely underestimated.
Marine fisheries have a direct impact on the resources they exploit, but also have indirect effects on other species. For a long time, marine resource management has been conducted on a stock-by-stock basis, neglecting the complexity of interactions within marine ecosystems. By-catches and the destruction of habitats by fishing gear appear increasingly irreconcilable with sustainable fisheries management. A more holistic view of ecosystem management has recently emerged with the ecosystem approach to fisheries…
Corals that occur in tropical seas are well known for their structural beauty. But corals are not restricted to the shallow waters of tropical seas. Well deep in the ocean, many species of corals compete in diversity and complexity with their shallower relatives. They are either known as cold-water, because some are able to live in temperatures as cold as 4 °C, or as deep-sea corals, because some species reach depths below 2000 or 4000 metres. There are as many species of cold-water deep-sea corals as shallow-water tropical corals…
During the last glacial maximum, the sea level was about 130 metres lower. With the melting of the ice caps that covered northern America and Europe, the sea rose and then stabilized about 3,000 years ago. Tide gauge observations indicate that the sea has begun to rise again. All evidence suggests that the current sea level rise is related to global warming. Thermal expansion of the oceans explains part of the observed rise in sea level…
This small marine area, which has seen the birth of many religions and most of the great civilizations around it, is a very fragile domain, inherited from a very long geological history, and inexorably condemned to disappear like its great ancestors, to which the many mountain ranges surrounding it still bear witness
The sea is in constant exchange with the atmosphere. The wind deforms the surface of the sea and transmits energy to it. Air, and even more so water, absorbs solar radiation. The sea is a reservoir of heat, some of which is returned to the atmosphere. The spray washes away the components of the surface layer. Gases can pass through the surface of the sea. The oxygen produced by phytoplankton diffuses into the atmosphere when it is supersaturated. Carbon dioxide, produced by respiration, is consumed by phytoplankton. It enters as an element in the buffer system that determines the pH of the sea…
Non indigenous species have become a hot issue in recent decades in particular in the Mediterranean Sea. There are debates about the number and especially on positive and or negative effects of new entries, that are related to the very long history of Mediterranean biota and to the plurality of causes, both natural and anthropogenic, of the recent introductions. Although some aliens may be responsible for strong ecological impact and in particular for reducing the population of some native species, others as crustaceans and fish have become important fishery resource.
Like medicine, oceanography is entering the era of tomography, which focuses on the three-dimensional totality of the object under study and its temporal evolution. This revolution in oceanography is based on autonomous underwater robots, whose measurements are coupled with those of conventional mobile and fixed platforms and ocean observation satellites. This coupling results in integrated observation networks.
A dead zone is characterized by a deficit of dissolved oxygen in the water, causing the death by asphyxiation of marine fauna with low mobility and the migration of fish. Tolerance to low-oxygen waters varies greatly depending on the type of organism. Dead zones have grown exponentially since the 1960s, with serious consequences for ecosystems. The main cause is the massive application of fertilizers. Some dead zones are permanent; others are episodic. The ecological and economic consequences are significant.
The air-sea interface covers more than 70% of the Earth’s surface and plays an important role in global biogeochemical processes. At this interface, a micro-layer is formed by the accumulation of surfactants, proteins, amino acids, carbohydrates, lipids, phenols and various inorganic and organic pollutants in the contaminated zone. It constitutes a particular ecosystem, where various forms of life called neuston develop. A polluted micro-layer constitutes an unfavourable environment for the development of eggs and larvae.