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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 number of order of publication and with a color code based on the theme of the file and the related sub-themes linked to it.
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
How the ocean works
- Geosciences
- Seawater chemistry
- Biogeochemistry
- Climate, Ocean/Atmosphere interactions, ocean dynamics
Marine biodiversity
- Biodiversity studies
- Biological diversity, the appearance of Life
- Current threats to marine biodiversity
- Protection of biodiversity
Reefs Coral reefs are ecosystems with high biodiversity in which the a9> corals establish complex relationships with their environment, including bacteria, archaea, viruses, eukaryotic microorganisms, viruses, eukaryotic microorganisms, invertebrates and fish. Ultimately, keeping corals in an aquarium requires both scientific knowledge and experience. a36> scientific knowledge and practical experience, reflecting the intrinsic complexity of their natural habitats. By promoting these miniature reef ecosystems, aquarists contribute to efforts to conserve corals while acquiring a a59> better understanding of the beauty and the fragility of the marine environment a67>.
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The discovery in Brittany of fossils very similar to the Ediacaran jellyfish Cyclomedusa is presented by analyzing the Devonian fossiliferous geological environment of this region. A possible fossilization scenario is proposed, comparing it with current jellyfish strandings. A summary of the supposed evolution of these animals concludes this article.
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Microalgae are a world of biodiversity that is still largely unknown, which offers unexpected potential for development in the fields of energy, agriculture, and medicine. a17> the fields of energy, of nutrition, of
pharmacology, of cosmetics and of nutraceuticals. However, for these opportunities to be
economically viable, research must still overcome many challenges, particularly in order to
improve the production processes.
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.
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.
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.
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. Numerous species live in a wide range of depths. This fauna, whose biodiversity is underestimated, is adapted to an extreme environment, is unique and fragile, and is not a15> environment extreme, is unique and fragile, and will not be able to resist the impact of climate 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 distribution of species, habitat stability, and links between the seabed, water column, and surface waters. Human activities on the high seas damage essential vertical and horizontal links. 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.
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 species, concerns focus on selachians, sturgeons, and European eels, as well as groupers and tuna. Sensitive and protected habitats damaged by illegal fishing are mainly Posidonia seagrass beds, coralligenous bioconcretions, calcareous red algae pavements, and deep white corals.
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 and cover the bodies of most of the approximately 1,150 species of sharks and rays currently identified.
Cutaneous denticles owe their name to their dermo-epidermal structure, which is 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 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.
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.
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 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.
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 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
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.
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.
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.
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…
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…
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.
