oceans aware: inform, inspire, involve
the more you know about the ocean the more you can do to protect and restore it
ocean life
It is thought that somewhere between 50 and 80% of life on Earth lives in the ocean but as scientists estimate that we’ve only explored 20% of the ocean, any attempt at estimating the number of different species that make up marine life, whether plankton (those which float), nekton (those which swim) or benthos (those living on the ocean floor) is impossible. According to the International Ocean Commission of UNESCO, 75-90% of the estimated 1–2 million marine species remain undiscovered, with a much cited scientific article from 2011 (How Many Species Are There on Earth and in the Ocean?) estimating that 91% of ocean species have yet to be classified..
From 2000 to 2010, an international project, the Census of Marine Life, assessed the diversity, distribution, and abundance of marine life, involving 2,700 scientists from over 80 States. The scientific results were reported in 2010 at the Royal Institute in London. The census produced the most comprehensive inventory of known marine life ever compiled and catalogued, with 30 million records as of January 2011, a solid basis for future research. The results of the census are maintained and updated in a number of databases on national, regional and international levels. Nowadays, the World Register of Marine Species (WoRMS) and its sister site, the World Register of Deep-Sea Species (WoRDSS), aim to provide an authoritative and comprehensive list of names of marine organisms.
The Ocean Biodiversity Information System (OBIS) emanates from the Census of Marine Life and was adopted as a project under IOC-UNESCO’s International Oceanographic Data and Information (IODE) programme in 2009. According to their website, now more than 20 OBIS nodes around the world connect 500 institutions from 56 countries. Collectively, they have provided over 45 million observations of nearly 120,000 marine species, from bacteria to whales, from the surface to 10,900 metres depth, and from the Tropics to the Poles. The datasets are integrated so you can search and map them all seamlessly by species name, higher taxonomic level, geographic area, depth, time and environmental parameters.
The Ocean Census, an alliance of ocean advocates founded by the Nippon Foundation and Nekton, aims to “accelerate the speed of species discovery, setting humanity an ambitious target of finding 100,000 new species over the next decade”. They support scientific expeditions to biodiversity hotspots, collect specimens at the Ocean Census Biodiversity Centres using high resolution imaging, DNA sequencing and machine learning to speed and scale up the process of discovery, connect taxonomists all over the world to draw on the data set and make it freely accessible to scientists, marine policymakers and the public.
An parallel project aimed at protecting marine life is the Global Marine Species Assessment (GMSA), initiated in 2005 by the IUCN Species Survival Commission to assess the extinction risk of 20,000 marine species for inclusion on the IUCN Red List of Threatened Species. According to their website, the project aims to produce the baseline data and comprehensive analyses needed to develop targeted and coordinated marine conservation planning and action at global, regional, and national levels.
Jeffrey Hamilton/Unsplash
An estimated 1 or perhaps even 2 million species of animals inhabit the oceans, with millions more bacteria, other microbes and viruses. Just 240,000 marine species have been documented.
Thomas Kelley/Unsplash
Marine life varies in size from some types of zooplankton which are no more than 2 micrometres to the largest mammal in the world, the blue whale which can reach up to 30 metres in length and weigh 150 tonnes.
Jonas Von Werne/Unsplash
About 2,000 new species are described by marine scientists every year, on average it takes 13.5 years to describe a new species, from the point of discovery to the publication of a scientific paper.
Marine life can be divided into invertebrates and vertebrates.
Invertebrates include plankton, both phytoplankton which are tiny plants that use photosynthesis to convert carbon dioxide to oxygen and are responsible for the production of between 50 and 80% of the planet's oxygen, and zooplankton, which are tiny animals that eat phytoplankton and serve as prey for larger animals like krill, shrimp, fish and even whales. The most common marine invertebrates are sponges, cnidarians (such as corals, anemones and jellyfish), marine worms, lophophorates, molluscs, arthropods (insects, crustaceans, and arachnids), echinoderms and the hemichordates. Plants such as sea grasses and algae and seaweeds are also included in this group.
Vertebrates include marine mammals like cetaceans (whales, dolphins, and porpoises), pinnipeds (seals, sea lions, and walruses), sirenians (manatees and dugongs), marine fissipeds (polar bears and sea otters), reptiles (turtles, sea snakes, salt water crocodiles and marine iguanas), fish (an estimated 20,000 species inhabit the ocean) and seabirds (from penguins to gulls).
A great place to find out about all of these is the MarineBio Glossary of marine life. Oceana’s Marine life encyclopedia is also an excellent source for photos and facts about marine life.
The marine food chain is explained in the Marine Food Web: A Simple Guide, which sets out the 5 trophic levels as follows:
Primary producers (phytoplankton; e.g. diatom) which make food from sunlight/chemicals.
Primary consumers (zooplankton & other herbivores; e.g. copepods) which eat phytoplankton.
Secondary consumers (medium-sized carnivores; e.g. sardines) which eat herbivores.
Tertiary consumers (large marine carnivores; e.g. tuna) which eat other carnivores.
Apex predators (e.g. killer whales, saltwater crocodiles or sharks) which have no natural enemies.
Of importance in the marine food chain are also the bacteria which decompose any dead organic material (plant or animal remains) and animal waste and then release it into the food chain as energy and nutrients.
What threats does marine life face and what are we doing to protect it?
In the Anthropocene, marine biodiversity is facing new and ever-growing pressure and our still limited knowledge of marine life means that it is impossible to know how many species we are losing or perhaps have already lost. The main threats faced by marine life are as follows, all of which are addressed in other sections on this site:
Over-fishing, destructive fishing practices such as bottom trawling and bycatch and Illegal, Unreported and Unregulated Fishing (see section on ocean resources)
Pollution: ghost gear, plastic, runoff, oil spills and dumping (see section on ocean pollution)
Habitat destruction as a result of extractive practices (see sections on ocean resources)
Climate change, in particular rising ocean temperatures (see section on the ocean-climate nexus)
Changes to the chemical balance of water: with more carbon, less oxygen and increased levels of chemicals like nitrogen or phosphate (see section on ocean pollution)
Ship strikes: with growing commercial fleets the number of collisions with cetaceans is rising and pose a serious threat, especially in the case of endangered species or isolated populations.
The good news is that numerous international and national organizations are working to protect marine life, either focusing on a specific region, a specific habitat or a specific species. They all agree on the basic steps needed to protect and preserve marine life and to restore it to its former glory. One of the best conservation measures is the establishment of marine protected areas (see ocean protection). Fighting climate change is of course another fundamental step, others include preventing unsustainable fishing practices and dumping and reducing pollution, and individual actions to ensure that your own ocean footprint is as small as possible (see the section on what you can do).
Examples of organizations working to conserve marine life include the Secretariat of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), Polar Bears International and the International Whaling Commission (IWC).
Find out more about sea turtles
Find out more about whales
Find out more about polar bears
Nick Polanszky/Coral Reef Image Bank