Marine Biodiversity: State of Knowledge

Submitted by ward.appeltans on Mon, 2012-06-25 03:21

Status of our knowledge on ocean biodiversity, gaps, and potential for discovery

From Special Side Event on Oceans - UN Conference on Sustainable Development
20 June 2012, 09.00-10.30
Venue: T-9 (RioCentro, Rio de Janeiro, Brazil)
Theme: Knowing our Ocean
Prepared by: Patricia Miloslavich – Universidad Simón Bolívar, Venezuela

Ocean life is extremely diverse, connected, and under severe pressure from human activities. The first baseline of information of what lives in the ocean is contained in the world’s largest online repository of open-access, geo-referenced data which is the Ocean Biogeographic Information System (OBIS). OBIS is a legacy of the Census of Marine Life (, a program that significantly advanced our knowledge of marine biodiversity, distribution, and abundance in the last decade (2000-2010). OBIS is presently under the umbrella of the Intergovernmental Oceanographic Commission (UNESCO) global data system which compiles data on marine species and their locations that serves researchers, students, and policymakers, helping them to identify areas that remain unexplored and where more research might be targeted ( 

Number of Records in OBIS

Map showing the density of observations by 5x5 degree squares in the OBIS database. Darker (red) squares indicate higher density of records. Observations are most numerous in shallow waters, near the coast, and near or between developed nations. The Southern Pacific shows a huge gap in knowledge. Image: Edward Vanden Berghe, Ocean Biogeographic Information System. Data updated in May, 2012


The estimate of known marine species is nearly 250,000. This known diversity represents only a fraction of the real biodiversity, not only because the vast majority of the ocean still remains unexplored (estimates range up to 95%) but because new species discoveries continue even in relatively well known areas. Nearly half of all known biodiversity is represented by only three groups: crustaceans, mollusks, and fish, which are also the best known groups, with the longest taxonomic history. Many of these species are also commercially important. Microbial diversity jumps the numbers of species orders of magnitude. One liter of seawater, for example, may contain more than 38,000 different kinds of bacteria, and in a gram of sand, between 5,000 and 19,000. Most of this microbial diversity is predominantly represented by rare rather than common species. Worldwide, major gaps exist in sampling effort and taxonomic expertise. In this regard, knowledge of biodiversity is related to the availability of local and regional species identification guides. Therefore, capacity building in this aspect is fundamental because it will facilitate the discovery of new species and help to identify and understand species of economic and ecological importance.


Life occurs everywhere in the ocean, even in unexpected or extreme places such as hydrothermal vents with extremely high temperatures (more than 400 °C) or in anaerobic conditions (without oxygen). On the one hand, a global analysis of the distribution of coastal species shows highest species richness in the tropics, and marine hot spots appear around the Philippines, Japan, China, Indonesia, Australia, India, Sri Lanka, South Africa, the Caribbean and the southeastern United States. On the other hand, oceanic species richness peaks in temperate latitudes. An analysis of species richness in more than 25 regions of the world, confirms high marine biodiversity in Japan, Australia, and the China Seas, and shows high endemicity (species confined to a particular region) or uniqueness, between 22% and up to 48%, in South America, Australia, New Zealand, South Africa and Antarctica, all within the southern hemisphere.


The world’s oceans are highly connected through animal movement. Such movements may result from natural migration, either horizontally or vertically, or in response to changing ocean conditions, such as temperature. Impressive animal migration distances range from about 6,000 kilometers (Atlantic bluefin tuna, Thunnus thynnus), to a round trip of 64,000 kilometers (sooty shearwater, Puffinus griseus), which represents the longest-ever electronically recorded migration.


Life in the seafloor depends to a large extent on the delivery of food produced by living beings near the surface, and while diversity peaks in tropical and temperate areas, abundance seems to peak in temperate to much colder areas. The most abundant group in the ocean are the microbes. Microbes account for more than 90% of the ocean’s biomass and are essential to maintaining Earth’s habitability and functioning. Microbes are responsible for more than 95% of respiration in the oceans, but also influence climate, recycle nutrients, decompose pollutants, and constitute the base of the food web that supports all life on the ocean. Some of this microbial life occurs as mats of filamentous bacteria that extend for hundreds of kilometers in the deep-sea margins of the continents. For larger fishes and other vertebrates, historical records indicate a decline of about 90% of top predators in comparison to past levels. Recovery, though typically very slow, may be possible when protective measures are taken. Despite such alarming declines, the ocean still holds plenty of marine life which requires appropriate management and conservation measures.


Big scientific challenges related to marine biodiversity

An organized international community working in collaboration established a first snapshot of life in the global ocean, which they presented in late 2010. This community recognizes that their work is incomplete and that many challenges related to marine biodiversity knowledge and understanding still remain. To address such challenges, a science planning committee devised a new initiative, Life in a Changing Ocean ( which was presented and discussed in consultation with the larger scientific community at the 2nd World Conference in Marine Biodiversity held at Aberdeen, Scotland in September 2011. The goal of this initiative is to advance discovery and expand marine biodiversity knowledge to support healthy and sustainable ecosystems through an integrated global view of marine life that will fill knowledge gaps and answer questions needed to effectively manage and sustain ocean ecosystems. The community agreed that the main scientific challenges related to marine biodiversity can be integrated across three interrelated and interconnected themes: (1) Biodiversity Discovery in Time and Space, (2) Biodiversity and Ecosystem Services and Functions, and (3) Biodiversity and Human Exploitation.


The main challenges related to the first theme, Biodiversity Discovery in Time and Space, are:

  • how to improve baseline knowledge on marine biodiversity data including movement and distribution of species, that will support ocean governance processes while providing capacity building on identification tools (e.g. DNA barcoding) especially to areas in which marine biodiversity is poorly known.
  • to understand how do species diversity, distribution, and abundance vary in relation to space and temporally varying environments and to be able to identify organisms that can serve as early warning systems of change in an ecosystem that might allow for mitigating actions to be taken.

The main challenges related to the second theme, Biodiversity and Ecosystem Services and Functions, are:

  • to elucidate global patterns in ecosystem functioning and services that marine organisms provide, and how they vary among ecosystems.
  • to clarify generality and specificity in relationships between biodiversity and ecosystem functioning and services.
  • to produce scenarios on how these relationships might be modified by global climate change and other drivers.

The main challenges related to the third theme, Biodiversity and Human Exploitation, are:

  • to understand how have marine ecosystems changed since first human impacts along with the nature and scale of processes and mechanisms behind the reorganization of marine community structure and assemblages associated with biodiversity changes.
  • to elucidate what is needed to achieve sustainability in terms of management and recovery strategies and how do these differ for different species and ecosystems.

Role of the IOC in advancing marine biodiversity knowledge

As an organization with a global leadership role in ocean sciences, the IOC can make a difference in communicating the importance of marine biodiversity knowledge to ocean health and human well being. The IOC can help to meet these goals through:

  1. Support and promotion of global and local initiatives addressing key data, knowledge, and science capacity gaps.
  2. Association with key global scientific projects aimed to building baselines, understanding the role of biodiversity, and promoting sustainability under the pressures of a changing ocean.
  3. Support and facilitation of an international network of scientists and other stakeholders working towards providing science and scientifically based solutions to problems related to ocean health and variations in ocean goods and services.
OBIS is a project of:
IODE Sponsored by:
Martin International and Les Grands Explorateurs
With in-kind support from:
Marine Geospatial Ecology Lab, Duke University
Universidad Simón Bolívar Flanders Marine Institute

OBIS strives to document the ocean's diversity, distribution and abundance of life. Created by the Census of Marine Life, OBIS is now part of the Intergovernmental Oceanographic Commission (IOC) of UNESCO, under its International Oceanographic Data and Information Exchange (IODE) programme.