A comprehensive study by an international group of scientists
suggests that the global oceans may be home to up to one million
species, of which only about 226,000 have been identified and described
to date. This means that as much as 75 percent of all marine species
have yet to be discovered. The rate of discovery has accelerated in
recent decades, and most unknown species could be identified, named, and
described by the end of this century.
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| Zanclea orientalis, a small jellyfish of the
class Hydrozoa, from Moorea. The bell is less than one centimeter (about
one-third of an inch) across. Collected as part of the Moorea Biocode
project. Photo credit: Allen Collins, NEFSC/NOAA |
Understanding how many marine species exist is important to provide
a baseline for what we know or don’t know about life in the ocean.
That knowledge also aids conservation and global biodiversity efforts
as information about extinction rates become better known.
NOAA zoologist Allen Collins from the NEFSC’s National Systematics
Laboratory is a co-author of the study, considered the first
comprehensive inventory of marine species world‑wide. “The Magnitude
of Global Marine Species Diversity” was published online November 15
in
Current Biology and is scheduled to appear in print December 4.
While many of the unknown species are thought to be smaller
organisms, such as plankton and tiny bottom dwellers, where animal
diversity is likely to be high, there are most likely some large
animal species that are still unknown. Researchers estimate that as
many as eight new species of cetaceans (whales, dolphins and
porpoises) have yet to be identified.
Collins was among more than 120 of the world’s leading taxonomists
and species identification experts to contribute to the study of
global biodiversity using the World Register of Marine Species
(WoRMS). The registry, an open access, online database created by
scientists from 146 institutions in 32 countries, serves as a central
repository to access information. WoRMS is maintained at the Flanders
Marine Institute in Belgium.
Lead author Ward Appeltans of the Intergovernmental Oceanographic
Commission of the United Nations Educational, Scientific and Cultural
Organization (UNESCO), says the team has catalogued about 226,000
marine species, excluding marine bacteria. An estimated 58,000-72,000
species in museums and collections are waiting to be described.
Previous estimates of the number and diversity of global marine
species have ranged from 500,000 to as many as ten million, with most
estimates exceeding one million. The widely varying estimates came
from a variety of methods, ranging from expert opinion polls to models
projecting rates of species descriptions based on the accumulation of
higher taxa. Once the database was set up for this new study, experts
in each area of expertise estimated how many species they thought
were undiscovered. Those estimates were checked against a statistical
model the WoRMS team constructed based on the rate of species
discovery. The result was a total number of undiscovered species
somewhere between 320,000 and 760,000. When added to the roughly
226,000 marine species already described and in the register, the
revised total is closer to one million.
Collins says a lot of scholarly work has been duplicated because of
a lack of a central database to check information about what has
already been found. “It takes a lot of time and careful examination of
historic records and specimens to determine correct species names,
especially when there may be many different names and descriptions of
the same animal, commonly known as synonyms.”
Collins, an expert in jellyfish, hydroids, corals, and glass
sponges, began working on the study more than two years ago, and is
one of two NOAA Fisheries scientists involved in the project. William
Perrin of the Southwest Fisheries Science Center in La Jolla,
California, a marine mammal specialist, studies the species
classification and ecology of cetaceans.
In the past decade, more species have been discovered than ever
before, an average of 2,000 discoveries each year. The rate of
discovery is increasing because of a greater focus on biodiversity and a
growing number of researchers interested and involved in describing
new species. New technologies are available that allow researchers to
access previously unexplored areas of the world and to better study
specimens in the laboratory.
This new study complements the Census of Marine Life and other
recent efforts to understand what lives in the oceans. Mike Vecchione,
Director of the National Systematics Laboratory and a researcher
actively involved in global species exploration, says a better
understanding of marine species is critical for managing the
ecosystems in which these species live.
Vecchione notes that scarce conservation resources cannot be
allocated rationally without knowing what lives where. “This requires
the ability to identify species so that we can determine their
distribution and monitor their abundance. Basic observations are
needed before hypotheses about patterns and trends of biodiversity can
be proposed and tested. Consistent species names are needed for
scientists, managers, and the public to communicate with each other in
addressing problems and developing solutions.”
“It is very exciting, and pretty amazing when you look at the
numbers,” Collins said of the recent report. “While these are best
estimates from a group of researchers considered experts in their
respective areas, people have taken a more careful approach in the
past few years to track species and their names, top to bottom.”
The scientists at NOAA’s National Systematics Laboratory, located
in the National Museum of Natural History at the Smithsonian
Institution in Washington, DC, each year identify new species from
around the world. Collins says he and his colleagues receive a steady
stream of inquiries from researchers seeking help in identifying
species, “and the numbers grow each year.”
