Marine biodiversity
linked to ocean temperature
In an unprecedented effort that was published online on the July
28,by the international journal Nature, a team of scientists mapped and
analysed global biodiversity patterns for over 11,000 marine species
ranging from tiny zooplankton to sharks and whales. The researchers
found striking similarities among the distribution patterns, with
temperature strongly linked to biodiversity for all thirteen groups
studied. These results imply that future changes in ocean temperature,
such as those due to climate change, may greatly affect the distribution
of life in the sea.
The
scientists also found a high overlap between areas of high human impact
and hotspots of marine diversity. Much research has been conducted on
diversity patterns on land, but our knowledge of the distribution of
marine life has been more limited. This has changed through the
decade-long efforts of the Census of Marine Life, upon which the current
paper builds.
The authors synthesised global diversity patterns for major species
groups including corals, fishes, whales, seals, sharks, mangroves,
seagrasses, and zooplankton. In the process, the global diversity of all
coastal fish species has been mapped for the first time.
The researchers were interested in whether there are consistent
"biodiversity hotspots" -- areas of especially high numbers of species
for many different types of marine organisms simultaneously. They found
that the distribution of marine life showed two fundamental patterns:
coastal species such as corals and coastal fishes tended to peak in
diversity around Southeast Asia, whereas open-ocean creatures such as
tunas and whales showed much broader hotspots across the mid-latitude
oceans.
The scientists also tested whether these global patterns could be
consistently explained by one or more environmental factors.Temperature
was the only factor found to be linked with the distribution of all
species groups, with the availability of habitat also playing a
role.Says lead author Derek Tittensor of Dalhousie University, "it was
striking how consistently temperature was linked with marine diversity.
This relationship suggests that ocean warming, such as that due to
climate change, may rearrange the distribution of oceanic life."
Co-author Walter Jetz of Yale University notes "while we are
increasingly aware of global gradients in diversity and their associated
environmental factors, our knowledge of patterns in the ocean has lagged
behind that of patterns on land. Our study attempts to help overcome
this disparity."
The study also assessed the overlap between hotspots of marine
diversity and human impacts, i.e. the combined effects of fishing,
habitat alteration,climate change and pollution.
Human impacts were found to be particularly concentrated in areas of
high diversity, suggesting the potential for severe species losses in
these regions. Says co-author Camilo Mora of Dalhousie University, "the
combined effects of exploitation, habitat alteration, pollution and
climate change are threatening the diversity of life in the global
ocean. Our research provides further evidence that limiting ocean
warming and other human impacts will be particularly important in
securing these hotspots of marine biodiversity into the future."
Co-author Boris Worm of Dalhousie University also highlights the need
to maintain biodiversity in the face of these impacts: "biodiversity and
the functioning of ecosystems are often tightly coupled, with highly
diverse ecosystems providing more goods and services that benefit human
beings, as well as being more resilient in the face of disturbance, than
less diverse ecosystems. The observed concentration of human impacts in
our richest marine areas is a worrying indication of our growing
footprint in the oceans."
-ScienceDaily |