HAVANA, April 5 (Reuters) - During some summers, as the
Caribbean water temperatures climb, the luminous coral colonies
of gold, green and blue that ring the island nation of Cuba give
way to patches of skeletal white.
The technicolor streaks of darting tropical fish flash less
frequently. The rasping sounds of lobsters go quiet.
While Cubas marine life has suffered from overfishing and
pollution, there is mounting evidence that the warming of waters
due to climate change may be taking a large toll as well -- both
off the island's coast and globally.
Research published Monday finds that the total number of
open-water species declined by about half in the 40 years up to
2010 in tropical marine zones worldwide. During that time, sea
surface temperatures in the tropics rose nearly 0.2 degree
Celsius. (Study: https://bit.ly/31KA1mC)
"Climate change is already impacting marine species
diversity distribution," with changes being more dramatic in the
Northern Hemisphere where waters have warmed faster, said study
co-author Chhaya Chaudhary, a biogeographer at Goethe
While numerous factors like overfishing have impacted
tropical species, the study published in the Proceedings of the
National Academy of Sciences found a strong correlation between
species decline and rising temperature.
Fish species diversity tended to either plateau or decline
at or above 20C (68 Fahrenheit), the researchers found.
'BLINK OF AN EYE'
While past studies have shown that ocean warming is driving
some species to migrate to cooler waters, the new study attempts
to gauge that impact more broadly -- analyzing data on 48,661
marine species including fish, mollusks, birds and corals since
1955. (Data source: https://obis.org/about/)
The dataset is a representative sample of 20% of all named
open-water and seabed-dwelling marine species - like corals and
sponges, researchers said.
The number of species attached to the seafloor remained
somewhat stable in the tropics between the 1970s and 2010,
according to the study. Some were also found beyond the tropics,
suggesting they had expanded their ranges.
In other words, scientists say, species that can move are
"In geological history, this has occurred in the blink of an
eye," said Sebastian Ferse, an ecologist at the Leibniz Centre
for Tropical Marine Research who was not involved with the
study. "To see such changes occurring so rapidly is something
For fixed species like corals, moving is not an option.
"One of the big questions is Will coral reefs as ecosystems
and corals as species be able to move north or south enough fast
enough to adjust to a changing climate?" Ferse said.
Having fleets of fish and other swimmers shift rapidly to
more temperate waters could devastate the coral ecosystems they
leave behind -- along with any fishing and tourism industries
that rely on them.
Such changes can have a really huge impact on some of the
most vulnerable human communities around the planet, said
Stuart Pimm, a conservation scientist at Duke University not
involved in the study.
For Cuba, such an impact could unravel the island nations
efforts to manage its underwater gardens although its corals
have been less stressed by coastal development and pollution
than corals elsewhere. They are considered more resilient to
"It's impressive to return to an area that experienced
significant bleaching the year before, but looks perfectly
healthy a year later," said Daniel Whittle, who heads the
Caribbean program at the Environmental Defense Fund.
Cuba opened its first coral reef nursery four years ago to
research which species coped best with warming and eventually to
repopulate depleted reefs. The country is also restoring coastal
mangroves, which serve as fish nurseries and shelter.
Chaudhary and her colleagues plan next to look at which
tropical species were in decline or were migrating.
(Reporting by Sarah Marsh; Editing by Lisa Shumaker)