Nav: Home

Invasive species of coral boasts amazing capacity for regeneration

June 05, 2018

Detected for the first time in Brazil on the coast of the Southeast region in the late 1980s, when oil and gas prospecting began in the Campos Basin offshore of Rio de Janeiro, sun corals of the genus Tubastraea are now spreading very swiftly throughout the rocky shores and cliffs of Brazilian islands and are considered to be biological invaders.

Once biodiverse and multicolored, the reefs in Búzios Island - part of the municipality of Ilhabela, Sao Paulo State, also located at the Southeast - are now covered with orange stripes. In some places, no bare rock or other species of coral can be seen.

"The reefs around Búzios Island are in an irreparable condition," said Marcelo Kitahara, a professor in the Marine Science Department of the Federal University of São Paulo (DCMAR-UNIFESP) in Santos, Brazil. Kitahara heads a project supported by the Sao Paulo Research Foundation - FAPESP to study the phylogenomics of two species and the links between their evolution and climate change.

The genus Tubastraea comprises seven species, all native to the tropical waters of the Indian Ocean and Pacific. Only two, T. coccinea and T. tagusensis, are also found in the southwest Atlantic. Both are invasive species.

The first Brazilian sightings were recorded in the Campos Basin in the 1980s, followed by the discovery of colonies on reefs off the southern coast of Rio de Janeiro State in the 1990s. Since then, sun coral has been found across over 3,000 km of the Brazilian coastline, from Santa Catarina in the South to Ceará in the Northeast.

"Management action is still possible in some places, but this requires the complete manual removal of all colonies," Kitahara said. "If nothing is done to stop its advance, sun coral could potentially colonize the entire Brazilian coast."

A study showing the surprising capacity of sun coral to regenerate had its results published in the Journal of Experimental Marine Biology and Ecology. The lead author is PhD student Bruna Louise Pereira Luz, a biologist affiliated with the Federal University of Paraná (UFPR) and currently in Australia studying sun coral at James Cook University, Townsville, near the Great Barrier Reef, under supervision of Kitahara.

"Sun coral colonies multiply at a great speed in areas such as these. We set out to understand how and why," said Kitahara. On one of the findings - only made possible through a lab-conducted experiment - they also revealed that sun coral regeneration process gets faster as water temperature increases.

Possible influence of Oil & Gas industry

The appearance of these invasive species just when oil and gas production began was not unique to Rio de Janeiro. The Gulf of Mexico also has vast offshore oilfields, and sun coral has been found on the Mexican coast since the early 2000s. There are even records of sun coral attached to the hulls of ships.

"We can't be totally sure that offshore oil drilling in the Campos Basin resulted in the invasion of our coast by sun coral, but all the evidence points to this conclusion," said the FAPESP project coordinator.

A coral reef is a limestone skeleton built by colonies of thousands of tiny animals called coral polyps. Most reef-building corals contain photosynthetic algae that live in their tissues. The corals and algae have a symbiotic relationship: the polyps provide the compounds required by the algae for photosynthesis, and the algae provide the polyps with nutrients. Other types, including sun coral, can grow and proliferate without algae.

"Because it has no algae, sun coral isn't confined to places with sunlight for photosynthesis. It typically occurs at depths of up to 20 meters, but sightings have been recorded at 110 meters. On rocky shores and underwater cliffs, polyps build huge numbers of colonies and cover 100% of the substrate," Kitahara explained.

During this process, they drive out the native coral, devastating ecological relations with the marine fauna that depend on or inhabit it.

Reorganization of stem cells

To investigate the mechanisms that enable sun coral to adapt so successfully and proliferate rapidly in various marine environments, the researchers collected a colony of T. coccinea and another of T. tagusensis from Búzios Island.

In the laboratory, the researchers removed from each colony 120 fragments composed of skeleton with living tissue but lacking mesenteries, mouths and tentacles. The samples of each species were then separated into two groups of 60, one with very small fragments (3.5-11 mm²) and another with slightly larger fragments (11-53 mm²). All 240 fragments were placed separately in containers with filtered seawater.

For each combination of species and fragment size, individuals were further separated into three groups of 20 fragments and maintained at a constant temperature of 24 °C (historically the average surface water temperature in the region), 27 °C (the average sea surface temperature in summer) or 30 °C (observed during heat waves).

Finally, the effects of the presence of food were tested by adding equal amounts (10 ml) of live zooplankton every other day to half of the containers.

The fragments were photographed on the first day of the experiment and when the mouth and complete polyp were first observed. Only 41 of the 240 fragments, or 17.1%, underwent tissue necrosis and death. The other 199 fragments (86.9%) regenerated. Of these, 21 (9% of the entire sample) displayed an alternative regeneration pattern, with the formation of two polyps instead of one.

Regardless of the species, coral fragment survival was affected only by temperature. The survival rate was highest at 24 °C. There was no difference between the fragments kept at 27 °C and those kept at 30 °C. Food supply and fragment size did not affect survival.

Regeneration was found to include the following stages. After initial tissue retraction, mouth rudiments became noticeable, sometimes two for a single fragment. Subsequent development consisted either of tissue reorganization around the mouth rudiments, leading to the formation of two small, distinct polyps, or the reabsorption of one of the rudiments, in which case significant tissue differentiation around the remaining mouth rudiment resulted in a larger polyp.

"We observed a very interesting phenomenon," Kitahara said. "From a cellular viewpoint, there was a reorganization of stem cells. The polyp in formation consumed tissue as a source of energy to prioritize the production of other body parts."

The results of the experiment generally indicated faster regeneration rates at higher temperatures. The fastest mouth regeneration for fragments without contact with food was 23 days at 24 °C or 18 days at 30 °C. However, fragments kept at 27 °C in contact with living zooplankton displayed 30% faster mouth development. This suggests optimal mouth development at the intermediate temperature (27 °C), provided there is contact with food.

Fragments of both species developed into complete polyps in approximately 25 days at 27 °C and 30 °C. Unfed individuals of the species T. coccinea took approximately 41 days to achieve polyp formation.

As Kitahara explained, the fact that sun coral regenerates faster at higher temperatures is highly germane to its invasive success. Most native corals on the Brazilian coast suffer bleaching when surface water temperatures rise.

"They lose color," said the FAPESP-funded researcher. "Warmer water interferes with the metabolism of their symbiont algae. Bleached coral survives only for a few days. If the temperature remains high, it dies. The bleaching or death of native coral opens up an opportunity for substrate invasion by sun coral."

The next steps in this line of research, according to Kitahara, will be to sequence sun coral's genome, on the molecular side, and, on the ecological side, to investigate the biological aspects of its invasion and how it affects native marine fauna.

The future does not appear promising for native corals on the Brazilian coast, in Kitahara's opinion. For sun coral, on the contrary, it appears to be bright. On one hand, global climate change and rising seawater temperatures help the invader, which regenerates faster in warmer water, while native corals risk dying. Not to mention the prospect of expanding oil production in Brazilian waters.
-end-
About São Paulo Research Foundation (FAPESP)

The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. For more information: http://www.fapesp.br/en.

Fundação de Amparo à Pesquisa do Estado de São Paulo

Related Climate Change Articles:

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.
Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.
Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.
Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.
A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.
Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).
Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.
Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.
Could climate change cause infertility?
A number of plant and animal species could find it increasingly difficult to reproduce if climate change worsens and global temperatures become more extreme -- a stark warning highlighted by new scientific research.
Predicting climate change
Thomas Crowther, ETH Zurich identifies long-disappeared forests available for restoration across the world.
More Climate Change News and Climate Change Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.