Corals fight back against global warming


This 2013 video is about Cladocora caespitosa coral in the Mediterranean.

From the University of Barcelona in Spain:

Survival strategy found in living corals which was only seen in fossil records

October 15, 2019

Some corals can recover after massive mortality episodes caused by the water temperature rise. This survival mechanism in the marine environment -known as rejuvenation- had only been described in some fossil corals so far. A new study published in the journal Science Advances reveals the first scientific evidence of the rejuvenation phenomenon in vivo in Cladocora caespitosa coral colonies, in the marine reserve in Columbrets, in the coast of Castellón (Spain).

The authors of the study are the experts Diego Kersting and Cristina Linares, from the Department of Evolutionary Biology, Ecology and Environmental Sciences from the Faculty of Biology and the Biodiversity Research Institute (IRBio) of the University of Barcelona.

Heatwaves, more and more common in Mediterranean

The Mediterranean Sea is one of the most affected areas by climate change and the increase of heatwaves. “We are used to hear and read on the general impacts related to the climate change, but we rarely get news on the life recovery after impacts related to global warming,” says Diego Kersting, first author of the article and researcher at the Free University of Berlin (Germany).

Since 2002, Kersting and Linares have been monitoring 250 coral colonies of Cladocora caespitosa in the marine reserve in Columbrets, an area for studies on the effects of climate change on the marine environment. This coral -the only one able to create reefs in the Mediterranean Sea– is listed as an endangered species, mainly because of the mortalities associated with global warming.

Experts had described that the unusual rise of water temperature in summer was killing many of these Mediterranean coral colonies. For instance, during the summer of 2003, one of the hottest ones, “the 25% of the surface occupied by these corals in Columbrets disappeared due a loss of the colonies,” says the authors of the study.

Some coral polyps survive under extreme conditions

In a Mediterranean Sea with higher and higher temperatures and frequent heatwaves, the survival alarms for these species had already rang. However, the long-run monitoring of the coral in Columbrets revealed a surprising result: some coral colonies that were considered lost years ago show some living parts.

According to the experts, this kind of recuperation was possible thanks to a procedure named rejuvenation. In particular, under stress conditions -for instance, excessive water warming-, some polyps in the coral colonies which are dying are able to become smaller until they can abandon their calcareous skeleton.

In this reduced state, these polyps can survive under extreme conditions which cause the death of the other polyps in the colony. When conditions improve, polyps recover its common size and form a new calcareous skeleton. Afterwards, they reproduce by budding until the dead colony recovers.

A hidden survival strategy

According to the authors, this survival strategy had been unnoticed until now due the external good image the colonies show once they have recovered, which masks the mortality that had taken place before. “The real story of these colonies can only be found if controlled every year, over the years, or if we study the skeleton, since the process leaves characteristic features!, warn Kersting and Linares.

So far, researchers had found signs of this rejuvenation only in Paleozoic corals, which lived hundreds of millions of years ago. Therefore, the results of this study will enable making comparisons between the in vivo observations and the description through the fossils, and therefore knowing the implication of these kinds of survival processes and adaptation in corals.

This discovery provides new perspectives for the survival of the only reef coral in the Mediterranean, which has a slow growth -about 3 mm per year- and a limited ability to create new colonies. “However, it is hard for these mechanisms to balance the serious increase of the frequency and severity of the heatwaves in the Mediterranean, so it is necessary to act urgently in order to slow the causes of climate change, and dedicate enough resources to maintain these monitoring procedures in the long run,” warn the authors.

Threats to coral reefs are everywhere — rising water temperatures, ocean acidification, coral bleaching, fishing and other human activities. But new research shows that 3-D printed coral can provide a structural starter kit for reef organisms and can become part of the landscape as fish and coral build their homes around the artificial coral: here.

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Global warming hurts, fish help, coral


This 2016 video is called 2 Hours of Beautiful Coral Reef Fish, Relaxing Ocean Fish, & Stunning Aquarium Relax Music 1080p HD.

From the Georgia Institute of Technology in the USA:

Warming impedes a coral defense, but hungry fish enhance it

October 2, 2019

Summary: Corals exude chemical defenses against bacteria, but when heated in the lab, those defenses lost much potency against a pathogen common in coral bleaching. There’s hope: A key coral’s defense was heartier when that coral was taken from an area where fishing was banned and plenty of fish were left to eat away seaweed that was overgrowing corals elsewhere.

Corals create potions that fight bacterial attackers, but warming appears to tip the scales against the potions as they battle a bacterium common in coral bleaching, according to a new study. Reef conservation may offer hope: A particular potion, gathered from reefs protected against seaweed overgrowth, proved more robust.

The protected Pacific reefs were populated by diverse corals and shimmered with colorful fish, said researchers who snorkeled off of Fiji to collect samples for the study. Oceanic ecologists from the Georgia Institute of Technology compared coral potions from these reefs, where fishing was prohibited, with those from heavily fished reefs, where seaweed inundated corals because few fish were left to eat it.

The medicated solutions, or potions, may contain a multitude of chemicals, and the researchers did not analyze their makeup. This is a possible next step, but here the researchers simply wanted to establish if the potions offered any real defense against pathogens and how warming and overfishing might weaken it.

Conservation matters

“I thought I probably wouldn’t see antibiotic effects from these washes. I was surprised to see such strong effects, and I was surprised to see that reef protections made a difference,” said the study’s first author, Deanna Beatty.

“There is a lot of argument now about whether local management can help in the face of global stresses — whether what a Fijian village does matters when people in London and Los Angeles burn fossil fuels to drive to work,” said Mark Hay, the study’s principal investigator, Regents Professor and Harry and Linda Teasley Chair in Georgia Tech’s School of Biological Sciences.

“Our work indicates that local management provides a degree of insurance against global stresses, but there are likely higher temperatures that render the insurance ineffective.”

Adding heat

The researchers collected three coral species along with seawater surrounding each species at protected reefs and at overfished reefs. In their Georgia Tech lab, they tested their solutions against the pathogen Vibrio coralliilyticus at 24 degrees Celsius (75.2 Fahrenheit), an everyday Fijian water temperature, and at 28 degrees (82.4 F), common during ocean heating events.

“We chose Vibrio because it commonly infects corals, and it’s associated with coral bleaching in these warming events. It’s related to other bleaching pathogens and could serve as a model for them as well,” Hay said.

“We chose 24 C and 28 C because they’re representative of the variations you see on Fijian reefs these days. Those are temperatures where the bacteria are more benign or more virulent,” Beatty said.

The data showed that warming disadvantaged all potions against Vibrio and conservation aided a potion from a key coral species. The team, which included coauthor Kim Ritchie from the University of South Carolina Beaufort, published its study in the journal Science Advances on Oct. 2. The research was funded by the National Institutes of Health’s Fogarty International Center, the National Science Foundation, and the Simons Foundation.

Deeper dive into the experiment

Seaweed hedges

The unprotected reefs’ shabby appearance portended their effects on the one potion associated with a key coral species.

“When you swim out of the no-fishing area and into the overfished area, you hit a hedge of seaweed. You have about 4 to 16% corals and 50 to 90% seaweed there. On the protected reef, you have less than 3% seaweed and about 60% corals,” Hay said.

Hay has researched marine ecology for over four decades and has seen this before, when coral reefs died off closer to home.

“Thirty years ago, when Caribbean reefs were vanishing, I saw overfishing as a big deal there, when seaweed took over,” he said, adding that global warming has become an overriding factor. “In the Pacific, many reefs that were not overfished have been wiped out in warming events. It just got too hot for too long.”

Distilling potion

The potions are products of the corals and associated microbes, which comprise a biological team called a holobiont.

To arrive at potions focused on chemical effects, the researchers agitated the coral holobionts and ocean water then freeze-dried and irradiated the resulting liquid to destroy remnants of life that could have augmented chemical action. Some viruses may have withstood sterilization, but it would have weakened any effect they may have had, if there were any.

Then the researchers tested the potions on Vibrio.

“All of the solutions’ defenses were compromised to varying extents at elevated temperatures where we see corals getting sick in the ocean,” Hay said.

But reef protection benefited the potion taken from the species Acropora millepora.

“The beneficial effect in the solution tested in the lab was better when Acropora came from protected areas, and this difference became more pronounced at 28 degrees Celsius,” said Beatty, who finished her Ph.D. with Hay and is now a postdoctoral researcher at the University of California, Davis.

Acropora architecture

Of the three species with potions that were tested, Acropora millepora may be a special one.

It is part of a genus — larger taxonomic category — containing about 150 of the roughly 600 species in Pacific reefs, and Acropora are core builders of reef structures. They grow higher as sea level rises, helping maintain healthy positions for whole reefs.

“Acropora are big and branching and make lots of crevices where fish live. The evolution of lots of reef fish parallels the evolution of Acropora in particular,” Hay said.

If fish can hang on, they may buy Acropora more time, and coral reefs perhaps, too.

These researchers coauthored the study: Deanna Beatty, Jinu Valayil, Cody Clements, and Frank Stewart of Georgia Tech. The research was funded by the National Institutes of Health (grant 2 U19 TW007401-10), the National Science Foundation (grant OCE 717 0929119), the Simons Foundation (grant 346253), and the Teasley Endowment.

A new study revealed a more complex view than current standard predictions of coral bleaching events caused primarily by heat stress; rather, the scientists found that bleaching is driven by a variety of stressors, and each region responds differently: here.

Predators, good for other Bahamas reef fish


This 2017 video says about itself:

Inside the Struggle to Save an Endangered Grouper Species | National Geographic

Follow dedicated wildlife authorities in Belize as they strive to protect the endangered Nassau grouper.

From North Carolina State University in the USA:

Predators and hidey-holes are good for reef fish populations

October 1, 2019

New research highlights two factors that play a critical role in supporting reef fish populations and — ultimately — creating conditions that are more favorable for the growth of both coral reefs and seagrass.

“Previous work has shown mixed results on whether the presence of large predator species benefits reef fish populations, but we found that the presence of Nassau grouper (Epinephelus striatus) had an overall positive effect on fish abundance,” says Enie Hensel, a former Ph.D. student at North Carolina State University and lead author of a paper on the work. “We also found that habitat complexity benefits both fish abundance and species richness, likely because it gives fish a larger variety of places to shelter.” This is consistent with previous work.

“One of the surprises here was that the effect of predator presence on fish abundance was comparable to the effect of habitat complexity,” Hensel says.

To better understand the effect of these variables, researchers constructed 16 artificial “patch” reefs in shallow waters off the coast of Great Abaco Island in The Bahamas. Eight of the reefs consisted of cement-filled cinder blocks, mimicking degraded reefs with limited habitat complexity. The remaining eight reefs consisted of unfilled cinder blocks and branching pipe structures, mimicking the more complex physical environment of healthier reefs.

Once in place, the researchers waited for groupers to move in and claim the new reef territory. The groupers were large juveniles, ranging in size from 16-33 centimeters. The researchers then removed the groupers from four of the degraded reef sites and from four of the complex reef sites. Groupers that were removed were relocated to distant reefs.

Researchers monitored the sites for 60 days to ensure that the grouper-free reefs remained free of groupers. At the end of the 60 days, the researchers assessed the total number of fish at each reef site, as well as the total number of fish species at each site.

The differences were significant.

Fish abundance, or the total number of fish, was highest at sites that had both a resident grouper and complex habitat. Abundance at these sites ranged from 275 fish to more than 500 — which is remarkable given that each reef was less than a meter long in any direction. By comparison, sites that had simple structures and no grouper had fewer than 50 fish on average. Simple structures with predators had around 75 fish, while complex sites without grouper had around 100.

“We think the presence of the grouper drives away other predators, which benefits overall fish abundance,” Hensel says. “And a complex habitat offers niches of various sizes and shapes, which can shelter more and different kinds of fish than a degraded, simple habitat.”

The presence of grouper had little or no effect on species richness, or the number of different species present at each site. However, habitat complexity made a significant difference. Complex sites had 11-13 species, while degraded sites had around seven.

“We found that the sites with complex habitats and the presence of predators had fish populations that were actually larger than what we see at surrounding, similar-sized natural reefs,” Hensel says. “That’s because the natural reefs in the area are all degraded due to a variety of stressors.

“We also found that the presence of grouper on complex reefs led to a significant jump in the population of Tomtate grunts (Haemulon aurolineatum),” Hensel says. “That’s good news, because Tomtates are a species that provides a lot of ecosystem services, which would be good for creating conditions that are more amenable to both coral reef growth and seagrass growth.

“Currently, my colleagues and I are building from these findings in two directions. We’re measuring long-term community and ecosystem level responses to coral restoration or the reintroduction of structurally complex habitat; and we are also measuring long-term biological and physiological responses of fishes residing on restored reefs. For the latter, Haley Gambill, an undergraduate at NC State, is measuring changes in the age and growth of grunts.

“It’s also worth noting that this is an area that was hit hard by Hurricane Dorian. Because we’ve done so much reef population work in that area, I’m hoping to return to do some work that can help us understand how extreme weather events can affect these ecosystems.”

The work was done with support from the National Science Foundation under grants 0746164 and 1405198.

Great Barrier Reef coral fights for survival


This December 2014 video says about itself:

In what has been described as the “world’s biggest orgy”, coral on Australia’s Great Barrier Reef has spawned in one of nature’s most amazing and rarely-seen shows. In an even rarer occurrence, the coral put on an encore performance, re-producing – or spawning – for the second time in two months, releasing millions of eggs and sperm into the waters of the Great Barrier Reef to fertilise. This almost unseen “split-spawning” event had marine scientists and tourists marvelling in delight.

From the University of Queensland in Australia:

Strange coral spawning improving Great Barrier Reef’s resilience

August 6, 2019

A phenomenon that makes coral spawn more than once a year is improving the resilience of the Great Barrier Reef.

The discovery was made by University of Queensland and CSIRO researchers investigating whether corals that split their spawning over multiple months are more successful at spreading their offspring across different reefs.

Dr Karlo Hock, from UQ’s School of Biological Sciences, said coral mass spawning events are one of the most spectacular events in the oceans.

“They’re incredibly beautiful,” Dr Hock said.

“On Australia’s Great Barrier Reef, all coral colonies typically spawn only once per year, over several nights after the full moon, as the water warms up in late spring.”

Study co-author Dr Christopher Doropoulos from the CSIRO Oceans & Atmosphere said sometimes however, coral split their spawning over two successive months.

“This helps them synchronise their reproduction to the best environmental conditions and moon phases,” he said.

“While reproductive success during split spawning may be lower than usual because it can lead to reduced fertilisation, we found that the release of eggs in two separate smaller events gives the corals a second and improved chance of finding a new home reef.”

The research team brought together multi-disciplinary skills in modelling, coral biology, ecology, and oceanography, simulating the dispersal of coral larvae during these split spawning events, among the more than 3800 reefs that make up the Great Barrier Reef.

They looked at whether the split spawning events more reliably supply larvae to the reefs, as well as whether the ability to exchange larvae among the reefs is enhanced by them.

UQ’s Professor Peter J. Mumby said split spawning events can increase the reliability of larval supply as the reefs tend to be better connected and have more numerous, as well as more frequent, larval exchanges.

“This means that split spawning can increase the recovery potential for reefs in the region.

“A more reliable supply of coral larvae could particularly benefit reefs that have recently suffered disturbances, when coral populations need new coral recruits the most.

“This will become more important as coral reefs face increasingly unpredictable environmental conditions and disturbances.”

Dr Hock said the research also revealed that the natural processes of recovery can sometimes be more resilient than originally thought.

“However, even with such mechanisms in place, coral populations can only withstand so much pressure,” he said.

“It all ends up being the matter of scale: any potential benefits from split spawning might be irrelevant if we don’t have enough coral on these reefs to reproduce successfully.

“Mitigating well-established local and global threats to coral reefs — like river runoffs and carbon dioxide emissions — is essential for their continued survival.”

The study between UQ, CSIRO and ARC Centre of Excellence for Coral Reef Studies was published in Nature Communications.

Scientists have completed a landmark study on how to save coral reefs in the Indian and Pacific Oceans: here.

GIANT ROCK COULD HELP HEAL BARRIER REEF A “raft” of floating pumice rock the size of Manhattan is drifting toward Australia, bringing along new marine life that could help with the recovery of the Great Barrier Reef’s corals, half of which have been killed in recent years as a result of climate change. [CNN]

The first documented discovery of ‘extreme corals’ in mangrove lagoons around Australia’s Great Barrier Reef is yielding important information about how corals deal with environmental stress, scientists say. Thirty-four species of coral were found to be regularly exposed to extreme low pH, low oxygen and highly variable temperature conditions making two mangrove lagoons on the Woody Isles and Howick Island potential ‘hot-spots’ of coral resilience: here.

New, lower-cost help may soon be on the way to help manage one of the biggest threats facing the Great Barrier Reef. That threat is pollution from land making its way downstream by way of the many rivers and streams that flow into coastal waters along the reef. The size of the reef — which stretches for 2,300 kilometres along the Queensland coast — makes it extremely hard to get an idea of what’s happening in real-time. Now, in collaboration with scientists at the Queensland Department of Environment and Science, researchers at the ARC Centre of Excellence for Mathematical and Statistical Frontiers (ACEMS) have developed statistical predictive tools that could lead to the deployment of many more low-cost sensors in those rivers and streams: here.

Small fish crucial for coral reef biodiversity


This 2018 video is called The Coral Reef: 10 Hours of Relaxing Oceanscapes | BBC Earth.

From the Smithsonian Institution in the USA:

Live fast, die young: Study shows tiny fishes fuel coral reefs

May 23, 2019

Scientists have long sought to understand how coral reefs support such an abundance of fish life despite their location in nutrient-poor waters. According to a new study published May 23 in the journal Science, an unlikely group fuels these communities: tiny, mostly bottom-dwelling creatures called “cryptobenthic” reef fishes.

The study shows that these fishes perform a critical role on coral reefs, supplying almost 60% of consumed fish food by constantly replenishing their populations in a rapid cycle of life and death.

“Scientists have puzzled over coral reefs for centuries, wondering how such productive, diverse ecosystems survive in what is essentially a marine desert,” said lead author Simon Brandl, formerly with the Smithsonian’s Tennenbaum Marine Observatories Network and currently a postdoctoral research fellow with Simon Fraser University. “It’s remarkable to find that these tiny, almost universally overlooked fishes actually serve as the cornerstone of coral-reef fish communities.”

Cryptobenthic reef fishes, such as gobies, blennies or cardinalfishes, are the smallest of all marine vertebrates. Although they vary in size, the tiniest cryptobenthics will never reach 1 inch and weigh almost nothing. Other coral-reef dwellers eat these fishes in large quantities, most within the first few weeks of their existence.

Instead of disappearing, however, cryptobenthic fish populations somehow flourish in the face of constant predation. The researchers solved this paradox by studying the larvae of reef fishes. While the larvae of most fish species disperse into the open ocean, where only a few survive, cryptobenthics behave differently. Brandl and his team found that most cryptobenthic larvae appear to remain close to their parents’ reefs, yielding many more survivors among their babies. These larvae then rapidly replace cryptobenthic adults eaten on the reef, sustaining the growth of larger reef fishes.

“We found that cryptobenthic fish larvae absolutely dominate the larval-fish communities near reefs, which provides a continuous stream of new generations of tiny fish as a food source for other reef creatures,” said Carole Baldwin, co-author on the study and curator of fishes at the Smithsonian’s National Museum of Natural History. “It’s incredible that these fishes contribute so much to coral reefs. They’re so small that historically we haven’t recognized their enormous significance.”

Scientists from Australia, Canada, France and the United States contributed to this research. The team studied cryptobenthics in Belize, French Polynesia and Australia, combed decades of data on coral-reef fish larvae and developed a population model to better understand how cryptobenthics contribute to the diet of coral-reef dwellers.

The study began in 2015, when Brandl was a postdoctoral fellow at the Smithsonian’s Marine Global Earth Observatory (MarineGEO), but these tiny fishes are more relevant today than ever. As coral reefs undergo dramatic declines, their fish communities — and the people who depend on them — may be in jeopardy. The researchers hope that the vast diversity of cryptobenthics and their unique way of life can make them a resilient foundation for coral reefs.

Red Sea coral reef wildlife, video


This video says about itself:

The Incredible Sea Life of the Red Sea Coral Reef | BBC Earth

Simon Reeve dives into the Red Sea to get close to its incredible fish and marine wildlife.

Scientists offer a new way to accurately map coral reefs using a combination of Earth-orbiting satellites and field observations. This first-ever global coral reef atlas contains maps of over 65,000 square kilometers (25,097 square miles) of coral reefs and surrounding habitats: here.