Studying coral with microscopes, new method


This July 2016 video says about itself:

A new microscope mimics the human eye to study the intimate lives of coral

A new microscope gives unprecedented access to the lives of coral, from feeding to kissing, on the ocean floor.

Video Editor: Leigh Anne Tiffany

Video provided by: Jaffe Lab for Underwater Imaging, Scripps Institution for Oceanography at UC San Diego

Music: Blue Dot Sessions via Creative Commons

From the Marine Biological Laboratory in the USA:

Microscope allows gentle, continuous imaging of light-sensitive corals

June 30, 2020

Summary: Many corals are sensitive to bright light, so capturing their dynamics with traditional microscopes is a challenge. To work around their photosensitivity, researchers developed a custom light-sheet microscope (the L-SPI) that allows gentle, non-invasive observation of corals and their polyps in detail over eight continuous hours, at high resolution.

Corals are “part animal, part plant, and part rock — and difficult to figure out, despite being studied for centuries,” says Philippe Laissue of University of Essex, a Whitman Scientist at the Marine Biological Laboratory. Many corals are sensitive to bright light, so capturing their dynamics with traditional microscopes is a challenge.

To work around their photosensitivity, Laissue developed a custom light-sheet microscope (the L-SPI) that allows gentle, non-invasive observation of corals and their polyps in detail over eight continuous hours, at high resolution. He and his colleagues, including MBL Associate Scientist and coral biologist Loretta Roberson, published their findings this week in Scientific Reports.

Coral reefs, made up of millions of tiny units called polyps, are extremely important ecosystems, both for marine life and for humans. They harbor thousands of marine species, providing food and economic support for hundreds of millions of people. They also protect coasts from waves and floods, and hold great potential for pharmaceutical and biotechnological discovery.

But more than half of the world’s coral reefs are in severe decline. Climate change and other human influences are gravely threatening their survival. As ocean temperatures rise, coral bleaching is afflicting reefs worldwide. In coral bleaching, corals expel their symbiotic algae and become more susceptible to death.

“The L-SPI opens a window on the interactions and relationship between the coral host, the symbiotic algae living in their tissues, and the calcium carbonate skeleton they build in real time,” Roberson says. “We can now track the fate of the algae during [coral] bleaching as well as during initiation of the symbiosis.”

Roberson is also using Laissue’s imaging technology to measure damage to corals from “bioeroders” — biological agents like algae and sponges that break down a coral’s skeleton, a problem exacerbated by ocean acidification and increasing water temperatures.

Corals discovered off Greenland


This 29 June 2020 video says about itself:

Captioned video showing and describing a new soft coral garden habitat discovered deep off the coast of Greenland.

From University College London in England:

Soft coral garden discovered in Greenland’s deep sea

June 29, 2020

A deep-sea soft coral garden habitat has been discovered in Greenlandic waters by scientists from UCL, ZSL and Greenland Institute of Natural Resources, using an innovative and low-cost deep-sea video camera built and deployed by the team.

The soft coral garden, presented in a new Frontiers in Marine Science paper, is the first habitat of this kind to have been identified and assessed in west Greenland waters.

The study has direct implications for the management of economically important deep-sea trawl fisheries, which are immediately adjacent to the habitat. The researchers hope that a 486 km2 area will be recognised as a ‘Vulnerable Marine Ecosystem’ under UN guidelines, to ensure that it is protected.

PhD researcher Stephen Long (UCL Geography and ZSL (Zoological Society London)), first author on the study, said: “The deep sea is often over-looked in terms of exploration. In fact, we have better maps of the surface of Mars, than we do of the deep sea.

“The development of a low-cost tool that can withstand deep-sea environments opens up new possibilities for our understanding and management of marine ecosystems. We’ll be working with the Greenland government and fishing industry to ensure this fragile, complex and beautiful habitat is protected.”

The soft coral garden discovered by the team exists in near-total darkness, 500m below the surface at a pressure 50 times greater than at sea-level. This delicate and diverse habitat features abundant cauliflower corals as well as feather stars, sponges, anemones, brittle stars, hydrozoans, bryozoans and other organisms.

Dr Chris Yesson (ZSL), last author on the study, said “Coral gardens are characterised by collections of one or more species (typically of non-reef forming coral), that sit on a wide range of hard and soft bottom habitats, from rock to sand, and support a diversity of fauna. There is considerable diversity among coral garden communities, which have previously been observed in areas such as northwest and southeast Iceland.”

The discovery is particularly significant given that the deep sea is the most poorly known habitat on earth, despite being the biggest and covering 65% of the planet. Until very recently, very little was known about Greenland’s deep-sea habitats, their nature, distribution and how they are impacted by human activities.

Surveying the deep sea has typically proved difficult and expensive. One major factor is that ocean pressure increases by one atmosphere (which is the average atmospheric pressure at sea level) every 10 metres of descent. Deep-sea surveys, therefore, have often only been possible using expensive remote operating vehicles and manned submersibles, like those seen in Blue Planet, which can withstand deep-sea pressure.

The UK-Greenland research team overcame this challenge by developing a low-cost towed video sled, which uses a GoPro video camera, lights and lasers in special pressure housings, mounted on a steel frame.

The lasers, which were used to add a sense of scale to the imagery, were made by combining high-powered laser pointers with DIY housings made at UCL’s Institute of Making, with help from UCL Mechanical Engineering.

The team placed the video sledge — which is about the size of a Mini Cooper — on the seafloor for roughly 15 minutes at a time and across 18 different stations. Stills were taken from the video footage, with 1,239 images extracted for further analysis.

A total of 44,035 annotations of the selected fauna were made. The most abundant were anemones (15,531) and cauliflower corals (11,633), with cauliflower corals observed at a maximum density of 9.36 corals per square metre.

Long said: “A towed video sled is not unique. However, our research is certainly the first example of a low-cost DIY video sled led being used to explore deep-sea habitats in Greenland’s 2.2million km² of sea. So far, the team has managed to reach an impressive depth of 1,500m. It has worked remarkably well and led to interest from researchers in other parts of the world.”

Dr Yesson added: “Given that the ocean is the biggest habitat on earth and the one about which we know the least, we think it is critically important to develop cheap, accessible research tools. These tools can then be used to explore, describe and crucially inform management of these deep-sea resources.”

Dr Martin Blicher (Greenland Institute of Natural Resources) said: “Greenland’s seafloor is virtually unexplored, although we know is it inhabited by more than 2000 different species together contributing to complex and diverse habitats, and to the functioning of the marine ecosystem. Despite knowing so little about these seafloor habitats, the Greenlandic economy depends on a small number of fisheries which trawl the seabed. We hope that studies like this will increase our understanding of ecological relationships, and contribute to sustainable fisheries management.”

Shipwreck Coral Reefs, video


This 24 June 2020 video says about itself:

Exploring Shipwreck Coral Reefs

Next on Blue World, Jonathan learns how to dive without a scuba tank by holding his breath a long time! But first, he investigates shipwrecks that are turning into coral reefs. All of this today on Jonathan Bird’s Blue World!

Restoring Mexican coral reefs, video


This 17 June 2020 video says about itself:

Oceanographer and National Geographic Explorer Paola Rodriguez works to restore coral reefs in her native Mexico. Once thought impossible, Paola and her team are proving that reefs can recover from even serious damage if given a chance.

How deep sea corals grow, new research


This December 2016 video from the USA says about itself:

In the deep waters off Florida’s Atlantic coast grow magnificent structures, capable of reaching 300 feet in height. These are the corals of the deep sea. Porcelain-white and centuries-old, few humans have seen these delicate reefs. The Ivory Tree Coral, Oculina varicosa, and Lophelia pertusa flourish in harsh, sunless environments, yet these branch-like formations provide food and shelter for a variety of deepwater organisms. Rich in biodiversity, this mysterious underwater kingdom is threatened by destructive fishing practices such as bottom trawling. However, a recently proposed 23,000 square mile marine protected area could save these fragile reefs from ruin.

Changing Seas follows scientists 50 miles offshore on a unique expedition to further pinpoint the locations of these thousand-year-old coral mounds. Using cutting-edge technology, experts from three of the country’s premier ocean research institutions have joined forces to investigate portions of Florida’s seafloor. The science team lives aboard a research vessel for seven days. Their mission: To scan the ocean bottom and create detailed maps using specially built Autonomous Underwater Vehicles or AUVs. Their results could help save Florida’s corals of the deep. But what will they find?

From the University of Hawaii at Manoa:

Surprising growth rates discovered in world’s deepest photosynthetic corals

June 15, 2020

New research published in the journal Coral Reefs revealed unexpectedly high growth rates for deepwater photosynthetic corals. The study, led by Samuel Kahng, affiliate graduate faculty in the University of Hawai’i at M?noa School of Ocean and Earth Science and Technology (SOEST), alters the assumption that deep corals living on the brink of darkness grow extremely slowly.

Leptoseris is a group of zooxanthellate coral species which dominate the coral community near the deepest reaches of the sun’s light throughout the Indo-Pacific. Symbiotic microalgae (called zooxanthellae) live within the transparent tissues some coral — giving corals their primary color and providing the machinery for photosynthesis, and in turn, energy.

Deeper in the ocean, less light is available. At the lower end of their depth range, the sunlight available to the Leptoseris species examined in the recent study is less than 0.2% of surface light levels. Less light dictates a general trend of slower growth among species that rely on light for photosynthesis.

Previous studies suggested that photosynthetic corals at the bottom of the ocean’s sunlit layer grow extremely slowly — about 0.04 inch per year for one species of Leptoseris. Until recently, there were very few data on growth rates of corals at depths greater than about 225 feet given the logistical challenges of performing traditional time series growth measurements at these depths.

Kahng, who is also an associate professor at Hawai’i Pacific University, collaborated with SOEST’s Hawai’i Undersea Research Laboratory (HURL), the Waikiki Aquarium, National Taiwan University and Hokkaido University to collected colonies of Leptoseris at depths between 225 and 360 feet in the Au’au Channel, Hawai’i using HURL’s Pisces IV/V submersibles. The research team used uranium-thorium radiometric dating to accurately determine the age of the coral skeletons at multiple points along its radial growth axis — much like one might determine the age of tree rings within a tree trunk.

“Considering the low light environment, the previous assumption was that large corals at these extreme depths should be very old due to extremely slow growth rates,” said Kahng. “Surprisingly, the corals were found to be relatively young with growth rates comparable to that of many non-branching shallow-water corals. Growth rates were measured to be between nearly 1 inch per year at 225 feet depth and 0.3 inches per year at 360 feet depth.”

The research team found that these low light, deep water specialists employ an interesting strategy to dominate their preferred habitat. Their thin skeletons and plate-like shape allow for an efficient use of calcium carbonate to maximize surface area for light absorption while using minimal resources to form their skeleton. These thin corals only grow radially outward, not upward, and do not thicken over time like encrusting or massive corals.

“Additionally, the optical geometry of their thin, flat, white skeletons form fine parallel ridges that grow outward from a central origin,” said Kahng. “In some cases, these ridges form convex spaces between them which effectively trap light in reflective chambers and cause light to pass repeatedly through the coral tissue until it is absorbed by the photosynthetic machinery.”

The strategic efficiency of Leptoseris enabling its robust growth rates in such low light has important implications for its ability to compete for space and over-shade slower-growing organisms.

“It also illustrates the flexibility of reef-building corals and suggests that these communities may be able to develop and recover from mortality events much faster than previously thought,” said Kahng.

Coral reef fish evolution, new research


This 2018 video says about itself:

The Coral Reef: 10 Hours of Relaxing Oceanscapes | BBC Earth

Sit back, relax and enjoy the colourful world of coral reefs as we take you on a journey through some of the most vibrant parts of our blue planet with this 10-hour loop.

From the ARC Centre of Excellence for Coral Reef Studies in Australia:

Big vegetarians of the reef drive fish evolution

June 2, 2020

Summary: New research finds fish diets, not geography, dictate how fast species evolve.

A new study reveals the diets of reef fish dictate how fast different species evolve. The breakthrough adds another piece to the fascinating evolutionary puzzle of coral reefs and the fishes that live on them.

“Up until now we knew that many factors could have influenced the pace of reef fish evolution, but these factors were never examined altogether,” said Alexandre Siqueira, the study’s lead author from the ARC Centre of Excellence for Coral Reef Studies at James Cook University (Coral CoE at JCU).

“By building an evolutionary ‘tree of life’ for nearly all fishes associated with reefs, we were able to examine the variation in rates of species formation and ask what drives it,” said co-author Dr Peter Cowman, also from Coral CoE at JCU.

The ‘tree of life’ contains more than 6,000 fish species that live on coral reefs across the globe. Ecological and geographical data — such as diet and geographical range — were also gathered for the majority of these species.

The authors were surprised to find that what really matters in reef fish evolution isn’t geography, but what fish eat and how big they get.

“We found that the fastest way to have more species, or biodiversity, on a reef is to be big and vegetarian,” said co-author Professor David Bellwood, also from Coral CoE at JCU.

“Herbivores, such as surgeonfishes and parrotfishes, are key to the ecological diversity of coral reefs today.”

The study suggests these fishes also made way for today’s coral reefs to evolve and flourish.

“By feeding on the algae that compete with corals, herbivorous fishes may have also helped corals to expand through time,” Mr Siqueira said.

“In turn, this expansion in the corals allowed the diversification of other reef fish groups that depend on them.”

And these herbivorous fishes — big and small — still maintain coral reefs to this day.

The study offers a new way of looking at reefs with a functional, rather than taxonomic, approach. Very little is known about the functional evolution of reefs: what they do and how they work. Scientists previously only looked at how many reefs there were and what species were present.

“In this study it was important to understand the origins of the functional role a fish species plays on a reef — not just the species itself,” Dr Cowman said.

Today’s coral reefs differ from their early counterparts. It was only during the Miocene, less than 23 million years ago, that herbivorous fish species developed features that allowed them to explore different areas of the reef.

“Because of this, today’s reefs are highly dynamic and have a fast turnover. These herbivores are the key element that established modern coral reefs,” Prof Bellwood said.

“Understanding how reefs are constructed throughout their evolution means we can reach a better understanding of the fundamental processes that maintain them in a healthy state today,” Mr Siqueira said.

Saving a coral reef in the Philippines


This 29 May 2020 video says about itself:

Grandpa’s Reef – 360 | National Geographic

Travel with us to the Philippines, where a young girl takes up her grandfather’s lifelong pursuit of protecting an endangered coral reef. Inspired by true stories, this virtual reality experience will take you diving on some of the world’s most beautiful reefs. For a better viewing experience, watch in a VR headset using the YouTube app.

Corals use colours to fight bleaching


After a warm spell, some corals, like these Acropora corals in New Caledonia in the Pacific Ocean, turn bright hues instead of bleaching white. The corals boost their production of pigments after losing the beneficial algae that live in their cells, a study finds. Photo: Richard Vevers/The Ocean Agency, XL Catlin Seaview Survey

After a warm spell, some corals, like these Acropora corals in New Caledonia in the Pacific Ocean, turn bright hues instead of bleaching white. The corals boost their production of pigments after losing the beneficial algae that live in their cells, a study finds. Photo: Richard Vevers/The Ocean Agency, XL Catlin Seaview Survey.

By Carolyn Wilke, May 29, 2020 at 8:00 am:

Neon colors may help some corals stage a comeback from bleaching

Coral pigments act as a sunscreen and may make a more hospitable home for returning algae

For some corals, going bright may be part of their fight against bleaching.

Higher-than-normal ocean temperatures can cause some corals to bleach and lose the beneficial algae that dwell within their cells. Those algae help feed the corals and give them their color, so bleached corals can become bone white, and may struggle to survive (SN: 4/7/20). But when some corals bleach, they turn neon hues from red to blue to purple.

A new study finds that those flashy colors may be part of a response that can help the corals recover from bleaching and reunite with their algal partners.

“It’s visually very striking, but … there was surprisingly little information” on how and why colorful bleaching happens, says Elena Bollati, a marine biologist at the National University of Singapore.

Some researchers suspected that with the algae gone, the bleached corals’ vivid natural colors shone through. But the new work suggests a different dynamic. In the lab, certain wavelengths of light appear to trigger an uptick in a coral’s production of pigments, which act as a sunscreen to create a more hospitable home for the returning algae, Bollati and colleagues report May 21 in Current Biology.

The research “shows that some of these corals are trying to protect themselves with really spectacular side effects,” says Daniel Wangpraseurt, a coral reef scientist at the University of Cambridge who was not involved with the study.

A survey of bleaching events in the world’s oceans from 2010 to 2019 revealed that some corals’ neon colors corresponded with mild heat stress, caused by a long spell of warmer waters or a brief temperature spike. In most cases, the colors appeared two to three weeks after the heat stress events, says Bollati, who did the work while at the University of Southampton in England.

In the lab, the scientists simulated mild bleaching by exposing coral colonies to a slow ramp up in temperature. As the team turned up the heat, the amount of algae, detected by the red light they emit under a certain wavelength of light, in cells plummeted. A few weeks after the heat stress, the corals bumped up their levels of a fluorescent compound, the pigment that gives them color. The scientists also found that an imbalance of nutrient levels could cause colorful bleaching.

After losing their algae, an increased exposure to blue light in sunlight may play a role in this rise in pigment production, the team found. Healthy, unbleached corals rely on algae’s pigments to absorb some sunlight. Without the algae, more light — including its blue wavelengths — can enter and bounce around inside the corals’ skeleton structure. That added reflection boosts the exposure of the corals’ living tissue to light.

A bombardment of blue light prompted bleached corals to start pumping out more of their own protective pigments, the researchers found. The scientists also observed that that vividly colored areas of the corals more quickly regained their symbiotic algae than areas with less pigment.

Corals “have this capacity to fight back,” says University of Southampton marine biologist Jörg Wiedenmann, who was part of the research team. “They are by no means doomed” after one bleaching event. But, he cautions, their long-term survival depends on people acting to limit climate change so that corals don’t experience more stress than they can handle.

Coral reef conservation, new research


This 13 August 2018 video says about itself:

Summer Island’s 3D Printed Artificial Coral Reef

The Edition explores how 3D technology may bring ‘summers’ of hope to coral reefs in the Maldives, drowning amidst seas of neglect.

From the University of Cambridge in England:

3D-printed corals could improve bioenergy and help coral reefs

April 9, 2020

Researchers from Cambridge University and University of California San Diego have 3D printed coral-inspired structures that are capable of growing dense populations of microscopic algae. Their results, reported in the journal Nature Communications, open the door to new bio-inspired materials and their applications for coral conservation.

In the ocean, corals and algae have an intricate symbiotic relationship. The coral provides a host for the algae, while the algae produce sugars to the coral through photosynthesis. This relationship is responsible for one of the most diverse and productive ecosystems on Earth, the coral reef.

“Corals are highly efficient at collecting and using light,” said first author Dr Daniel Wangpraseurt, a Marie Curie Fellow from Cambridge’s Department of Chemistry. “In our lab, we’re looking for methods to copy and mimic these strategies from nature for commercial applications.”

Wangpraseurt and his colleagues 3D printed coral structures and used them as incubators for algae growth. They tested various types of microalgae and found growth rates were 100x higher than in standard liquid growth mediums.

To create the intricate structures of natural corals, the researchers used a rapid 3D bioprinting technique originally developed for the bioprinting of artificial liver cells.

The coral-inspired structures were highly efficient at redistributing light, just like natural corals. Only biocompatible materials were used to fabricate the 3D printed bionic corals.

“We developed an artificial coral tissue and skeleton with a combination of polymer gels and hydrogels doped with cellulose nanomaterials to mimic the optical properties of living corals,” said Dr Silvia Vignolini, who led the research. “Cellulose is an abundant biopolymer; it is excellent at scattering light and we used it to optimise delivery of light into photosynthetic algae.”

The team used an optical analogue to ultrasound, called optical coherence tomography, to scan living corals and utilise the models for their 3D printed designs. The custom-made 3D bioprinter uses light to print coral micro-scale structures in seconds. The printed coral copies natural coral structures and light-harvesting properties, creating an artificial host-microenvironment for the living microalgae.

“By copying the host microhabitat, we can also use our 3D bioprinted corals as a model system for the coral-algal symbiosis, which is urgently needed to understand the breakdown of the symbiosis during coral reef decline,” said Wangpraseurt. “There are many different applications for our new technology. We have recently created a company, called mantaz, that uses coral-inspired light-harvesting approaches to cultivate algae for bioproducts in developing countries. We hope that our technique will be scalable so it can have a real impact on the algal biosector and ultimately reduce greenhouse gas emissions that are responsible for coral reef death.”

Researchers at School of Biological Sciences and Swire Institute of Marine Science, The University of Hong Kong have developed a new method for determining what corals eat, and demonstrated that reliance on certain nutritional sources underpins their bleaching susceptibility in warming oceans: here.