Coral Reefs

Podcast: The Rainforests of the Sea

Ocean Matters - New episode available now

Episode 2: The Rainforests of the Sea

Coral reefs are some of the most diverse ecosystems in the world. They’re very special places, covering less than one percent of the seafloor but home to nearly a quarter of all ocean species at some point in their life cycle.

In this episode of Ocean Matters, physicist and oceanographer Helen Czerski explores the state of reefs in some of the most remote parts of our planet. She learns about the latest research techniques being used by scientists and how archives of old dead corals are helping in the fight to save the corals of our future – and why we need to act so urgently?

Come with us on this scientific adventure. Subscribe now, wherever you get your podcasts, so that you never miss an episode of Ocean Matters.

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Coral Reefs

Ocean Matters – New Podcast Series

New Podcast series, Ocean Matters, has officially launched on Wednesday 27th January 2021

Our ocean is the earth’s defining feature. But the blue of our blue planet is so much more than just a colour. It is rich with life and plays an important role in keeping our planet stable and healthy. Worryingly, we are seeing our ocean change, for the worse. In Ocean Matters, join oceanographer and physicist Helen Czerski as she meets the scientists who are working to save our ocean and marine life in one of the most remote parts of our planet. Together, we’ll explore how the cutting-edge research science that’s going on there – and other places we visit – is helping to protect species across the world, and better understand what needs to be done to save our seas. Come on this adventure.

Episode One: Troubled Water – Our Ocean’s History

To quote Maya Angelou, “you can’t really know where you’re going, until you know where you have been.” In this first episode, physicist and oceanographer Helen Czerski, explores our ocean’s recent past. What was the ocean like 200 years ago? How does that compare with today – and what does that difference reveal? Join Helen as she discovers watery secrets in the Natural History Museum’s archive, learns what old newspapers can reveal about the impact of our fishing history, and meets one of the scientists who helped to set up one of the largest marine protected areas in the world.

Come with us on this scientific adventure.

Subscribe now, wherever you get your podcasts, so that you never miss an episode of Ocean Matters.

Coral Reefs

Robotic Diver Reveals the Secrets of Deep-Sea Tropical Reefs

Scientists working in the Indian Ocean Region hope their findings can help conserve shallow-water coral reefs

Shallow-water coral reefs are one of the world’s most important and diverse ecosystems. These tropical habitats are facing rapid destruction by human interference and ocean warming but they may have a hidden saviour deeper below the surface: mesophotic reefs.

Lying at depths of up to 150 metres, these remote marine ecosystems have remained largely unexplored for decades. But now a team of University of Plymouth scientists, led by Nicola Foster, are using a robotic submersible to gather coral samples from mesophotic reefs in the isolated the area surrounding the Chagos Archipelago region. They hope to identify whether these reefs can play a role in supporting shallow-water corals. A new video reviews this vital research.

“When we first descended below 60metres we were amazed at the colourful abundance of life,” says Foster. “It was an incredible privilege to be one of the first people to see these reefs and all the life they support”.

Uncovering hidden species

The team had hoped to find that mesophotic corals are genetically related to shallow-water corals. If this is the case, they could help repopulate damaged reefs in shallower waters. Video footage to date has revealed very few coral species that inhabit both reefs, and it seems unlikely that they are closely related.

However, whilst genetic analysis continues, the research is revealing other uplifting insights into mesophotic reefs.

“We’ve discovered extensive, diverse coral communities that are positively thriving between 40 and 150 metres,” says Foster. “These reefs host huge biodiversity and potentially rare and endemic species.

“Like shallow-water reefs, mesophotic reefs support the marine ecosystem by providing food, regulating climate, offering essential nursery habitats and providing shoreline protection. It’s vital that we protect the mesophotic reefs to maintain the support they provide to shallow-water reefs.”

Their ongoing research to reveal the reefs’ secrets ties closely into the Bertarelli Foundation’s recent seminar ‘Secret Biodiversity: Uncovering Hidden Species and Behaviours’.

Deep diving

The state-of-the-art remotely operated vehicle (ROV) the team are using to survey the reefs is equipped with on-board lights and a camera system which streams high-resolution video to a surface unit on the boat. This means researchers can observe coral communities in real-time at depths where sunlight is limited. Capable of diving to depths of up to 1,000 metres, the ROV is also able to collect biological samples using its manipulator arm.

The ROV is especially useful for exploring mesophotic reefs in the MPA surrounding the Chagos Archipelago; because of its remoteness, human divers are not able to dive more than 25 metres below the surface.

A united effort across the Indian Ocean Region

As part of the Bertarelli Foundation’s Marine Science Programme, Foster’s team share data and collaborate with other experienced researchers from a range of disciplines.

“We’re planning another cruise,” says Foster. “We’ll be documenting where mesophotic reefs occur within the MPA and describing their diversity. We want to see how they connect with shallow reefs and with other mesophotic reefs around the Chagos Archipelago and the wider Indian Ocean.”

The Bertarelli Foundation and the Garfield Weston Foundation fund this research as part of the Bertarelli Marine Science Programme.

Coral Reefs

Webinar: Secret Biodiversity – Uncovering Hidden Species and Behaviours

Secret Biodiversity: Uncovering Hidden Species and Behaviours

The second of the new marine science seminar series was held online on Tuesday 13^th October. This session looked at ‘Secret Biodiversity: Uncovering Hidden Species and Behaviours’ and featured a fantastic panel of international experts chaired by Dr Dominic Andradi-Brown of WWF.

A recording of the seminar is available to watch here:

Here are answers to some of the remaining questions which there wasn’t time to answer during the live session.

Have you noticed any specific behaviours between shark clans or pairs that may be acting to keep their social bonds strong? An equivalent to grooming in primates so to speak!

David Jacoby: With the technology we are working with acoustic telemetry we are already pushing the boundaries of what we can understand about behaviour. Our techniques are inference methods as we cannot actually directly measure social behaviour in the same way that we would for grooming interactions in primates. The challenge we face is studying animals that we will never see again and that travel long distances under water – hence the combined approaches of the camera tags with the acoustic tags. We’ve done a little work on leadership in these sharks and find that females are more likely to lead away from the reef than males who are more likely to follow. I would say that strong social bonds are maintained by the duration of time these individuals spend together. I really does seem as though they have quite tight knit communities. Hopefully the technology will progress sufficiently soon that we can measure and importantly retrieve data on direct social interactions in wild sharks.

Are there other species of sharks known to have the similar social groups such as grey reef sharks?

David Jacoby: There are a number of other species that have been shown to be social including (but not limited to) manta rays, blacktip reef sharks, small spotted catsharks, lemon sharks etc. So, it seems that social behaviour is not necessarily uncommon in sharks. The study I presented is the first however to suggest that sharks can maintain social preferences over many years, and that perhaps the mechanism driving structure is one of information exchange about foraging locations.

Is there any ex situ conservation work on Chagos brain coral? Would an in situ conservation intervention be possible?

Bryan Wilson: A great question, essentially underpinning the biggest challenge to my research at the moment, here at the University of Oxford. The Chagos Marine Protected Area is a wonderfully difficult location to get to but I’m always so very aware that it is this remoteness that drives its incredible biodiversity. And in that regard, both in situ and ex situ conservation work on the Chagos brain coral are inherently “difficult”. Limited access to the area means that the regular monitoring and management that in situ work would require is problematic, whilst the administrative (and not least, ethical) issues of removing and transporting critically endangered species overseas for studies are a major concern. However, I’m spending a good deal of my time looking into how we might solve these critical problems – and collecting gametes and/or larvae from spawning Ctenella chagius for ex situ conservation seems to be the most logical way forward, essentially minimising physical perturbation of the adult colonies in situ, whilst also allowing for a more amenable means of transporting live biological specimens out of the territory. I’m hoping that with the wonderful ongoing collaboration and support of the Zoological Society of London and Horniman Museum and Gardens, we shall ultimately be successful in this venture!

Is the amount of boring algae associated with the health of the corals?

Bryan Wilson: Another very pertinent question and absolutely on my current research radar – the data that I presented during the presentation is very much at the cutting edge of what we know about this species and as I only received this microbiome data back very recently, I haven’t as of yet had the time to fully delve into it. Major biological and ecological statements will also have to be tempered by my small (N = 7) sample number – however, with the serendipitous discovery of this “Aladdin’s Cave” of colonies in the northern atolls, I am relishing the opportunity to return the MPA and sample more extensively.

Do if you think the Chagos brain coral could be the panda of coral reefs? Or does it represent the general survival chances of Chagos coral reefs?

Bryan Wilson: That’s a salient point and one that I’ve discussed with many of my colleagues. Whilst I won’t deny that I have become very attached to the idea (bordering on all-consuming passion!) of conserving this iconic species, it’s important to place this coral – like Giant Pandas – in the greater contextual framework of an environment under stress. We’re seeing the degradation of reefs on a global scale, and the reduction and loss of a number of coral species – in the Chagos MPA, Ctenella chagius is the species most threatened, teetering on the very brink of extinction – but other coral species will surely follow in the years to come if we don’t act now. And so I believe that if we can save Ctenella and put in place a conservation framework to recover corals such as these, then we may have a greater chance of halting the decline in biodiversity on these reefs.

Is there any work being done on the presence of potential toxins from manmade sources like agricultural pesticides and herbicides in the water around the Chagos Archipelago?

Currently this work is not funded as part of this marine science programme but there is interest in developing this work in the near future.

Coral Reefs

Webinar: Rats, Seabirds and Reefs – Holistic Approaches to Island Restoration

Rats, Seabirds and Reefs: Holistic Approaches to Island Restoration

On Tuesday 15^th September, the first of a new series of marine science seminars was held online. The session, “Rats, Seabirds and Reefs: Holistic Approaches to Island Restoration” featured an international scientific panel chaired by Professor Heather Koldewey.

A recording of the seminar is now available to watch here:

Below are answers to some of the remaining questions which there wasn’t time to answer during the live session.

What is our current understanding of how higher nutrient levels around rat free islands influence coral bleaching susceptibility in the Chagos Archipelago?

Casey Benkwitt: In lab studies, higher natural nutrient levels (like those from seabirds or fish) have been shown to reduce coral bleaching susceptibility. But, our field surveys in the Chagos Archipelago from before versus ~3 years after the 2015/2016 mass bleaching event did not show increased coral resistance around rat-free islands (i.e., coral loss was similar around rat-free and rat-infested islands). There are a few possible explanations for this difference between lab and field studies – one is that seabird nutrients reduce bleaching susceptibility during less extreme heat waves, but the 2015/2016 event was so intense and prolonged that it overpowered any benefits of seabird nutrients. Even though resistance wasn’t higher around rat-free islands, we’re now looking at whether reefs around rat-free islands recover more quickly, which is possible given the high cover of CCA and high biomass of herbivores near these islands. If you want more info, see Benkwitt et al. 2019 in Global Change Biology where we answer this question in detail!

Do you think there could be a carrying capacity of seabird populations in the Chagos archipelago based on fish productivity in the open ocean in which they can feed. i.e. could recovery of seabird numbers also be limited by food availability?

Pete Carr: A good question that has not been answered anywhere in the world regarding seabird recovery to the best of my knowledge. I suspect there is a prey availability carrying capacity cap, other top predators in different ecosystems most certainly are. It would be an interesting question to try and answer. With the methodology from my talk and the data I have, we could calculate the maximum number of breeding pairs if all islands were cleared of rats and rewilded to option C (the real time rewilding to savanna and native forest). I am guessing there are papers giving food consumption by seabirds (e.g. Danckwerts et al, 2014 for WIO). So you could get an order of magnitude of the prey needed. How one could calculate if there is that amount of prey available in Chagos is not a question I could answer. Be nice to think about it though.

Which of the three models presented would be the most practical in terms of cost effectiveness and value to the ecosystem?

Pete Carr: Based upon Casey’s talk (and Graham et al., 2018), that proves the cross-ecosystem benefits of seabird islands, plus, maximising breeding numbers of seabirds that could possibly be a source for depleted seabird populations elsewhere in the Indian Ocean, it would be logical to go for the highest totals – Option C. Option A did not restore a seabird-driven ecosystem (92% of island not being available to breeding seabirds because it is abandoned plantation) and therefore is not a viable rewilding option. Option B cannot be achieved in reality as I said, one cannot create wetlands on porous coral or, beach in an environment where there are “shifting sands” depending on prevailing winds and tides – and is not necessary because RSF graphs proved and the pie charts demonstrated we only need (and can only) create two habitats, savanna (read open areas) and native forest. Not so much a true CBA but a logical decision making process.

In Kenya, the government banned the use some chemicals used to eradicate the Indian House Crows which are believed to be a threat to other indigenous birds which they feed on within Mombasa Island and along other cities in the coastline. Is there an effective way of eradicating the crows without posing any danger within the community where they mostly feed?

Sarah Havery: Without knowing the specific details it is difficult to suggest whether eradication is possible or not – given the location it is likely that long-term control to reduce the population would be the most feasible approach. There have been some successful bird eradications from islands in the Seychelles, which I believe was achieved by shooting.

Breeding success studies are ongoing across Seychelles for several species, as expected there is lower breeding success on islands with rats but we also have population decline on an island with no rats. Restoration will/should lead to seabird population increase but other factors may also interfere with population recovery, like food availability. Have you been investigating this in the Chagos Archipelago? Are there breeding success studies for seabirds on the Chagos Islands?

Pete Carr: We are not investigating food availability (but suspect as a result of this webinar it may be researched in the future and see above). Please read Carr et al., 2020 in Bird Conservation International for the latest assessment on breeding seabirds.

Coral Reefs

The Heat is on for the Survival of Chagos Archipelago’s Coral Reefs

Original post:

Back-to-back heatwaves kill more than two-thirds of coral.

The heat is on for the survival of the Chagos Archipelago's coral reefs.

ZSL scientists have shown the devastating effects of back-to-back heatwaves in the region surrounding the Chagos Archipelago. Coral cover was reduced by 60% in 2016 and by a further 30% in 2017. Nonetheless, this also indicates that some coral species have a higher resilience to rising temperatures thus offering some hope for the future.

Although representing les than 1% of our marine habitats coral reefs harbour a quarter of marine life. There are strong economic, conservation and scientific reasons for us to safeguard these reefs in a changing world.

In 2015 an eight weeklong heatwave struck the Chagos Archipelago, causing the seawater of the area to be unusually hot for a prolonged period. Researchers compared surveys of the reef before and after the heatwave in order to map the changes and harm it caused to the reefs. Evidence from 2015’s observations shows a 60% reduction in coral cover in the MPA. This included a dramatic 86% decline in the branching Acropora species that was previously a dominant reef building coral.

A year later, and before any recovery was possible, this region was subject to another bleaching event caused by a four-month long heatwave. Using data from Peros Banhos atoll an estimated 68% of the remaining corals had bleached. This suggest that around 70% of the reef area covered by corals was lost between 2015/2017.

Although more severe than the first heatwave, the second did less damage than the previous one. The first one killed corals most vulnerable to heat stress, leaving the more resilient colonies to try and survive the second. The fact that a few species have a higher heat tolerance is a glimmer of hope. According to Dr. Catherine Head the increasing severity and occurrence of heatwaves will inhibit shallow reefs ability to regenerate from bleaching events. It previously took 10 years for coral reefs to regenerate in BIOT, there is a high probability that the more vulnerable coral species will completely die off in the near future if these bleaching events become more frequent.

Preliminary reports from 2019 suggest a grim future for the Indian Ocean Region’s reefs as another heatwave was recorded and observations made of the start of yet another bleaching event of unknown impact. Research is key to understanding how corals adapt to rising sea surface temperatures and how we can positively impact their recovery.

Coral Reefs

The Impact of Black Rats on Coral Reefs

Original post:

The Impact of Rats on the Health of Coral Reefs

The British Indian Ocean Territory includes the Chagos Archipelago and 58 small islands. Some of which are home to black rats (Rattus rattus), while others luckily remained rat-free.

Researchers in the Bertarelli Programme in Marine Science studied both islands, with and without rats, to see what effect the presence of rodents has on the health of the surrounding coral reefs.

The presence of back rats on islands in BIOT results from human exploration of our seas. Many islands around the world have been completely taken over by black rats that we accidentally introduced through ships years ago. Upon arrival on these seabirds-filled islands rats began to eat their eggs, chicks and even full-grown adults. This had disastrous consequences on native seabird populations on these invaded islands, 90% of tropical islands saw their bird population crash.

Thankfully, a small number of islands were spared and could act as a haven for the remaining frigate birds, boobies, terns and shearwaters. In BIOT, 18 of the 58 islands remained rat free.

Professor Nick Graham commented: “The rat-less islands are full of noisy birds, the sky is full, and the smell is strong – because of the bird’s guano deposits on the island. If you visit an island with rats, there is almost no seabirds. “

On rat-free islands, seabirds, including boobies, frigate birds, noddies, shearwaters and terns, roam for hundreds of miles to feed out in the open ocean. Upon their return to the island, they deposit rich nutrients from the fish they eat. These nutrients then spread into the surrounding waters and affected the biology of reef systems.

The results, published in Nature, are clear: the fish on reefs adjacent to the rat-less islands grew faster and bigger than that of the fish living in islands infested by rats.

Therefore, rat-filled islands have an indirect impact on the already fragile reef, since seabirds provide nutrient rich guano to the surrounding reef.

Since coral reefs are constantly affected by changes in ocean temperature and with coral bleaching frequency increasing, this research suggests that the elimination of invasive species such as rodents could be an important way to increase the resilience of these critical habitats while also restoring native populations of seabirds.

To date 500 islands have been gradually de-ratted and, according to Dr. Graham, 2-3M$ is necessary to fully de-rat BIOT.

Coral Reefs

How do you Know if a Coral Reef is Growing or Shrinking?

Original post:

How do you know if a coral reef is growing or shrinking?

Dr. Ines Lange, a marine biologist and postdoctoral research fellow at the University of Exeter, as well as a project partner in the Bertarelli program on marine science, participated in an exploration of coral reefs in the British Indian Ocean Territory.

Here is her report from a wet and windy Indian Ocean: Professor Chris Perry and I are studying the carbonate budgets of coral reefs around the islands of the Chagos Archipelago. Chris has developed the “Reef Budget” method that we use to calculate how much carbonate is produced by coral and calcifying algae, and how much is eroded by grazers such as sea urchins and fish, as well as by internal bioerosion from boring worms and microorganisms. The results provide a metric on reef “health” informing on its growth or erosion.

The reefs in Salomon and Peros Banhos atoll that we have visited so far have displayed a massive decline in coral cover due to severe bleaching in 2016, which resulted in carbonate production rates dropping to one third of 2015 values. Nonetheless, many Porites and some Acropora colonies survived the bleaching event, and there are large numbers of small recruits of different species. We found many live encrusting coral, especially in the understory of reef structure. Thanks to the abundance of herbivorous fish, the substrate is clean from macroalgae. Calcareous algae that cover the dead coral substrate continue to produce a significant amount of carbonate, which “glue” the reef structure together and provide a great substrate to recruit more coral. We therefore hope that the once glorious coral reefs will recover quickly in the coming years.