Coral Reefs

Webinar: The Future of Coral Reefs in a Warming World

The Future of Coral Reefs in a Warming World

In the latest of the Bertarelli Foundation’s marine science seminars, Helen Czerski was joined by Dr Gareth Williams from Bangor University who described his work modelling and mapping how reefs in the Indian Ocean might look very different under the different climate change scenarios – and the adaptation ability of corals to warming seas.

Kim Hum from the Nature Conservancy explained how she has used Dr Williams’ models to help protect the coral reefs off the coast of Hawai’i. And finally, Ambassador Peter Thomson gave his thoughts on the importance of the ocean in addressing climate change – and the role of marine science in protecting the ocean.

Following the short talks, members of the public had the opportunity to ask questions about this fascinating topic to Dr Czerski, Dr Williams and Dr David Obura from CORDIO East Africa.

Speakers:

Dr. Helen Czerski
Dr. Gareth Williams – Bangor University
Kim Hum – The Nature Conservancy
Amb. Peter Thomson – UN Secretary General’s Special Envoy for the Ocean
Dr. David Obura – CORDIO East Africa

You can watch a recording of the seminar below:

Coral Reefs

The Impact of Black Rats on Coral Reefs

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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.