Thursday, December 26, 2019

Some Hope for Coral Reefs

Environmental & Science Education
Climate Change
Endangered Species
Earth Systems
Earth Science
Edward Hessler

There is hope for coral reefs, well some. Maybe 30% might be alive by mid-century. To put this in perspective, half of the planet's coral reefs are already gone. The causes include climate change, of course, but also fishing, dredging, pollution, and habitat change due to development.

In a feature report in the science journal Nature, Amber Dance takes us on a tour of how scientists and conservationists are testing a variety of strategies to assist schools until the climate stabilizes. This includes breeding experiments, growing and replanting, "genetically manipulating corals to tolerate climate change, adding beneficial microbes to reefs, "finding the reefs that have the best natural chances of survival and helping them to stay alive.

Dance takes us to the Mote Marine Laboratory (Florida) where a large reef restoration project is underway. It makes use of "artificial, ocean-based nurseries" where corals are raised and then planted. Recovery begins to occur in about a year and "eventually, the planted chunks will fuse into larger corals." There are differences in growth as well as techniques for fast-growing branching corals and "mound and boulder corals" which grow on the order of "a couple of millimeters per year."

Another approach is assisting reproduction of Elkhorn coral (Acropora plmata). Sperm and eggs are collected and paired up, the embryos placed in a nursery, "a floating pool in the sea that is protected from predators. A few days later, larvae settled on 3D-printed, starfish-shaped structures. When the corals reach about fingernail size, divers will wedge these substrates into the crevices of needy reefs."
This has been tried "in reefs off Mexico, Florida, the Bahamas, the Dominican Repurblic, Bonaire, Australia, Palau and Guam." The problem is cost.

Dance reports on a survey of reefs and reef health in the Great Barrier reef neighborhood. "Almost 450 reefs" were found "that had ben affected very little by recent warming events and had retained more than 10% coral cover--the minimum at which the reef can build more skeleton than it's likely to lose (but still well below the area's coral cover in decades past)."

How do reefs manage to survive heat?  Some live in naturally warm waters and are adapted to this temperature regime, others live in locations protected by cold currents, while others "are served by currents that provide a constant plankton buffet."  The challenge is to protect them.

While coral reefs have suffered in the past--"corals are part of a lineage that is more than 400 million years old. They've endured global water temperatures that have swung between 10 and 32C, and carbone dioxide levels up to quadruple those of today. But they've never before had to endure such rapid warming." (emphasis added)

However there is a hard reality and this is the temperature change.  Even if "limiting global warming to 1.5C above the 1990 levels, the target of the 2018 Paris agreement, 70-90% of reefs would be lost." This "target is looking more and more unrealistic. If the climate warms by 2C...losses of greater than 99%" are projected.

The essay includes an infographic--map and text--of reefs with a high chance of surviving warming conditions. It shows the so-called '50 Reefs' project, 'Super Reefs,' existing marine protected areas and coral reefs. The hope is that nations will create new Marine Protected Areas for these regions.

In this short video (2m09s) one restoration approach is shown. The aim is to "replenish damaged reefs using coral larvae bred in the lab."

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