Monthly Archives: November 2017

Bleaching isn’t always death knell for corals

Published November 11, 2017 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2017 Susan Scott

Many scientists believe that the Earth is headed for a sixth wave of mass extinctions, with humans rushing the rate. Corals will be among those affected, but one small sign of encouragement is that some corals are adapting to changing conditions. Susan Scott snorkels off Kelso Reef, Australia. Courtesy Craig Thomas

Since I returned from Australia last week, people have been asking what I think about coral reef bleaching. Do I believe humans are causing it, and, if so, can we fix it?

The questions refer to reports of corals turning white in areas of Australia’s Great Barrier Reef, and other reports about Hawaii’s reefs. Between 2014 and 2015, scientists found bleaching in 56 percent of corals off the Big Island, 44 percent off West Maui and 32 percent around Oahu.

So-called bleaching occurs when overly warm ocean water causes corals to ditch their algae. The corals’ clear bodies then expose the white calcium carbonate cups that support them.

Researchers theorize that this occurs because overheating causes the plants to make more oxygen, and too much of the gas creates free radicals, a single O instead of the usual O2. Lone oxygen atoms are toxic to animal cells.

The good news is that bleached coral isn’t necessarily dead coral. A coral can live for a while without its plants because its tentacles sting and eat passing animal plankton. When the water later cools, such as after El Nino years, live bleached corals catch algae drifting past in the water. When the plants multiply, they put the color back in corals’ cheeks.

Because bleached corals eventually need carbs, however, if the water stays warm, the corals can’t replenish their crops and die.

This isn’t the first time on Earth that corals have been in trouble. The first reefs formed 490 million years ago, and since then five mass extinctions caused by asteroids, climate change, volcanoes and sometimes more subtle changes killed all reef-building corals. The extinctions took 1 million to 2 million years each, and hundreds of millions of years for new species to evolve.

Most scientists believe we’re on the verge of a sixth extinction. The difference this time is that we humans are rushing the rate. What would normally take 140,000 years for a species to disappear now takes 100.

Homo sapiens is one of those species. In their bright white way, reef-building corals are our putting us on red alert. We are paving the road to our own extinction.

I doubt we humans will mend our ways in time. Our animal instincts to reproduce, fight, and segregate families and tribes from one another make uniting for a common cause tough.

But because species evolve to changing conditions, there’s hope. Some corals are adapting to higher water temperatures and doing just fine. Perhaps, as human and wildlife suffering escalates worldwide, our species will evolve to become less selfish.

In the meantime, there’s tremendous beauty left on the planet, and we should get out there and enjoy it. And who knows? By each of us volunteering to the charity of our choice, we may be accelerating our species’ evolution to altruism.

Spiral float is unique to 1 species of cuttlefish

Published November 4, 2017 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2017 Susan Scott

Each cuttlefish species has a distinct shape, size and ridge pattern in their buoyancy bone. Cuttlefish bones from Horseshoe Bay, Magnetic Island, Queensland, Australia, are displayed. ©2017 Susan Scott

I’m home from Australia after several outstanding voyages to the outer reefs of the Great Barrier Reef Marine Park. As is often the case, though, a highlight of the trip was a beach walk where I found perfectly intact shells of two kinds of cuttlefish: the common cuttlefish (Sepia) and the ram’s horn cuttlefish (Spirula).

These weren’t rare finds because the creatures’ skeletons are common on beaches here. In collecting some of the shells, though, and looking them up in a new doorstop book I bought for the boat, I was in for a surprise. When I studied invertebrate zoology in the 1980s, I misread a textbook caption, and since then have been merrily spouting half-truths about cuttlefish.

Cuttlefish belong to a group of creatures known as cephalopods, a class of mollusk (snails, clams, etc.) that includes nautilus, squids and octopuses. About 120 species of cuttlefish live throughout the world, but you won’t find their skeletons in Hawaii or on beaches in the Americas. Cuttlefish existed before Earth’s land masses split into continents, and that process isolated cuttlefish from some ocean areas.

Cuttlefish look like roly-poly squid, both having two big eyes and 10 tentacles around the mouth that reach out and grab anything they can catch, including other cuttlefish. In turn, just about every marine predator in the world, from fish to dolphins to seabirds, eats cuttlefish.

Most people know cuttlefish from the white, oval shells called cuttlebones that we hang in our pet bird cages as calcium supplements. Pet supply companies don’t have to search hard for the product. The bones float after the cuttlefish dies, and the white rafts of every size, from 1 to 20 inches long, litter Australia’s water surfaces and beaches.

In life, the cuttlefish’s porous calcium-type bone lies under its skin along its back like a flat backbone. By adding or removing air and water in the bones’ spaces, the animal controls its buoyancy.

The tiny cuttlefish species called the ram’s horn, however, lacks a flat cuttlebone along its back. Instead, near its rear end lies an internal spiraled shell, this species’ buoyancy controller. After the ram’s horn cuttlefish dies, its spiral also floats and drifts ashore.

My decades-old error was thinking (and telling anyone who would listen) that the spiral floats were inside all cuttlefish. In fact, each cuttlefish species has its own distinct shape, size, texture and ridge pattern in its buoyancy bone. My aha moment was in learning that the 3/4-inch-tall spirals come from a single deep-sea species, and that it has the charming common name of ram’s horn cuttlefish.

This is why, even after squishing my face and blistering my heels with weeks of superb snorkeling, beach walks remain high on my list of favorite activities.

As does buying heavy, expensive marine animal guides.