Archive for August, 2014

Lost Sea Stars

Saturday, August 9th, 2014

Sea stars – we used to call them starfish – are truly alien beings, at least to us.

We and all other vertebrates, arthropods, worms, most mollusks and sundry others, are all bilaterally symmetrical, with a head and a brain and a bunch of sense organs at the front end. But, except when they are minute planktonic larvae, this isn’t true for sea stars and the rest of the echinoderms.

Early bipinnaria larvae of a sea star are ciliated, drift with the plankton, and are extremely small (bio.rutgers.edu)

Early bipinnaria larvae of a sea star are ciliated, drift with the plankton, and are extremely small (bio.rutgers.edu)

They are radially symmetrical, meaning they are more or less the same on every radius from their midpoint. They don’t have a head at one end and a tail at the other. They haven’t got either. They have a mouth in the middle on their ventral side, which is the side they attach to things with.

On that same side of each radial arm they have hundreds of little extendable and sticky tube feet, supported by a hydraulic system that also keeps their bodies relatively firm but quickly leaks out if they are removed from water. A sea star feeds mostly on bivalve mollusks which it opens by pulling on the two shells with its tube feet until the exhausted bivalve can no longer stay shut, and then it pushes its stomach out through its mouth and digests the bivalve in its shell.

The northern sea star, Asterias vulgaris, feeding on a small mussel bed on the coast of Maine (visualphotos.com)

The northern sea star, Asterias vulgaris, feeding on a small mussel bed on the coast of Maine (visualphotos.com)

It has a ring of nervous tissue around its mouth, not a central brain at all. It has simple vision using a light sensitive eye spot at the end of each radial arm. If a healthy sea star loses a few arms to a predator, it just grows new ones, tube feet, eye spots and all.

Could anything be much more alien to us as bilateral vertebrates? If we ever find complex life on another planet, it could be just as alien, quite a challenge to interspecies communication.

Sea stars have yet another very dramatic feature. If a sea star is unhealthy, gets infected with a pathogen of some sort, it turns to mush, and its various legs walk off in different directions, tearing it apart. Just now we’re seeing a lot of this.

Ochre sea stars, Pisaster ochraceus, are often exposed at low tide on rocky parts of the Pacific coast (biology.fullerton.edu)

Ochre sea stars, Pisaster ochraceus, are often exposed at low tide on rocky parts of the Pacific coast (biology.fullerton.edu)

A disease, or a bunch of diseases, has hit most sea star species on the Pacific coast of North America from Southern California to British Columbia, and something similar has hit some of the sea stars on the Atlantic Coast as well – in Maine, New Jersey and Florida.

Disease has hit sea stars before, just as it has other echinoderms such as sea urchins, and their populations have recovered after a while. But nothing like what has happened on the Pacific Coast has ever been seen before. There are a lot of sea star species there. The mortality of five species is huge, resulting in local extinctions. Some mortality has been documented in seven more. And seven further species are probably infected, but we lack documentation.

Sunflower seastars, Pycnopodia helianthoides, have also beed devasted by disease (en.wikipedia.org)

Sunflower seastars, Pycnopodia helianthoides, have also beed devasted by disease (en.wikipedia.org)

Dead sea stars on the Pacific coast are hard to miss, and the press has covered this event well. A particularly useful web site keeps everyone updated and allows them to add their observation of the growing mass of mush. It’s worth visiting.

The disease has a name: Sea Star Wasting Disease. But that doesn’t mean anything. We have no idea what is killing the sea stars. It could be a virus, or it could be bacteria, or a fungus, or a ciliated parasite, or pollution, or all of these, or none of these.

We simply haven’t got a clue.

A few labs are looking, but the search is slow at best. In any case, experience tells us that if pathogens are eventually identified, it will still be uncertain, and far too late.

Have we somehow caused this? We will probably never know.

Meanwhile, we can only hope that the sea stars recover, returning to their keystone status in their communities, and reminding us again how radically different a living being can be.

The Great Barrier Reef : We Barely Knew You

Wednesday, August 6th, 2014

We are going to lose our coral reefs within the next century – including the greatest of them all, the Great Barrier Reef. Warming ocean temperatures, coral bleaching, and ocean acidification will kill them. This is without the overfishing, habitat destruction and pollution that already seriously stress them. Some very tolerant and adaptable coral species will probably persist, but the reefs will crumble.

The Great Barrier Reef extends for 1430 miles close to the coast of northeast Australia, with 3000 separate reefs or cays, and hundreds of islands (cairnsdiveadventures.com.au)

The Great Barrier Reef extends for 1430 miles close to the coast of northeast Australia, with 3000 separate reefs or cays, and hundreds of islands (cairnsdiveadventures.com.au)

Coral reef biologists continue to have depressing annual meetings. Individuals, scientists, NGOs and other organizations all continue to search for ways to protect reefs and give them more time to adapt to what lies ahead. But what lies ahead is bleak indeed.

What to do? Just accept it and watch it happen? Find some way to prevent it? Though much has been written about this, Ian McCalman’s new book The Reef is an intriguing contribution.

Historian Iain McCalman book The Reef takes us from Captain Cook's imperial invasion to the impact of current climate change,

Historian Iain McCalman book The Reef takes us from Captain Cook’s imperial invasion to the impact of current climate change,

It is, to start with, a very fine book. It tells the history of our emerging understanding of the Great Barrier Reef through the journals and accounts of 20 people, in 20 chapters, starting with Captain Cook’s trip up the GBR Inner Passage in 1770, one he was lucky to survive with his repaired ship still floating.

Captain Cook on his first trip mapped the coasts of New Zealand and Eastern Australia (gbrexperience.com)

Captain Cook on his first trip mapped the coasts of New Zealand and Eastern Australia (gbrexperience.com)

Then some of the naturalists on board subsequent navigating trips by other ships used the opportunity to get to know the Aborigines and the geology and some of the biology of the reef. The naturalists mainly counted species, all well known long before that by the coastal Aborigines.

Some castaways from ships wrecked on various parts of the reef at the north end near Torres Straight were saved and adopted by Aborigines, and lived to tell their remarkable stories about the people who were radically different from their popular reputation as savage, violent and ignorant cannibals.

And then in the early 1900s came the trained naturalists and scientists who began more serious study of the reef. Maurice Young’s year long expedition in 1929, leading a team of 14 scientists (amazingly for its time, 6 were women) revealed a lot about corals and their commensal and possibly symbiotic algae (known as zooxanthellae).

The colors of coral come from their symbiotic zooxanthellae that are expelled when ocean surface temperatures rise a couple of degrees, bleaching the corals (lovethesepics.com)

The colors of coral come from their symbiotic zooxanthellae that are expelled when ocean surface temperatures rise a couple of degrees, bleaching the corals (lovethesepics.com)

Yonge and the team wrote extensively about the year, drawing attention to the great uniqueness of the GBR – and unintentionally attracted hordes of tourists with all their collateral damage. So close to the mainland, the unprotected reef became stressed by resorts, pollution, uncontrolled fishing, destructive dynamiting, and growing interest by oil and gas companies.

All of this provoked the increasing concern of the conservationists and ecologists emerging over the past half century. In 1979, after great conflict among the players, the GBR Marine Park was finally created. In 1981 UNESCO designated it a World Heritage Site.

McCalman concludes the personal narratives with an account of the naturalist and coral expert, Charlie Veron, who early on recognized the growing threats to coral reefs from climate change. He published his own fine book in 2009 with the sobering title A Reef in Time: the GBR from Beginning to End.

Charlie Veron's book tells the history of the GBR and its imminent end (amazon.com)

Charlie Veron’s book tells the history of the GBR and its imminent end (amazon.com)

At the very end of his book, McCalman tries not to leave us in fatalistic despair about the reef by sharing the anecdotes of some very resilient humans, determined to not give up.

But that is not enough.

The only real hope for any kind of coral reef survival is rapid reduction of CO2 emissions. We need to dispel the myths that prevent the US, Canada and other nations from taking action. And we need to nourish plausible new ideas, like the cap-and-dividend proposal of US Congressman Chris Van Hollen which even libertarians seem to like.

But all of this has happened far too quickly. Just under three centuries will have passed from our ‘discovery’ of the GBR to its probable destruction at our hands.

We thought we would have more time together.