Saboteurs of the Sea - West Wind Hardwood

Ship’s sunk in battle, docks wrecked by aerial bombs, or vessels lost in storms – all these are visible, audible and entirely understandable forms of destruction.  But ever since man launched his first primitive wooden craft, there has been an equally destructive force at work – unseen, silent and often unsuspected.

Teredo navalis, commonly called the naval shipworm or turu is a species of saltwater clam.  Latin: teredo = woodworm or borer; navis = ship.  A marine bivalvemollusc in the family Teredinidae of the genus Teredo. Like other species in this family, this bivalve is called a shipworm, because it resembles a worm in general appearance, while at the anterior end it has a small shell with two valves that is adept at boring through the wood.  These shipworms, also called by mariners as the ‘termites of the sea, were native to the Caribbean Sea but have managed to ‘eat’ their way around the world. Though the Teredo serves an ecological value in degrading timber that falls to the ocean, it has also caused considerable damage to wooden boats even since man first ventured out to sea.  

“Some primal shipworm found some wood,
And tasted it and found it good.
That is why your cousin May
Fell with the dock in the sea today!”

Good Intentions by Ogden Nash, Little, Brown and Company ©1942

These boring clams weakened unprotected wooden hulls of ships to the point that they break apart in the open sea without any warning.  The Greeks and the Phoenicians certainly knew about them since 3,000 BC, lathering the hulls of their ships with wax and tar to keep them away.  The Romans used combinations of lead, tar and pitch to cover their boats.

These boring clams weakened unprotected wooden hulls of ships to the point that they break apart in the open sea without any warning.  The Greeks and the Phoenicians certainly knew about them since 3,000 BC, lathering the hulls of their ships with wax and tar to keep them away.  The Romans used combinations of lead, tar and pitch to cover their boats. 

Unbeknownst to Columbus, his first voyage to the Caribbean Sea in 1492 exposed his ships to the world’s most Teredo-infested waters, likely due to the higher salinity of the Caribbean.  The ships that arrived later brought back Teredo to Europe, where they can be found even as far away as the North Sea, having adapted to the cold environments.  The fourth voyage of Columbus to the Americas in 1502 came to a disastrous end when all his ships sank due to damage resulting from Teredo.  His ships were,

“… rotten, worm-eaten … more riddled with holes than a honeycomb… With three pumps, pots and kettles, and with all hands working, they could not keep down the water which came into the ship, and there was no other remedy for the havoc which the worm had wrought… my ship was sinking under me…”

The original document of Columbus of this document was written in 1502.
This text of the present edition was prepared from and proofed against The Voyages of Christopher Columbus, Being the Journals of his First and Third, and the Letters Concerning his First and Last Voyages, to Which is Added the Account of his Second Voyage Written by Andres Bernaldez. Now newly translated and edited, with an Introduction and Notes, by Cecil Jane. London: The Argonaut Press, 1930. For the present edition, all preliminaries and notes have been omitted except those for which the author is responsible. All editorial notes have been omitted except those that indicate significant textual variations. Line and paragraph numbers contained in the source text have been retained. In cases where the source text displays no numbers, numbers are automatically generated. In the header, personal names have been regularized according to the Library of Congress authority files as “Last Name, First Name” for the REG attribute and “First Name Last Name” for the element value. Names have not been regularized in the body of the text.

Columbus was forced by these small clams to land on Jamaica. He and his crews were marooned for a year before being rescued.

In 1579, Sir Francis Drake spent over a month on the Californian coast repairing the Golden Hind, which had been damaged by shipworms. And there are claims that shipworm appetites might have been a factor in the English defeat of the Spanish Armada in 1588. The Spanish had remained docked in marine waters off Portugal for several months before engaging the English, providing plenty of time for infiltration of ship’s timbers by the Teredo that would have weakened and slowed the vessels.

The problem of Teredo is mentioned in William Smith’s book, “Bird of Prey” in the Courtney Series.

These same worms caused the collapse of the wooden supports used for the dikes (dike revetments) in The Netherlands in 1731 causing flooding, 250 years after the first voyage of Columbus.  Only the timely replacement of the outer surfaces of the dike with stones prevented more catastrophes.  

The behaviour of the shipworm inspired Marc Brunel, a French engineer, to devise a method, which he patented to tunnel under the Thames River in England, the first of its kind ever built under a river bed.  By 1820, Port London had become the center of the world’s largest traffic jam.  Consignments intended for the southern (and most heavily populated) parts of Britain had to be heaved onto creaking ox carts and hauled through the docklands and across London Bridge, which had been built in the 12th century and was as cramped and impractical as its early date implies. This was a situation intolerable to a city with London’s pride.  Another bridge was out of the question—it would deny sailing ships access to the Pool of London—and ambitious men turned their thoughts to driving a tunnel beneath the Thames instead. 

Brunel’s technique called the “tunnelling shield” made use of his observations while working on a shipyard on how the valves with fine ridges were used by the Teredo to drill through the wood while protecting itself from being crushed.  The Teredo also secretes a calcium-rich framework that coated the inside surface of the tube, keeping it stable and crush-proof. 

In the eighteenth century, the English Royal Navy resorted to coppering the bottoms of its ships in an attempt to prevent the damage caused by shipworm.  But even the copper cladding was not certain protection from the “worm”, as this famous poem by Henry David Thoreau (1817-1862) attests:

 … The vessel, though her masts be firm,
Beneath her copper bears a worm …
Far from New England’s blustering shore,
New England’s worm her hulk shall bore,
And sink her in the Indian seas …

-(Excerpted from “Though all the Fates” 1849)

Experiments by the Dutch in the 19th century proved the inefficacy of linseed oil, metallic paint, powdered glass, carbonization (burning the outer layers of the wood), and any of the usual biocides such as chromate copper arsenate.  They also attempted covering wooden pylons with precisely arranged iron nails, but this too had no lasting effect. In 1878 it was discovered that creosote was an effective deterrent, though to work best it had to be applied to soft, resinous woods like pine; in order to work on harder woods such as oak, special care had to be taken to ensure the wood was completely permeated by the creosote. 

The Teredo’s arrival to the San Francisco Bay around 1920 heralded destruction.  Wharves, piers, jetties and piling started collapsing in San Francisco Bay between 1919 and 1921, resulting in almost 20 billion dollars worth of damage in today’s money.  

The mouth of the Hudson River of New Jersey and New York was once considered a dead waterway, devoid of fish life because of the overwhelming industrial pollution since the 1930’s.  Ship captains used to sail their boats through NY harbor just to kill off shipworms and barnacles.  That’s how polluted it was.  In 1972, the US Federal Clean Water Act limited discharge into the rivers and proactively revitalized the waterways.  By the 1990’s fish had returned.  And so did the Teredo, with a vengeance.  During this period also saw the voluntary ban by the lumber industry on the use of creosote and CCA (chromated copper arsenate) to prevent further leaching of the toxic chromium and arsenic to the environment.  These wood preservatives prevented fungi from rotting the wood away and also quite good at killing off the shipworms as well.  The environmentally sound actions had unintended consequences—piers and piling that no longer used preservatives started collapsing, hollowed through by Teredo worms.

Purpleheart timbers are considered a species of choice in a marine environment. The photo below is a piece of purpleheart sent to us by a customer from a Boat Yard in Prince Rupert.  It was proof of the voracious appetite and strength of these shipworms.

It has been estimated that ship timbers needed replacement every eight years on average, largely due to damage from Teredo wood-boring. At this rate, it is clear that this marine clam has had a tremendous impact on terrestrial ecology, too – huge tracts of coastal forests around the world have been cut down to replace damaged hulls of the ships of all the colonial powers as they travelled the seas. And all that travel introduced these clams all over the world as affected ships brought the animals with them.  In the Baltic Sea, pine trees can become riddled with tunnels within 16 weeks of being in the water and oak within 32 weeks. We’ve all seen driftwood on our local beaches.

Economic Value?  So far, we have seen no large commercial value for Teredo lumber.  We have sold Western Red Cedar Toredo boards to New York for art frames.  We have sold these same boards to The Sandbar Restaurant on Granville Island (Vancouver, BC).  They used these planks for panelling throughout the restaurant.

We have Western Red Cedar Toredo paneling in our office.  It’s busy but if used in small quantities, it’s quite pleasant.

In Thailand, some natives plant pieces of soft wood at the mouths of streams.  Later they raise the wood and eat the shipworms inside it.  Australian aborigines have high regard for their food value.

Teredo make a special Philippine delicacy called tamilok, appreciated by natives of Palawan Island and Aklan Province of Panay Island,  where extensive mangrove forests serve as home for the clams.   It is prepared raw as a ceviche or kinilaw in the local language, with vinegar, chili peppers and onions.  It is a delicacy that is certainly not for the timid.  A first-time taster described the tamilok as “seawater that is made into jelly with a dash of oyster in it”.  However, Jan and I have prepared uni – raw sea urchin roe and sea cucumber.  So why not?!

Traditionally, locals reserve tamilok for celebrations and special events, but have begun to regularly harvest the clams to meet the demands of tourism. Unfortunately, the surge of tamilok interest poses a threat to mangrove ecosystems. So try and limit yourself to one. Despite growing inside them, tamilok don’t grow on trees.

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