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A:The transportation of undesirable
marine species on ships and through water ways.
That's the best simple description I can
give. To give some historical back ground; before humans sailed
the seas the type of organisms that are the focus of this discussion,
had only floating debris and ocean currents for suitable transport.
Some reports state that these buggers didn't even like coastal
environs. Sailing ships made of timber were a perfect media for
the organisms and they would have speeded up the natural transport
of them. Events like the California gold rush, apparently brought
many new varieties into San Francisco bay as ships converged
there from all over the world. Though I am not aware of any research
to verify, I would imagine the same thing occurred on the Queensland
coast with the spectacular Palmer river gold rush. Cairns and
Cooktown, for example, were established as ports to service those
fields that were worked by people from all over but especially
Chinese.
A handicap the lumbering old tubs had for
transporting 'bugs' was their slow speed and circuitous routes.
Whatever they acquired in the way of vermin, the crop had to
be able to withstand a variety of seawater temperatures and salinity.
For example on a voyage from England to Australia with another
load of convicts, the ships would begin in the gulf stream waters
of the north Atlantic, cross the tropics off Africa or South
America, then into the Southern Ocean before raising Australia
some three months later. Much of the sea life clinging or boring
into the timber would not survive the changes in environment
but some would. Of the specie that did survive the voyage, much
of it would fail to win the battle of competition with the already
well entrenched locals but some might.
Where voyages began and terminated in a
similar environment, the little buggers would have the best chance
for survival but then in that situation, they were probably already
there by effort of nature. Then came the great canals!
The opening of the Suez Canal connected
the Indian Ocean and the Mediterranean Sea. Instead of taking
months to make the voyage through several climates and environments,
a ship could transit the canal in a couple days without the spectacular
climate changes of the alternative route. The Panama Canal was
even better. Though there would be changes in salinity in the
passage, the interval was quick and many would survive. Before
the Panama Canal the only connection between the two great Oceans
was the hostile and frigid waters off Antarctica and the cape.
Finally, post WWII shipping with their
effective anti-fouling paints, (the active ingredients were copper
and mercury which were improvements over the old lime and arsenic
era) and high speeds were thought to be much less of a risk.
Sadly, (for us, not the bugs) not necessarily so. Some of the
little macroalgae, tubeworms, molluscs, bryozoans and barnacles
became resistant to the poisons and created a substrate for the
others. Mercury was found to stay in the oceanic food chain and
caused nasty little problems in humans like deformity and death
and the speed issue that some were so sure was a good thing back
fired when they found out it had a plus side for the Hobos of
the Hulls. Besides the quick transit of otherwise unfriendly
environment allowing survival of the bugs, it was found that
the arrival of the fouled ship in some harbours triggered a reproduction
cycle as a result of the water temperature change that saw the
'ejaculation' of clouds of spores.
Tributyltin or tbt or just Tin, whatever
you call it, was good while it lasted. For over twenty years
it was the anti-foul to use. Shipping company's loved it as well
as yachties and why not, it worked. Problem was though, it was
as tough on desirable creatures as it was on the undesirable
ones. Though yachties were forbidden from using it many years
ago, Australian government vessels and international shipping
continued to use it right up till 2004 when it was internationally
banned . |
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What can you do? The shipping must
go on. Ballast water was one area that was clearly a problem
and fairly manageable. The tiny spores that some of the organisms
use for reproduction, may survive for long periods in the ballast
water. One notable stuff up that was pretty reliably attributed
to a Russian vessel in North America, allowed the establishment
of the 'Zebra Mussel' in the Great Lakes that has been a real
pain in the ballast for the USA. The ship had loaded water in
the Caspian Sea, where the critters are from, and hadn't pumped
the water outside the Seaway as it should have. There is now
an international accord regarding ballast water in shipping.
Besides ballast water, ships have a variety
of places to hide the hobo's. Ships have DDSS (dry dock support
strips) that can not be entirely painted. These large devises
support and balance the ship when dry. By % of area ships probably
leave as much un-painted as any yacht. They also have their sea
chest's which can contain huge growths. This is the water inlet
chamber for engine cooling, ballast etc. The IMO (International
Maritime organisation) is the treaty body that regulates environmental
requirements for shipping. Their policy requires ships to be
serviced only within five years which was probably acceptable
in the days of TBT. Even if a ship is used in ideal circumstances
it will have a large quantity of fouling by the time it reaches
its scheduled service time. A fouling of 1.5 KG per square metre
is common according to research. Add those numbers up for a 300
metre long vessel with a typical 4 metre draft and even without
considering nooks, crannies, sea chests, bilge curve etc, that
comes to about 3,600 KG of organisms collected from all over
the globe perhaps. Tons of the stuff! An LPG tanker studied/surveyed
in New Zealand that had been in port for just three months had
a growth that was estimated at 11KG of fouling per square metre!
The length of the vessel wasn't specified
but say a likely length of at least two hundred metres by 4 draft.
Again using the most simple math, ignoring the curves and hiding
places still comes to 17,600KG!! On that vessel, “25 species
were identified. Almost all the species present were exotic,
most were alive and many were reproductively viable.”
Of course being in port contributed to
the fouling on that vessel but the fact the fouling was exotic
was proof that the vessel was well fouled while in normal service,
before arrival.
Where does that leave us?? As far as I've
been able to determine at this time, yachts, ships or tinnies,
makes no difference. Copper is the active ingredient in your
anti-fouling paint with perhaps a shot of herbicide in some.
That “grass” you see at the waterline is usually the
first to form over the slime and it is everywhere around the
world, just like the tubeworms on your prop. Most other types
of fouling on your pleasure craft will depend on your location.
If a bug was originally from somewhere else, it almost certainly
came to your happy shore by ship sometime in the last 200 years.
Though most organisms that can migrate, have by now, doesn't
mean there aren't more yet.
How do you tell native from exotic?? The
answer to that question can get very fuzzy. Humans have been
crossing the oceans by ship for thousands of years. The research
gives examples of specie that were thought to have been transported
and later found to have been native. Nature has had a hand as
well with flotsam and even sea creatures like whales and turtles.
Some are easier to pick but educated speculation remains the
best answer possible for the most part. |
