Sailors of the really old times had a problem. Their watercraft were buoyant. Normally, in relation to boats, this is considered to be a good thing. Sinking is generally thought of as being somewhat of an inconvenience to the carrying out of maritime operations.
The early watercraft were marvels of their time but they could be pretty unmanageable and weren’t much good for sailing on anything other than placid rivers and lakes. Sailing such a watercraft on the open sea would have been… a touch risky.
The solution to such problems lay in the evolution of the design of boats and ships. Inventions such as the hull, the keel and so on transformed the ancient dug-outs first into boats and then ships.
One innovation was the adoption of ballast, which helps a ship to maintain its draught, list, weight distribution, stability, manoeuvreability, and trim (the difference between how low the prow is in the water compared with the stern).
On sailing vessels of centuries ago, the presence of ballast lowered the centre of gravity of the vessel, which helped give the vessel stability in respect of the pressure of the wind in its sails. Without enough ballast, a sailing vessel could capsize. The commercial wooden sailing vessels of old would have typically used solid ballast such as sandbags, stone, rocks and the like. Ballast stones would be loaded / unloaded as necessary to help stabilise a vessel as it loaded / unloaded cargo. And so, ballast of rock and stone built up into piles at docks. Higher quality rock and stone ballast might be scavenged and used in construction materials.
Although the advent of steel-hulled steam-ships did not change the need for ballast, it did change the form of ballast. Steam ships were more stable than sailing ships and new technologies – such as more precisely machined parts, valves, pumps and the like, made liquid ballast much more do-able than before, and liquid ballast became more desirable than solid ballast.
Liquid ballast is much more modifiable and flexible than solid ballast – it is much easier to alter the amount liquid ballast by pumping it in / out of the ship compared with transferring solid ballast ashore / onboard. Obviously, for ships, water is available to be taken as ballast at all times and in huge quantities.
The advent of steel-hulled steamships led to the introduction of the ballast tank and the use of water – fresh, brackish, or sea-water – as ballast. It also led the way to the introduction of invasive alien species.
Life finds a way
Although the various lakes, rivers, seas and oceans of the world are physically connected, the ecological zones – and therefore the types of life within them – are separated by geographic features (continents, other land-masses, distance), currents and, especially, temperature.
Life that has evolved in, say, cool northern water, might not be able to survive in warm tropical water. It might, however, be able to survive in cool southern water. Tiny creatures, or the tiny spawn of creatures, might also be limited to specific localities such as rivers, estuaries or even large lakes. They never had the ability to escape their local environment. Microscopic living organisms never had the ability to get from one side of the planet to the other.
They never had that ability, that is, until ships began to take water into their tanks. The invention of the ballast tank (and associated equipment) enabled microscopic aquatic organisms to hitch-hike from one side of the planet to the other. And once they got that opportunity, they took it.
It came from beneath the sea!
In 1903, the phytoplankton Odontella (Biddulphia sinensis) (a microscopic plant alage) made a surprise appearance in the North Sea. It was a surprise because it was normally found in Chinese waters. It wasn’t native to the chilly northern European waters.
But, nonetheless, it was there.
The problem, of course, was the ship’s ballast tanks and intake of ballast waters provided a way for all kinds of microscopic hitch-hikers and not just our good buddy, Biddulphia sinensis, to travel vast distances.
This is a problem.
Species prevalent in their native range often have predators and other systems that keep their numbers in check. When released from their home range, population numbers of transplanted species can spiral out of control. Invasive species become pests in large numbers because, among other things, they can alter habitat, foul marine or riverine intake pipes, out-compete local species for food, eat the local wildlife, spread disease, disrupt fishing, release toxins, can foul beaches (thereby affecting tourism) and can result in variety of other unpleasant effects.
Indestructible… insatiable
Let’s look at one particular problematic pest. In Australia, the “North Pacific Seastar” (Asterias amurensis) arrived here from the shallower seas and estuaries of, unsurprisingly, the Northern Pacific, around Japan.
Asterias amurensis is a vigorous and enthusiastic eater, liking nothing better than to scoff bivalves (that’s clams, mussels, scallops, and oysters to you and me), barnacles, worms, starfish, sea urchins, other sea stars, and a variety of other Australian natives. This particular seastar is a threat to valuable native commercial species and also to local endangered wildlife, such as the very rare Australian Spotted Handfish (which became endangered with the arrival of Asterias amurensis. And that’s not a coincidence).
In the northern Pacific, Asterias amurensis is preyed upon by other seastars, crabs, possibly snails, and it is also parasitised by a variety of species including unicellular organisms, shrimps, other crustaceans, and worms, among other things.
Here, in Australia, not so much.
According to the Australian National Introduced Marine Pest Information System, the Australian Great Spider Crab (Leptomithrax gaimardii) has been reported to prey upon the troublesome starfish in the wild. In the laboratory, Coscinasterias muricata (an Australian and New Zealand starfish) has also made a snack of our associate, Asteria amurensis.
Other controls include dumping large amounts of salts or other chemicals such as calcium oxide in the water in which they live. Extensive dredging of the area will also kill this seastar. But, as can be imagined, these solutions present their own challenges and problems. Immersing Asterias amurensis in freshwater will kill it… but this is somewhat difficult in the ocean. Diver collection and manual cutting of the seastars was costly, time-consuming and it backfired as each part was able to regenerate and grow a new organism as long as it had access to the central disc of the seastar.
In short, once established, a population of Asterias amurensis is very hard to control, let alone eradicate.
Asteria amurensis is just one of a range of ballast-water transported invasive pests in Australia. Other prolific invaders include the European Fan Worm (Sabella spallanzanii), the Asian Kelp (Undaria pinnatifida), and the European Green Crab (Carcinus maenas), all of which have a negative effect on the local environment.
In addition to the ecological problems caused by invasive alien marine species, the economic costs are enormous. Cuthbert et al (2021) estimated the global cost of aquatic invasions to be in the region of US$345 billion. Worse, costs are thought to increasing exponentially over time and Cuthbert et al reckoned it was at least US$23 billion in 2020.
This is pest control
Article 196 of the UN Convention on the Law of the Sea obligates all states to fight marine invasive species. The article reads: “States shall take all measures necessary to prevent, reduce and control pollution of the marine environment resulting from the use of technologies under their jurisdiction or control, or the intentional or accidental introduction of species, alien or new, to a particular part of the marine environment, which may cause significant and harmful changes thereto”.
The IMO’s Marine Environment Protection Committee adopted its International Guidelines for preventing the introduction of unwanted aquatic organisms and pathogens from ships’ ballast water and sediment discharges at MEPC 50 in 1991. A series of updates followed and, after 14 years, the International Convention for the Control and Management of Ships’ Ballast Water and Sediments was adopted by a diplomatic conference held at IMO HQ in London on 13 February 2004. However, because of the complexities of international diplomacy and politics, it was another 13 years before the Ballast Water Convention entered into force on 8 September 2017.
The Convention aims to prevent the spread of marine invasive species by requiring all international ships to manage their ballast waters (and sediments) to a set standard, to carry a ballast water record book and and international ballast water management certificate.
In summary the Convention (and associated regulations):
- imposes general obligations to give effect to the Convention and to prevent, minimize and eliminate the transfer of marine pests through the control and management of ballast water
- requires countries to ensure that ports and terminals to have adequate reception facilities for the reception of sediments where cleaning or repair of ballast tanks occurs
- requires countries to promote and facilitate scientific and technical research on ballast water management; and monitor the effects of ballast water management in waters under their jurisdiction
- requires ships to be surveyed and certified and enables Port State Control officers to verify that a ship has a valid certificate, to inspect the ballast water record book and to sample the ballast water and to ensure that the ship will not discharge ballast water until it can do so without presenting a threat of harm
- requires all possible effort to be made to avoid a ship being unduly detained
- requires ships to have a ballast water record book (and to use it) and a ship-specific ballast water management plan
There are a wide range of other obligations and requirements. Meanwhile, a wide range guidelines have been developed by IMO member states and several of these have been further revised. A wide range of guidelines have since been adopted as resolutions of the Marine Environment Protection Committee.
A range of ballast water technologies are commercially available and include filtration systems, chemical disinfection, ultra-violet treatment, de-oxygenation and heat, among others.
Do you want to know more?
Implementing the Ballast Water Management Convention
“Invaders from the sea” IMO-BBC Documentary
National Introduced Marine Pest Information System
International Convention for the Control and Management of Ships’ Ballast Water and Sediments
