Ballast water is essential for effective operation of a vessel; however it also contributes to life and invasion of alien species present only in ballast water that invades marine ecology and displaces native organisms. Alien species enter ballast water through a barrier that directs water into flood-able holds or ballast tanks; small organisms/alien species enter with the water and sometimes stick to the barrier itself. The barrier, also is not properly maintained most of the time; leaving the alien species/larvae and eggs on the surface.
Another way aliens travel is on hulls and anchors as fouling organisms, less common vector than ballast. Firstly, alien species are organisms that arrive in a foreign area due to factors such as human activity; they flourish and reproduce due to either absence of predators and parasites. Such species are not only capable of causing environmental damage but also damage to economy and human health; each to a different degree where some species of aliens from ballast water can even contribute to extinction of species they displace.
Economic damage by those species is also serious as it creates direct economic loss in the form of rising management/control cost as the species drastically alter ecosystems in commercial and recreational spheres of maritime as water properties are modified, run-off dynamics and fire frequencies are altered; all those ecological changes may also affect future marine operations.
Alien species get introduced in different ways with ballast water discharge being the main source; along with aqua-culture escapes and even intentional or accidental introductions into the marine ecology. Globalisation is one of the main factors which gives birth to foreign species as it is discovered to increase frequency by orders of magnitude which non-native organisms get introduced to local ecosystems; ballast water and boat hulls being the most common means of transport. Ballast is any material whose weight is used to stabilize/balance an object which leads ballast water to be used to stabilize a vessel when its cargo hold is empty; discharging when cargo is loaded. Ballast water is usually picked up at port, a place of shallow water and a habitat of some living organisms; larvae and eggs of organisms are common.
According to IMO, the most dangerous alien species are zebra mussels and the Chinese mitten crab where the former travels on hull of ships; damaging ships and port structures along with clogging of water pipes. Chinese mitten crab interferes with commercial fishing and causes soil erosion by digging and competes with local population; along with affecting humans by being a host for a parasitic infection which causes lung flukes.
So far, we have established that alien species are harmful to all sides of maritime; from commercial to ecological spheres warranting counter measures which would control this threat. Mussels and crabs are the most common of the alien species found in our ports with their numbers rising due to one factor; absence of natural predators.
However, in Germany and the UK mitten crabs were controlled by means of using traps; placed on the shore at times of migration of the crabs. Traps are long nets held by a hoop . Also, mitten crabs are a delicacy in the far east which gives opportunity for capitalising on the alien invasion by sending the crabs off to restaurants.
Mussels, however create a greater challenge as they have few natural predators and an intense spawning cycle which creates large numbers which are impossible to control without total destruction of an entire ecology. Some attempts to control population were mimicking of male mussel hormones to trigger females to release eggs and disrupt the reproductive cycle in long term. They attach to hard surfaces which can be ship hulls, walls and even pipes.
However, natural predators have little guarantee of controlling the alien population as introduced predators are less likely to consume the alien species altogether. The only potential predators that have a chance to consume the mussels are other organisms that historically consume shellfish.
While not the biggest issue in maritime it does cause major problems that affect the industry in serious ways; each with their own results. Zebra mussels consume water plankton and other micro-organisms which make the water clearer; making sunlight penetrate water and help in growth of seaweed which hinder movement of vessels. Mitten crabs affect the industry due to its migratory patterns, burrowing and feeding patterns; where the former causes sediment erosion and collapses leeves and dikes; also affecting shipping and even fishing.
So far, we have seen that the fast pace of globalisation and demand of maritime transport facilitates travel of alien species; however since a living organism is persistent by nature and hence evolves to adapt to changes; leading us to the factor of mutation, making control harder.
What sparks mutation in maritime aliens? Factors that associate with transport mechanisms; most commonly ballast water and occasionally anchors and hulls. Anti-fouling/toxic paints used on both, while prevent aliens from attaching do have a chance to still be chosen as some aliens become immune to the toxins and remain attached.
Ballast water, the most common vector seen more attention with 8 innovations in its treatment;
- Ballast water exchange which takes place in open ocean environment where fresh ballast is pumped in and old ballast is removed; making it harder for aliens to breed but still providing scope for them to live on. Serious flaws include constraints of sea conditions and situations when ballast exchange is illegal.
- Filtration which separates organisms by size but leaving out the smaller ones which have a chance to invade other ecosystems, warranting another treatment.
- Chemical biocides are used in low-volume vessels where there is less ballast; however the main issue is with cost of the chemicals and toxic residue which would be hazardous for the crew and environment.
- Ultraviolet light combined with physical separation destroys micro-organisms; high priority for recent research.
- Heat treatment of ballast water comes from waste heat energy from ship engines and applied in transit; however the main flaw is that it will increase growth of heat-loving algae and system corrosion.
- Ultrasound produces extreme pressure and temperature changes that destroy micro-organisms; however issues arise with large scale, consistent applications which involve energy requirements, costs and equipment durability.
- Ozone treatment is used in small-scale water treatment; however in shipping it reacts with bromides in seawater which increases corrosion and ineffective against some micro-organisms.
- De-oxygenation using Nitrogen gas which reduces corrosion/oxidation from sea water and removes oxygen by binding to the molecule; creating unfavourable conditions for bacteria to live and reproduce.
So far we saw how aliens can be controlled and what problems they cause if the control is absent. Aliens come in different forms and this list of species ranges from micro-organisms to crustaceans and shellfish; along with the different effects they have on the marine ecology which ranges from ecology to economy. Aliens grow exponentially in terms of migration, reproduction and evolution which can have catastrophic results if no attention is paid to this. To add to the problem, aliens lack natural predators which warrants more attention from us, maritime professionals to pay special attention to our ports and vessels.
While there exist 8 methods mentioned above they have flaws that are complicated to address; it is up to us to divert the approach to avoid of fix flaws.