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Marine Alien Species

Author: Leticia Greyling ~ National Ports Authority of South Africa

( Article Type: Explanation )

Ships’ ballast water as a vector
Roughly 12 billion tonnes of ballast water is transferred around the world every year, which means that at any one moment, it is estimated that over 4 500 individual species are being carried around the globe in this water in ships’ holds. Invasive marine species are a major threat to the world’s oceans today, whether introduced either intentionally – for economic or agricultural purposes – or accidentally via tourism, travel and trade.

Ballast water is essential for the safe and efficient handling of the ship during voyage and while they enter port. It controls the stability and the trim of the vessel and balances the stresses on the ship’s hull. This allows for efficient steering within coastal waters and is important for efficient fuel consumption. Ballast water is essentially a surface water sample of immense volume taken in from a port, making it inevitable that significant amounts of organisms find their way into ballast tanks of ships.

The problem arises when ballast water taken up by a ship contains unwanted marine organisms. These may be bacteria and other microbes, planktonic species, small invertebrates and the spores, eggs and larvae of larger species. This is compounded by the fact that almost all marine species have planktonic stages in their life cycle, which may be small enough to pass through a ship’s ballast water-intake ports and pumps. In essence, this means that even species with large adult stages or attached to the seabed when mature, may still be transported in ballast water.

These are a real concern for the local coastal communities and subsistence collectors who are dependent on these marine resources for their daily survival, as well as at a national level.

Ballast water accounts for 41% of the marine introductions in South African waters and the impact of algal blooms have been especially strongly felt, with crayfish walkouts, mass fish mortalities and abalone shellfish fatalities being among the most significant causes of concern.

Exact costings of damage to the South African economy are still underway, but ballast water-carried Comb Jelly invasions in the Black Sea cost an average of US$500 million per year. Likewise, the European Zebra Mussel has been introduced to the Great Lakes via ballast water and invaded more than 40% of the US waterways, where it fouls water intake pipes and so forth. Damages there have resulted in costs escalating to over US$5 billion to date. There is, therefore, a serious threat not only to natural biodiversity, but also to human health, and potential losses for mariculture and associated industries.

Ballast water management
A breakthrough came at an international diplomatic conference in February 2004 when the international Convention for the Control and Management of Ships’ Ballast Water and Sediments was adopted by the International Maritime Organisation (IMO). In South Africa, no formal ballast water regulations exist, though voluntary compliance with IMO guidelines is encouraged and a management structure is being developed. South Africa has formalised a national Ballast Water Management Task Team, which includes government authorities such as the Department of Environmental Affairs and Tourism: Marine and Coastal Management Directorate and the Department of Transport, as well as other stakeholders such as the National Ports Authority of South Africa and the South African Maritime Safety Authority. Through this Task Team, a national ballast water policy is being drafted and reviewed, and ratification of the IMO Convention is being investigated.

Although the development of appropriate port and other management plans is essential for the implementation of consistent procedures, there still remain key challenges in addressing the risk of marine species being transferred via ballast water:

  • Surveys – comparative baseline data is generally not available and species identification and taxonomy expertise is scarce within South Africa (and the wider region).
  • Legislative framework – a national policy needs to be adopted and ratification of the International Convention for the Control and Management of Ships’ Ballast Water and Sediments addressed.
  • Treatment – efforts should go into research and development of treatment technologies.
  • Management – clear delineation of roles and responsibilities is essential for the implementation of international and national requirements.
  • Co-operation – regional co-operation and assistance should be provided to developing countries to help them implement ballast water management.