Thousands of marine species and plants and algae are transported
from their native range to "new" areas. These species are called
non-native species (sometimes referred to as alien or invasive
species). Species can be introduced to non-native environments
accidentally or deliberately. Introductions and transfer of
non-native marine species to their non-native environment mainly
occurs by the transport and discharge of ballast
water , and to a lesser extent by transport of fouling organisms on hulls or through aquaculture.
Deliberate introductions occur through the import and release of
fish and bivalves for commercial purposes in new locations. Other
species living in or on these commercial species may be
accidentally introduced, at the same time unless careful
precautions are taken.
Effects of the introduction of invasive/non-native species
Once established in a new region, non-native species may
invade new areas adjacent to the occupied area by natural
dispersal, e.g. via transport in water currents in the case of many
seaweeds and phytoplankton.
Non-native species may displace native organisms by preying on
them or out-competing them for resources such as for food, space or
both. In some cases this has led to the elimination of indigenous
species from certain areas. Occasionally non-native species can
reproduce with native species and produce hybrids, which will alter
the genetic pool (a process called genetic pollution), which is an
irreversible change. When an invasive species has established
itself in the marine environment, it is likely to be impossible to
get rid of it.
With the import and introduction of commercial species into
European waters, some native species have become threatened.
International aspects
UK is bound by international agreements such as the Convention
on Biological Diversity, the United Nations Convention on the Law
of the Sea, The Convention on the Conservation of Migratory Species
of Wild Animals (Bonn 1979), The Convention on the Conservation of
European Wildlife and Natural Habitat (Bern1979) and the EC
Habitats and Species Directive. All of these aim to protect
biodiversity and endangered species and habitats, and include
provisions requiring measures to prevent the introduction of, or
control of, non-native species, especially those that threaten
native or protected species.
In response to the growing concern about the increase in
damage caused by non-native species, the International Maritime
Organisation (IMO) member countries have agreed to develop a
mandatory international Convention to regulate and control ballast
water transfers.
In Europe there is a ban on the use of Tributyl tin on hulls
of ships that are under 25 metres in length. IMO adopted a
resolution in 1999 that prohibits the application of TBT to ships
by 1. January 2003, and a complete ban by January 2008.
Ballast water is fresh or salt water that is held in the
ballast tank cargo holds of ships to provide stability during
voyage. The tanks are most commonly filled with water and emptied
off the coastline, in estuaries and in bays where freshwater and
saltwater meets.
Antifouling paints are applied to coat the bottom of
ships to prevent alga and molluscs becoming attached to the hull of
the boat. The use of TBT(Tributyl tin) is very harmful for the
marine environment and even very low concentrations have effects on
snails, such as altering their reproduction system. It accumulates
in the food chain, which results in high concentrations in marine
mammals.
Further reading/links to other websites
IUCN Guidelines for the Prevention of Biodiversity Loss caused
by Alien Species. A guide to Designing Legal and Institutional
Frameworks on Alien Invasive Species".
http://www.iucn.org/Commission for the protection of the marine environment of the
North-East Atlantic (OSPAR).
http://www.ospar.org/