Marine Bioinvasion


Introduction of an alien species into an environment is referred to as bioinvasion. These non-native species may cause widespread destruction by rapidly taking over an area and/or by eliminating native species. With increased globalization, biological invasion of non-native species into native biodiversity of any bioregion is a threat to cope with, and the consequences of such invasions are being realized increasingly in recent years.

Means of marine bioinvasion:

Bioinvasions can occur naturally, intentionally or unintentionally. Naturally, invasions can occur due to dispersion through propagation and can accelerate due to changes in the environmental conditions. Intentional introduction takes place mainly for economic purposes, such as for aquaculture/mariculture activities in the marine environment. An unintentional translocation of organisms in the marine environment mostly takes place through shipping.1,2,3

Shipping has been recognized as the major vector for bioinvasion in the marine environment due to the potential of organisms to get attached to the hull of the ships and the possibility of organisms to get transported through ship ballast water at different life cycle stages.1,2,3 Ballast is any material used to weigh down and/or stabilize ships. For many years, ships carried rocks and/or metal as solid ballast. Nowadays ships use sea water as ballast.

When a ship empties its cargo, it takes in water as ballast to maintain its stability and structural integrity, and when it loads cargo, the ballast water is discharged usually in the vicinity of ports just before the loading of cargo. Sea water which is loaded for ballast purposes contains a range of organisms and their offspring's.1,2,3

In recent times, worldwide shipping activities have increased manifold, mainly due to the increase of global trade. This has resulted in the translocation of organisms via ship hull and ballast water to distant ports facilitating bioinvasion, causing much economic loss and a multitude of human health hazards. It is estimated that over 4000 species of invertebrates, algae and fishes are transported through shipping every day.1,2,3

In any bioinvasion-related study, it is important to have a clear picture of the biodiversity. In order to predict the introduction of exotic species, basic information about indigenous species, their natural history, community structure and biodiversity of systems is essential. Detection of bioinvasion demands careful and sustained monitoringto achieve detailed information on biodiversity and ecosystem functioning. Though not much attention is paid to this problem in Indian waters, the incidences of introduction show an upward trend in other parts of the world, and has been implicated in economics and human health.1,2

Comparison of the pre-1960 faunal survey data for the Indian Seas with that for the post-1960 period showed that 205 non-indigenous taxa were introduced in the post-1960 period and shipping activity is considered as a possible major vector for many of these introductions.2,4

Facts & Figures

  • Shipping is the backbone of the global economy and facilitates transportation of 90% of commodities worldwide. Translocation of organisms through ship hulls and ballast water is considered an important bioinvasion vector.
  • The introduction of new species can have a direct impact on society and human health by affecting the fisheries sector.
  • . Since ballasting and de-ballasting are primarily done in the port areas during loading and unloading of cargo, the port environment serves as gateways for the introduction of alien species.

Sustainable Tips

  • Ballast water has been considered as one of the important vectors for the spread of these organisms; hence appropriate quarantine measures are needed at the receiving ports to treat ballast water

References: (i) Anil A.C., Venkat K., Sawant S.S., Dileepkumar M., Dhargalkar V.K., Ramaiah N., Harkantra S.N., Ansari Z.A. 2002. Marine bioinvasion: concern for ecology and shipping. Current Science 83 (3): 214-218 (2) Anil A.C. 2012. A perspective of marine bioinvasion. Eds: S. Sonak. TERI Press: 203-213. (3) Globallast. 2001. Stopping the ballast water stowaways. London: International Maritime Organization. 8 pp. [Global Ballast Water Management Programme, March 2001, International Maritime Organization] (4) Subba Rao, D.V. 2005. Comprehensive review of the records of the biota of the Indian seas and introduction of non-indigenous species. Aquatic Conservation: Marine and Freshwater Ecosystems 15:117-146