Ballast water bringing invasive species to coasts

The expansion of seaports and minor ports could pave the way for the arrival of invasive species in coastal areas. Scientists fear that ballast water carried by ships is providing a vehicle to bring in exotic species.

A recent survey by the Department of Aquatic Biology and Fisheries, University of Kerala, had recorded the presence of as many as 10 invasive species in the biodiversity-rich intertidal habitats of the Kerala coast. They include one seaweed, one species of bryozoan, one species of mollusc and seven species of ascidian.

Shipping is a factor

According to a paper presented by R. Ravinesh and A. Biju Kumar of the department at an international conference on aquatic exotics, the distribution of invasive species reported from the Kerala coast is likely to have been assisted by shipping. The paper says that the expansion of ports in Kerala has opened ways for the introduction of alien species in marine and coastal areas.

The authors point out that the colossal loads of ballast water carried by ships could transport fish, viruses, bacteria, algae, zooplankton and benthonic invertebrates to harbours at a faster pace. The survey also recorded the presence of a sea slug called Winged Thecacera ( Thecacera Pennigera ) in the southwest coast of India. Originally reported from the Atlantic coast of Europe, the presence of sea slug is currently reported from South Africa, West Africa, Pakistan, Japan, Brazil, eastern Australia and New Zealand.

Ballast water is one of the biggest transporters of non-native marine species. Studies done by experts have indicated that over 10,000 marine species are being transported across the world in ballast water carried by ocean-going vessels for stability and safety. Ballast water is discharged when the ship enters a new port, releasing alien organisms into the local waters.

Very few of the invasive species establish a beachhead in their newfound homes, but those that do have the potential to wreak havoc on the ecosystem by preying on local species or competing with them for food and habitat space. Ballast water is also considered a vehicle for toxic algae causing red tides and harmful algal blooms.

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Printable version | Jun 20, 2021 1:15:14 AM |

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