174. Ballast water may be carried onboard by ships to maintain stability and improve maneuverability during
transit. Introduction of which one of the following is regarded as the major threat in release of untreated
ballast water?
(1) pathogenic microbes.
(2) terrestrial inputs of pollutants.
(3) invasive marine species.
(4) algal blooms.

Invasive Marine Species in Ballast Water: A Growing Environmental Threat

Ballast water is essential for stabilizing ships during voyages, especially when cargo is unevenly loaded or absent. However, this same process has become a global ecological concern, primarily due to the unintentional transport of invasive marine species.

What Is Ballast Water?

Ships take in ballast water from coastal regions, ports, or oceans to maintain buoyancy and stability. This water, however, contains a diverse array of marine organisms — from plankton and larvae to microbes and small invertebrates.

When the ship reaches a new port and releases the ballast water, these non-native species are introduced into unfamiliar marine ecosystems.

Why Are Invasive Species a Threat?

Invasive marine species can:

• Outcompete native species for food and habitat

• Disrupt local ecosystems and food chains

• Spread diseases or parasites

• Cause economic damage to fisheries and aquaculture

• Reduce biodiversity in the long term

A notorious example is the zebra mussel, which originated from Eastern Europe and was spread across North America through ballast water — wreaking havoc on water systems and infrastructure.

Other Options Explained

• (1) Pathogenic microbes: While potentially harmful, they are not the primary concern compared to invasive species.

• (2) Terrestrial inputs of pollutants: These are not typically transported via ballast water.

• (4) Algal blooms: Though ballast can contribute to their spread, invasive species pose a broader and more consistent risk.

Global Response and Regulations

To combat this threat, the International Maritime Organization (IMO) adopted the Ballast Water Management Convention, which requires ships to:

• Treat ballast water before discharge

• Exchange ballast water in the open ocean

• Install ballast water management systems (BWMS)

Conclusion

The release of untreated ballast water is a major vector for the spread of invasive marine species, threatening biodiversity, economy, and the health of marine environments worldwide. Addressing this issue is vital for sustainable global shipping and environmental protection.