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Mollusks and the environment


For centuries, ships carried solid ballast in the form of stones, sands or metals. Today's vessels use water as ballast, which makes it much easier to load and unload a ship, and is more economical and efficient than solid ballast. But what is ballast?

When a ship is unloaded, ie unloaded, it becomes very light. So that there is no danger of flotation, your tanks receive ballast water to maintain stability, balance and structural integrity. When the ship is loaded and becomes heavier, water is no longer needed and is thrown overboard. A serious environmental problem arises when ballast water contains marine life.

A ship, for example, fills its holds with seawater and a Brazilian port in the Atlantic Ocean and travels to Hong Kong, China. There he receives cargo and dumps the ballast into the Pacific Ocean. In so doing, this ship probably introduces species from one ecosystem into a different one; because, with seawater, thousands of marine species enter and leave the ship, such as bacteria and other microbes, small invertebrates and eggs, cysts and larvae of various species.

  • What effects can this have on food chains and webs where these species are being introduced?
  • Will there be competition between species that occupy similar ecological niches?
  • Will natural species of that environment disappear?
  • Can introduced species from other ecosystems reproduce intensely if they do not have predators to control?

These are just some of the questions to ask regarding this question.

Ballast water movement is estimated to provide daily transportation of at least 7,000 species between different regions of the globe. The vast majority of species carried in ballast water do not survive the voyage because of the ballast filling and dumping cycle, as well as the internal conditions of the tanks, hostile to the survival of organisms.

Even for those who continue to live after the journey and are thrown into the sea, the chances of survival in new environmental conditions, including predatory actions and / or competing with native species - are greatly reduced.

However, when all factors are favorable, an introduced species, by surviving and establishing a breeding population in the host environment, can become invasive, competing with native species and multiplying in large proportions.

In addition to environmental imbalances, disease-causing bacteria can be introduced and cause contamination of filter molluscs such as oysters and mussels used in human food, causing paralysis and even death.

The list goes on with hundreds of examples of important economic and ecological impacts that affect human health around the world. It is even feared that diseases such as cholera could be carried in ballast water.

In cases of oil spills, there are several procedures to seek environmental recovery, but unlike this and other forms of marine pollution, the effect of invasive marine species is in most cases irreversible and represents one of the largest threats to the world's oceans!

Solution in sight!

In 2005, the Brazilian government signed in London the International Convention on Ship Ballast and Sediment Control and Management. The Convention, approved in February last year by the International Maritime Organization (IMO), aims to reduce the introduction of alien species through ballast water from ships. The adoption of a new ballast water convention had been under discussion for 10 years because of the major economic and environmental implications. Brazil was the second country to sign the agreement that depends on the accession of 30 countries, representing 35% of the world fleet tonnage, to enter into force.

In anticipation of the international convention, which may take up to 20 years to come into force, the Brazilian Navy is discussing the publication of a Maritime Authority Standard (Normam), stipulating that all ships destined for Brazilian ports exchange the water from ballast at least 200 miles from the coast and 200 meters deep.