17 September 2008

Toxic marine paint and Singapore snails

Today, WWF announced a milestone in the global ban on tributyltin (TBT) - one of the most toxic chemicals deliberately released into the sea.

Singapore intends to accede to the ban in 2009.

What has snails got to do with this?

from Tributyltin canned
WWF 17 Sep 08;
full article also on the wildsingapore news blog

What is tributyltin (TBT)?
Barnacles, algae and mussels naturally attach themselves to hard surfaces in the sea, including on the sides of ships. Such fouling growths will impede smooth passage of the ship and increase fuel consumption. Antifouling paints are thus applied to ships to prevent such growths. TBT is an organic additive often used in such marine antifouling paints.

Why is TBT bad for marine life?
TBT leaks out from the paint and into the surrounding water, affecting marine life and seeping into the food chain.

Heard of sea snails changing sex, or oysters seeing their hard shell going all soft and mushy? These are but two known adverse TBT effects on marine species. The decline of commercially harvested oysters along the Atlantic coast of France and the UK has been attributed to TBT contamination. TBT has also been found far from shipping lanes in albatrosses, whales and fish.

But we have probably only begun to see the long term effects of TBT on marine ecosystems, as the poison is stored in sediment and re-enters the food chain when the sea bottom is stirred up by passing vessels in ports and shallow areas.

What is being done about TBT poisoning?
The International Convention on the Control of Harmful Antifouling Systems for Ships was adopted on 5 Oct 01 and obliges its signatories to ensure that no vessels using TBT-containing paint go under their flag or call at their ports.

Today, 34 states have ratified the agreement. All 168 member states of the International Maritime Organization (IMO) are being urged to join.

WWF has been lobbying for the ban of TBT for more than a decade. At the end of the 1990’s, WWF, together with some leading shipping companies and paint manufacturers, initiated the 2003 Group, whose members voluntarily banned the use of TBT on their vessels and develop toxics-free alternatives.

The Convention will enter into force 12 months after 25 States representing 25% of the world's merchant shipping tonnage have ratified it.

What is Singapore's position on this?
Singapore has been a member of the IMO since 1966.

The Port Marine Notice No. 6 of 2006 dated 6 Mar 2006 informs the shipping community of MPA’s plan for Singapore to accede to the International Convention on the Control of Harmful Anti-Fouling Systems on Ships (AFS CONVENTION) in 2009.

Some extracts ...
MPA is preparing ground work with a view to accept the Convention in 2009. We understand that major paint manufacturers have stopped manufacturing harmful anti-fouling systems containing organotins compounds. It is also expected that most of the ships to which the Convention applies will voluntarily comply with the Convention by 1 Jan 08. The MPA has no intention to apply the Convention before the Convention comes into force for Singapore.

Operators of shipyards are urged to take early action to ensure that collection, handling and disposal of harmful anti-fouling systems are carried out in a safe and environmentally sound manner to protect human health and the environment in accordance with the requirements of the National Environment Agency, Singapore.

Does Singapore get a lot of ships? Yes we do. Singapore has a humungous fleet, enormous numbers of ships from all over the world stop by, and we have a mind-boggling number of shipyards on our shores.

Singapore's fleet is among the 10 largest worldwide.
from A celebration of all things nautical David Hughes, Business Times 17 Sep 08

On average, Singapore attracts some 140,000 vessel calls annually. There are about 1,000 ships in the port at any one time. Singapore remains a focal point for some 200 shipping lines with links to more than 600 ports in over 120 countries worldwide.
from the MPA website

Singapore also has 89 shipyards on our shores.
from Seven shipyard deaths in 7 weeks Teh Joo Lin, Straits Times 24 Jul 08

What scientific work is being done in Singapore to monitor TBT pollution?
The Tropical Marine Science Institute of the National University of Singapore has been involved in work to develop bioindicators of TBT.

from Preserving the Tropical Marine Environment
Tan Lay Leng, Innovation Magazine Vo. 2 No. 2 (undated)

some extracts ...
A worldwide ban on the use of TBT will come into force in a few years' time, but no one expects environmental levels to decrease anytime soon because of its universal usage and slow degradation in polluted sediment. Monitoring of environmental pollutants is expensive and time-consuming, owing to the minute quantities involved and the sophisticated instrumentation required for chemical analyses.

About 30 years ago, scientists in the US found that female marine snails, upon long-term exposure to TBT, developed male characteristics, such as a penis, a phenomenon now referred to as "imposex" or the imposition of male characters on females. More recently the discovery was made that the extent of imposex is proportional to the amount of TBT to which the snails are exposed - high environmental concentrations implied larger (pseudo)penes in females.

Scientists at TMSI now use selected indigenous marine snails living on Singapore coasts as bioindicators of TBT. They have previously verified that local marine snails show imposex (Figure 1), and researchers now direct their attention to determining whether these snails can be used as reliable and accurate indicators of organotin pollution. Ideally, by picking up a female snail and measuring the length of the pseudopenis, they can estimate the ambient level of TBT!

Thus the study of something as seemingly innocuous as marine snails can help us better understand and manage wider impacts on our marine life.

1 comment:

  1. That is a really interesting write-up! Great work!
    Very well put together!

    Now, why is MPA taking a 'backseat' instead of a more active role in protecting our marine environment?

    ReplyDelete

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