ocean red alert

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Earth Matters

Ocean red alert

By SARAH SABARATNAM sarah_s

 

April 30: CAPTAIN James Cook, the British explorer and astronomer who

travelled through many oceans for his expeditions around the world, observed

that shellfish were poisonous during certain times of the year.

 

Hundreds of years later, we discover that this is a natural phenomenon and

happens when a higher than normal concentration of algae produces a toxin

that affects the central nervous system of fish, so that they are paralysed

and can " t breath. When algae reproduce in dense concentrations or " bloom " ,

they discolour the ocean waters, making them red, hence the name " red tide " .

However sometimes the discolouration is also brown, green or even yellow,

which actually makes " red tide " a misnomer. Yet the name has stuck.

 

Because algae cells are tiny and form the base of the food chain, they

sometimes produce very serious problems for humans, even death on occasions.

The cells are among the thousands of living marine phytoplankton species but

distinct as they produce toxins.

 

When these toxin-producing algae undergo a harmful algal bloom (HAB), they

are consumed in large quantities particularly by clams, mussels and oysters.

 

Because these are filter-feeding animals, often a high concentration of the

harmful algae remains in their systems.

 

When humans consume these tainted shellfish, they could become sick with

neurotoxic shellfish poisoning (NSP) or paralytic shellfish poisoning (PSP).

Symptoms include dizziness, numbness and gastrointestinal distress.

 

Fish normally just die and are washed out to shore and birds that eat them

are also affected.

 

If a HAB occurs close to a fish or shrimp farm, millions of ringgit in

losses will result.

 

According to Choo Poh Sze, head of the Fisheries Research Institute " s

Aquatic Ecology Section, Malaysia has seen almost yearly incidents of HABs

in Sabah waters but only sporadically in Peninsular Malaysia.

 

The latest case was in Kelantan where a family ate lokan, a type of

shellfish that was collected from the coast.

 

" A family of six got sick, one child died, " said Dr Gires Usup, from the

Marine Science Programme of Universiti Kebangsaan Malaysia. Both Choo and

Gires confirm that tests done by both their departments found that the

shellfish concerned were loaded with PSP toxins.

 

" Generally, " says Choo, " such incidences have been increasing all over the

world. " What causes this increase? According to Choo, no one reason that can

be pinpointed, however recent studies have shown that as pollution increases

so will the incidences of HABs.

 

" Humans are producing the nutrients that these HABs feed on, in amounts far

exceeding that required in the environment, " said Prof Donald M. Anderson,

senior scientist from the Woods Hole Oceanographic Institution " s Biology

Department based in Massachusetts, the United States. He was in Kuala Lumpur

recently to present a paper on " New Technologies for Monitoring, Predicting,

and Controlling Red Tides and Harmful Algal Blooms " at Malaysia University

of Science and Technology.

 

Red tides need nitrogen, phosphate and nitrate, which is present in

fertilisers that are released into streams and rivers and finally, the

ocean, he said.

 

" Point sources of pollution like pig farms, agriculture farms and human

waste are major sources of nutrients for red tides. " Evidence of the

relationship between the increase of HAB incidences and pollution abound.

 

For instance, Japan suffered from major water pollution problems from as

early as the 1860s with damages resulting in the loss of human life. As

rapid industrialisation took root, so did disasters such as the

methylmercury-induced Minamata disease, cadmium contamination and serious

oil spills.

 

In the 1970s these incidents occurred with increasing frequency.

 

Among them were the massive extermination of marine biota including cultured

yellow tail in the Seto Inland Sea in the 1970s due to red tides in a

magnitude and frequency that was alarming.

 

The Japanese government responded with an Interim Law for Conservation of

the Environment of the Seto Inland Sea in 1973. This law was revised in 1978

and renamed the Law Concerning Special Measures for Conservation of the

Environment of the Seto Inland Sea. Comprehensive measures were taken to

protect the sea, including limiting the total amount of pollutant loads

released into the designated water bodies.

 

Since then the frequency of red tides in Japan has steadily decreased.

 

In China, as prawn farms and the use of fertiliser increased, so did the

frequency of red tides.

 

Anderson said that aquaculture does enhance the problem.

 

" Many coastal areas that have mangroves and wetlands absorb nutrients from

pollution by denitrifying them (to remove nitrogen and its compounds from

pollutants and send them up into the atmosphere). If you rip them out and

build a fish farm there, you reduce the ecosystem " s ability to process

nitrogen. " Further, he says, fish farms are often criticised for producing

lots of nutrients.

 

" A large fish farm releases nutrients that equals the pollution loading of a

small city. " Thus fish farms, especially those in secluded areas, can

increase the problem.

 

Aquaculture sites are also constantly monitored and the fish tested, so it " s

much easier to detect if there is anything toxic in the water at any point

of time.

 

Finally, for HABs to be effective, they must have something to harm, and a

fish farm typically is easy victim. A large resource can be affected almost

overnight.

 

Anderson brought good news that there are increasingly efficient methods and

technologies being introduced to identify what is in our waters.

 

In the US, satellite remote sensing technology has been successfully used to

monitor the presence of HABs, their movement in the oceans and how they are

affected by various factors like sea surface temperatures and wind.

 

According to Gires, Malaysia does have some monitoring programmes for red

tides, but not for every toxin that could be there and could catch us off

guard.

 

But Anderson says that " the important thing is to test for the ones that

have been known to occur in the area. " By knowing what is in the water, he

says, we will be able to take mitigating measures. This includes monitoring

shellfish and fish catches where there is a HAB; keeping shellfish out of

the market when they are suspected to be tainted; and moving aquaculture

cages away from an area when a bloom has been forecasted.

 

He says prevention measures should include controlling the flow of nutrients

into the coast.

 

So far, a known method for HAB control that has worked is clay flocculation.

This procedure includes spraying certain types of clay over the surface of

the ocean where high concentrations of harmful algae have been detected.

 

The clay becomes heavy and expands as it sinks, pushing the toxic cells down

with them. In some cases the algae are killed.

 

In Korea, the use of clay on a large scale (100,000 tonnes) in 1996 reduced

up to RM100 million losses to fish farms.

 

Clay flocculation is said to be an ideal method so far, as it is low cost,

uses natural materials, and has low environmental impact.

 

The question that remains is, at the rate we are polluting our rivers and

oceans (only 11 per cent of sewage in Asia is treated), what is the

possibility of us waking up one morning and finding the whole ocean red? " In

certain areas, there is a pretty good possibility, " said Anderson. " And the

odds will continue to go up if pollution continues. "

 

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