Scientists have developed an early warning system for potentially poisonous shellfish - one which operates long before the fish arrives on the dinner table.
Shellfish are filter feeders, vacuuming up food and other materials from their surroundings. Along with their food, they can absorb toxins released by harmful algae when these organisms are present.
The toxins can accumulate inside the shellfish, remaining undetected until they are eaten by humans, causing diarrhetic shellfish poisoning [DSP], a non-lethal syndrome.
Some of the algal toxins are lethal. Animals have been known to suffer instantaneous death after consuming one type of toxin produced by harmful algae - cyanobacteria - in freshwater sources.
Ecotoxicology is the science which studies toxins occurring in the environment. Researchers in Cork Institute of Technology (CIT) are developing sensitive methods of detecting these toxins in marine and fresh waters, as well as identifying and isolating previously unknown toxins.
It is not an easy task. These toxins can occur in extremely low levels - so they do not show up in most tests. The procedure for discovering whether a toxin is present is "similar to testing of athletes for traces of an illegal drug", stated Dr Kevin James, director of CIT's Ecotoxicology Research Unit.
Until relatively recently, the existence of these toxins was unknown, as the symptoms they produced in humans who ate the shellfish were similar to existing conditions such as gastroenteritis. This often resulted in mis-diagnosis, said Dr James, who leads the CIT research.
These detection techniques have a useful preventative value because the shellfish can be tested before they are brought ashore. Previously, tests were performed on shellfish after they were harvested and if they were contaminated, the entire stock was destroyed. With preventative testing, a positive result means the crop would not be brought in, helping to reduce losses for the producer.
There is a wide range of algal forms which are potentially harmful, include cyanobacteria in freshwater sources, and marine phytoplankton in the sea.
The research team has, over the past decade, succeeded in discovering and isolating 10 new types of toxin originating from harmful algae.
These discoveries include the toxin group azaspiracids, which were first isolated from shellfish in Killary Harbour in 1995. They come from marine phytoplankton. Since then, these toxins have been found in shellfish stocks around Europe.
In freshwater sources, neurotoxins produced by cyanobacteria in the State's lakes were found in 1994.
The neurotoxin from cyano bacteria, anatoxina, killed dogs who ingested it at Caragh Lake, Co Kerry, and Lough Derg, Co Tipperary. These neurotoxins, however, do not present the same problems for humans.
Worse for humans, however, are the type of cyanobacteria in freshwater sources that produce the toxin microcystins, which can damage the liver and promote cancer growth.
The main focus of the research in Cork is on developing analytical methods for detecting the toxins. Shellfish and algae samples are taken and the toxins are isolated.
The research involves international co-operation with other scientists. Once a novel toxin has been isolated, it is sent to Japan, where collaborators determine the toxin's unique chemical structure. This allows researchers to refine their detection methods for the toxin.
It is difficult to predict where harmful algae might bloom, but high-risk times can be identified, particularly during the summer, when the water is warmer.
Last year's frequent bay closures cost the shellfish industry £7 million, with a consequent 30 per cent drop in output. The Irish Shellfish Association (ISA) had warned in 1994 of the need for adequate funding and support for toxin management.
The Minister for State for the Marine, Mr Byrne, approved £2.5 million to help compensate for heavy losses. He also sought a fundamental review of the role of relevant agencies in shellfish testing.
dfahy@irish-times.ie