Wednesday 15 September 2004
Cultured pearl production is a key driver of sustainable economic development in several Pacific nations. Empirical observations have shown that different oyster stocks produce pearls with distinct characteristics.
For instance, Manihiki Island (Cook Islands) is renowned for pearls with a unique coloration. In French Polynesia, before the massive transfer of spat between the many atolls of the Tuamotu, each island produced pearls identifiable by their color, luster, and orient — factors that largely determine their price and competitiveness in the market.
Following these large-scale exchanges, these distinctive traits have gradually faded.
Towards Genetic Identification of Stocks
To preserve diversity and the unique qualities of pearls, it is essential to establish precise genetic fingerprints of the different populations. This would make it possible to implement targeted management strategies and ensure better traceability in aquaculture.
Researchers’ Response
Hatchery operators are requesting reliable scientific data to produce the spat desired by pearl farmers, while also protecting the biodiversity and economic value of the various stocks.
To meet this demand, researchers are using two DNA-marking techniques:
• Amplified Fragment Length Polymorphism (AFLP)
• Microsatellite DNA analysis
Specimens have been collected from hatcheries in Hawaii, the Federated States of Micronesia, and the Marshall Islands, as well as from natural stocks, in order to establish a solid genetic basis for future selection and conservation strategies.
Wednesday 1 September 2004
Measuring metal pollution in tropical seas requires precise and cost-effective techniques. Direct measurement of metals in seawater remains difficult because it demands frequent sampling, expensive equipment, and specialized expertise.
Moreover, heavy metals are often trapped in sediments, and water sampling can miss pollution peaks that occur when these sediments are resuspended by storms or other disturbances.
Bivalves as Bioindicators
In the absence of suitable methods, filter-feeding bivalves such as mussels (Mytilus edulis) are commonly used as biological accumulators to detect pollutants.
The “mussel watch” system has proven to be a very effective tool and remains the most comprehensive method for monitoring coastal metal pollution in the United States. However, these species are restricted to temperate zones and do not offer a solution for oligotrophic tropical waters.
Pearl Oysters: Ideal Sentinels
Research has shown that pearl oysters (genus Pinctada) are an excellent complement for monitoring warm waters. They are widely distributed throughout the South Seas, are sessile, have long lifespans, and are well-suited for bioaccumulation studies.
Initial trials on the Hawaiian pearl oyster (P. margaritifera galtsoffi) revealed a strong capacity for heavy metal accumulation. Tests conducted in controlled tanks showed steady bioaccumulation of copper, cadmium, and zinc, proportional to the concentrations in the water and the duration of exposure.
Towards Enhanced Environmental Monitoring
These results have led to the establishment of field monitoring standards. Early studies conducted in Hawaii have provided preliminary environmental data. A second series of trials confirmed significant temporal variability in metal accumulation.
Researchers are now expanding their work to include other metals such as strontium, cobalt, and lead. Measuring radioactive isotopes of strontium and cobalt could become a valuable tool for ecological restoration and the repopulation of South Pacific atolls (Bikini, Enewetak, Christmas Island, Mururoa) that were once used for atmospheric and underwater nuclear tests by the United States, the United Kingdom, and France.
