Microalgae 'detective' developing faster way to identify species that cause harmful algal blooms

Hundreds of dead fish washed up along the shores of Lim Chu Kang jetty, after a wave of plankton bloom, on March 7, 2015. PHOTO: ST FILE

SINGAPORE - In the watery world of microalgae, only a handful of them are potentially harmful to humans or fish.

But identifying these microscopic organisms can be challenging. Among the 5,000 microalgae species globally, only 250 are potentially harmful. Such microalgae of concern can either produce potent toxins or multiply dramatically, consuming oxygen in the water and killing fish.

A researcher from the Nanyang Technological University's (NTU) Asian School of the Environment is now developing a faster way of identifying these organisms with a hand-held device that can deliver results within a day.

Current methods of pinning down the identity of microalgae species can take up to a few days, with scientists observing them under special microscopes or running toxicity tests.

The researcher behind the ongoing effort, PhD student Christaline George, 34, said a portable device that can more quickly and accurately reveal what is swimming in the seas will allow researchers and the authorities to keep an eye on water quality more easily.

This way, traces of troublesome species can trigger mitigation strategies before a bloom occurs.

One of the most disastrous algal blooms in Singapore happened in 2015 in the Johor Strait, killing over 500 tonnes of fish bound for the dinner table and causing 77 coastal farms to lose millions of dollars. One farmer put his losses at $1.3 million.

"We can't prevent or always accurately predict occurrences of harmful algal blooms. The only way forward could be to regularly monitor for the microalgal species in the waters and manage the problem before it strikes," Ms George told The Straits Times.

"If we know what species we're dealing with, we can tailor the mitigation strategies accordingly. Some species produce toxins, which can lead to shellfish poisoning in humans," she added.

Mitigation measures used globally include diluting the waters to disperse the bloom, and harvesting seafood early during or before a bloom.

Ms George is working with a series of software with the aim of identifying microalgae species through sequencing fragments of their DNA (genetic code). Since these fragments are unique to each species, they can serve as a "fingerprint" for each of them.

Ms Christaline George is developing a faster way of identifying the organisms behind algal blooms with a hand-held device. PHOTO: NTU ASIAN SCHOOL OF THE ENVIRONMENT/FACEBOOK

This process, known as DNA meta-barcoding, is similar to the way barcodes on products in shops work.

Such barcodes - or DNA markers - work only if there is a database to compare them against.

But there could be challenges with identification if the information on the database is not robust enough.

For instance, if the genetic sequence associated with a species on a database is not long enough, or does not include the DNA marker region of the sample, then the organism cannot be identified accurately.

Therefore, Ms George is developing a database comprising long DNA sequences of marker regions from microalgal species in the waters surrounding Singapore.

The Singapore Food Agency (SFA) said it regularly monitors indicators of water quality, such as plankton count and occurrence of harmful algal blooms, at the coastal fish farming sites.

"This allows SFA to give farmers early warning when adverse conditions are detected, so that they can take the necessary precautionary measures," said the agency.

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