By Soledad S. Garebad

The University of the Philippines Visayas (UPV) intensively studies three microalgae species, namely, Tetraselmis sp., Nannochloropsis sp., and Chaetoceros calcitrans. These species, which are commonly used in aquaculture, are cultured by the batch system in laboratories and are continuously being monitored for quality control.

This is made possible through the Program on the Development of Algal Paste from Microalgae under the National Aquafeeds Research and Development Program A. The Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (PCAARRD) is currently funding a project to utilize the three species for mass production of algal pastes, the microalgae concentrate of which is used for rotifers, shrimp larvae, and other aquaculture commodities.

Microalgae are natural aquatic products gaining attention for their potential as ideal feeds for aquaculture purposes. They are considered one of the most important aquatic organisms for their many uses in various fields, and are the fastest growing plants, with their doubling time measured in hours.

Currently, microalgae are produced commercially for high-value nutritional products, wastewater treatment applications, and for aquaculture, using everything from closely controlled laboratory methods to less predictable methods in outdoor tanks or ponds. Algal mass production is dependent on algal strains, the weather, and culture techniques.

The UPV program includes culturing; once the algae have reached their peak density, they are harvested and prepared using flocculant (a chemical which induces particles to clump). Concentrated cells thus collected are transferred to a new container for another settling process then filtered until pastes are formed.

The algal paste can be used as an alternative to on-site algal culture, especially when rations of live microalgae are insufficient. In paste form, microalgae can be kept under refrigerated conditions without sacrificing its nutritional quality for several months.

Microalgal paste is an instant feed that can be applied easily for aquaculture purposes at any time for fish stock. Commercial algal paste costs range from US$ 50/liter (L) to US$ 150/L, depending on the species.

With microalgal paste, worries about phytoplankton culture and maintenance can be reduced, if not eliminated. Algal paste as an alternative for live microalgae production will surely benefit local industries, particularly milkfish, shrimp, and tilapia hatcheries by lowering their production and labor costs.

Microalgal pastes are now being produced at the Institute of Aquaculture, College of Fisheries and Ocean Sciences of the UPV in Miag-ao, Iloilo. Now on its second year of implementation, experiments are being conducted to further verify the pastes’ nutritional quality and shelf life.

This appeared in Agriculture Monthly’s February 2014 issue.