A microscopic algae ("microalgae") could provide a complete and sustainably sourced supplemental diet to boost the robustness of managed honeybees, according to research published in the journal Apidologie by scientists with the U.S. Department of Agriculture's Agricultural Research Service (ARS).

Poor nutrition in honeybees is often an underlying factor in colony losses because malnutrition amplifies the detrimental effects of parasites, pathogens and pesticides, ARS said, adding that habitat loss, decreases in flowering plant diversity and large tracts of crop monoculture all can potentially contribute to lessening natural pollen sources that provide bees with essential nutrition.

Now, research by ARS entomologists Vincent Ricigliano and Michael Simone-Finstrom has shown that the microalgae Arthrospira platensis (commonly called spirulina) has a nutritional profile that closely resembles pollen. Spirulina is a part of family of blue-green algae — single-celled organisms that exist individually or in chains or groups.

Ricigliano and Simone-Finstrom found that spirulina is rich in essential amino acids and lipids required by bees, with levels matching those found in tested pollen samples, ARS said in an announcement. The two scientists are both with the ARS Honey Bee Breeding, Genetics & Physiology Research Laboratory in Baton Rouge, La.

"Our work is a pioneering first look into the nutritional and functional properties of a single microalga and how well it corresponds to what is needed in a complete pollen substitute for the honeybee," Ricigliano explained.

In addition to being rich in essential amino acids necessary for protein synthesis, immune function and colony growth in honeybees, spirulina also contains prebiotics that support the growth of healthy gut bacteria.

Commercial beekeepers have become increasingly reliant on artificial pollen substitute diets to nourish colonies during periods of pollen scarcity as well as to bolster colony size before they fulfill pollination service contracts, ARS noted.

Currently available commercial diets for bees usually incorporate a variety of ingredients like soy, yeast, wheat, lentils and milk proteins in an effort to supply balanced nutrition, but these diets are sometimes deficient in essential macronutrients (proteins, lipids, prebiotic fibers), micronutrients (vitamins and minerals) or antioxidants, ARS said.

"So, the need to scientifically improve the efficacy of pollen substitutes can be considered vital to modern beekeeping, and we need to think about how we can do it in a sustainable way," Ricigliano said.

Microalgae can be sustainably grown on a large scale with a minimal amount of water and few chemical inputs. It can even be grown in places where soybeans and other crops cannot be grown.

"All it takes are shallow ponds, nutrient salts and sunlight to produce highly nutritious microalgae," Ricigliano said.

The researchers are now testing the microalgae diet in a field setting to make sure the diet is attractive to bees and supports colony growth. The excellent nutrition profile of spirulina suggests that there are likely other microalgae that could serve honeybees well, Simone-Finstrom pointed out.

"We have also begun development of new microalgae strains to address other aspects of bee health, including targeted nutrition strategies," Ricigliano added.