Efficacy of a microalgal feed additive in commercial honey bee colonies used for crop pollination

Authors: MCMENAMIN, ALEXANDER - Orise Fellow; Weiss, Milagra; Meikle, William; Ricigliano, Vincent

Submitted to: ACS Agricultural Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2023
Publication Date: 8/15/2023
Citation: McMenamin, A., Weiss, M., Meikle, W.G., Ricigliano, V.A. 2023. Efficacy of a microalgal feed additive in commercial honey bee colonies used for crop pollination. ACS Agricultural Science and Technology. 3(9):701-834. https://doi.org/10.1021/acsagscitech.3c00082.
DOI: https://doi.org/10.1021/acsagscitech.3c00082

Interpretive Summary: Honey bees are fed artificial diets to compensate for reduced floral resource in the environment and to bolster colony population growth. In this study, we tested the effects of a spirulina microalgae-augmented diet on commercial bee colonies in an agriculturally intensive desert environment over four months leading up to early spring almond pollination. One hundred honey bee colonies were used in a randomized block design that was replicated at two apiary sites. Colonies were fed a pollen-free artificial diet or the same diet augmented with 25% spirulina microalgae. Unfed colonies were randomly assigned within treatment blocks as a negative control. We measured colony population size, brood production, thermoregulation, and a panel of molecular biomarkers associated with nutritional status, stress responses, and gut microbiota. Hive brood imaging and continuous temperature data enabled sensitive detection of diet effects. Spirulina-augmented feed significantly improved colony brood production and thermoregulation. Bees fed spirulina had distinct expression profiles of nutrition and stress response genes that were primarily driven by apiary site. Relative abundance of the bee gut symbiont Snodgrassela alvi was significantly positively associated with larger brood areas but was not impacted by diet. We conclude that spirulina is a sustainable feed additive with potential to improve crop pollination efficiency by supporting larger, healthier honey bee colonies.

Technical Abstract: Pollinators are experiencing nutritional deficiencies related to habitat loss and climate change, posing major threats to the ecosystem services they provide. Honey bees managed for crop pollination are fed artificial diets to offset reduced floral pollen in the environment and to stimulate colony population growth. Here, we evaluated the effects of a spirulina microalgae-augmented diet on commercial bee colonies in an agriculturally intensive desert environment over four months leading up to early spring almond pollination. One hundred honey bee colonies were used in a randomized block design that was replicated at two apiary sites. Colonies were fed a pollen-free artificial diet or the same diet augmented with 25% spirulina microalgae. Unfed colonies were randomly assigned within treatment blocks as a negative control. We measured colony population size, brood production, thermoregulation, and a panel of molecular biomarkers associated with nutritional status, stress responses, and gut microbiota. Hive brood imaging and continuous temperature data enabled sensitive detection of diet effects. Spirulina-augmented feed significantly improved colony brood production and thermoregulation. Bees fed spirulina had distinct expression profiles of nutrition and stress response genes that were primarily driven by apiary site. Relative abundance of the bee gut symbiont Snodgrassela alvi was significantly positively associated with larger brood areas but was not impacted by diet. We conclude that spirulina is a sustainable feed additive with potential to improve crop pollination efficiency by supporting larger, healthier honey bee colonies.