MANAGED HONEY BEE POPULATIONS ARE EXPERIENCING HISTORIC AND UNSUSTAINABLE LEVELS OF COLONY LOSS THAT THREATEN THE BEEKEEPING INDUSTRY AND FOOD SECURITY IN THE UNITED STATES. THESE LOSSES ARE ATTRIBUTED TO A NUMBER OF STRESSORS SUCH AS PATHOGENS, PESTICIDES, AND HABITAT LOSS, BUT MOUNTING EVIDENCE INDICATES THAT MALNUTRITION IS A MAJOR FACTOR WITH BOTH DIRECT AND INDIRECT EFFECTS. COMMERCIAL BEEKEEPERS HAVE BECOME INCREASINGLY RELIANT ON ARTIFICIAL POLLEN SUBSTITUTE DIETS AS LANDSCAPES SHIFT TO AGRICULTURALLY INTENSIVE MONOCULTURES THAT DO NOT MEET THE NUTRITIONAL REQUIREMENTS OF BEES. THEREFORE, IMPROVING THE EFFICACY AND SUSTAINABILITY OF POLLEN SUBSTITUTES CAN BE CONSIDERED VITAL TO MODERN BEEKEEPING. MICROALGAE ARE PROLIFIC SOURCES OF PLANT?BASED NUTRITION WITH MANY SPECIES EXHIBITING BIOCHEMICAL PROFILES THAT ARE COMPARABLE TO POLLEN. OUR CURRENT DATA INDICATE THAT MICROALGAE ARE RICH IN ESSENTIAL PROTEINS AND LIPIDS THAT ARE READILY METABOLIZED BY BEES. FURTHER, RAPID GROWTH RATES AND BIOMASS PRODUCTION ENABLE MICROALGAE TO SURPASS CURRENT PROTEIN FEED RESOURCES, SUCH AS SOY AND CORN, ON AN AREA BASIS USING NON-ARABLE LAND, REDUCING SOME ENVIRONMENTAL BURDENS OF INTENSIVE AGRICULTURE THAT NEGATIVELY IMPACT POLLINATORS.IN THIS PROPOSAL, WE OUTLINE APPROACHES FOR DEVELOPMENT AND TESTING OF NOVEL FEED TECHNOLOGIES CAPABLE OF SIMULTANEOUSLY ADDRESSING MULTIPLE HONEY BEE STRESSORS. FIRST, WE WILL CONDUCT COMPREHENSIVE ASSESSMENTS OF THE EFFECTS OF DIFFERENT MICROALGAE SPECIES ON INDIVIDUAL BEE NUTRITIONAL PHYSIOLOGY AND MICROBIOME FIDELITY. SECOND, WE WILL MEASURE THE EFFECTS OF SUPPLEMENTAL FEEDING AT THE COLONY LEVEL IN COMMERCIAL OPERATIONS THROUGH PARTNERSHIPS WITH BEEKEEPER AND QUEEN BREEDER STAKEHOLDERS. THIRD, WE WILL DEVELOP AND TEST THE EFFICACY OF NOVEL MICROALGAE STRAINS WITH ALTERED MACRO- AND MICRONUTRIENT RATIOS THAT ADDRESS SPECIFIC HONEY BEE NUTRITIONAL REQUIREMENTS. FINALLY, WE WILL DEVELOP AND TEST THE EFFICACY OF NOVEL MICROALGAE STRAINS TO IMPROVE RESISTANCE AGAINST PATHOGENS AND PARASITES. THE PROPOSED WORK WILL PROVIDE VALUABLE INFORMATION REGARDING THE NUTRITIONAL AND FUNCTIONAL PROPERTIES OF A NOVEL POLLEN SUBSTITUTE, AS WELL AS APPROACHES TOWARDS DEVELOPING FEED-BASED THERAPEUTICS TO IMPROVE HONEY BEE HEALTH.