Micrograph of Monoraphidium minutum 26B-AM in BG-11 medium. Photo credit: Scott Edmundson, PNNL.

The single-celled, crescent-shaped green alga Monoraphidium minutum 26B-AM was collected by Dr. Louis Brown as a cold-hardy pond contaminant during winter field cultivation studies as part of the National Association for the Advancement of Bioproducts and Biofuels (NAABB) outdoor pond cultivation of Chlorella sorokiniana in Pecos, TX. This alga was originally suggested to be a species of Kirchneriella by microscopic identification, but subsequent isolation and molecular identification under the Regional Algal Feedstock Testbed (RAFT) project by Dr. Judith Brown’s laboratory at the University of Arizona indicated it was more closely related to Monoraphidium minutum. During the RAFT project, it was extensively characterized by the Pacific Northwest National Laboratory and field tested in outdoor pond conditions in Arizona, Texas, and New Mexico, proving a promising organism for winter cultivation (https://www.osti.gov/biblio/1492217). This strain is currently (2019) the winter season benchmark for the Algae DISCOVR (Development of Integrated Screening, Cultivar Optimization, and Verification Research) project (https://discovr.labworks.org/identification-high-productivity-winter-and-summer-season-discovr-strains-climate-simulation-leaps). As of 2019, it remains the most promising winter algal strain for outdoor pond production of biomass over the winter season (Dec-Feb) at the DOE-BETO Algal Productivity-State of Technology (SOT) field test site in Mesa, Arizona (AzCATI, Arizona State University). Monoraphidium minutum 26B-AM is highly susceptible to crashing at temperatures over 35°C (Edmundson and Huesemann 2019, in preparation).