Effects of B Vitamins on Experimental Pond Phytoplankton Communities Across a Stoichiometric Gradient

Nutrient stoichiometric ratios are major drivers of phytoplankton community composition, biomass accumulation, toxin production, and resource utilization of harmful algal blooms and harmful cyanobacterial blooms globally. In addition to the macronutrients of nitrogen (N) and phosphorous (P), micronutrients, such as B vitamins, help drive the underlying cellular biogeochemistry that influences community composition during blooms. To investigate the role of vitamins B1, B7, and B12 across stoichiometric gradients, forty-eight hour 1 L bioassays were conducted with and without B vitamin additions across twelve experimental limnocorrals with N:P stoichiometric ratio amendments of 2.2, 16, 55, and 120 and three control ponds at the University of Mississippi's Field Station in Oxford, MS, USA. B vitamin additions significantly decreased photosynthetic efficiencies in all phytoplankton groups (ANOVA: Cyanobacteria: F = 20.4445, Chlorophytes: F = 10.9612, and Diatoms: 19.6326, all p < 0.001). Additionally, there was a significant increase in the community fraction of chlorophytes (ANOVA: F = 165.5831, p < 0.001) with no significant effect in the community fraction of cyanobacteria (ANOVA: F = 22.8375, p = 0.1646) or diatoms (ANOVA: F = 1.17, p = 0.2834). Cryptophytes were only present in one limnocorral and were not included in the initial analysis. These results underscore the need to better understand multiple micronutritional drivers of phytoplankton communities across stoichiometric gradients.