High-throughput well plate approach illustrates strain specific variation in picocyanobacteria nitrogen and phosphorus usage

Abstract

In the wake of water body eutrophication influenced by major nutrient influxes from agriculture and urban runoff, there have been global increases in the growth of phytoplankton species. The environments created appear to favour the growth of cyanobacteria in comparison to other primary producers. The smallest group of these organisms, known as picocyanobacteria, is uniquely adapted to grow and dominate aquatic environments following a period of nutrients saturation. Due to the small nature of these organisms’ identification outside of genomic testing can be a difficult task, as such minor morphological differences can be hard to identify using microscopic techniques. Despite being closely related and similarly classified, many picocyanobacteria have been highly specialized in their environment based on conditions such as salinity, nutrient availability, and light. This study implemented the use of a high-throughput well plate design to expose three strains of picocyanobacteria to a fully crossed experimental matrix of five phosphorus concentrations (0 μM, 0.5 μM, 3.0 μM, 5.0 μM, and 7.0 μM), four nitrogen concentrations (0 μM, 5.0 μM, 30.0 μM, and 70.0 μM), and three-light levels (30, 100 or 300 μmol photons m-2 s-1), to determine if niche determination based on nutrients and light is an effective method of understanding and characterizing the growth of picocyanobacteria strains. Cyanobium sp. CZS25K, Cyanobium sp. CZS48M, and Synechocystis sp. PCC6803 were examined for this study. Statistical modelling demonstrated distinct strain-specific variations between the uses of nutrients and light for growth. Nitrogen and phosphorus concentrations were demonstrated to influence the growth of CZS25K. Nitrogen and light levels were essential for the growth of CZS48M. In contrast, PCC6803 growth rates were most sensitive to environmental nitrogen availability. These results may help support and inspire studies examining phytoplankton growth and adaptation mechanisms. This knowledge is becoming increasingly valuable for global monitoring and management of accelerated phytoplankton growth.