Effects of spectral light quality on the growth, productivity, and elemental ratios in differently pigmented marine phytoplankton species

Effects of light quality on the growth, productivity, and cellular composition of three uniquely pigmented marine phytoplankton species were characterized. To accomplish this, cultures of Prochlorococcus marinus, Synechococcus sp., and Thalassiosira weissflogii were grown under three commercially available LEDs as well as a fluorescent growth light. Despite having equal photosynthetically active radiation, light quality and thus photosynthetically usable radiation differed between the treatments. Growth was unaffected in all species tested, yet primary productivity was affected in P. marinus and Synechococcus sp. All species regulated cellular carbon and nitrogen quotas as a direct response to light spectra, while cellular chlorophyll a was regulated in Synechococcus sp. and T. weissflogii only. Analysis of pigment ratios revealed minor acclimations in some of the cultures and photophysiological analysis indicated changes in the photoacclimation state between different light environments. These results show that while the species used in our experiment are able to maintain growth when exposed to lights of varying quality, underlying cellular metabolism and biochemistry can be affected. The data presented here highlight the importance of carefully choosing a lighting environment with a defined spectral quality when designing laboratory-based experiments or setting up bioreactors for biomass generation. HighlightWith light emitting diode-based growth lights becoming available to researchers, it is important to consider the spectral quality of light when designing experiments to understand responses of phytoplankton to environmental conditions.