Linking peak intensity of mechanically stimulated bioluminescence and cell surface area in dinoflagellates

Mechanically stimulated bioluminescence (MSL) is present in most planktonic clades and marine ecosystems. The first flash kinetic parameters (FFKPs) and spectral properties are often species specific, making MSL a powerful tool for in situ ID and biodiversity assessments. The peak intensity (PI) of mechanically stimulated bioluminescence was measured for five species of dinoflagellates: Alexandrium monilatum, Lingulodinium polyedra, Pyrocystis fusiformis, Pyrocystis noctiluca and Pyrodinium bahamense. Peak intensity was assessed with respect to organism cell surface area and volume, building upon Seliger's rule, where previously a relationship was found linking cell surface area and total mechanically stimulated light (TMSL) ( Buskey and Swift, 1990). These dinoflagellate species were chosen to cover a wide range of peak intensities (108 to 1010 photons/s) and surface area (104 to 106μm2). Individual cells were isolated and individually photographed under a compound microscope, where cell size was measured. They were then dark-adapted and first flash emission from mechanical stimulation was measured with the Underwater Bioluminescence Assessment Tool (UBAT) from Seabird Scientific (www.seabird.com). Distributions of PI and surface area across all species were compared using non-parametric ANOVAs and a linear regression model, uncovering a strong positive correlation and strength of fit across all species between peak intensity and both cell surface area and volume. This study provides insight into understanding and potentially predicting the bioluminescence of organisms often responsible for significant primary and secondary productivity in marine waters with subsequent global impacts on fisheries and ecology. Bioluminescence measurements may also be a powerful tool for understanding plankton composition, ecology, and diversity.