3D spatial point patterns of bioluminescent plankton: a map of the ‘minefield’

As the open ocean environment lacks points of refuge from visual predators, it has favored the evolution of extraordinary adaptations for optical concealment, such as vertical migration, transparency and counterillumination. Bioluminescent plankton, which respond to a mechanical disturbance with a flash of light, are ubiquitous in the ocean and potentially a threat to any organism seeking darkness as a means to evade detection. Estimating encounter probabilities for organisms maneuvering through luminescent ‘minefields’ requires characterization of the three-dimensional distribution patterns of the potential light emitters. In order to measure nearest neighbor distances (NNDs) of bioluminescent biota, we have developed a spatial plankton analysis technique (SPLAT) for 3D reconstruction and statistical analysis of the spatial point patterns of identified bioluminescent displays. Analysis of aggregations of bioluminescent biota in the Gulf of Maine (Wilkinson Basin) revealed that encounter probabilities were highest in the temperature minimum zone (temperature