In situ characterization of Saccharina latissima (Phaeophyceae) growth rates at varying light intensities

Abstract

Kelp species provide crucial ecosystem services in nearshore habitats, and the health of these populations and the food webs they support has arisen as a pressing concern as oceanic conditions continue to change. This study aimed to evaluate the relationship between light availability and kelp primary productivity in the model species Saccharina latissima (sugar kelp) by measuring in situ growth at various depths on a kelp “ladder”. It determined that the kelp grown at 10 meters below the surface showed significantly less growth (change in area, cm2) than the other treatments (p = 0.01) potentially due to the fact that the photosynthetically active radiation (PAR) (239.29 µmol photons m-2 s-1) that reaches to this depth is below the threshold for chlorophyll-saturated photosynthesis. Coupled with spatial kelp abundance models and carbon content ratios, these results are a potential foundation for future tools estimating large scale kelp productivity across depth.