found that the depth of the 25.1 σT isopycnal, which is associated with the threshold NO3 concentration for kelp growth, accounted for 71% of the variability in kelp density near Pt. Loma, CA. Kelp plants at greater depths may occupy nutrient refugia that may lead to a higher quality surface canopy. The spatial differences may also be a factor of the age structure of the canopy fronds. Variation in the production and growth of fronds in different nutrient and light conditions, coupled with intrinsic frond senescence, may lead to variability in age structure, pigment concentration, and photosynthetic performance. Clearly, the environment of the entire plant can have an effect on the condition of the canopy and there is much work to done on relating bathymetric variability to changes in giant kelp canopy processes.