Coastal Nitrogen Drives Respiration Quotient in the Southern California Bight

Abstract. Southern California Bight coastal waters are dynamic and strongly influenced by a changing climate. An increased respiration quotient has been found during high temperature and low nitrogen conditions. These observations are specific to open ocean conditions, and their applicability to coastal environments is uncertain. To disentangle the controlling factors in a coastal environment, we examined environmental conditions, particulate organic matter, and the respiration quotient over five years in the Southern California Bight. Our study revealed clear seasonal variation in environmental conditions and biological parameters. We detected higher than previously reported respiration quotient ratios in open ocean regions. We found a strong inverse relationship between respiration quotient, nitrate and chlorophyll. Our findings also suggest that changes in community structure, triggered by nutrient shifts and a local oil spill, affected the range in respiration quotient and explains some of the variability measured. As climate continues to impact coastal regions, variable r_-O2:C patterns and its controls assists in accessing subsurface oxygen concentrations and in turn the health of our coastline.