As hypoxic conditions spread in our oceans,indices that quickly and efficiently assess oxygen content in sediment pore water,and habitat quality are increasingly becoming desirable.Depth to the apparent redox potential discontinuity(aRPD) in sediment is one such index;however,the relationship between aRPD depth and oxygen content is still unclear.We quantified oxygen content in sediment pore water with a dissolved oxygen(DO) probe,utilizing luminescent technology,to determine how DO concentration varies with depth in the sediment,and with position relative to the aRPD(above versus below) on an intertidal mudflat in the Bay of Fundy,Canada.Based on generalized linear regression models,we found that depth in the sediment was a poor predictor of pore water DO concentration,while position in the sediment relative to the aRPD was a good predictor.Further,sediment above the aRPD had higher DO content than sediment below.We maintain that aRPD depth is a good measure of relative oxygen content in sediment pore water,as well as habitat quality.However,we recommend caution as the factors that influence aRPD depth arc numerous and variable;therefore,the relationship between aRPD depth and DO content should be experimentally confirmed in any system of interest before aRPD depth is used as an indicator. As hypoxic conditions spread in our oceans, indices that quickly and efficiently assess oxygen content in sediment pore water, and habitat quality are increasingly desirable. Depth to apparent viox potential discontinuity (aRPD) in sediment is one such index; however, the relationship between aRPD depth and oxygen content is still unclear. We quantified oxygen content in still sediment, with luminescent oxygen (DO) probe, utilizing luminescent technology (above versus below) on an intertidal mudflat in the Bay of Fundy, Canada. Based on generalized linear regression models, we found that depth in the sediment was a poor predictor of pore water DO concentration, while position in the sediment relative to the aRPD was a good predictor.Further, sediment above the aRPD had higher DO content than sediment below. We maintain that aRPD depth is a good measure of relative oxygen content in sediment pore water, as well as habitat quality. However, we recommend caution as the factors that influence that aRPD depth arc numerous and variable; therefore, the relationship between aRPD depth and DO content should be experimentally confirmed in any system of interest before aRPD depth is used as an indicator