Assessment of RBRcoda T.ODO performance on long-term deployment and profiling in Bedford Basin

Rui Zhang1, Clark Richards2, Mark Halverson1, Jon Taylor1, Eric Siegel1 and Greg Johnson1, (1)RBR Ltd, Ottawa, ON, Canada, (2)Fisheries and Oceans Canada, Halifax, NS, Canada
The RBRcoda T.ODO is a new low-power optical dissolved oxygen (DO) sensor available with three time constants: slow (30s), standard (8s), and fast (1s). To assess the performance of the T.ODO on long-term mooring and profiling applications, field tests were conducted in Bedford Basin (Halifax, Canada) from September 2018 to December 2018. The measurements were compared to data collected using a Sea-Bird Scientific CTD with SBE43 dissolved oxygen sensor and to water bottle samples (Winkler titration) collected from a rosette. For mooring applications, the results indicated that the slow foil is stable and accurate over a 4-month period, with an average difference of -0.36 mL/L and -0.19mL/L between bottle samples and SBE43, respectively. The difference between T.ODO and bottles may be partly due to temporal and spatial variations in DO. For profiling, the results showed that fast foil readings match the SBE43 readings closely, with an average differences of -0.05 mL/L. The standard foil outputs delayed signals relative to the fast foil when profiling, as expected. After application of the Fozdar et al. (1985) sharpening algorithm, the corrected signal has a much smaller standard deviation difference and the measurement lag was improved compared to the fast foil.