Estimating daily primary production and nighttime respiration in estuaries by an in situ carbon method

Catherine M Coupland, University of Rhode Island


A Dawn Dusk Dawn Carbon method was developed to estimate daily primary productivity and respiration in Narragansett Bay at 9 Narragansett Bay Fixed Site Monitoring Network stations. The method utilizes YSI temperature, salinity, and pH measurements and measured alkalinity values. The method was compared to a previously verified Dawn Dusk Dawn Oxygen method for Narragansett Bay developed by Smith (2011). The methods compared well with correlations coefficients between 0.69 – 0.96 for all four categories (surface production, surface respiration, bottom production, and bottom respiration) and both summers. In all categories, 2014 comparisons were more highly correlated than 2013. Metabolic rate sensitivity to pH and alkalinity analyses, pH stability, and accuracy, were conducted to quantify error. The YSI pH sensors were stable over the dawn-dusk-dawn time period (i.e. 24 hours), with an average change between 15 minute readings of 0.01 units. Based on the manufacturers stated accuracy for the YSI sensor of 0.2 pH units, the surface metabolic rate estimates could be under or over estimated by -11 to 23% if the pH sensor was reading low or high by a systematic 0.2 unit offset. The bottom estimates could be over estimated by 8 to 11%, based on the same offset. The metabolic rate estimates are not significantly affected by a change in alkalinity, with ANOVA p values >0.9 for all categories and two stations. Four comparisons between a Satlantic SeaFET pH sensor and YSI pH sensors were conducted with four variable results due to differing environmental deployment conditions, three of four comparisons indicated a linear trend between the two sensors. The metabolic rates vary spatially throughout the Bay both summers 2013 and 2014. A north to south gradient in metabolic rates persists through the West Passage both summers, with the exception of North Prudence. North Prudence exhibits anomalously low metabolic rate estimates compared to surrounding sites. Previous studies around the North Prudence site have indicated a well mixed water column, with bottom water reaching the surface. This may be artificially lowering the estimates of surface production at the North Prudence site.

Subject Area

Biological oceanography|Biochemistry

Recommended Citation

Catherine M Coupland, "Estimating daily primary production and nighttime respiration in estuaries by an in situ carbon method" (2015). Dissertations and Master's Theses (Campus Access). Paper AAI1596028.