Benthic respirometer
Project Manager/Lead Engineer: Brent Roman
Lead Scientist: Jim Barry

The upgraded benthic respirometer (BRS) will have expanded capabilities that will support more detailed study of benthic carbon cycling, physiological studies of individual benthic and midwater animals, and will allow manipulative experiments to evaluate the impacts of acid injection, relevant for studies of carbon dioxide (CO₂) sequestration. Carbon cycling studies will include measurement of rates of carbon remineralization and nutrient regeneration, not possible with the present system, as well as the benthic community response to artificial perturbations (e.g. food injection). Physiological studies will include measurements of metabolic rates of individual animals, ammonia excretion, and metabolic responses to food input, CO₂ changes, etc.

The current benthic respirometer measures oxygen (O₂) with an intensity-based optrode that is difficult to calibrate and is prone to drift over the course of a deployment. Until recently, we were aware of no optrode technology for measuring CO₂ directly. So, the current system infers CO₂ concentration from the pH measurement. This assumes that the only gas present that changes pH significantly is CO₂ . When other factors change the environment's pH, this technique will yield an incorrect CO₂ result.

We propose to adapt recently developed medical technology for in vitro analysis of dissolved blood gasses for use in the benthic environment. These optrode-based medical instruments already reliably and accurately measure O₂, pH and CO₂ dissolved in blood. One of our tasks to characterize the behavior of this bench-top instrument's three different types of optrode probes at benthic pressures and temperatures.