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Evaluation of factors affecting the electrochemical measurement of total free sulfide in marine sediments

National Peer Review Process – National Capital Region

February 26 – 28, 2019
St Andrews, New Brunswick

Co-Chairpersons: Jay Parsons and Ingrid Burgetz


Fisheries and Oceans Canada (DFO) is responsible for the regulation and management of the aquaculture industry throughout Canada under the Aquaculture Activities Regulations, defining the conditions under which an aquaculture operator may deposit organic material under s.36 of the Fisheries Act. DFO recognizes that there are interactions between aquaculture operations and the natural environment. The risks associated with these interactions are considered and addressed through a suite of regulatory tools. Examples of such tools include requiring that aquaculture operators monitor the oxic state of the seafloor beneath farms, and having defined thresholds and associated management actions that are required should the regulatory thresholds be exceeded.

Under the Aquaculture Activities Regulations, the aquaculture industry is required to conduct seafloor monitoring of finfish aquaculture sites. The measurement of redox and sulfide from sediment samples is an accepted standard practice for soft-bottom seabeds. The protocols for conducting sampling, and for the measurement of redox and sulfide from sediment samples are outlined in the regulations and associated monitoring standard.

The currently applied DFO monitoring protocols used at marine finfish sites were adopted by DFO during the development of the Aquaculture Activities Regulations, and incorporate some regional differences in Provincial program design.  Specifically, these protocols may result in differences in the time between sample collection and the measurement of redox and sulfide in the samples, as well as differences in the temperature at which samples are held prior to processing.  DFO Aquaculture Management have asked for information on the effects of several factors on the measurement of sulfides in sediment samples, and have requested Science advice to support the development of a nationally harmonized approach to the collection and testing of sediment sulfide as a proxy for oxic state.


The objectives of this meeting are to determine: 

  1. What is the relationship between sediment sample storage time and the total free sulfide measured as compared to total free sulfide measured immediately upon sediment sample collection?
  2. What are the effects of sediment sample storage conditions (i.e. temperature, vacuum-sealed, etc.) on the measurement of total free sulfide over time as compared with measurement of sample total free sulfide immediately upon sample collection?
  3. Are these relationships consistent across sediment types and/or total free sulfide concentrations?
  4. Are these relationships consistent across benthic sample acquisition methodologies?
  5. What combination of storage conditions and storage time post collection would result in expected total free sulfide measurements within +/- 5%, 10% and 15% of the value obtained from measuring total free sulfide immediately following sediment sample collection?
  6. Are there other steps in the ISE total free sulfide measurement protocol to which differences will result in different measured concentrations of total free sulfides?
  7. Characterize the natural spatial variability of sediment sulfide levels.

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Expected Participation


Participation to CSAS peer review meetings is by invitation only.

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