Use of visual data in benthic enrichment classification

Abstract

Artificial eutrophication continues to be a primary concern associated with aquaculture practices. In Canada, monitoring benthic health in response to organic enrichment is used to manage these impacts and maintain the desired oxic state in surface sediments. However, results of this study suggest that traditional methods using sulfide concentrations alone are unable to distinguish between oxic and sub-oxic conditions. This work demonstrates that the homogenization of subsamples combined with limitations of a single parameter classification resulted in 93% of hypoxic stations, defined by known biochemical and geochemical visual signatures, were being underestimated and ranked as oxic by sulfide data. Surface video and in situ sediment profile imagery (SPI) data, including a validated use of the apparent redox potential discontinuity (aRPD) as a proxy for redox state, or sulfide concentrations, were integrated into two visual based benthic health indices. Parameters used in the two indices are supported by published sensitivity studies, thus supporting the use of visual proxies in benthic enrichment classifications to define the currently underestimated hypoxic condition resulting from sulfide concentrations alone.