Research Document - 2014/063

Applicability of the use of visual indicators [presence of Beggiatoa and/or Opportunistic Polychaete Complexes (OPC)] to identify benthic changes due to aquaculture on various substrates

By Hamoutene, D., Sheppard, L., Mersereau, J., Oldford, V., Bungay, T., Salvo, F., Dufour, S., and Mabrouk, G.

Abstract

Data from sampling conducted on aquaculture sites as well as information extracted from industry monitoring reports were used to evaluate the applicability of using Beggiatoa and OPC as indicators of benthic change due to aquaculture. The first set of data analyzed pertains to monitoring reports completed at cage edge; Beggiatoaand OPC presence were then noted with no assessment of coverage. Changes to the habitat monitoring protocols were implemented in June of 2011 with protocols changing from cage edge sampling to transect sampling (with transects located around the cage array). Data collected via transect sampling were analyzed to search for trends across sites in relation to distance to cage, and to evaluate variability between stations located in the same direction. Beggiatoa and OPC were not present at reference sites and were found to be associated with aquaculture activities. Beggiatoa and OPC presence correlate with known indicators of aquaculture activities such as flocculent presence, offgasing and sulfides (up to a certain concentration). Beggiatoa and OPC were found to decrease with distance from cage though exhibiting patchy distributions. Despite this patchiness, average differences in Beggiatoa and OPC coverage between stations along transects in the same direction were less than 10 %. When transforming data into dummy variables (absence/presence) we found the same trends suggesting that the presence/absence of these organisms could also be used as an adequate trigger to inform on waste deposition at finfish sites.

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