PARR-2011-NL-14 - Project Expansion
Identification of the food sources of opportunistic polychaete (OPC) worms found at finfish aquaculture sites on the south coast of Newfoundland

(Project Expansion of PARR 2011-NL-14 entitled: Evaluating Beggiatoa and OPC as indicators of benthic habitat condition on hard ocean substrates using visual data collected seasonally at new finfish aquaculture sites and near the end of production at established sites)

Indicators of benthic habitat conditions have not yet been developed to support HADD (Harmful Alteration Disruption Destruction) determinations at finfish aquaculture farms located over hard ocean substrates in Newfoundland.  Although biological and geochemical variables have been identified to assess changes in benthic conditions on soft bottom substrates near finfish farms, these are not appropriate for use on hard substrates as they require the acquisition of sediment grabs.  Two indicators used on soft substrates may have utility on hard substrates because they are conspicuous members of the benthic fauna and are known to occur near finfish sites on hard substrates.  Beggiatoa is a genus of bacteria that forms dense mats in areas at the interface of oxic and anoxic conditions and is associated with elevated sulphide levels.  The second potential indicator is a group of polychaete species (the opportunistic polychaete complex, OPC).  Over the past few years, finfish growers on the south coast of Newfoundland have observed dense associations of worms identified as species of the family Dorvilleidae on hard substrates under fish farms. It is suspected that the accumulation of organic matter coming from fish feed and faeces has triggered the development of these worm complexes on hard bottoms. It is unclear how dorvilleids feed, although it was suggested that they might feed on methanotrophic bacteria and that their bioturbation activities might enhance nutrient cycling and help to remediate sediments

Fisheries and Oceans Canada researchers in Newfoundland are investigating how OPCs might help accelerate the decomposition of organic matter originating from fish farms (i.e., feed and fish faeces), aid in nutrient cycling under farm cages, as well as sulfide detoxification (a by-product of organic enrichment). They are also investigating the relationship of OPC with Beggiatoa.  From video analyses of farm sites, it is not clear whether OPCs and Beggiatoa occur together on the ocean bottom or whether the presence of one group excludes the occurrence of the other.

To answer some of these questions researchers will attempt to determine the origin of the organic matter consumed by OPCs through the use of stable isotope analysis.  Analyses of OPCs sampled at three sites with different enrichment levels (i.e., first year production, second year production and a fallowed site) will help determine if OPC food sources vary with changes in benthic conditions.  The results of this research will help understand the potential role of opportunistic polychaetes in consuming organic matter and potentially mitigating the effects of organic buildup under farm cages.  In addition, their role in relation to the presence/absence of Beggiatoa on the ocean bottom (are they consuming this bacteria?) will help better characterize the dynamics of benthic communities impacted by aquaculture wastes.

Principal investigator:
Dounia Hamoutene, Northwest Atlantic Fisheries Centre, St. John's, NL;
Tel.: (709) 772-5872; Email: Dounia.Hamoutene@dfo-mpo.gc.ca

Team members:
Lee Sheppard, DFO-Newfoundland and Labrador region

1-year project expansion (2012/13)