Spatial and temporal changes in epibenthic communities at deep, hard bottom aquaculture sites in Newfoundland

Temporal Bacterial Surveillance of Salmon Aquaculture Sites Indicates a Long Lasting Benthic Impact With Minimal Recovery

“…Cluster membership of samples was not dictated by fallow length or production, but we observed that the average biodiversity and mode of cage distance increased when comparing high impact, intermediate impact and low impact clusters, respectively (Table 1). Correlations between distance from cage and benthic impact are not novel and have been observed in other bacterial – as well as macrobenthic – aquaculture surveillance studies (Keeley et al, 2014; Dowle et al, 2015; Hamoutene et al, 2015; Salvo et al, 2017). Surprisingly, the high impact cluster contained samples from a wide range of fallow and production lengths (3–35 months), indicating that benthic environments directly below pens remain highly impacted and do not return to a low or intermediate impact status, even after extensive fallowing, in line with what was previously reported for epibenthic fauna at the investigated sites (Salvo et al, 2017).…”

“…Correlations between distance from cage and benthic impact are not novel and have been observed in other bacterial – as well as macrobenthic – aquaculture surveillance studies (Keeley et al, 2014; Dowle et al, 2015; Hamoutene et al, 2015; Salvo et al, 2017). Surprisingly, the high impact cluster contained samples from a wide range of fallow and production lengths (3–35 months), indicating that benthic environments directly below pens remain highly impacted and do not return to a low or intermediate impact status, even after extensive fallowing, in line with what was previously reported for epibenthic fauna at the investigated sites (Salvo et al, 2017). While other studies have shown recovery within the first 3 months, and significant recovery after 2 years of fallowing (Keeley et al, 2014, 2015) such recovery was unfortunately not observed at the sites investigated here.…”

“…Accumulation of flocculent matter causes an increase in oxygen consumption by bacteria and consequently lowers oxygen availability within the sediment, creating hypoxic and anoxic conditions along with elevated concentrations of sulfides and/or methane (Hargrave et al, 2008). Such biogeochemical changes may negatively impact naturally occurring communities, often leading to their decline (Jusup et al, 2009; Salvo et al, 2017). The effects of organic enrichment on the benthos have been widely studied, especially on soft substrates, and aquaculture activities typically lead to changes in macrofaunal succession (Karakassis, 2000) and decreases in species diversity (Zhulay et al, 2015).…”

“…To overcome these obstacles, drop-camera visualization is currently being utilized in NL to monitor organic enrichment (Fisheries and Oceans Canada, 2015). Drop-camera monitoring along the south coast of NL has revealed that white microbial mats and opportunistic polychaete complexes (OPC) are indicators of organic enrichment as they are closely associated with the accumulation of organic matter at aquaculture sites (Salvo et al, 2015, 2017). However, this method has its drawbacks as it only provides a visual representation of the conditions at the seafloor and lacks the ability to clearly detect intermediate levels of disturbance (Salvo et al, 2017).…”

Measurement of Aquaculture Chemotherapeutants in Flocculent Matter Collected at a Hard-Bottom Dominated Finfish Site on the South Coast of Newfoundland (Canada) After 2 Years of Fallow

“…However, some differences exist in temperature ranges (measured during 50 days in the fall) with 2-9.2 • C for the production site and 2.4-15.2 • C at the fallowed site (Hamoutene et al, 2016). Low temperatures (Anderson et al, 2005) may slow recovery processes, and accumulated OM could sustain opportunistic taxa over long periods and limit the recruitment of epibenthic organisms (Brooks et al, 2004;Salvo et al, 2017a). However, some authors question the temperature effect on recovery in cold environments, arguing that native microbial populations are adapted to local conditions (Arndt et al, 2013).…”