Assessment of biodiversity and functional changes in NL benthic communities associated with aquaculture activities

PARR-2016-NL-09

Description

Salmon aquaculture situated along the south coast of Newfoundland is located over hard ocean substrate, and monitoring for the effects of organic enrichment from salmon aquaculture activities relies on visual monitoring techniques. Regulatory thresholds are based on the extent of visual indicators of organic enrichment surrounding a farm, as a proxy for the management objective of no greater than 50% biodiversity loss. This project built on past and on-going research, and focused on addressing three key knowledge gaps important for improving our understanding of the impact of finfish aquaculture located over hard bottom substrates. First, a better knowledge of the natural communities was established through completion of a reference database of the natural Newfoundland benthic communities in areas of aquaculture development. This provided better documentation of the biodiversity hot spots and/or the areas with low natural richness. Through a paired/matched comparison of baseline data (reference) with biodiversity data post-aquaculture, areas with 50% or greater biodiversity loss and the associated indicator presence were evaluated. Second, a characterization of the functional change of the natural benthic communities was completed. Thirdly, species richness and biodiversity data was analyzed through linear mixed-effects (LME) models to examine whether species richness on the seafloor beneath and adjacent to aquaculture sites could be explained using available variables (visual indicators, distance, depth, and fallow period when applicable. The results from this research help to inform the evaluation of the current regulatory indicators and thresholds used for benthic organic enrichment monitoring for finfish aquaculture located over hard bottom substrates in NL, as defined in the Aquaculture Activities Regulations.

Findings

Benthic organisms were generally sparse and patchy in distribution at hard bottom sites in Newfoundland. Sites had low natural taxa richness. The dominant groups were: anemones, coralline algae, brittle stars, and other algae. Groups such as coralline algae are unique and more sensitive to disturbance despite being located in areas classified as low productivity. Other habitats observed were kelps (e.g., Little Bay, NL) and sponges (e.g., Little Passage, NL). There was no obvious zonation in taxa present across depth differences. There was a significant reduction in the number of benthic taxa near the fish farm cage area. Presently, the effects of finfish aquaculture on benthic communities at hard bottom sites on the East Coast are assessed using visual indicators of organic enrichment, namely bacterial mats, opportunistic polychaetes, and/or barren substrates (i.e., with no visible epifauna). Video data collected for regulatory purposes before and after aquaculture production was used to document (1) change in epibenthic taxon richness (TR) and its discriminatory power in determining aquaculture impact and (2) the association between TR change and the presence of visual indicators. Decreases in TR were associated with visual indicator presence, validating the use of a suite of visual indicators to detect organic deposition. Importantly, visual indicators should be considered together in the context of regulation, given that relationships between TR and indicators were not linear when the latter are considered individually. Based on the results of this study, the Canadian Aquaculture Activities Regulations (2015) thresholds of 70 % of the locations visually detect OPC Beggiatoa or similar bacteria or barren substrate would likely correspond to a 100 % reduction in taxa richness. The usage of a suite of visual indicators instead of one should be assessed to homogenize approaches within the Canadian context for hard-bottom site regulatory approaches and thresholds.

Publications

Salvo F., Mersereau J., Hamoutene D., Belley R., Dufour S., 2017. Spatial and temporal changes in epibenthic communities at deep, hard bottom aquaculture sites in Newfoundland. Ecological Indicators, 76, 207-218.

Hamoutene D., Salvo F., Belley R., Lush L., Hendry C. and Marshall K. 2017. An evaluation of benthic monitoring baseline assessments completed as part of the regulatory requirements for aquaculture finfish site applications on the South Coast of Newfoundland. Can. Tech. Rep. Fish. Aquat. Sci. Fs97 6/3222E-PDF: v + 25 p.

Hamoutene D., Salvo F., Cross S., Dufour S., Donnet S. (2018) Linking the presence of visual indicators of aquaculture deposition to changes in epibenthic richness at finfish sites installed over hard bottom substrates. Environmental Monitoring and Assessment 190(12). DOI: 10.1007/s10661-018-7108-2

Salvo F., Marshall K., Hamoutene D., 2018. Mesocosm trials to determine survival of Ophryotrocha cyclops (Salvo, 2014) to different oxygen conditions. Ecological indicators 89: 572-575 https://doi.org/10.1016/j.ecolind.2018.02.025

Program Name

Program for Aquaculture Regulatory Research (PARR)

Year(s)

2016 to 2018

Principal Investigator

Dounia Hamoutene
Research Scientist, Northwest Atlantic Fisheries Centre
Email: Dounia.Hamoutene@dfo-mpo.gc.ca