Freshwater finfish cage aquaculture: Development of sediment biogeochemical indicators for regulation of freshwater cage aquaculture

Description

Benthic macroinvertebrates contribute to chemical and microbial in-sediment processes; they play a major role in waste assimilation (recycling waste) and in the transfer of carbon and energy from aquaculture wastes to higher trophic levels within lake ecosystems (i.e., they eat the waste and grow larger, thus becoming a bigger source of food for species higher up in the food chain). The deposition of biochemical oxygen demanding (BOD) matter (waste) from freshwater finfish cage farms directly impacts the abundance and diversity of benthic invertebrates found in the immediate vicinity of the cage. Assemblages of these invertebrates become dominated by species that are seemingly more tolerant of lower oxygen conditions created by the deposition of BOD matter. Preserving the function of benthic invertebrate communities is necessary given their role in organic carbon cycling near freshwater aquaculture farms. Benthic invertebrates are typically used as indicators of benthic condition; however, sample collection and taxonomic identification of the various species within a monitoring program framework are both time consuming and costly. The development of a reliable, readily measurable proxy for benthic invertebrate indicators would expedite the process of sediment monitoring. Such a proxy is contingent on a well-established relationship to the invertebrate community structure and requires testing across a range of locations to ensure cross-region applicability.

The objective of this project is to study the biogeochemistry of sediments receiving a gradient of aquaculture wastes, and to identify thresholds of geochemical changes in freshwater sediments that are associated with major changes in the structure of the invertebrate community. The project will describe the gradient of effects of organic carbon deposition on the biology and geochemistry of the freshwater benthic environment. Identifying biogeochemical thresholds associated with major changes in community abundance and structure will support the development of regulatory thresholds for managing the deposit of aquaculture wastes at levels that would maintain an acceptable degree of benthic alteration. This knowledge will support the assessment of risk associated with the deposits of BOD material, and will contribute to the development of regulatory standards and monitoring protocols for aquaculture-affected sediments, including fallowing practices for freshwater aquaculture, by identifying potential sediment recovery targets.

Findings

N/A

Publications

N/A

Multimedia

Our scientists – From coast to coast to coast – Megan Otu

Program Name

Program for Aquaculture Regulatory Research (PARR)

Year(s)

2014 - 2017

Ecoregion(s)

Central Canada: Lake Winnipeg, Nelson River Drainage Basin

Principal Investigator(s)

Cheryl Podemski
Research Scientist, Environmental Sciences Division, Freshwater Institute
501 University Crescent, Winnipeg, Manitoba
Email: Cheryl.Podemski@dfo-mpo.gc.ca

Team Member(s)

Megan Otu

Cyndi Wlasichuk

Jian Zhang

Doug Geiling