Understanding the Biogeochemical Impacts of Fish Farms Using a Benthic-Pelagic Model

Abstract

Sustainable development of the salmon farming industry requires knowledge of the biogeochemical impacts of fish farm emissions. To investigate the spatial and temporal scales of farm impacts on the water column and benthic biogeochemistry, we coupled the C-N-P-Si-O-S-Mn-Fe transformation model BROM with a 2-dimensional benthic-pelagic transport model (2DBP), considering vertical and horizontal transport in the water and upper 5 cm of sediments along a 10 km transect centered on a fish farm. The 2DBP model was forced by hydrophysical model data for the Hardangerfjord in western Norway. Model simulations showed reasonable agreement with field data from the Hardangerfjord in August 2016 (correlations between the model and observations were significant for most variables, and model biases were mostly <35%). The model predicted significant impacts on seafloor biogeochemistry up to 1 km from the fish farm (e.g., increased organic matter in sediments, oxygen depletion in bottom water and sediments, denitrification, metal and sulfur reduction), as well as detectable decreases in oxygen and increases in ammonium, phosphate and organic matter in the surface water near to the fish farm.

Reduced physiological performance in a free-living coralline alga induced by salmon faeces deposition

“…Deposition rates up to 70 g DW m −2 d −1 were measured in the vicinity of a farm in a shallow location, with high production levels (Keeley et al 2019). A severe im pact of intensive production farms is generally associated with poor currents and water circulation, which may drastically damage benthic ecosystems due to the lack of oxygen in the sediment (Soto & Norambuena 2004, Yakushev et al 2020). The protection of vulnerable ecosystems is of major concern and farms are now monitored regularly to assess their impacts on the surrounding environment.…”

Mathematical Modeling of the Phytoplankton Populations Geographic Dynamics for Possible Scenarios of Changes in the Azov Sea Hydrological Regime

“…The three-dimensional mathematical model of biogeochemical cycles, combined with the model of hydrodynamics, used in this work, makes it possible to predict the spatialtemporal dynamics of the main phytoplankton populations more accurately compared to the two-dimensional models discussed above [12,13,15,16], taking into account the changing hydrological regime, their consumption of nutrients, the transition of nutrients from one form to another. In contrast to the two-dimensional model used in [14], the three-dimensional model of hydrodynamics makes it possible to more accurately model wave processes under conditions of a complex, dynamically changing the geometry of the reservoir, friction on the bottom and wind stress on the free surface, turbulent and advective heat and mass transfer in three coordinate directions, Coriolis forces, river flows, precipitation and evaporation, heat and salt transportation.…”

“…Biogeochemical processes in marine ecosystems are modeled by Norwegian scientists together with Russian researchers. Therefore, in work [15], the complex of C-N-P-Si-O-S-Mn-Fe transformation model BROM and the 2-dimensional benthic-pelagic transport model (2DBP) were applied to analyze the impact of salmon farms on the water column and benthic biogeochemistry. Hydrophysical model data for the Hardangerfjord in western Norway were applied for the 2DBP model.…”

Insight into real-world complexities is required to enable effective response from the aquaculture sector to climate change

“…Many Norwegian salmon farms are located in fjords, and studies have shown that warming is leading to reduced oxygen levels in some areas [55]. Deoxygenation can reduce assimilative capacity [55,116]. Precipitation and runoff will contribute organic matter to the fjord or coastal environment and the associated microbial activity could affect overall assimilative capacity of the environment [117].…”