Benthic Dynamics
AquaModel now provides a detailed and comprehensive description of the fate of uneaten feed and fish feces deposited in the sediments beneath the farms.
Other models compute the amount of organic particulate waste reaching the sediments, but not the fate or concentration of total organic carbon or sulfide in the sediments as is the case with AquaModel. Other models do not have a functional resuspension module to allow waste particles to be tracked and assimilated as they move across the sea bottom with higher water current velocity, an important feature of many well sited fish farms.
AquaModel:
- Provides separate tracking of waste feed and waste fish fecal materials with adjustable coefficients for settling rates, deposition speeds, resuspension speeds and oxidation rates
- Tracks changes in the relative abundance of aerobic and anaerobic organisms
- Tracks the remineralization of waste carbon by anaerobic organisms that respire sulfate rather than oxygen
- Tracks the production of hydrogen sulfide by the anaerobes
A portion of hydrogen sulfide in seawater is toxic, and is a key indicator of excess loading by farms. Along with sediment total organic carbon content or rate of deposition, it is commonly used to monitor fish farm environmental compliance.
The development of the benthic routine is an important accomplishment of this project. The benthic routine addresses the question of whether the deposition of organic waste in the vicinity of the farm will adversely influence the taxonomic composition and abundance of the benthic invertebrate community and the fluxes of oxygen and hydrogen sulfide between the sediments and overlying waters.
The physical processes of the routine consist of the transport of fish feces and uneaten feed to the bottom as well as their deposition and consolidation. The bio-chemical processes consist of the growth of aerobic and anaerobic taxa of the benthic community as determined by the rates of organic deposition beneath the pens. Growth of these communities will increase the demand for oxygen which could potentially result in the production of hydrogen sulfide if too much organic carbon containing waste is confined to a given area.
AquaModel’s benthic dynamics results have been compared to monitoring results and published studies and were found to accurately describe the extent and intensity of sea bottom effects.