The salmon aquaculture industry in Scotland has long fought against the suggestion that phosphorus and nitrogen containing compounds excreted by salmon, indeed all animals, act as nutrients in the growth of phytoplankton in marine ecosystems. These, in turn, can result in what are called plankton or harmful algae blooms.
These can be of sufficient magnitude to rob seawater of its oxygen content and some, particularly zooplankton, which in succession feeds off the micro-plants (phytoplankton), can be specifically toxic to other organisms including humans. The so-called red tide is a manifestation of this.
A recent scientific report undertaken by Australia’s Environment Protection Authority (EPA, Tasmania) related to continuing concerns of the deterioration in water quality at Long Bay, Tasmania concluded “It is clear that some indicators respond to the presence of nutrients from the finfish lease and that the spatial extent and degree of response reduces within weeks of the lease becoming fallow. These findings suggest that the phytoplankton biomass is in part coupled with the status of nutrients released from the lease and surrounding environment.”
This is of particular relevance to Loch Long and aquaculture development in its headwaters at Bienn Reithe, as there is no intention to contain these nutrient pollutants and any flushing action aiding dispersal is limited.