Nutrient discharge from aquaculture operations in function of system design and production environment
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Date
2012-09
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Publisher
Wiley Publishing Asia Pty Ltd
Abstract
In aquaculture, nutrient loading is defined as the difference between nutrients
supplied with fertilizers and feed and nutrients harvested in the form of finfish,
crustaceans, molluscs and seaweeds. On average, the production of finfish and
crustaceans results in a net nutrient loading, while for the production of molluscs
and seaweeds the nutrient loading is negative. In marine and brackish water aquaculture,
on a global scale, more nutrients are extracted than added to the environment.
However, in freshwater, more nutrients are loaded than extracted. In 2008,
the global aquaculture production of finfish and crustaceans resulted in an environmental
loading of 1.7 million metric tonnes of nitrogen (N) and 0.46 million
metric tonnes of phosphorus (P). This nitrogen loading represents 0.9% of the
human input to the N-cycle and 0.4% of the global N-cycle. For phosphorus, the
loading from finfish and crustacean aquaculture represents 2.3% of the global
annual fertilizer supply. With cage aquaculture, nutrients are directly discharged
to the environment. Mitigation measures should be shared equally between all
polluters involved. For land-based aquaculture, the development of water re-use
systems is still in its infancy. Although still a minor contributor to global aquaculture
production, recirculation technology shows that control and mitigation of
pollution from aquaculture is possible. A 15–20 year goal should be to have all
inland aquaculture operations applying water re-use and purification technology
and generating useful (waste) outputs in addition to standard aquaculture
products.
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Keywords
nitrogen, nutrient budgets, nutrient loading, phosphorus, recirculating aquaculture systems