Aquaculture Production is a Large, Spatially Concentrated Source of Nutrients in Chinese Freshwater and Coastal Seas

As Chinese aquaculture production accounts for over half
of the
global aquaculture production and has increased by 50% since 2006,
there is growing concern about eutrophication caused by aquaculture
in China. This paper presents a model-based estimate of nutrient flows
in China’s aquaculture system during 2006–2017 using
provincial scale data, to spatially distribute nutrient loads with
a 0.5° resolution. The results indicate that with the increase
in fish and shellfish production from 30 to 47 million tonnes (Mt)
during 2006–2017, the nitrogen (N) release increased from 1.0
to 1.6 Mt/year and that of phosphorus (P) from 0.1 to 0.2 Mt/year.
Nutrient release from freshwater aquaculture was concentrated in Guangdong,
Jiangsu, and Hubei, and that from mariculture in Shandong, Fujian,
and Guangdong. Aquaculture is an important strongly concentrated nutrient
source in both freshwater and marine environments. Its nutrient release
is >20% of total nutrient inputs to freshwater environments in
some
provinces, and nutrients from mariculture are comparable to river
nutrient export to Chinese coastal seas. Aquaculture production and
nutrient excretions are now comparable to those of livestock production
systems in China and need to be accounted for when analyzing causes
of eutrophication and harmful algal blooms and possible mitigation
strategies.