Mariculture: significant and expanding cause of coastal nutrient enrichment

Abstract

Mariculture (marine aquaculture) generates nutrient waste either through the excretion by the reared organisms, or
\nthrough direct enrichment by, or remineralization of, externally applied feed inputs. Importantly, the waste from
\nfish or shellfish cannot easily be managed, as most is in dissolved form and released directly to the aquatic
\nenvironment. The release of dissolved and particulate nutrients by intensive mariculture results in increasing
\nnutrient loads (finfish and crustaceans), and changes in nutrient stoichiometry (all mariculture types). Based on
\ndifferent scenarios, we project that nutrients from mariculture will increase up to six fold by 2050 with exceedance
\nof the nutrient assimilative capacity in parts of the world where mariculture growth is already rapid. Increasing
\nnutrient loads and altered nutrient forms (increased availability of reduced relative to oxidized forms of nitrogen)
\nand/or stoichiometric proportions (altered nitrogen:phosphorus ratios) may promote an increase in harmful algal
\nblooms (HABs) either directly or via stimulation of algae on which mixotrophic HABs may feed. HABs can kill
\nor intoxicate the mariculture product with severe economic losses, and can increase risks to human health.