The Haber Bosch-harmful algal bloom (HB-HAB) link

Large-scale commercialization of the Haber–Bosch (HB) process is resulting in intensification of nitrogen (N) fertilizer use worldwide. Globally N fertilizer use is far outpacing that of phosphorus (P) fertilizer. Much of the increase in N fertilizers is also now in the form of urea, a reduced form of N. Incorporation of these fertilizers into agricultural products is inefficient leading to significant environmental pollution and aquatic eutrophication. Of particular concern is the increased occurrence of harmful algal blooms (HABs) in waters receiving nutrient enriched runoff. Many phytoplankton causing HABs have physiological adaptive strategies that make them favored under conditions of elevated N : P conditions and supply of chemically reduced N (ammonium, urea). We propose that the HB-HAB link is a function of (1) the inefficiency of incorporation of N fertilizers in the food supply chain, the leakiness of the N cycle from crop to table, and the fate of lost N relative to P to the environment; and (2) adaptive physiology of many HABs to thrive in environments in which there is excess N relative to classic nutrient stoichiometric proportions and where chemically reduced forms of N dominate. The rate of HAB expansion is particularly pronounced in China where N fertilizer use has escalated very rapidly, where soil retention is declining, and where blooms have had large economic and ecological impacts. There, in addition to increased use of urea and high N : P based fertilizers overall, escalating aquaculture production adds to the availability of reduced forms of N, as does atmospheric deposition of ammonia. HABs in both freshwaters and marginal seas in China are highly related to these overall changing N loads and ratios. Without more aggressive N control the future outlook in terms of HABs is likely to include more events, more often, and they may also be more toxic

The Haber Bosch-harmful algal bloom (HB-HAB) link

Large-scale commercialization of the Haber–Bosch (HB) process is resulting in intensification of nitrogen (N) fertilizer use worldwide. Globally N fertilizer use is far outpacing that of phosphorus (P) fertilizer. Much of the increase in N fertilizers is also now in the form of urea, a reduced form of N. Incorporation of these fertilizers into agricultural products is inefficient leading to significant environmental pollution and aquatic eutrophication. Of particular concern is the increased occurrence of harmful algal blooms (HABs) in waters receiving nutrient enriched runoff. Many phytoplankton causing HABs have physiological adaptive strategies that make them favored under conditions of elevated N : P conditions and supply of chemically reduced N (ammonium, urea). We propose that the HB-HAB link is a function of (1) the inefficiency of incorporation of N fertilizers in the food supply chain, the leakiness of the N cycle from crop to table, and the fate of lost N relative to P to the environment; and (2) adaptive physiology of many HABs to thrive in environments in which there is excess N relative to classic nutrient stoichiometric proportions and where chemically reduced forms of N dominate. The rate of HAB expansion is particularly pronounced in China where N fertilizer use has escalated very rapidly, where soil retention is declining, and where blooms have had large economic and ecological impacts. There, in addition to increased use of urea and high N : P based fertilizers overall, escalating aquaculture production adds to the availability of reduced forms of N, as does atmospheric deposition of ammonia. HABs in both freshwaters and marginal seas in China are highly related to these overall changing N loads and ratios. Without more aggressive N control the future outlook in terms of HABs is likely to include more events, more often, and they may also be more toxic

Hindcasts and future projections of global inland and coastal nitrogen and phosphorus loads due to finfish aquaculture

A global model is used to calculate feed and nutrient budgets for freshwater and marine omnivorous and carnivorous aquacultural finfish production. The model uses national production data for the period 1970–2010 and the Millennium Ecosystem Assessment scenarios for production and management for 2010–2050. Results indicate that annual nutrient release to the freshwater (1.2 million tonnes of N and 0.1 million tonnes of P in 2010) and marine aquatic environments (0.3 million tonnes of N and 0.05 million tonnes of P) increased less rapidly than fish production, mainly due to improving feed conversion. In the coming five decades, annual nutrient release to freshwater environments may increase to 1.5–2.1 million tonnes of N and 0.1–0.2 million tonnes of P, depending on the production scenario and assumptions on feed conversion and the share of integrated aquacultural production. At present, the global contribution of freshwater aquaculture to nutrient loading of rivers is small. This is the same conclusion reached for the assessment of nutrient export from shellfish aquaculture (Bouwman et al., 2011). However, particularly in Asia, nutrient loading from freshwater fish production and from seaweed and shellfish production is an important factor that should be accounted for when developing models for estimating river nutrient export. Compared to chicken meat and egg production, freshwater aquaculture is a rapidly growing and important cause of the anthropogenic acceleration of the N and P cycles in many parts of the world, and this is especially pronounced in Asia