The Rings of Power: managing nutrient cycles in aquatic food webs above and beyond primary producers

Abstract. Global nutrient cycles (biogeochemical flows of nitrogen and phosphorus; N, P) are at a tipping point. In aquatic systems, natural food webs facilitate nutrient digestion and decomposition, but nutrient assimilation is poor. The current approach to understanding and managing nutrient cycles in aquatic systems needs to integrate animal nutritionist thinking. It is not the supply or stoichiometry of elements (carbon (C), N, P) in the food web but the supply and stoichiometry of specific biomolecular packages in which they come (aka Rings of Power) that decides the state of nutrient cycles (slow/fast, low/high) in all trophic levels above primary producers. Animal nutritionists often maximize N and P retention efficiency in animal production systems by expanding the scope of homeostatic control of nutrient deposition in animals. By spiking specific biomolecular packages in the diet (e.g., Rings of Power, such as specific amino acids, lipid classes, carbohydrate subfractions like starch), it is possible to alleviate energy–nutrient transfer barriers from food to biomass. Under the influence of “Rings of Power”, free N and P excretion is minimized and protein (N-bound), phospholipid, and apatite-rich (P-bound) biomass is maximized. Combining such expertise with food web (plankton) ecology, we can develop nature-based, regenerative aquaculture solutions in hypertrophic inland standing waterbodies (which accumulate nutrients) to slow down N and P cycles by curbing the metabolic N and P throughput of consumer communities (omnivorous fish, zooplankton) and suppress eutrophication.