title: 15N tracer application to evaluate nitrogen dynamics of food webs in two subtropical small-scale aquaculture ponds under different managements.
abstract: Small, semi-intensively managed aquaculture ponds contribute significantly to the food security of small-scale farmers around the world. However, little is known about nutrient flows within natural food webs in such ponds in which fish production depends on the productivity of natural food resources. (15)N was applied as ammonium at 1.1 and 0.4 % of total nitrogen in a traditionally managed flow-through pond and a semi-intensively managed stagnant pond belonging to small-scale farmers in Northern Vietnam and traced through the natural food resources over 7 days. Small-sized plankton (1-60 μ m) was the dominant pelagic biomass in both ponds with higher biomass in the stagnant pond. This plankton assimilated major portions of the applied tracer and showed a high sedimentation and turnover rate. High re-activation of settled nutrients into the pelagic food web was observed. The tracer was removed more quickly from the flow-through pond than from the stagnant pond. A steady nutrient supply could increase fish production.
authors.affiliation: a Institute of Aquaculture Systems and Animal Nutrition in the Tropics and Subtropics (480B) , University of Hohenheim , Stuttgart , Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Pucher
authors.forename: Richard
authors.initials: R
authors.lastname: Mayrhofer
authors.forename: Mansour
authors.initials: M
authors.lastname: El-Matbouli
authors.forename: Ulfert
authors.initials: U
authors.lastname: Focken
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism*; D017756:Aquaculture / Q000379:methods*; D018533:Biomass; D004784:Environmental Monitoring / Q000379:methods*; D020387:Food Chain; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000378:metabolism; D010933:Plankton / Q000737:chemistry; D061005:Ponds / Q000032:analysis*; D014329:Tropical Climate; D014744:Vietnam
chemical_list: D064751:Ammonium Compounds; D009587:Nitrogen Isotopes; D009584:Nitrogen
keywords: food web; natural food resource; nitrogen-15; semi-intensive aquaculture; stable isotope tracer technique