Growth of the diatom Chaetoceros calcitrans in sediment extracts from Artemia franciscana ponds at different concentrations of nitrogen and phosphorus

This study was carried out with the aim to optimize the growth of the diatom Chaetoceros calcitrans (C. calcitrans) to feed Artemia franciscana. This is based on management of both quantities and ratios of nutrients dissolved in the water column, especially nitrogen (N) and phosphorus (P). To this end, algae were inoculated in media prepared from the extracts of Artemia pond sediments to relate their growth with the availability of N and P present in these extracts. Algal responses to different levels of dissolved inorganic nitrogen (DIN), dissolved reactive phosphorus (DRP) and to widely varying DIN:DRP ratios in the water column were examined by adding inorganic N (6.6–76 mg N L− 1) and P (0.01–0.2 mg P L− 1) to the media at different combinations. In all media, inoculation of algae at a density of 50 × 103 cells mL− 1 resulted in an exhaustion of DRP after five days. Adding inorganic P to the media stimulated algae to assimilate more N and increased algal densities (R2 = 0.70, P < 0.001) and biomass (R2 = 0.68, P < 0.001). In contrast, adding inorganic N decreased algal production. The densities of algae decreased logarithmically when DIN:DRP ratios increased from 50 to 910. Below DIN:DRP 150, the densities and biomass of algae were strongly dependent on the initial concentrations of DRP. When DIN:DRP ratios exceed 150, algal densities and biomass were constantly low, regardless the availability of DRP. In these media, supplying DRP to reach concentrations above 0.06 mg P L− 1, while maintaining DIN:DRP below 150, is suitable for the growth of C. calcitrans.