Operation of light–dark cycles within simple ecosystem models of primary production and the consequences of using phytoplankton models with different abilities to assimilate N in darkness

• Published in: Journal of plankton research 2003-01, Vol.25 (1), p.83-92
• Main Authors: Flynn, Kevin J., Fasham, Michael J. R.
• Format: Article
• Language: English
• Subjects: Ammonium; Ammonium compounds; Animal and plant ecology; Animal, plant and microbial ecology; Bacillariophyceae; Biological and medical sciences; Competition; Diatoms; Dinophyta; Diurnal; Ecosystem models; Food organisms; Food webs; Fundamental and applied biological sciences. Psychology; Light; Phytoplankton; Predators; Primary production; Sea water ecosystems; Synecology; Temporal variations; Zooplankton
• ISSN: 0142-7873; 1464-3774; 1464-3774
• DOI: 10.1093/plankt/25.1.83

We compare the output of a nitrogen–phytoplankton–zooplankton (NPZ) model and of a hypothetical diatom–flagellate competition scenario operating in continuous light or in a diurnal light–dark cycle of equal daily photon dose. Within these models, phytoplankton were configured with contrasting abilities to assimilate nitrogen in darkness. If only a single phytoplankton group is being considered then it appears unnecessary to describe the diurnal light cycle. However, given the minimal additional processing time required to include the light cycle when running complex biological models, inclusion is recommended where model output is used to provide an insight into the behaviour of the organisms and food webs. This is particularly so for considering temporal variations in the use of ammonium and nitrate (pertaining to the f ratio for new production) by different phytoplankton groups and hence the interaction between these organisms and their zooplankton predators that regenerate ammonium. In that instance it is important to endow the phytoplankton model with a capacity for dark N assimilation commensurate with the type of organism (namely diatom or non-diatom) being considered. Such different capabilities likely affect competition and succession of these groups in nature and do affect these interactions in simulations.