title: Micro-scale variability enhances trophic transfer and potentially sustains biodiversity in plankton ecosystems.
abstract: We develop moment closure approximations to represent micro-scale spatial variability in the concentrations of nutrients (N), phytoplankton (P) and zooplankton (Z) in an NPZ model, which we apply to examine the impact of different levels of micro-scale variability on both ecosystem dynamics and trophic transfer. Accounting explicitly for both the mean-field and fluctuating components of each prognostic variable in the NPZ model yields different dynamics for the mean-field concentrations, as well as lower phytoplankton biomass and greater zooplankton biomass, compared to the conventional NPZ model without micro-scale variability. The biomass of zooplankton consistently increases with increasing total micro-scale variability, and a minimum threshold of such variability is required for the existence of stable steady state solutions in the NPZ closure model. Compared to the conventional NPZ model, the domain of parameter space over which stable solutions exist is larger than for the NPZ closure model, and this stable domain widens with increasing total variability. The latter result suggests that natural systems with greater micro-scale variability may have the potential to sustain greater biodiversity. We find that with the NPZ closure model: (1) the stability domains increases with micro-scale variability, (2) increase of the level of total micro-scale variability enhances trophic transfer, i.e. increases the biomass of zooplankton, and (3) the coefficient of variation (CVP) of phytoplankton increases with micro-scale variability.
authors: Department of Ocean Sciences, Tokyo University of Marine Science and Technology, Minato-ku, Tokyo 108-8477, Japan; Department of Mathematics, Institute of Science, Banaras Hindu University, Varanasi 221005 India. Electronic address: anupam240@gmail.com.
authors: Anupam
authors: A
authors: Priyadarshi
authors: Department of Ocean Sciences, Tokyo University of Marine Science and Technology, Minato-ku, Tokyo 108-8477, Japan; Public Health Foundation of India, Delhi NCR 44, Gurgaon 122002, India. Electronic address: sandipccmb@gmail.com.
authors: Sandip
authors: S
authors: Mandal
authors: Marine Ecosystem Dynamics Research Group, Research and Development Centre for Global Change, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi, Kanazawa-ku, Yokohama 236-0001, Japan. Electronic address: lanimal@jamstec.go.jp.
authors: S Lan
authors: SL
authors: Smith
authors: Department of Ocean Sciences, Tokyo University of Marine Science and Technology, Minato-ku, Tokyo 108-8477, Japan. Electronic address: hide@kaiyodai.ac.jp.
authors: Hidekatsu
authors: H
authors: Yamazaki
mesh_terms: D044822:Biodiversity; D008954:Models, Biological; D010839:Phytoplankton / Q000502:physiology*
keywords: Coefficient of variation; Food chain; Intermittency; Spatial heterogeneity