Population dynamics theory of plankton based on biomass spectra (original) (raw)

Non-linear dynamics in marine-phytoplankton population systems

Marine Ecology Progress Series, 2004

Although non-linear density-dependence has been widely emphasized in population dynamics studies, the existence of non-linear exogenous forces have been less explored. In particular, we propose that the formulation of population dynamics models that include both non-linear endogenous (i.e. feedback structure) and exogenous (e.g. climatic) responses is relevant for understanding how climate variability affects natural systems. Here we show that single-species non-linear logistic models for marine phytoplankton in combination with non-linear exogenous forces capture observed population oscillations very well. Our results suggest that general population dynamic theory represents a useful tool for understanding the natural fluctuations of phytoplankton populations. Altogether we document what might be called a switch-on/switch-off dynamics in the phytoplankton population dynamics in relation to climate variability. We suggest the importance of, and the need for, linking population dynamics processes at local and regional scales to processes at the ecosystem level, thus reflecting a macroecological perspective of marine pelagic systems.

Biomass dynamics of the phytoplankton under impact of the nutrient

Procedia Environmental Sciences, 2012

The phytoplankton production is a basis for a life activity of all species in every aquatic ecological system. Remote sounding methods make it possible to estimate chlorophyll concentration on the ocean surface. The data from remote sounding methods and the data of a nutrient concentration enable us to calculate and model the phytoplankton abundance. These calculations provide a possibility for the description of the phytoplankton production processes. We present here some models for the dynamics of the phytoplankton biomass. The qualitative properties of the solutions of these models are investigated. Strategically activities of the cell are defined by its internal state and by the environmental conditions. The state of the cell depends on nutrients. Our mathematical models describe the abundance dynamics for phytoplankton's community and dynamics of the cellular nutrients content. The models are based on the systems of differential equations. These models may be open or closed relative to the matter. The open models describe the chemostat processes. We investigate the property of the solutions of these models. The closed models have a infinite set of the positive solutions. The open models have a finite set of the non-negative solutions. The algorithm for finding the stable equilibrium solutions in open models is constructed. The theorems about the stable equilibrium solutions are proved with help the methods of structural analysis. These models describe the phytoplankton dynamics in the Black Sea.

Bottom–up and top–down forcing in a simple size-structured plankton dynamics model

Journal of Marine Systems, 2008

A size-structured plankton dynamics model is developed and used to explore the effects of variations in bottom-up and top-down forcing upon the biomass spectrum, size-structured patterns in primary production, and the flux of energy from primary producers to fish. Parameters and mechanisms controlling the steady-state model response to bottom-up forcing via nutrient enrichment and top-down forcing via fluctuations in planktivorous fish are first diagnosed. Results are then compared with mean observed biomass spectra from three ecosystems spanning a broad range of productivity. Solutions using parameters within empirical ranges can recreate trends in the biomass spectrum across these systems. The zooplankton gross growth efficiency is critical for matching the steady-state slopes of the spectra. Variability in export sources and zooplankton half-saturation constants both provide ways of matching the mean biomass. Results support the model's potential to provide mechanistic insights and testable quantitative hypotheses for the dynamics underlying observed biomass spectra.

Mathematical analysis of plankton population dynamics

Malaysian Journal of Fundamental and Applied Sciences

Harmful algal blooms (HABs) event that causes enormous economic loss and health effect raises concerns among environmentalists. In this paper, a mathematical model of interaction between nutrient, toxin-producing phytoplankton (TPP), non-toxic phytoplankton (NTP), zooplankton, and toxic chemicals is proposed to study on how the process of these HABs occurred. The model of interaction is represented by Ordinary Differential Equations (ODEs) and stability analysis of the model is conducted. Several conditions for the system to be stable around trivial and interior equilibrium point are obtained. From the analysis, it is observed that under nutrient limitation, the amounts of toxic chemicals secreted out by the TPP are increased. As a result, NTP population and zooplankton population are affected by the situation. If this situation is prolonged, this will result in the extinction of both populations. Overall, this study shows that TPP release more toxic chemicals when the nutrient is l...

On a cell-growth model for plankton

Mathematical Medicine and Biology, 2004

The frequency distribution of diatoms (microscopic unicellular alga with silicified cellwalls, found as plankton) is shown to evolve in time as a steady-size distribution with constant shape, scaled by time. This distribution is preserved when the division occurs at a fixed size into two daughter cells of half-size. In cases where the parameters for growth, division frequency, dispersion and mortality are constants, the frequency distributions can be found explicitly and thus provide a benchmark for computations in more complex cases.

Perturbation Effects on Biomass of Higher Trophic-Level in Planktonic Ecosystems

2021

Perturbations are well known for change in qualitative behavior of physical / bio-physical systems. Plankton systems are more vulnerable to perturbations due to rich diversity in their size, mass and traits-affinity. Phytoplankton biomass productions depends upon various factors such as nutrient uptake, excretions, mortality, mineralization and recycling processes of nutrients. In this study, we investigate dynamics of the basic compartment models consisting of nutrient (N), phytoplankton (P) and detritus (D) and we observe how perturbations change their dynamics and ecological balance. From our analysis, we observed that perturbations / heterogeneity enhance phytoplankton biomass and support coexistence in plankton ecosystems. A measurable quantity called coefficient of variation of phytoplankton (CVp) which is the ratio of standard deviation and mean of phytoplankton increases with perturbations / heterogeneity. The robust pattern of CVp and biomass with varying level of perturbat...

Density estimation of plankton size spectra: a reanalysis of IronEx II data

Journal of Plankton …, 2010

Many critical processes of ecosystem function, including trophic relationships between predators and prey and maximum rates of photosynthesis and growth, are size-dependent. Size spectral data are therefore precious to modellers because they can constrain model predictions of size-dependent processes. Here we illustrate a multi-step statistical approach to create size spectra based on a reanalysis of plankton size data from the IronEx II experiment, where iron was added to a marked patch of water and changes in productivity and community structure were followed. First, bootstrapping was applied to resample original size measurements and cell counts. Kernel density estimation was then used to provide nonparametric descriptions of density versus size. Finally, parametric distributions were used to obtain parameter estimates that can more easily be applied in models. A major advantage of this approach is that it provides confidence envelopes for the density distributions. Our analyses suggest three basic distributional patterns of cell concentration versus logarithm of equivalent spherical diameter for individual taxa. Composite size-densities of heterotrophs and photoautotrophs reveal important aspects of the coupling between protist grazing and the phytoplankton community.