46.1C: Studying Ecosystem Dynamics - Biology

46.1C: Studying Ecosystem Dynamics - Biology

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Many different models are used to study ecosystem dynamics, including holistic, experimental, conceptual, analytical, and simulation models.

Learning Objectives

  • Differentiate between conceptual, analytical, and simulation models of ecosystem dynamics, and mesocosm and microcosm research studies

Key Points

  • A holistic ecosystem model quantifies the dynamics of an entire ecosystem.
  • Scientists can use experimental systems, such as a microcosms or mesocosms, to study ecosystems under controlled laboratory conditions.
  • A conceptual model uses flow charts to show the interactions between living and nonliving components of the ecosystem.
  • An analytical model uses simple mathematical formulas to predict the effects of environmental disturbances on an ecosystem’s structure and dynamics.
  • A simulation model predicts the effects of environmental disturbances using complex computer algorithms; they are usually fairly-reliable predictors.

Key Terms

  • mesocosm: a small portion of the natural environment that is brought under controlled conditions for experimental purposes
  • microcosm: an artificial, simplified ecosystem that is used to simulate and predict the behaviour of natural ecosystems under controlled conditions

Research into Ecosystem Dynamics: Ecosystem Experimentation and Modeling

Ecosystem dynamics is the study of the changes in ecosystem structure caused by environmental disturbances or by internal forces. Various research methodologies measure ecosystem dynamics. Some ecologists study ecosystems using controlled experimental systems, while some study entire ecosystems in their natural state; others use both approaches.

Holistic Ecosystem Model

A holistic ecosystem model attempts to quantify the composition, interaction, and dynamics of entire ecosystems. A food web is an example of a holistic ecosystem model, which is the most representative of the ecosystem in its natural state. However, this type of study is limited by time and expense, as well as its limited feasibility to conduct experiments on large natural ecosystems.

Experimental Systems

For these reasons, scientists study ecosystems under more controlled conditions. Experimental systems usually involve either partitioning a part of a natural ecosystem that can be used for experiments, termed a mesocosm, or by re-creating an ecosystem entirely in an indoor or outdoor laboratory environment, which is referred to as a microcosm. A major limitation to these approaches is that removing individual organisms from their natural ecosystem or altering a natural ecosystem through partitioning may change the dynamics of the ecosystem. These changes are often due to differences in species numbers and diversity, but also to environment alterations caused by partitioning (mesocosm) or re-creating (microcosm) the natural habitat. Thus, these types of experiments are not totally predictive of changes that would occur in the ecosystem from which they were gathered.

As both of these approaches have their limitations, some ecologists suggest that results from these experimental systems should be used only in conjunction with holistic ecosystem studies to obtain the most representative data about ecosystem structure, function, and dynamics.

Ecosystem Models

Scientists use the data generated by these experimental studies to develop ecosystem models that demonstrate the structure and dynamics of ecosystems. Three basic types of ecosystem modeling are routinely used in research and ecosystem management: conceptual models, analytical models, and simulation models.

A conceptual model consists of flow charts to show interactions of different compartments of the living and nonliving components of the ecosystem. A conceptual model describes ecosystem structure and dynamics and shows how environmental disturbances affect the ecosystem, although its ability to predict the effects of these disturbances is limited.

Analytical and simulation models are mathematical methods of describing ecosystems that are capable of predicting the effects of potential environmental changes without direct experimentation, although with limitations in accuracy. An analytical model is created using simple mathematical formulas to predict the effects of environmental disturbances on ecosystem structure and dynamics.

A simulation model is created using complex computer algorithms to holistically model ecosystems and to predict the effects of environmental disturbances on ecosystem structure and dynamics. Ideally, these models are accurate enough to determine which components of the ecosystem are particularly sensitive to disturbances. They can serve as a guide to ecosystem managers (such as conservation ecologists or fisheries biologists) in the practical maintenance of ecosystem health.

Modelling approaches for studying the microbiome

Advances in metagenome sequencing of the human microbiome have provided a plethora of new insights and revealed a close association of this complex ecosystem with a range of human diseases. However, there is little knowledge about how the different members of the microbial community interact with each other and with the host, and we lack basic mechanistic understanding of these interactions related to health and disease. Mathematical modelling has been demonstrated to be highly advantageous for gaining insights into the dynamics and interactions of complex systems and in recent years, several modelling approaches have been proposed to enhance our understanding of the microbiome. Here, we review the latest developments and current approaches, and highlight how different modelling strategies have been applied to unravel the highly dynamic nature of the human microbiome. Furthermore, we discuss present limitations of different modelling strategies and provide a perspective of how modelling can advance understanding and offer new treatment routes to impact human health.

Georgia Institute of Technology School of Biological Sciences | Georgia Institute of Technology | Atlanta, GA | Georgia Institute of Technology | Atlanta, GA

The inaugural class of Brook Byers Institute for Sustainable Systems (BBISS) Graduate Research Assistant (GRA) Scholars was recently selected for a 2-year program of working, studying, and training as an interdisciplinary sustainability research team.

Alberto Stolfi is teaming up with Shu Jia to link novel biological discovery with transformative imaging technology. Liang Han and Costas Arvanitis will explore sound, vibration, and cell membrane proteins to develop noninvasive neuroscience tools.

New Georgia Tech research finds that elephants dilate their nostrils in order to create more space in their trunks, allowing them to store up to 5.5 liters of water. They can also suck up three liters per second — a speed 30 times faster than a human.

Synthetic biology: Engineered stable ecosystems

Co-culture of bacterial cells engineered with quorum-sensing and self-lysis circuits allows coupled oscillatory dynamics and stable states, opening the way to engineered microbial ecosystems with targeted dynamics and extending gene circuits to the ecosystem level.

Microbial ecosystems are characterized by cooperative interactions among species, where changes in the population of one species can affect the others in positive and negative ways. One important interaction is competition for a common essential nutrient, where the competitive exclusion principle, also known as Gause's law, states that there is no coexistence steady state. Microbial populations are also subject to this law, leading to difficulty in maintaining stable co-culture of desired strains. However, coexistence can occur if additional ecological interactions produce temporal oscillations, for instance, in predator–prey dynamics 1 . In this case, it is desirable to first attain the steady state of one culture while maintaining the presence of other species. In this issue of Nature Microbiology, Scott et al. 2 use synthetic biology techniques to engineer an orthogonal population control system with no unintended cross-talk for two strains of Salmonella, which allows for coupled oscillatory behaviour and long-term co-culture of two populations at steady state.

Integrating movement ecology with biodiversity research - exploring new avenues to address spatiotemporal biodiversity dynamics

Movement of organisms is one of the key mechanisms shaping biodiversity, e.g. the distribution of genes, individuals and species in space and time. Recent technological and conceptual advances have improved our ability to assess the causes and consequences of individual movement, and led to the emergence of the new field of 'movement ecology'. Here, we outline how movement ecology can contribute to the broad field of biodiversity research, i.e. the study of processes and patterns of life among and across different scales, from genes to ecosystems, and we propose a conceptual framework linking these hitherto largely separated fields of research. Our framework builds on the concept of movement ecology for individuals, and demonstrates its importance for linking individual organismal movement with biodiversity. First, organismal movements can provide 'mobile links' between habitats or ecosystems, thereby connecting resources, genes, and processes among otherwise separate locations. Understanding these mobile links and their impact on biodiversity will be facilitated by movement ecology, because mobile links can be created by different modes of movement (i.e., foraging, dispersal, migration) that relate to different spatiotemporal scales and have differential effects on biodiversity. Second, organismal movements can also mediate coexistence in communities, through 'equalizing' and 'stabilizing' mechanisms. This novel integrated framework provides a conceptual starting point for a better understanding of biodiversity dynamics in light of individual movement and space-use behavior across spatiotemporal scales. By illustrating this framework with examples, we argue that the integration of movement ecology and biodiversity research will also enhance our ability to conserve diversity at the genetic, species, and ecosystem levels.

Keywords: Biodiversity conservation Community dynamics Individual based modeling Landscape genetics Long distance movement Mobile links Species coexistence.

Ecosystem: It&rsquos Structure and Functions (With Diagram)

An organism is always in the state of perfect balance with the environment. The environment literally means the surroundings.

The environment refers to the things and conditions around the organisms which directly or indirectly influence the life and development of the organisms and their populations.

“Ecosystem is a complex in which habitat, plants and animals are considered as one interesting unit, the materials and energy of one passing in and out of the others” – Woodbury.

Organisms and environment are two non-separable factors. Organisms interact with each other and also with the physical conditions that are present in their habitats.

“The organisms and the physical features of the habitat form an ecological complex or more briefly an ecosystem.” (Clarke, 1954).

The concept of ecosystem was first put forth by A.G. Tansley (1935). Ecosystem is the major ecological unit. It has both structure and functions. The structure is related to species diversity. The more complex is the structure the greater is the diversity of the species in the ecosystem. The functions of ecosystem are related to the flow of energy and cycling of materials through structural components of the ecosystem.

According to Woodbury (1954), ecosystem is a complex in which habitat, plants and animals are considered as one interesting unit, the materials and energy of one passing in and out of the others.

According to E.P. Odum, the ecosystem is the basic functional unit of organisms and their environment interacting with each other and with their own components. An ecosystem may be conceived and studied in the habitats of various sizes, e.g., one square metre of grassland, a pool, a large lake, a large tract of forest, balanced aquarium, a certain area of river and ocean.

All the ecosystems of the earth are connected to one another, e.g., river ecosystem is connected with the ecosystem of ocean, and a small ecosystem of dead logs is a part of large ecosystem of a forest. A complete self-sufficient ecosystem is rarely found in nature but situations approaching self-sufficiency may occur.

Structure of Ecosystem:

The structure of an ecosystem is basically a description of the organisms and physical features of environment including the amount and distribution of nutrients in a particular habitat. It also provides information regarding the range of climatic conditions prevailing in the area.

From the structure point of view, all ecosystems consist of the following basic components:

1. Abiotic Components:

Ecological relationships are manifested in physicochemical environment. Abiotic component of ecosystem includes basic inorganic elements and compounds, such as soil, water, oxygen, calcium carbonates, phosphates and a variety of organic compounds (by-products of organic activities or death).

It also includes such physical factors and ingredients as moisture, wind currents and solar radiation. Radiant energy of sun is the only significant energy source for any ecosystem. The amount of non-living components, such as carbon, phosphorus, nitrogen, etc. that are present at any given time is known as standing state or standing quantity.

2. Biotic Components:

The biotic components include all living organisms present in the environmental system.

From nutrition point of view, the biotic components can be grouped into two basic components:

(i) Autotrophic components, and

(ii) Heterotrophic components

The autotrophic components include all green plants which fix the radiant energy of sun and manufacture food from inorganic substances. The heterotrophic components include non-green plants and all animals which take food from autotrophs.

So biotic components of an ecosystem can be described under the following three heads:

1. Producers (Autotrophic components),

3. Decomposers or reducers and transformers

The amount of biomass at any time in an ecosystem is known as standing crop which is usually expressed as fresh weight, dry weight or as free energy in terms of calories/metre.

Producers (Autotrophic elements):

The producers are the autotrophic elements—chiefly green plants. They use radiant energy of sun in photosynthetic process whereby carbon dioxide is assimilated and the light energy is converted into chemical energy. The chemical energy is actually locked up in the energy rich carbon compounds. Oxygen is evolved as by-product in the photosynthesis.

This is used in respiration by all living things. Algae and other hydrophytes of a pond, grasses of the field, trees of the forests are examples of producers. Chemosynthetic bacteria and carotenoid bearing purple bacteria that also assimilate CO2 with the energy of sunlight but only in the presence of organic compounds also belong to this category.

The term producer is misleading one because in an energy context, producers produce carbohydrate and not energy. Since they convert or transduce the radiant energy into chemical form, E.J. Kormondy suggests better alternative terms ‘converters’ or ‘transducers’. Because of wide use the term producer is still retained.

Those living members of ecosystem which consume the food synthesized by producers are called consumers. Under this category are included all kinds of animals that are found in an ecosystem.

There are different classes or categories of consumers, such as:

(a) Consumers of the first order or primary consumers,

(b) Consumers of the second order or secondary consumers,

(c) Consumers of the third order or tertiary consumers, and

(d) Parasites, scavengers and saprobes.

These are purely herbivorous animals that are dependent for their food on producers or green plants. Insects, rodents, rabbit, deer, cow, buffalo, goat are some of the common herbivores in the terrestrial ecosystem, and small crustaceans, molluscs, etc. in the aquatic habitat. Elton (1939) named herbivores of ecosystem as “key industry animals”. The herbivores serve as the chief food source for carnivores.

(b) Secondary consumers:

These are carnivores and omnivores. Carnivores are flesh eating animals and the omnivores are the animals that are adapted to consume herbivores as well as plants as their food. Examples of secondary consumers are sparrow, crow, fox, wolves, dogs, cats, snakes, etc.

These are the top carnivores which prey upon other carnivores, omnivores and herbivores. Lions, tigers, hawk, vulture, etc. are considered as tertiary or top consumers.

(d) Besides different classes of consumers, the parasites, scavengers and saprobes are also included in the consumers. The parasitic plants and animals utilize the living tissues of different plants and animals. The scavengers and saprobes utilize dead remains of animals and plants as their food.

Decomposers and transformers:

Decomposers and transformers are the living components of the ecosystem and they are fungi and bacteria. Decomposers attack the dead remains of producers and consumers and degrade the complex organic substances into simpler compounds. The simple organic matters are then attacked by another kind of bacteria, the transformers which change these organic compounds into the inorganic forms that are suitable for reuse by producers or green plants. The decomposers and transformers play very important role in maintaining the dynamic nature of ecosystems.

Function of Ecosystem:

An ecosystem is a discrete structural, functional and life sustaining environmental system. The environmental system consists of biotic and abiotic components in a habitat. Biotic component of the ecosystem includes the living organisms plants, animals and microbes whereas the abiotic component includes inorganic matter and energy.

Abiotic components provide the matrix for the synthesis and perpetuation of organic components (protoplasm). The synthesis and perpetuation processes involve energy exchange and this energy comes from the sun in the form of light or solar energy.

Thus, in any ecosystem we have the following functional components:

(i) Inorganic constituents (air, water and mineral salts)

(ii) Organisms (plants, animals and microbes), and

(iii) Energy input which enters from outside (the sun).

These three interact and form an environmental system. Inorganic constituents are synthesized into organic structures by the green plants (primary producers) through photosynthesis and the solar energy is utilized in the process. Green plants become the source of energy for renewals (herbivores) which, in turn become source of energy for the flesh eating animals (carnivores). Animals of all types grow and add organic matter to their body weight and their source of energy is complex organic compound taken as food.

They are known as secondary producers. All the living organisms whether plants or animals in an ecosystem have a definite life span after which they die. The dead organic remains of plants and animals provide food for saprophytic microbes, such as bacteria, fungi and many other animals. The saprobes ultimately decompose the organic structure and break the complex molecules and liberate the inorganic components into their environment.

These organisms are known as decomposers. During the process of decomposition of organic molecules, the energy which kept the inorganic components bound together in the form of organic molecules gets liberated and dissipated into the environment as heat energy. Thus in an ecosystem energy from the sun, the input is fixed by plants and transferred to animal components.

Nutrients are withdrawn from the substrate, deposited in the tissues of the plants and animals, cycled from one feeding group to another, released by decomposition to the soil, water and air and then recycled. The ecosystems operating in different habitats, such as deserts, forests, grasslands and seas are interdependent on one another. The energy and nutrients of one ecosystem may find their way into another so that ultimately all parts of the earth are interrelated, each comprising a part of the total system that keeps the biosphere functioning.

Thus the principal steps in the operation of ecosystem are as follows:

(1) Reception of radiant energy of sun,

(2) Manufacture of organic materials from inorganic ones by producers,

(3) Consumption of producers by consumers and further elaboration of consumed materials and.

(4) After the death of producers and consumers, complex organic compounds are degraded and finally converted by decomposers and converters into such forms as are suitable for reutilization by producers.

The principal steps in the operation of ecosystem not only involve the production, growth and death of living components but also influence the abiotic aspects of habitat. It is now clear that there is transfer of both energy and nutrients from producers to consumers and finally to decomposers and transformers levels. In this transfer there is a progressive decrease of energy but nutrient component is not diminished and it shows cycling from abiotic to biotic and vice versa.

The flow of energy is unidirectional. The two ecological processes—energy flow and mineral cycling which involve interaction between biotic and abiotic components lie at the heart of ecosystem dynamics. The principal steps and components of ecosystem are illustrated in Fig. 3.1.

Population Size and Density

Figure 1. Australian mammals show a typical inverse relationship between population density and body size. As this graph shows, population density typically decreases with increasing body size. Why do you think this is the case?

Populations are characterized by their population size (total number of individuals) and their population density (number of individuals per unit area). A population may have a large number of individuals that are distributed densely, or sparsely. There are also populations with small numbers of individuals that may be dense or very sparsely distributed in a local area. Population size can affect potential for adaptation because it affects the amount of genetic variation present in the population. Density can have effects on interactions within a population such as competition for food and the ability of individuals to find a mate. Smaller organisms tend to be more densely distributed than larger organisms (Figure 1).

Massive plankton blooms with very different ecosystem impacts

"The big mystery about plankton is what controls its distribution and abundance, and what conditions lead to big plankton blooms," said Dennis McGillicuddy, Senior Scientist and Department Chair in Applied Ocean Physics and Engineering at the Woods Hole Oceanographic Institution (WHOI).

Two new papers explore this question and provide examples of conditions that lead to massive plankton blooms with vastly different potential impacts on the ecosystem, according to McGillicuddy, co-author of both papers. Both papers also point to the importance of using advanced technology -- including Video Plankton Recorders, autonomous underwater vehicles, and the Ocean Observatories Initiative's Coastal Pioneer Array -- to find and monitor these blooms.

In one paper, Diatom Hotspots Driven by Western Boundary Current Instability, published in Geophysical Research Letters (GRL), scientists found unexpectedly productive subsurface hotspot blooms of diatom phytoplankton.

In the GRL paper, researchers investigated the dynamics controlling primary productivity in a region of the Mid-Atlantic Bight (MAB), one of the world's most productive marine ecosystems. In 2019, they observed unexpected diatom hotspots in the slope region of the bight's euphotic zone, the ocean layer that receives enough light for photosynthesis to occur. Phytoplankton are photosynthetic microorganisms that are the foundation of the aquatic food web.

It was surprising to the researchers that the hotspots occurred in high-salinity water intruding from the Gulf Stream. "While these intrusions of low?nutrient Gulf Stream water have been thought to potentially diminish biological productivity, we present evidence of an unexpectedly productive subsurface diatom bloom resulting from the direct intrusion of a Gulf Stream meander towards the continental shelf," the authors note. They hypothesize that the hotspots were not fueled by Gulf Stream surface water, which is typically low in nutrients and chlorophyll, but rather that the hotspots were fueled by nutrients upwelled into the sunlight zone from deeper Gulf Stream water.

With changing stability of the Gulf Stream, intrusions from the Gulf Stream had become more frequent in recent decades, according to the researchers. "These results suggest that changing large?scale circulation has consequences for regional productivity that are not detectable by satellites by virtue of their occurrence well below the surface," the authors note.

"In this particular case, changing climate has led to an increase in productivity in this particular region, by virtue of a subtle and somewhat unexpected interaction between the physics and biology of the ocean. That same dynamic may not necessarily hold elsewhere in the ocean, and it's quite likely that other areas of the ocean will become less productive over time. That's of great concern," said McGillicuddy. "There are going to be regional differences in the way the ocean responds to climate change. And society needs to be able to intelligently manage from a regional perspective, not just on a global perspective."

The research finding demonstrated "a cool, counterintuitive biological impact of this changing large scale circulation," said the GRL paper's lead author, Hilde Oliver, a postdoctoral scholar in Applied Ocean Physics and Engineering at WHOI. She recalled watching the instrument data come in. With typical summertime values of about 1-1.5 micrograms of chlorophyll per liter of seawater, researchers recorded "unheard of concentrations for chlorophyll in this region in summer," as high as 12 or 13 micrograms per liter, Oliver said.

Oliver, whose Ph.D. focused on modeling, said the cruise helped her to look at phytoplankton blooms from more than a theoretical sense. "To go out into the ocean and see how the physics of the ocean can manifest these blooms in the real world was eye opening to me," she said.

Another paper, A Regional, Early Spring Bloom of Phaeocystis pouchetii on the New England Continental Shelf, published in the Journal of Geophysical Research: Oceans (JGR: Oceans), also was eye opening. Researchers investigating the biological dynamics of the New England continental shelf in 2018 discovered a huge bloom of the haptophyte phytoplankton Phaeocystis pouchetii.

However, unlike the diatom hotspots described in the GRL paper, Phaeocystis is "unpalatable to a lot of different organisms and disrupts the entire food web," said Walker Smith, retired professor at the Virginia Institute of Marine Science William and Mary, who is the lead author on the JGR: Oceans paper. The phytoplankton form gelatinous colonies that are millimeters in diameter.

When Phaeocystis blooms, it utilizes nutrients just like any other form of phytoplankton would. However, unlike the diatoms noted in the GRL paper, Phaeocystis converts biomass into something that doesn't tend to get passed up the rest of the food chain, said McGillicuddy.

"Understanding the physical-biological interactions in the coastal system provides a basis for predicting these blooms of potentially harmful algae and may lead to a better prediction of their impacts on coastal systems," the authors stated.

Massive blooms of the colonial stage of this and similar species have been reported in many systems in different parts of the world, which Smith has studied. These types of blooms probably occur about every three years in the New England continental shelf and probably have a fairly strong impact on New England waters, food webs, and fisheries, said Smith. Coastal managers need to know about these blooms because they can have economic impacts on aquaculture in coastal areas, he said.

"Despite the fact that the Mid-Atlantic Bight has been well-studied and extensively sampled, there are things that are going on that we still don't really appreciate," said Smith. "One example are these Phaeocystis blooms that are deep in the water and that you are never going to see unless you are there because satellites can't show them. So, the more we look, the more we find out."

Mission and Vision

Vision Statement

Conduct ecosystem-based research and assessments of living marine resources, with a focus on the Northeast Shelf, to promote the recovery and long-term sustainability of these resources, and to generate social and economic opportunities and benefits from their use.

Mission Objectives

Research and Monitoring

Understand and predict changes to marine ecosystems and their subsystems affecting living marine resources, fisheries, habitats, ecosystem condition, productivity, aquaculture, and the generation of net National benefits.

Scientific Advice

  • Develop and provide the scientific foundation for management programs that has an ecosystem-based framework.
  • Enhance society's capability to respond to changing ecosystem conditions and to manage risk by developing science-based decision tools.

Education and Outreach

Engage and interact with individuals, partners, schools, communities, and industries to facilitate information flow, to assure coordination and cooperation, and to provide technical assistance in the management of living marine resources and their habitats.

Annual Guidance Memo

Our Director provides annual guidance on activities that take place every year. Download the current Annual Guidance Memo.

Open Research

Data used in the dynamic linear models are available from the authors upon reasonable request.

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fwb13707-sup-0001-FigS1.pdfPDF document, 9.1 KB Fig S1
fwb13707-sup-0002-FigS2.pdfPDF document, 8.1 KB Fig S2
fwb13707-sup-0003-FigS3.pdfPDF document, 8.4 KB Fig S3
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fwb13707-sup-0008-FigS8.pdfPDF document, 33.4 KB Fig S8
fwb13707-sup-0009-Supinfo.docxWord document, 24.3 KB Supplementary Material

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