Chapter 7

• Ecological system


  Composed of biotic components, ranging from viruses and bacteria to higher organisms, plants and animals that interact with abiotic physical and chemical components, forming a basic ecological unit – the ecosystem
• Population


  A set of organisms of the same species
• Community


  A collection of various populations in an ecosystem
• Main factors in biological processes

  • Temperature dependence
  • Dependence of available substrate (Basic nutrition)
  • Organism size
  • Dependency on density
• Factors that affect the physiological processes of plants

  • Light intensity, and light availability
  • Light and water temperature
  • Oxygen levels and saturation in water
  • pH
• Succession


  A universal process of directional change in the community
• Types of succession

  • Primary succession - Involves the gradual establishment of biologic communities in an area that has not been occupied by life before
  • Secondary succession - Involves the reestablishment of biotic community in an area where biotic community was previously present
• Climax community


  A mature, stable community that is the final stage of ecological succession
• Indirect effects affecting succession

  • Water temperature
  • Nutrition
  • Parasitism
  • Predation
• Succession is the principal manifestation in the development of ecosystems
• Types of phytoplankton

  • Chlorophyta - Green in color due to chloroplast, mostly found in coastal waters
  • Cyanophyta - Mainly unicellular, blue due to phycocyanin pigment
  • Dinophyta - Motile unicellular algae, can be red, blue or yellow
  • Bacillariophyta - Microalgae with shell-like silica structure
  • Euglenophyta - Unicellular aquatic algae with flagella, exhibit characteristics of both plants and animals
• Factors lead to changes in the shape of some phytoplanktonic species

  • Light intensity
  • Light quality
  • Nutrient levels in the water
  • Osmotic pressure
  • Temperature
• Phytoplankters can associate themselves with photosynthetic or non-photosynthetic organisms
• Main features involved in the dynamics of phytoplankton

  • Primary productivity
  • Biomass
  • Species composition and fluctuations in communities
• Factors that affect the physiology, growth and reproduction of phytoplanktonic organisms

  • Light quality and quantity
  • Temperature
• Principal nutrients for phytoplankton

  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
  • Phosphorus
  • Sulphur
• Basis for the sustainability and reproduction of phytoplanktonic populations

  • Nitrogen - used to synthesize amino acids and proteins, sources include nitrate, nitrite and ammonium
  • Phosphorus - regulates productivity, role in intracellular molecular synthesis and ion transport
  • Carbon dioxide (CO2)
• Most conspicuous and consistent components of marine planktonic communities

  • Diatoms (Bacillariophyceae)
  • Dinoflagellates (Pyrrophyta)
  • Coccolithophorids (Haptophyceae)
• Associations of phytoplankton

  • Diatom-dominated associations - occur in turbulent waters, Cyclotella dominant in oligotrophic, Aulacoseira in eutrophic
  • Chrysophyta-dominated associations
  • Chlorophyta-dominated associations
  • Chlorophyta-dominated associations in eutrophic lakes
  • Dinoflagellate associations
  • Cyanobacteria-dominated associations
  • Cryptomonas associations
  • Nanoplankton and picoplankton associations
  • Photo-autotrophic bacteria associations
• Periphyton algae


  Found on the surface of rocks, submerged macrophyte vegetation, boat exteriors, and other natural and artificial surfaces in aquatic environments
• Aufwuchs is a complex and difficult to collect and study quantitatively
• Substratum heterogeneity and variations in periphytonic communities make classification difficult, particularly qualification of community processes
• Euperiphyton


  A community that is located on and adheres to a substratum by various mechanisms such as rhizoids, tubules, or other structures for fixation
• Factors affecting the photo-autotrophic algal community

  • Water temperature
  • Light intensity
  • Nutrient availability
• Turbidity


  A limiting factor in the growth and ecological dynamics of periphytic algae, can cause reduced biomass
• Higher photosynthetic rate at low light intensities is the main effect of light intensity
• Main features of macrophyte vegetation

  • Emergent macrophytes - produce aerial reproductive organs, located in shallow regions, usually perennial with developed rhizomes
  • Macrophytes with floating leaves - chiefly angiosperms occurring in regions with depths of 0.5 to 3.0 m
  • Submerged macrophytes - occur at all depths in the euphotic zone, but as angiosperms are limited to 10 m (1 atm of pressure)
  • Floating macrophytes - a group without roots in the substratum, which float freely, with various forms
• Types of macrophytes in relation to the water surface

  • Amphibious or semi-aquatic - able to live well both in the flooded areas and out of water
  • Emergent - rooted on the bottom, partially submerged and partially out of water
  • Floating fixed - rooted at the bottom with floating stem and/or branches and/or leaves
  • Floating free - not rooted in the bottom, can be carried by current, wind or animals
  • Submerged fixed - rooted in the bottom, with stems and submerged leaves, usually with only the flower out of water
  • Submerged free - not rooted on the bottom, totally submerged, generally with only flowers emerging
  • Epiphytic - lives on other aquatic plants
• Processes associated with succession, in terms of river pulsations, of macrophytes

  • Frequency of changes in level and pulse
  • Magnitude: intensity of drought or flooding periods
  • Variability: value of the standard deviation of the average maximum or minimum of a multi-year curve of hydrometric fluctuations
  • Recurrence - statistical probability that a flood or drought of a given magnitude will occur in a century or millennium
  • Amplitude - phase of duration of the drought or flood of a certain magnitude in a floodplain
  • Seasonality - seasonal frequency with which droughts or floods occur
• Factors affecting the production of submerged macrophytes

  • Solar radiation
  • Water turbidity and high phytoplanktonic levels
  • Temperature
  • Nutrient levels
  • Current velocity
  • Interspecific or intraspecific competition
  • The role of herbivorous predators
• Other factors that play a role in the productivity and biomass of floating aquatic macrophytes

  • Current velocity
  • Interspecific or Intraspecific competition
  • The role of herbivorous predators
• Aquatic macrophyte communities form extensive banks in lakes, reservoirs and rivers, and this accumulation of organic matter favours the development of a community of bacteria, periphyton, zooplankton and macro-zoobenthos
• Macrophytic banks are known as breeding areas for many fish species (nursery-grounds)