Trophic interactions

• scramble competition: using nutrients more efficiently than competitor
• interference competition: direct interference with competitor
• competition is stronger between individuals of same species (intraspecific) than between different species (interspecific)
• predation: consumption of animals

  herbivory: consumption of plants
• prey developed different defence mechanisms that cost energy and are thus only used when there is a predation risk
• phytoplankton are important primary producer in turbid lakes
• aquatic plants and algae that grow on bottom or on plants (periphyton) are most important biomass producers in clear ditches and ponds
• dead material from primary producers (detritus) accumulates at bottom and is food for bacteria and invertebrates
• trophic cascade (‘top-down theory’)

  • phytoplankton -> zooplankton -> planktivorous fish -> piscivorous fish
  • difference in abundances of species depending on which species are in system
• functioning of aquatic ecosystem

  • energy- and carbon cycle for production and decomposition
  • competition for light, nutrients and space
  • food web interaction