River Macroinvertebrates

• what are the two categories that most stream organisms are?

  attached or benthic
• what are benthic stream organisms?

  buried in soft sediments
• what are attached stream organisms?

  cling to hard surfaces or plants
• what organisms are found in the pelagic zone?

  strong swimmers, mostly vertebrates
• where do boundary layers form?

  in flowing water wherever water flows across a fixed surface
• what is a periphyton?

  a complex mixture of algae, microbes and detritus that grows on aquatic surfaces and sediments
• what are macrophytes?

  aquatic plants and macroalgae
• what is the role of macroinvertebrates?

  they fill the same role as zooplankton in pelagic food webs = they are grazers
• what are the four functional groups of macroinvertebrates?

  shredders, collectors, scrapers and predators
• what do shredders eat?

  coarse particulate organic matter - much of which is detritus that comes from terrestrial plants surrounding the stream
• what do collectors eat?

  fine particulate organic matter which comes from the coarse organic matter that has been broken down by shredders
• where do collectors tend to live?

  in sediments
• what do scrapers eat?

  periphyton by scraping them off of rocks and stream beds with their mouth parts
• what do predators eat?

  all other macroinvertebrates
• what are the two main groups of predators?

  ambush and hunting predators
• which are larger, rivers or streams?

  rivers
• what does the river continuum concept describe?

  the way that community composition and ecological function change along the length of a river as it increases in size or order
• what are streams classified by?

  their order or Strahler number
• what are the three factors which affect the river continuum concept?

  changing food sources, changing ratios in production and respiration and plankton
• where is coarse particulate matter most present?

  small streams
• where is periphyton most present?

  medium streams
• where is fine particulate organic matter most present?

  large streams
• where are shredders most present?

  small streams
• where are grazers most present?

  medium streams
• where are collectors and predators most present?

  everywhere