Lecture 9 - Microbes and plants

• food webs for microbes and plants in aquatic ecosystem can be detrital or light based
• microbes and plants play a key role in biogeochemical cycling
• liquid medium of aquatic ecosystems is very good for viral transmission
• viruses are important for population dynamics of aquatic organisms
• Arachae are single celled with no nucleus
• archaea reproduce by asexual fission or budding
• Archaea are common in all aquatic ecosystems
• bacteria are single celled with no nucleus
• bacteria are the most abundant group of organisms on earth
• bacteria does the heavy lifting in regards to nutrient/carbon cycle
• banter are key players in regulating flows of energy and nutrients in aquatic systems
• bacteria vary in morphology and is where are used to classify them
• molecular techniques are replacing the classification scheme for bacteria
• Cyanobacteria

  • photosynthetic
  • found in most aquatic habitats
  • N fixers
  • have gas vesicles that help with buoyancy
  • can produce toxins that limit grazing
• cyanobacteria are often associated with eutrophication lakes
• eutrophication -> lakes with increased nutrients
• cyanobacteria create algal blooms which can be very toxic
• blooms only occur in late summer in larger lakes
• protoctista = algae
• algae generate majority of primary production
• Rhodophyceae (Red algae)

  • most abundant in marine habitats
  • rare in freshwater except for streams
  • have phycobilin pigments that use Bluegreen light
• phycobilins in red algae causes red hue as well as enables the algae to inhabit densely shaded streams and deep waters
• Chrysophyceae (Golden Algae)

  • common component of phytoplankton in oligotrophic lakes
  • have two flagella
  • many are mixotropic
  • some form colonies
• mixotropic = photosynthetic and heterotrophic
• Bacillariophyceae (Diatoms)

  • important primary producer in freshwater
  • dominant taxa in benthic zones of lakes, streams and wetlands
  • important in pelagic zone in oligotrophic and mesotrophic lakes
  • has frustule
• frustule are silica-based cell wall and therefore cause diatoms to need an increased concentration of silicon
• frustules take many shapes and are unique to each species
• frustules are often used un paleolimnology srudies
• Dinophyceae (Dinoflagellates)

  • common in lentic habitats
  • sometimes in streams
  • live in water column
  • unicellular and free swimming
  • can have armour (cellulose plates)
  • some heterotrophic
• Eugenophyceae

  • unicellular
  • autotrophic and heterotrophic
  • can be in sediments
  • most common in eutrophic conditions
  • controlled movement
• which green algae is present in an ecosystem tells us a lot about the ecosystem
• the green algae are the most diverse group
• charophytes

  • more complex structures then chlorophytes
  • can grow up towards the light
  • not vascular
  • found in wetlands and benthic zones
• Protozoa

  • in in every habitat
  • abundant and diverse in freshwater
  • autotrophs and heterotrophs
  • most reproduce sexually
  • resistant to harsh environments
  • some are predators of bateria
  • some are parasitic
• Fungi

  • less common in aquatic habitats
  • most are saprophytes
  • unicellular and multicellular
• saprophytes -> important in the breakdown of detritus and a conditioning role and add in nutritional value to detritus
• plants in aquatic ecosystems are often called macrophytes
• plants can be abundant in shallow slow moving waters
• plants provide habitat for many organisms
• ecologically plants are most important in lakes