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Concepts in Stream Ecology

Concepts in Stream Ecology. Streams are ecosystems. Ecosystems. Communities of organisms and their physical, chemical, and biological environments. Major Abiotic Factors. Flow Light Temperature Chemistry Substrate. Flow. Water flow is the key factor in lotic systems

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Concepts in Stream Ecology

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  1. Concepts in Stream Ecology • Streams are ecosystems

  2. Ecosystems • Communities of organisms and their physical, chemical, and biological environments

  3. Major Abiotic Factors • Flow • Light • Temperature • Chemistry • Substrate

  4. Flow Water flow is the key factor in lotic systems Strength and speed of water flow can vary between systems and within a system based upon variability of friction with bottom or sides, obstructions, and incline Input can affect flow rate Erosion creates a variety of habitats: Riffles and pools

  5. Particular longitudinal and transversal shape

  6. Highly variable parameters of the ecosystem • Velocity and weight of water create momentum and shear stress at the sediment water interface • High variability • Velocity, momentum and shear stress • Transport of bedload • Turbidity and particulate matter • Nutrient and oxygen concentrations

  7. Stream Ecosystems • Mostly downstream fluxes of energy and matter • Lateral and vertical the riparian and hyporheic zones

  8. The riffle • Elevation drop • Higher velocity • Higher shear stress • More resuspension of fine sediments • Only bigger particles stay • Riffle contain gravel size stones at their surfaces

  9. The riffle • Relatively Shallow • Smaller cross section area • Obstacles relatively bigger • Woody debris go agroud • Leaf pack can develop

  10. How do all organisms find their requirements for life in streams? • Water? • Source of nutrients? • Source of energy? • Source of electron donor (oxygen)?

  11. Sources and sinks of oxygen in water • Sources: • Photosynthesis from autotrophs • Reaeration at the interface between water and atmosphere

  12. Reaeration • Partial pressure equilibrium between atmosphere and water • dissolved gas mole fraction of any gas, xi, at equilibrium conditions • PO2=0.2095 • The colder the water the higher the potential for oxygenated waters

  13. Reaeration (Cont’d) • DO values also depend on • The depth of the water • The velocity of the water • Water T°C

  14. Where is water fast and shallow in streams?

  15. Oxygen concentration highest in riffles!!!

  16. Can oxygen be a problem? • Oxygen content in streams and sediment driven by the ratio between supply and demand. • All organisms from bacteria to fish respire and consume oxygen • In sediment oxygen can be all consumed: anoxia • Oxygen: major driver of stream habitat and biogeochemical processes

  17. Challenges when an autotroph in a stream • Find a spot • Find a point of anchorage • Stay in place • Find light • Find nutrients • Avoid being grazed

  18. Autochthonous Vs. Allochthonous Autochtonous Energy sources derived from within the lotic system Photosynthesis and decomposition of organisms originating in the system Allochthonous Energy sources derived from outside the lotic system Leaves, twigs, fruits Feces and dead carcasses

  19. Biofilms

  20. Biofilms

  21. Increased water exchange in Biofilms

  22. Challenges for macrophytes in streams • Withstand the currents • Obtain nutrients from both sediment and water column

  23. Challenges when a fungus or Shredder • Have something to shred upon • Leaf packs, dead algae macrophytes

  24. Riparian plant community = stream organic dynamics

  25. Wood Mass Estimates (Valette, et. Al.) • Old Growth Streams = 8.33 kg/m² • Second Growth Streams = 0.05 kg/m²

  26. Challenges when a fungus or Shredder • Have something to shred upon • Leaf packs, dead algae macrophytes • Capture particulate matter • Clogging • Not getting washed away • Ability to hide

  27. Challenges when a fungus or Shredder • Have something to shred upon • Leaf packs, dead algae macrophytes • Capture particulate matter • Clogging • Not getting washed away • Ability to hide from current and predators

  28. Challenges for scrapers • Be were the biofilms are • Have oxygen • Withstand current • Hide or develop strategies against predators

  29. Challenges for filters and collectors • Have enough oxygen • Enough food • Not too many fine particles • Clogging • Hide from predators

  30. Challenges for invertebrate predators • The food chain above must exist • Have enough oxygen • Live where the preys live • Not get washed away Ephemeroptera

  31. Challenges for higher predators • Have enough oxygen • Find where the insects and fish are • Locations to rest, feed and reproduce • Depend on the entire food chain above

  32. Take home points: Where does energy come from? • Light for the autotrophs (autochtonous origin) • For most organisms: • Dead organic matter • Crucial importance of Fine Particulate Organic Matter (FPOM)

  33. Why would anyone want to live in a riffle? • Autotrophs • More light • More renewal of nutrients • Heterotrophs • More oxygen in water and sediment • Smaller cross section area thus higher probability of capturing food for the same volume scanned • Higher chance for obstacle for leaf packs • Woody debris essential as physical barriers

  34. Take home points: Why would anyone want to live in a pool? • Autotrophs • Less shear stress • Soft sediment for roots and for nutrient supply • Heterotrophs • Less shear stress (herbivores) • Soft sediment for habitat (Bivalva) • Fine particulates for detritivores

  35. Take home points: Small obstacles: key to ecosystem health

  36. Who lives in streams? • Bacteria, virus • Amoeba, rotifers • Plants: • Algae: microscopic and macroscopic • Bryophytes (mosses) • Angiosperms (flowering plants) • Fungi

  37. Who lives in streams? • Animals: • Protozoa: • Sponges (Bryozoa) • Macroinvertebrates • Acoelomate worms • Planaria or flatworm (Turbellaria) • Nematode or Threadworm, Horsehair worm (Nematoda) • Mollusca • Clams (Bivalva) • Snails (Gasteropoda) • Annelida • Leeches (Hirudinea or Achaeta) • Tubifex worm (Oligochaeta) • Bristle worms (Polychaeta)

  38. Who lives in streams? • Animals: • Macroinvertebrates (Cont’d) • Arthropods: • Spiders (Arachnida) • Crayfish, Water flea (Crustacea) • Stonefly, Mayflies, Caddisfly (Insects) • Vertebrates: • Vertebrates • Lamprey (Agnatha) • Fish (Osteichthyes) • Frogs (Amphibians) • Water snakes and turtles (Reptiles) • Kingfisher, Dipper (Birds) • Otter, beaver (Mammals)

  39. Algae: What do they look like? • Microscopic and macroscopic algae • Diatoms commonly comprise the dominate algal group in river biofilms in terms of species number and biomass.

  40. Aquatic mosses (Bryophytes) Zipper Moss – (Fissidens zippelianus) Christmas Moss (Vesicularia montagnei)

  41. Aquatic flowering plants Myriophyllum spp – Watermilfoils Water lilies – Nuphar spp Glyceria Fluitans

  42. Aquatic sponges Freshwater sponges are aquatic animals that grow in lakes, rivers, bogs, and streams attached to submerged rocks, sticks, logs, or aquatic vegetation. These sedentary animals feed by filtering small particles from the water, and so are thought to be sensitive indicators of pollution. The sponges may be colored green by algae that live inside their cells or they may be beige to brown or pinkish in color. Sponges can be delicate to very firm feeling but are not slimy or filmy. Some sponges prefer the underside of logs and sticks; these are usually not green in color.

  43. Acoelomate worms http://trc.ucdavis.edu/biosci10v/bis10v/media/ch16/blood_fluke.html Turbellarians or planarians (Turbellaria) possess a pharynx tube that extends to feed on whole small animals or suck tissues from dead or wounded prey.

  44. Nematods Nematodes exhibit a wide range of feeding habits: carnivorous, herbivorous and parasitic

  45. Horsehair worms Horsehair eggs are laid in the water in long strings where the adults live.  After hatching, the larvae penetrate some aquatic insect; they escape in some unknown way from this host and find their way into a second host; usually a beetle, cricket, or grasshopper; in the body cavity of the second host the larvae continue their development eventually passing out into the water where they become mature.  Since the adults live only in water, those that survive probably emerge from terrestrial (flying) insects, which constitute their second hosts, that chance to  drown in watering troughs and small ponds.

  46. Leeches • Leeches suck the blood of fishes, amphibians, birds, and mammals. They also eat snails, insect larvae, and worms

  47. Clams Freshwater mussels feed by filtering algae and small particles from the water. Most species have a larval stage that is parasitic on fish. Larvae are released by the female mussel and must locate a certain fish species or die. They usually attach to the host fish's gills or fins where they remain for a few weeks or months. Larval mussels rarely harm infected fish under natural conditions. If essential fish species are removed from the habitat, mussels will not be able to reproduce. Support muskrats, otters, wading birds and game fish

  48. Aquatic snails Aquatic snails are a crucial host to the flatworm parasite Herbivores

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