Stream Ecology I

1. Stream Ecology I • Abiotic components • Primary producers • Invertebrates • Vertebrates

2. 1. Abiotic Components • Important starting point for species and abundances • Environments that are structurally simple or extreme tend to support fewer species • High frequency of disturbance tends to diminish biological richness • Consider Four Components • Current • Substrate • Temperature • Water chemistry (sometimes)

3. Current (1) • Flow velocity, substrate size, and depth • Illustrates differences in habitat preferences

4. Current (2) • Shear stress • Where species are found depends on their ability to hold position and obtain resources • If a large event occurs, their ability to survive and recolonize

5. Substrate (1) • For benthic invertebrates, substrate provides platform and living space to attach, forage, and complete most of life cycle and refuge • Inorganic components • Bars, riffles, pools, and greater range of grain particles benefit many taxa and hyporeos • High silt levels—negative effect, reduces heterogeneity, filling interstitices, coating consumers and food resources • Organic components • Macroinvertebrates increase where fine organic matter occurs • Wood adds to mesoscale habitat

6. Substrate (2) Invertebrates

7. Substrate (3) • For fish, prefer some grain sizes • mud darter; sand darter • Spawning because of DO, sediment can be sculpted into nests • Insects also select particular substrates for oviposition (laying eggs) • Bedload transport likely provides unstable habitat and fewer food resources for benthic organisms

8. Temperature (1) • Determines metabolic rates of organisms, their distributions along a river’s reach, and success interacting with other organisms • Few are able to cope with very high temperature • most warm water fish have an upper limit of 30C • Trout grow rapidly until ~15 C

9. Temperature (2) • Temperature will affect species richness • Thermal niche for fish (cold < 19C; cool 19 to 22C ; warm > 22C • Overall fish diversity increases with temperature (all else being equal)

10. Temperature (3) • Temperature controls metabolism of all producers and ectothermic (cold-blooded) consumers • Photosynthesis and microbial activity are strongly temperature dependent, as a macroinvertebrates and fish • Daily growth rate of aquatic insects increases markedly with temperature

11. Importance of Abiotic Components in Stream Restoration • Value of habitat affected by characteristics and availability of abiotic components • Can affect species abundance • Can affect metabolic processes

12. 2. Primary Producers • Acquire their energy from sunlight and materials from non-living sources • In streams • Benthic algae • Macrophytes • Phytoplankton

13. Benthic Algae (1) • Virtually all substrates that receive light can support algae • Categorized based on size • Macroalgae: mature thallus (body) can be seen • Microalgae: cannot be distinguished without a microscope • Where they grow Stones: epilithon Sediment: epipelon Sand: episammon Wood: epixylon Other plants: epiphyton

14. Benthic Algae (2) Major growth forms of periphytons (algal complex)

15. Benthic Algae (3) For North America: 35% green algae 24% cyanobacteria

16. Benthic Algae (4) For North America: 21% diatoms 20% red algae

17. Benthic Algae (5) • Limiting factors • Light—affected by canopy emergence • Nutrients (P, N, SiO2) • Current (brings nutrients, but can dislodge algae) • Substrate (affects size) • Temperature (diatoms: 5 to 20C; green, yellow, brown: 15 to 30C; cyanobacteria: >30C) • Grazers can eat select species

18. Benthic Algae (6) Effect of light Effect of nutrients

19. Benthic Algae (7) • Net Primary Productivity (NPP) • Closed canopy: 0.01 to 0.1 g C/m2-day • Open canopy: 0.25 to 2 g C/m2-day • Most is consumed by herbivores or enters the pool of particulate detritus

20. Macrophytes (1) • Flowering plants, mosses, encrusting lichen, pond weeds, and large algal species • Important role as habitat and refugia for invertebrates and fish • Most found in standing water • Growth form: • Emergents rooted on banks and shoals • Floating-leaved taxa (rooted), margins of rivers • Free-floating (not attached; can form large mats) • Submerged (attached, typically mid-stream)

21. Macrophytes (2) Ribbonweed Duckweed

22. Macrophytes (3) Pondweed Bullrush

23. Macrophytes (4) • Limiting Factors • Coverage: 27 to 47% in mid-sized Appalachian streams • Hardness of water affects species • Current and high-flow events • Light: 90% increase in shade reduces plant biomass by 50% • Nutrients • Herbivory: mostly no effect

24. Macrophytes (5) • Primary Productivity • Net Primary Productivity: 3 g C/m2-day for submerged; ~10 to 20 g C/m2-day for emergents • Generally highest in medium sized rivers • Ample light, moderate current, low turbidity, minimal fluctuations in depth and discharge

25. Phytoplankton Suspended algae in water column: displaced cells from benthos, eroded material (sloughing), some in situ reproduction Generally abundance  1/Q Gross Primary Productivity: 0.6 to 1.7 g C/m2-day

26. Importance of Primary Producers in Stream Restoration • Net primary productivity in streams • nutrient uptake • carbon sequestration • Food (benthics) • Limiting factors for growth and abundance (abiotic, nutrients, herbivory) • Macrophytes—refugia and habitat

27. 3. Invertebrate Feeding • Food resources and individuals • Periphyton (eaten by scrapers) • Coarse particulate organic matter (CPOM)—eaten by shredders • Fine particulate organic matter (FPOM)—eaten by collectors • Animal prey—eaten by predators • Shaded headwaters—favor POM • Grazers—unshaded, stoney streams • Collectors—large turbid streams

28. Invertebrate Feeding (2) Based on food sources and acquisition mechanisms

29. Invertebrate Feeding (3) Herbivory

30. Invertebrate Feeding (4) Predators

31. Importance of Invertebrates in Stream Restoration • Important trophic level in streams • Indicators of stream impairment and degradation (e.g., indicator species)

32. 4. Vertebrates Fish 92% predators 8% herbivores

33. Spawning habitat with incubation of eggs Movement to spawn Movement to feed Movement to spawn Mosaic of feeding habitat(s) with favorable growth conditions Refugia from harsh environmental conditions (e.g., extreme temperatures or flows) with unfavorable growth conditions Movement to refuge hab 1 hab 2 Movement to feed hab 3 (from Schlosser and Angermeier, 1995) Fish and River Connectivity • Because stream fish have evolved in dynamic environments, they take advantage of, and depend on, a variety of habitats

34. Fish Swim Speed and O2 Consumption Burst Turbulent Sustained Prolonged Steady

35. Alteration of Swimming due to Turbulence 10-cm trout, 0.45 m/s flow velocity, cylinder added to flow (Liao, 2007)

36. Salmon using obstructions Rippled bed and cod Schooling and wake interference Trout choosing to swim behind obstructions Fish exploiting turbulence Fish entraining on small cylinders (Liao, 2007)

37. Importance of Vertebrates in Stream Restoration • Essential trophic level in streams • Socioeconomic importance • Connectivity: Fish need a variety of habitats • Fish respond to and exploit turbulence in rivers