Download - Stream Ecology I
Stream Ecology I
1. Abiotic components2. Primary producers3. Invertebrates4. Vertebrates
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)
• Flow velocity, substrate size, and depth– Illustrates
differences in habitat preferences
Current (1)
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
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
Substrate (2)
Invertebrates
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
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 30C
– Trout grow rapidly until ~15 C
Temperature (2)
• Temperature will affect species richness– Thermal niche for fish (cold < 19C; cool 19 to 22C ; warm > 22C– Overall fish diversity increases with temperature (all else being equal)
• 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
Temperature (3)
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
2. Primary Producers• Acquire their energy from sunlight and
materials from non-living sources• In streams
– Benthic algae– Macrophytes– Phytoplankton
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: epipelonSand: episammon Wood: epixylonOther plants: epiphyton
Benthic Algae (2)
Major growth forms of periphytons (algal complex)
Benthic Algae (3)
35% green algae
24% cyanobacteria
For North America:
Benthic Algae (4)
21% diatoms
20% red algae
For North America:
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 20C; green, yellow,
brown: 15 to 30C; cyanobacteria: >30C)– Grazers can eat select species
Benthic Algae (6)
Effectof light
Effect ofnutrients
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
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)
Macrophytes (2)
RibbonweedDuckweed
Macrophytes (3)
Pondweed
Bullrush
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
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
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
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
• Food resources and individuals1. Periphyton (eaten by scrapers)2. Coarse particulate organic matter (CPOM)—
eaten by shredders3. Fine particulate organic matter (FPOM)—eaten
by collectors4. Animal prey—eaten by predators
• Shaded headwaters—favor POM• Grazers—unshaded, stoney streams• Collectors—large turbid streams
3. Invertebrate Feeding
Invertebrate Feeding (2)• Based on food sources and acquisition mechanisms
Invertebrate Feeding (3)
Herbivory
Invertebrate Feeding (4)
Predators
Importance of Invertebrates in Stream Restoration
• Important trophic level in streams• Indicators of stream impairment and
degradation (e.g., indicator species)
4. Vertebrates
Fish
92% predators8% herbivores
Fish and River Connectivity• Because stream fish have
evolved in dynamic environments, they take advantage of, and depend on, a variety of habitats
Spawning habitat with incubation of eggs
Refugia from harsh environmental conditions (e.g., extreme temperatures or flows) with unfavorable growth conditions
Mosaic of feeding habitat(s) with favorable
growth conditions
Movement to spawn
Movement to refuge
Movement to feed
Movement to spawnMovement to
feed
(from Schlosser and Angermeier, 1995)
hab 1 hab 2
hab 3
Fish Swim Speed and O2 Consumption
Burst
SustainedProlonged Steady
Turbulent
Alteration of Swimming due to Turbulence
10-cm trout, 0.45 m/s flow velocity, cylinder added to flow
(Liao, 2007)
(Liao, 2007)
Salmon using obstructions
Rippled bed and cod Schooling and wake interference Trout choosing to swim behind obstructions
Fish entraining on small cylinders Fish exploiting turbulence
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