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