Biological Stream Functions Eve Brantley, Alabama Cooperative Extension System
Stream Functions Transport water Transport sediment Transport energy Aquatic organism habitat Terrestrial organism habitat
General stream characteristics • River Continuum Concept • Stream biology basics • Floodplain functions & values • Importance of Restoration
Restoration • Projects need an interdisciplinary team … stream restoration is more than just altering the size and shape of the channel.
Change in energy as streams flow from headwaters to mouths
Stream Gradient Headwater streams are typically small with greater velocity and a steeper gradient
Stream Gradient As these streams flow downhill, they meet up with other streams becoming a bigger slower moving body of water with less gradient
Stream Order Streams within watersheds are often classified hierarchically • Segments can be categorized by their order in the system A stream to one person may be considered a river by another, good communication tool
The smallest headwater streams are first order Stream Corridor Restoration: Principles, Processes, and Practices, 10/98, by the Federal Interagency Stream Restoration Working Group (FISRWG)."
The union of two first order streams creates a second order stream Stream Corridor Restoration: Principles, Processes, and Practices, 10/98, by the Federal Interagency Stream Restoration Working Group (FISRWG)."
The union of two second order streams creates a third order stream The union of two streams of order n creates a stream of order n+1 Stream Corridor Restoration: Principles, Processes, and Practices, 10/98, by the Federal Interagency Stream Restoration Working Group (FISRWG)."
Headwater streams are orders 1 – 3 Mid-sized rivers are orders 4 – 6 Large rivers are orders 7 – 12 About 85% of all stream miles in the U.S. are first to third order streams … close to 3 million miles. The Mississippi River is 12th order at its mouth.
Stream Gradient The decrease in stream gradient and energy along a stream’s route to its mouth is accompanied with changes in habitat and ecological communities.
The Concept of Connectivity Headwater streams are especially susceptible to watershed impacts
River Continuum Concept • Describes general changes in stream ecosystems from headwaters to the mouth • Identifies connections between the watershed, floodplain, and stream systems • Places site in context within a watershed, helping define and focus restoration goals Stream Corridor Restoration: Principles, Processes, and Practices, 10/98, by the Federal Interagency Stream Restoration Working Group”
Riffles Characterized by rapid flow carrying small particles in suspension, coarse sediments on stream bed, and removal of finer sediments
Importance of Riffles • Areas of oxygenation • Highly diverse substrate and habitat • Diverse macroinvertebrate population
Pools • Regions of slower water current characterized by the deposition of finer sediments
Importance of Pools • Refuge for fish during low flow, drought periods • Rest stop and food area for fish • Predator refuge for young fish
What is living in the stream? Biological diversity & abundance depends on diversity of available habitats
Benthic Macroinvertebrates Benthic = bottom dwelling organisms that live in, crawl upon, or attach themselves to the substrate Macroinvertebrate = can be seen without a microscope, no backbone
Common benthic macroinvertebrates include: • insects (stonefly, dragonfly) • annelids (aquatic earthworms, leeches) • crustaceans (amphipods, crayfish shrimps) • mollusks (clams and snails) 4 Functional Feeding Groups • Shredders • Grazers • Collectors • Predators
Shredders • Commonly found in leaf packs
Collectors – Filter Feeders • Filter organic matter from water column Caddisfly nets (philopotamids) in the current. Common below dams.
Grazers • Feeds on periphyton attached to rocks, large woody debris
Predators • Feed on other organisms
System changes with stream order • Orders 1 - 3 • Riffles with intermittent pools • Large substrate sediment size • Riparian vegetation shades stream, minimizes growth of algae and other aquatic plants • Coarse particulate organic matter from surrounding watershed important for stream ecosystem energy inputs
Cool water fish community • Darters • Shiners Macroinvertebrate community • Shredders in leaf packs • Collectors (filter feeders and gatherers)
System changes with stream order • Orders 4 – 6 • Ratio of riffles to pools decreases – there are greater stretches of depositional areas in the river • Substrate materials consist of more muds and lighter sediments • Increased sunlight with wider channels, primary productivity increases • Ecosystem shift to dependence on materials produced inside the channel & upstream
Shift in fish community • Greenbreast darter • Banded Sculpin Macroinvertebrate community • Collectors (filter feeders) • Grazers
System changes with stream order • Orders 7 – 12 • Few riffles areas are present • Bottom sediments consist of loose muds, silt, and organic detritus. • Bordered by marshes and swamps • Increased dependence on primary productivity • Continue receiving heavy inputs of dissolved and ultra-fine organic particles from upstream
Warm water fish community • Catfish • Sunfish Macroinvertebrate community • Increase in plankton • Decrease in macroinvertebrate diversity
What can cause a loss of aquatic habitat stream function? • Increase in sediment loads embeds substrate • Increase in temperature, decrease in dissolved oxygen • loss of riparian vegetation • widening of channel / shallow water • Loss of bed features (pools and riffles) • straightening of channel • pools and riffles fill in with increased sediment
Water Quality Impairments - AL • Draft 2002 Alabama 303(d) list: • 43% of Total Impaired Miles due to siltation • Sources of impairment include pasture grazing, urban runoff & storm sewers, agriculture, and unknown
How do we know? Measure stream health through: • Visual Assessments • Chemical / Physical monitoring • Bioassessments
Bioindicators • Aquatic macroinvertebrates are used to assess the relative health of a stream system and its watershed • relatively immobile -they will ‘take a hit’ with water pollution • are easy to capture, relatively abundant and easy to distinguish • have diverse communities with varying levels of tolerance to pollution
Hanging Rock Creek, NC Feeding TypeUpstreamDownstream Shredders 17 % 1% Collector/gatherer 21% 20% Scrapers/grazers 27% 38% Predators 14% 18% Filter-Feeders 21% 23% Courtesy David Penrose
Pollution Tolerance Levels • Highly sensitive to pollution or stream habitat alteration
Pollution Tolerance Levels • Wide range of tolerance to pollution or stream habitat alteration
Pollution Tolerance Levels • Generally tolerant of pollution or stream habitat alteration
EPT Index • This measures the total number of species within the orders Ephemeroptera (mayfly), Plecoptera (stonefly), and Trichoptera (caddisfly) • Mayflies, stoneflies, and caddisflies generally require high levels of dissolved oxygen • A high EPT Index generally indicates a stream and watershed with low disturbance and pollution levels
Adaptations to Living Underwater • Oxygen Gradient • Tube breathers (atmospheric O2) • Cutaneous breathers (dissolved O2) Rattailed maggot telescopic respiratory tube used to obtain air from the surface External gills of mayfly nymph obtain dissolved oxygen from water
2 tarsal claws on tips of legs Ventral attachment discs Anal attachment discs Riffles Life in a riffle means special adaptations to keep from drifting downstream • Clingers / Sprawlers • Tarsal or anal claws (stonefly nymphs) • Attachment discs (water penny / black fly) • Streamlined bodies and orientation to flow
Pools Adaptations to slow moving water (less dissolved oxygen) • Dragonfly - anal gills ventilation by repeated intake and expulsion of water from the rectal chamber • Midges - possess a form of hemoglobin that enables them to utilize small amounts of D.O. Blood Worms
Index of Biotic Integrity • Comprised of fish community parameters or metrics divided into categories*: • Species richness & composition • Trophic structure • Indicator species • Abundance and condition • Assists in quantifying changes in ecosystem health resulting from habitat degradation, flow alteration, and poor water quality *There are regional differences in IBI metrics
Suspended Sediment Effects • Clay particles can coat biologically active surfaces of plants and animals • Can abrade and suffocate periphyton and macrophytes • Reduced light penetration • Disrupt respiration and behaviors (feeding and reproduction)