rivers 1&2

general categories of aquatic habitats

• lentic- systems in which water doesn’t move or moves slowly, lakes & ponds

• wetlands- habitats where soil is saturated with water (at least temporarily)

• lotic- systems in which water flows, creeks, streams & rivers

characterizations of streams

• watershed size

• stream order

• discharge

• flow regime

• vegetation

lotic systems: rivers & streams

dynamic systems:

• the shape of a river is constantly changing

• rivers respond to the land it traverses

  • i.e. catchment area

catchment/ watershed/ basin

defined as a region that drains into lake, pond, or river

• catchments vary by:

  • size

  • soil type/ bedrock

  • vegetation present

• differences impact:

  • nutrients

  • pH

  • water color

  • large catchments= larger impact on chemistry

classification of streams

• based on order

  • 1st, no streams flowing into it

  • 2nd, two 1st order streams joining

  • 3rd, two 2nd order streams joining

  • 3rd order stream cannot be formed by 2nd + 1st

• headwater streams are orders 1-3

  • mid-sized rivers are 4-6

  • large rivers are orders 7-12

• ~85% of streams in the US are 1-3

low order streams

• headwater streams

• shaded

• coarse particulate organic matter provides resource base for consumer comunity

• allochthionous inputs

  • originating or formed somewhere other than the place where it is currently found

functional feeding groups

• shredder= coarse particulate organic material, e.g. leaf litter or wood

• grazer/ scraper= algae and associated material

• collectors= fine particulate organic material from stream bottom or water column

• predators= feed on other consumers

mid-order streams

• energy inputs change as stream broadens

  • light

  • CMOP

  • fine POM (FPOM)

• sunlight supports significant periphyton production

• shredders are replaced by grazers

• collectors are still abundant

• predator abundance about the same

high order streams

• energy sources continue to change

  • light

  • FPOM dominated

• primarily autochthonous inputs

• as streams widen the flow decreases

• turbid

• bottom substrate becomes finer

• phytoplankton & zooplankton become prevalent

• primarily collectors and predators

river continuum concept

• headwater streams (1-3)

  • most organic material allochthonous

  • respiration > production

  • lots of shredders & collectors

• midreach streams (4-6)

  • increasing autochthonous organic material

  • respiration < production

  • lots of collectors & grazers

• lower reach streams (>6)

  • large flux of organic material- water becomes more turbid

  • respiration > production

  • lots of collectors

water discharge & velocity

• discharge is volume per unit time

• velocity is how fast water is going (distance per unit time)

• discharge is not velocity

• flow can mean discharge or velocity

• hydrographs are a plot of discharge over time

human influences

• damming, channelization and excessive water use

• reservoirs allow sediments to settle ad make rivers downstream ‘sediment starved’

• dams fragment riparian habitat

• alteration of temperature regimes

restoration of rivers

• goal: restoration of natural hydrology and ecosystem functions

• reintroduction of natural riparian vegetation

• creation of macrohabitats (logs, pools, etc)

• improvement of water quality

• monitoring to assess restoration success

dam removal

• benefit: restore river connectivity

• issues: release of large amounts of sediment and accumulated toxins, permitting, training

transport of material by rivers and streams

• rivers carry materials dissolved from land to the sea

  • important part of the carbon cycle

  • N, P, S, & C

erosion

• under base flow, riffles are erosional habitats and pools are depositional habitats (opposite during floods)

• factors like presence of macrophytes can affect sediment trapping and transportation

mobile material

• suspended load (fine material suspended in the water column, turbidity or total suspended solids)

• bed load slides or rolls along the bottom

importance of transport of solid materials

• habitat alteration

• movement of rocks

• movement of contaminated sediments

transport of organisms

• drift: at any given time a small number of macroinverts may be suspended

• catastrophic drift can accidentally be triggered by floods or pollutants