Physical Factors: Current, Substrate, Temperature, and Oxygen Unit 1: Module 4, Lecture 3

Physical Factors: Current, Substrate, Temperature, and Oxygen

Unit 1: Module 4, Lecture 3

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s2

Objectives

Students will be able to: explain how current influences and effects the

type of organisms in a stream. predict and describe longitudinal sediment

distribution in a stream. classify sediment particles by size. describe how particle size influences aquatic

organisms. describe how temperature and oxygen levels

affect aquatic organisms in a stream.


Physical factors: Current, substrate, temperature, and oxygen

Module 4: Lecture 3 consists of three parts which you can do in whatever order suits your class: Physical factors Organic Matter Stream Chemistry.


Current influences: Ecological distribution Morphological adaptations An organism’s behavior

Current

A collembola with a rounded body, suiting it for areas of slow current.

www.dec.state.ny.us/website/dow/stream/orderpagetwo.htm

A mayfly larva with a dorsoventrally flattened body minimizing drag in current.

www.dec.state.ny.us/website/dow/stream/empfamilies.htm


Current and body shape

Sunfish and bullheads with broad body forms are adapted to slow current.

Stonecats and trout with streamlined body forms are adapted to fast current.

www.cnr.vt.edu/efish/families/ictaluridae.html

www.lambs-inn.com/new-images/ trout-sm.jpg

www.cnr.vt.edu/efish/families/ictaluridae.html

www.uga.edu/srel/Coal_Ash/sunfish.jpg


The distribution of diatoms, algae, and rooted macrophytes are influenced by current. Diatoms species can by sorted into taxa that are

adapted to slow and fast moving water. Attached algae appear to increase in abundance

in conditions with fast current and hard substrates.

Rooted macrophytes thrive in slow water with soft sediments.

Current


www.mountainspecs.com/creek.jpg

The effect of substrate on organisms

The diversity of materials making up the substrate of a stream make it complex and dynamic.

The composition of the substrate plays an important role in shaping what organisms inhabit a particular stream reach.

Due to other factors such as current, temperature, and oxygen levels it is important not to attribute the presence or absence of a specific species solely to the substrate type encountered at particular site.


The predominant substrate size decreases as you move downstream.

Longitudinal sediment distribution

www.shorelandmanagement.org/depth/rivers/04.html

Mean gradient

Distance downstream

Boulders and cobbles

Bed material size

Gravel Sand Silt


Chattahoochee River tributaries

Percent of bottom covered by various substrates


Particle size

Category Dia (mm) Wentworth scale

BoulderCobble

> 256 < -8

LargeSmall

128 - 25664 - 128

-7-6

Pebble LargeSmall

32 - 6416 - 32

-5-4

Gravel CoarseMediumSmall

8 - 164 - 82 - 4

-3-2-1

Sand Very CoarseCoarseMediumFineVery Fine

1 - 20.5 - 10.25 - 0.50.125 - 0.250.063 - 0.125

01234

Silt < 0.063 > 5www.enn.com/news/enn-stories/2000/02/02172000/alaska.jpg

www.aquatic.uoguelph.ca/rivers/chphys.htm



Organic matter as a substrate component

Organic materials ranging from plants stems to logs tend to function as substrates for organisms, while particles less than 1 mm in size may serve as food for macro invertebrates.

Diversity and density of invertebrates often increases with the presence of organic matter as part of the substrate.

As organic matter increases in stream substrates, macro invertebrate diversity tends to increase

www.mcmullans.org/ canal/lock_60.htm


Group Preferred Substrate

Lithophilous Gravel, Cobbles, Boulders

Psammophilous Sand

Xylophilous Wood

Phytophilous Plants

Faunal selection of substrates


Fish spawning habitat

Most stream dwelling fish select a hard substrate, ranging from large stones to mixed gravel on which to spawn.

The availability and distribution of a particular substrate type necessary for spawning is often critical in creating suitable habitat for a particular species.

www2.state.id.us/fishgame/fish/fishstocking/hatcheries/mccall.htmwww2.state.id.us/fishgame/fish/fishstocking/hatcheries/mccall.htm


This figure illustrates seasonal differences in the emergence of mayfly species that would in part be cued by temperature.

www.centralnewyorker.com/mayflyhatchchart.htm

The effect of temperature on organisms


Maximum daily temperature range in relation to stream order in temperate streams

www.aquatic.uoguelph.ca/rivers/chphys.htm

www.fermatainc.com/wis/



Oxygen

In most unpolluted streams dissolved oxygen is near saturation and is, therefore, of minor biological concern.

Current serves to deliver oxygen rich water to respiratory structures.

Fish can actively move water over gills, however, most invertebrates cannot and are dependent on current to deliver oxygen.

These organisms are referred to as respiratory conformers: their respiratory rate closely follows the ambient oxygen concentration.


Oxygen related adaptations

Fish actively swim and draw water over their gills

Macroinvertebrate larvae with conspicuous gills are respiratory conformers

Midge larvae with hemoglobin are adapted to live in poorly oxygenated stream sediments

www.usask.ca/biology/skabugs/flies/chiron.html

ww.usask.ca/biology/skabugs/Ephem/mayfly.html

www.cnr.vt.edu/efish/families/umbridae.html

Documents

Physical Factors: Current, Substrate, Temperature, and Oxygen Unit 1: Module 4, Lecture 3