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.

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s3 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.

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s4  Current influences:  Ecological distribution  Morphological adaptations  An organism’s behavior Current A collembola with a rounded body, suiting it for areas of slow current. A mayfly larva with a dorsoventrally flattened body minimizing drag in current.

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s5 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. trout-sm.jpg

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s6  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

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s7 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.

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s8  The predominant substrate size decreases as you move downstream. Longitudinal sediment distribution Mean gradient Distance downstream Boulders and cobbles Bed material size GravelSandSilt

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s9 Chattahoochee River tributaries  Percent of bottom covered by various substrates

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s10 Particle size CategoryDia (mm)Wentworth scale Boulder Cobble > 256< -8 Large Small PebbleLarge Small GravelCoarse Medium Small SandVery Coarse Coarse Medium Fine Very Fine Silt< 0.063>

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s11 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 canal/lock_60.htm

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s12 GroupPreferred Substrate LithophilousGravel, Cobbles, Boulders PsammophilousSand XylophilousWood PhytophilousPlants Faunal selection of substrates

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s13 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.htm

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s14  This figure illustrates seasonal differences in the emergence of mayfly species that would in part be cued by temperature. The effect of temperature on organisms

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s15 Maximum daily temperature range in relation to stream order in temperate streams

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s16 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.

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s17 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 ww.usask.ca/biology/skabugs/Ephem/mayfly.html