Stream Communities and River Continuum Concept

Stream Energy Inputs and FoodwebsBiofilms and Periphyton

Organic Matter TransformationsMacroinvertebrate Functional Feeding Groups

Seasonality of Stream CommunitiesRiver Continuum Concept

Stream Energy InputsDissolved organic matter (DOM) is being taken up by bacteria and fungi as part of the formation of fine particulate organic matter (FPOM), which is eaten directly by some filter feeding (collector) consumers.

Nutrients Spiral• Net unidirectional flow moves nutrient inputs downstream.

• The chemical form will change between those in particles and those dissolved in the flowing water.

• We largely view the benthic habitat as where most dissolved forms are taken up into particulate forms; however, this does happen in the water too, particularly for larger order streams (>7; aka rivers).

• Spiral length (S) is the sum of particle (Sp) plus dissolved (Sw) transport lengths.

Biofilms:

Substrate may be rock, woody debris, macrophytes, CPOM, or even certain animals.

Periphyton Community Controls

Periphyton MorphologyVelocity will influence the species and morphology; think boundary layers.

Organic Matter TransformationsImmediate leaching to DOM, which is used by bacteria or aggregates to FPOM.

Fungal colonization is critical as they possess cellulase enzymes.

Abrasion and shredder macroinverts release FPOM

Cold-Water Stream Foodweb with Functional Feeding Groups

Soil DOM and

FPOM!

Functional Feeding Groups

Shredders: Tear and eat CPOM for nutrition of microbial colonizers.

Scrapers: “Grazers” of biofilms and benthic algae.

Piercers: Suck juices from macrophytes.

Collectors: FPOM specialists.

Predators: Eat other inverts.

All produce FPOM in the form of feces!

Seasonal community succession in small cold-water streams…

• Why the drop-off in light at the stream surface?

• Can you detect a spring scour event?

• What happens to the leaves in the stream from spring to summer – by whom?

• Notice there is about a constant insect larvae biomass throughout the year. How can this happen?

River Continuum Concept

Study and understand the contents of Table 22.2!