Trophic relationships

Feeding roles in streams

Aquatic insects categorized:

• Food type and how food is obtained

• Feeding guilds = functional groups

Base of trophic relationship

• Productivity from?

• Microbial loop:– Fungi, bacteria– Use dissolved organic carbon (DOC)– Passed to protozoans, etc.

Invertebrate consumers

• Food resources: – Periphyton– Macrophytes– Detritus– Animals

Feeding roles

• Shredders– Leaves, associated microbiota (CPOM)– Chewing

– Trichoptera, Plecoptera, Diptera

CPOM = > 1 mm

Feeding Roles

• Suspension feeder / filterer-collector– FPOM and microbiota– Sloughed periphyton– Use setae, nets, etc.

– Net-spinning Trichoptera, Simuliidae, Ephemeroptera

Feeding Roles

• Deposit feeder / collector-gatherer– FPOM and microbiota– Browse, collect on surface, burrow

– Ephemeroptera, Chironomidae, Ceratopogonidae

FPOM = < 0.5 mm

Feeding Roles

• Grazer– Periphyton (mostly diatoms) by scraping– Macrophytes by piercing

– Ephemeroptera, Trichoptera, Diptera, Lepidoptera, Coleoptera

Feeding Roles

• Predator– Animals– Biting, piercing

– Odonata, Megaloptera, Plecoptera, Trichoptera, Diptera, Coleoptera

Terrestrial

Stream

CPOM

DOMLeaching

Microbes

Shredders

Feces FPOM

FPOM consumers

• Suspension and deposit feeders– Many adaptations for filtering– Philopotamidae caddisfly spins net

FPOM consumers

• Suspension feeder– Black fly larvae = Simulidae

FPOM consumers

• Deposit feeder = collector-gatherer– Some in sediments, some forage

Consumers of autotrophs

• Grazers, piercers– Graze periphyton– Scraping mouthpart adaptations– Water penny beetle larva Psephenus

Consumers of autotrophs

• Another grazer– Mayfly Stenonema– Brush algae, then collect it

Predators

• Most engulf prey entire or in pieces; others have piercing mouthparts

Problems with trophic classification

• Diet shifts with age and size

• Many very young invertebrates feed on fine detritus, then change