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