Developed by: Merrick, Richards Updated: August 2003 U1-m4-s1 Trophic Relationships.
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Transcript of Developed by: Merrick, Richards Updated: August 2003 U1-m4-s1 Trophic Relationships.
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s1
Trophic Relationships
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s2
Microbial Food Webs
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s3
Microbial Food Webs
Bacteria and Fungi Carbon flux evidence shows importance Makes resources available DOM Detritus
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s4
How might energy be transferred to fish?
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s5
Energy Transfer
Microbes consumed by protozoans & micro-metazoans Food particles are small (~5.0 µM bacterial cell) Several trophic transfers within microbial web Energy lost with each transfer:
typical models transfer 10% between levels 90% lost as entropy to system
More steps = more loss
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s6
Is this the only way to eat microbes?
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s7
Energy Transfer
Direct ingestion of biofilms! Scraping Ingestion with CPOM
Conversion to plankton Scouring
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s8Organic microlayer-microbial community on submerged objects in streams
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s9
Where is the production?
Bacterial production in the water column is modest
Benthic bacteria dominate community respiration We don’t know enough . . .
Looking for a good research topic: The importance of bacterial and fungal metabolism
to Carbon cycling in lotic ecosystems?
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s10
Who eats the bacteria?
Water column Bacterial size: average = 0.5 µm Few suspension feeders able to capture
that size prey:Black fly larvaeAsiatic clam Corbicula
Protozoans most likely grazers Flagellates - 5.0 µm in diameter Ciliates - 25 µm in diameter on average
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s11
Who eats the bacteria?
Benthic Associated with microlayers & periphyton
Benthic grazers of attached materialDeposit feeders that pass organic matter & associated microbes through their gut.
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s12Microbial Web
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s13
Looking and the slide why are bacteria important?
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s14Microbial Web
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s15
Microbial Food Webs: H2O column vs. benthos
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s16
Categorization of Trophic Relationships in Streams
How do we normally assign trophic relationships?
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s17
Trophic Relationships
Difficult to assign typical categories Producer, grazer, carnivore, top predator Trophic level
Assignment to guilds is easier Guild = species that consume a common resource and
acquire it in a similar fashion Provides subdivision in feeding roles for both inverts and
vertebrates Same as functional groups (FFG, Inverts)
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s18
Shredders Dominant food
Vascular macrophyte tissue Coarse particulate organic material (CPOM) Wood
Feeding mechanisms Herbivores - Chew and mine live macrophytes Detritivores - Chew on CPOM
Representatives Scathophagidae (dung flies) Tipulidae (crane flies)
Macroinvertebrate functional roles in organic matter processing
A caddisfly of the family Limnephilidae
www.oaa.pdx.edu/CAE/Programs/sti/pratt/feeding/inverts/shredder.html
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s19
Collectors Dominant food
Decompose fine particulate organic matter (FPOM) Feeding mechanisms
Filterers - Detritivores Gatherers - Detritivores
Representatives Filterers
• Hydropsychidae • Simulidae (black flies)
Gatherers• Elmidae (riffle beetles)• Chironomini• Baetis• Ephemerella• Hexagenia
Macroinvertebrate functional roles
A blackfly of the family Simulidae
A caddisfly of the family Hydroptilidae
www.oaa.pdx.edu/CAE/Programs/sti/pratt/feeding/inverts/collector.html
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s20
Scrapers Dominant food
Periphyton (attached algae) Material associated with periphyton
Feeding mechanisms Graze and scrape mineral and organic surfaces
Representatives Helicopsychidae Psephenidae (water pennies) Thaumaleidae (solitary midges) Glossosoma Heptagenia
Macroinvertebrate functional roles
A dipteran of the family Thaumaleidae
www.oaa.pdx.edu/CAE/Programs/sti/pratt/feeding/inverts/scraper.html
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s21
Predators Dominant food
Living animal tissue Feeding mechanisms
Engulfers - Attack prey and ingest whole animals Piercers - Pierce tissues, suck fluids
Representatives Engulfers
• Anisoptera (dragonflies)• Acroneuria• Corydalus (hellgrammites)
Piercers• Veliidae (water striders)• Corixidae (water boatmen)• Tabanidae (deerflies & horseflies)
Macroinvertebrate functional roles
A stonefly of the family Perlidae
A “true bug” of the family Notonectidae
www.oaa.pdx.edu/CAE/Programs/sti/pratt/feeding/inverts/predator.html
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s22
Ecological roles
Macroinvertebrates play a variety of roles in food webs.
Fig. 4.9, p.53 in Allan and Cushing, 2001
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s23
Feeding roles of invertebrate consumers in running waters
Feeding Role Food Resource Feeding Mechanism Examples
Shredder Non-woody CPOM: leaves & associated microbiota
Chewing and mining Several families of Trichoptera, Plecoptera, Crustacea: some Diptera, snails
Shredder/gouger Woody CPOM and microbiota, especially fungi
As above Occasional taxa among Dipter, Coleoptera, Tricoptera
Suspension feeder/filterer-collector
FPOM and microbiota, bacteria & sloughed periphyton
Collect particles using setae, specialized filtering apparatus or nets and secretions
Net-spinning Trichoptera, Simuliidae and some Diptera; some Ephemeroptera
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s24
Feeding roles of invertebrate consumers in lotic systems
Deposit feeder/ collector-gatherer
FPOM and microbiota, especially bacteria and organic microlayer
Collect surface deposits, browse on amorphous material, burrow in soft sediments
Many Ephemeroptera, Chironomidae and Ceratopogonidae
Grazer Periphyton, especially diatoms; and organic microlayer
Scraping, rasping and browsing adaptations
Several families of Ephemeroptera and Trichoptera; some Diptera, Lepidoptera, and Coleoptera
Predator Macrophytes Piercing Hydroptilid caddis larvae
Animal prey Biting and piercing Odonata, Megaloptera, some Plecoptera, Tricoptera, Diptera and Coleoptera
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s25
Which FFG/Guild?
Can be hard to determine Food resources don’t separate cleanly Leaf enriched w/ fungi supports algae & biofilm However, classifications can be helpful Changes based upon river characteristics
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s26
How would you identify food sources for invertebrate consumers?
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s27
Identifying food sources for invertebrate consumers?
Gut analysis Diatom frustules easy to ID Food of “soft” tissues turns to mush
Stable Carbon & Nitrogen Isotopic Analysis Isotopic ratios reflect the food source 13C/12C ratio In an animal’s tissue = record of recent feeding history Reflects assimilation, not just ingestion.
Link or sink? Zebra mussels
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s28
CPOM Consumers
Shredder-CPOM Linkage Why are invertebrates important to CPOM
breakdown?
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s29
Small Stream Model: Links between CPOM, fungi & bacteria
Model for a small stream within a temperate deciduous forest
CPOM -> FPOM Physical abrasion Microbial activity Invertebrate shredders
DOM release Chemical leaching Microbial excretion &
respiration Much C enters detrital
pools as feces and fragments
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s30
Who feeds?
Crustaceans Snails Insect Larvae
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s31
“Microorganisms on a leaf are like peanut butter on a cracker, with most of the nourishment provided by the peanut butter.”Cummins, 1974
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s32
Feeding preference of amphipods
Microbe growth
permitted
Antibiotics
Autoclaved
Amphipod - Gammarus sp.
Elm leaves consumed Exp. Design
Control (with microbes) + antibiotics + steam sterilization
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s33
Invertebrate Consumers
Prefer ‘conditioned’ leaves Conditioning by microbial colonization
Preference is for leaves at some peak stage of microbial growth.
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s34
How to measure microbial biomass?
ATP Relative N content Softening of leaf discs
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s35
Influence of conditioning time of discs of hickory leaves on utilization by Tipula abdominalis.
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s36
How do microbes help?
Microbial Production Conversion to microbe biomass
Microbial Catalysis Changes that render leaves more digestible Partial digestion of substrate by microbes Exoenzymes
The bulk of the energy comes from the leaf So Cummins was not quite on target
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s37
Leaf digestion by inverts?
Where is the cellulase? Found in some mollusks, crustaceans and
annelids Aquatic insects generally lack
Some have endosymbionts Tipula (Crane Fly)
Primary source is microbial: bacteria & fungi Exoenzymes
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s38
Contrasting feeding strategies of 2 CPOM detritivores
Gammarus fossarum Tipula abdominalis
Feeding mechanism Scrapes at leaf surfaces Chews entire leaf
Gut pH & digestive biochemistry
Anterior gut slightly acid Fore & midgut highly alkaline (up to 11.6)
Its own enzymes and fungal exoenzymes attack leaf carbohydrates
Result is high proteolytic activity but inactivation of fungal exoenzymes thus little activity toward leaf carbohydrates
Posterior gut is alkaline, would digest microbial proteins and some leaf proteins
Efficiency Highly efficient at processing conditioned leaves at low metabolic cost
Less dependent upon stage of conditioning, probably good at extracting protein, but at high metabolic cost.
Other attributes of feeding ecology
Highly mobile
Polyphagous
Low mobility
Obligate detritivore
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s39
Consumers of FPOM
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s40
Consumers of FPOM
Collector-FPOM linkage Poorly Understood Where captured?
suspension or substrate Rich sources
Sloughed periphyton Organic microlayers Particles from breakdown of CPOM
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s41
Suspension Feeding Ecology
Many suspension feeders at lake outlets Densities decrease downstream Blackflies 15X more abundant at outflow vs. 2 km downstream
Tricopteran net size dependent upon flow Fine mesh more efficient but creates more drag High flow => larger mesh size
Feeding on CPOM by one invertebrate makes more food available to FPOM consumers
32P labeled alder leaves: more label transferred to suspension feeders (of FPOM) in the presence of a shredder
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s42
Collector-FPOM-bacterial linkage modeled for a small stream with a temperate deciduous forest
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s43
Black-fly Ecology
Extensively studied: pests, carriers of disease Food size range: 1 - 350 µm May be reared on a bacterial suspension May manipulate flow vortices to enhance
feeding Not limited to suspension feeding
Scraping substrate using mandibles and labrum May deposit feed on FPOM May ingest animal prey
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s44
Filtering stance of a black fly larva
Filter apparatus: fringe of microtrichia
Boundary layer typically at roughly
the height of the upper fan
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s45
Deposit feeders
Least well understood guild Some taxa shift opportunistically between this
and shredding or collecting of FPOM Common in early instars - switch to more
specialized guilds later Many “bulk-feed” from 1 - many X body weight to
get enough nutrition from sediments Seem to have fewer morphological modifications
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s46
Who are they?
Swift Streams Mayflies, Caddisflies, Midges, Crustaceans,
Gastropod Molluscs Slow Currents (fine sediments)
Add oligochaetes and nemotodes
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s47
Vertebrates in Lotic Systems
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s48
Feeding Ecology of Riverine Fishes Fish are the principle vertebrates in streams. Others? Most stream fishes
invertivores > piscivores > herbivores North America: 55 / 700 species are herbivores
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s49
Are there morphological features that would tell us what a fish eats?
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s50
Feeding Ecology of Riverine Fishes You are what you eat?
Form follows function You can tell what a fish (mostly) eats by
Specialization of dentition Jaw shape Body form Alimentary tract
Many fish are flexible in feeding habits Some change feeding habits during life cycle
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s51
Trophic guilds of stream fishes for temperate N. America
Guild Description Occurrence by species
(%)
Comments for tropical streams
Piscivore Primarily fish, some Large inverts
16 May consume part or specialize on whole
Benthic invertebrate feeder
Primarily immature insects
33 Most common in small to mid-order streams
Surface & H2O column feeder
Consumes surface prey (terrestrial) & drift (zoops & inverts of benthic origin)
11 Diverse surface foods in forested headwaters and during seasonal flood
Generalized invertebrate feeder
Feeds at all depths 11 Similar category
Planktivore Midwater specialist on phyto-and zooplankton
3 Seasonally important in large rivers
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s52
Trophic guilds of stream fishes for temperate N. America
Guild Description Occurrence by species
(%)
Comments for tropical streams
Herbivore - detritivor
Bottom feeder ingesting periphyton and detritus: includes mud feeders with long intestinal tracts
7 Herbivory may be subdivided into micro- and macrophytes, and detritus feeders separated from mud feeders
Omnivore Ingests a wide range of foods: plant, animal, detritus
6 Similar category
Parasite Ectoparasite (e.g. lampreys)
3 Ectoparasite (e.g. candirú catfishes)
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s53
Multiple Jobs
Many fish are “flexible” feeders Must use the same care here as FFGs But,
morphology does follow function Incredible specialization
Nut eaters Fin/Eye/Scale eaters
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s54
Guilds change as environment changes
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s55
Profile of an Amazonian floodplain river, showing main channel, side arms, and extent of flooded forest.
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s56
Abundance of 3 fish feeding guilds in small forested streams in Panama(a) Cichlasoma & Pimelodus: generalized invertivores(b) Brycon: detritivore when small, omnivore when larger(c) catfish feeding on periphyton
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s57Lotic food webs
Developed by: Merrick, Richards Updated: August 2003 U1-m4-s58
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