Stream Organisms
Uni1: Module 4, Lecture 4
Objectives
Students will be able to:
 describe major characteristics of autotrophs.
 categorize autotrophs types by location.
 contrast seasonal variations in the growth of
periphyton communities.
 compare and contrast the four types of macrophytes.
 define and provide examples of stream
macroinvertebrates.
 provide examples of morphological adaptations to
water and interpret their significance.
 diagram the life cycles of aquatic insects.
 compare and contrast the functional roles of
macroinvertebrates in organic matter processing.
Developed by: Merrick, Richards
Updated: August 2003
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Stream organisms
 The slides on stream organisms are divided
into three sections:
 Autotrophs
 Invertebrates
 Fish
Developed by: Merrick, Richards
Updated: August 2003
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Autotrophs
 Autotrophs are organisms that acquire materials from
the environment and energy from sunlight in the
process of producing organic matter.
 Green plants, diatoms and filamentous algae, some
bacteria, and some protists make up the autotrophs in
lotic systems.
 In contrast, heterotrophs, such as fungi or fish gain
nutrients and energy by processing dead organic
matter.
 Functionally, autotrophs serve lotic communities by
making organic energy available to consumer
organisms at higher trophic levels.
www.glifwc.org/
Developed by: Merrick, Richards
Updated: August 2003
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Benthic autotrophs
 Benthic autotrophs grow on virtually all
surfaces receiving light in flowing waters
and are collectively referred to as the
periphyton community.
 Habitat specialization allows for
classification of benthic autotrophs into
groups;
 Species that grow on stones (epilithon)
 Species that grow on soft sediments (epipelon)
 Species that grow on other plants (epiphyton)
Developed by: Merrick, Richards
Updated: August 2003
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Periphyton
 Periphyton is a complex matrix of algae and
heterotrophic microbes attached to submerged
substrata in almost all aquatic ecosystems.
 It serves as an important food source for
invertebrates and some fish, and it can be an
important sorber of contaminants.
www.duluthstreams.org/understanding/algae.html
Developed by: Merrick, Richards
Updated: August 2003
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Periphyton components
 Lotic phytoplankton include:
 Algae
 Protozoans
phytoflagellates
Hoffman Image Gallery
(euglenophyta)
 Cyanobacteria
 These are small enough to remain
Hoffman Image Gallery
Biodidac
suspended in the water column and be
transported by currents.
www.cawthron.org.nz/periphyton_image.htm
Developed by: Merrick, Richards
Updated: August 2003
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Attached and benthic populations
 Many blue-green algae
Hoffman Image Gallery
grow attached on the
surface of rocks and
stones (epilithic forms),
Hoffman Image Gallery
on submerged plants
(epiphytic forms) or on
the bottom sediments
(epipelic forms, or the
benthos) of rivers.
 The epiphytic flora of
lotic communities is
usually dominated by
diatoms and green algae,
and blue-greens are of
less importance in this
community.
green algae
(chlorophyta)
Biodidac
blue-green algae
(cyanobacteria)
Diatoms
University of Wisconsin Botanical Images Collection
Developed by: Merrick, Richards
Updated: August 2003
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Seasonal succession in periphyton
communities
 Diatoms dominate
during the winter, spring,
and early summer
 Green algae and
cyanobacteria
populations increase
during the summer
 Benthic autotrophs
tends to decrease during
the summer as a result
of increased shading,
increasing again in fall
Developed by: Merrick, Richards
www.urbanrivers.org/web_images/diatoms.gif
Updated: August 2003
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Distribution of autotrophs: Lakes vs rivers
Image from Allan, Fig. 4.12, p. 105
Developed by: Merrick, Richards
Updated: August 2003
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Algal primary productivity
Photosynthesis
-Light
-Nutrient
-Velocity
- Temperature
- Chronic toxicity
Washout
Loading
Turbulent
diffusion
Algal biomass
Grazing
Respiration/Excretion
-Velocity
-Available substrate
Mortality
Sinking
-Acute toxicity
- Velocity
-High temperature
- Stress
www.epa.gov/waterscience/pc/wqnews/algal.gif
Developed by: Merrick, Richards
Updated: August 2003
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Macrophytes
 Westlake (1975a) identified four primary growth forms:
 1) Emergents occurring on river banks and shoals
typically are rooted in soil that is near or below the
waterline and have aerial leaves and reproductive
structures;
 2) Floating-leaved species occupy margins of slow
current areas, are rooted in submerged soils, and have
aerial or floating leaves and reproductive structures;
 3) Free-floating species are typically not attached to the
substrate and often form mats that entangle other
species in slow flowing tropical rivers;
 4) Submerged species are rooted to the substrate, have
submerged leaves, and are located in mid-channel to the
point of insufficient light penetration.
Developed by: Merrick, Richards
Updated: August 2003
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Macrophyte growth forms
 Emergents: banks and
shoals
 Floating-leaved: stream
margins
 Free-floating: slow
(tropical) rivers
 Submerged: midstream
(limited by light
penetration, current
speed, and substrate
type)
Emergent
cce.cornell.edu/onondaga/watersheds/images/milfoil.jpg
Floating-leaved
www.sthubertsisle.com/Lily%20pads.jpg
Free-floating
http://lakes.chebucto.org/VIEW/PIC/duckweed.jpg
Submerged
http://riverwoods.ces.fau.edu/riverwoods/display
.ihtml?pic=../photos/birdseyenupharsm.jpg
Developed by: Merrick, Richards
Updated: August 2003
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Macrophyte growth forms
 Aquatic macrophytes do not show adaptations
to life in rivers and streams.
 Consequently, they are limited to areas of little
current and suitable substrate.
 Most commonly these areas include; deltas,
backwaters, pools, beaver impoundments,
margins, banks, shoals, and contiguous
wetlands.
Developed by: Merrick, Richards
Updated: August 2003
U1-m4-s14
Basic macrophyte structure
 Success and maintenance
of macrophyte populations
in significant current can
be attributed to a few
adaptive characteristics.
 Tough, flexible stems and
leaves; attachment by
adventitious roots,
rhizomes, or stolons; and
vegetative reproduction
characterize most lotic
macrophyte species
(Hynes, 1970; Westlake,
1975a).
Stems and leaves
Adventitious roots
aquat1.ifas.ufl.edu/zizaqu2.jpg
Developed by: Merrick, Richards
Updated: August 2003
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Patchy distribution of macrophytes
 Macrophyte distribution and abundance
changes annually
www.glifwc.org/
Developed by: Merrick, Richards
Updated: August 2003
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Macrophyte consumers
 Even in streams that show
high macrophyte productivity,
a relatively small fraction of
the streams total energy
results from macrophyte
production.
 The fate of this primary
production includes
herbivory, secretion of
dissolved organic matter, and
decomposition.
 Herbivory is carried out in
large part by vertebrates,
including waterfowl, manatee,
grass carp, muskrat
(Westlake, 1975b), and
moose.
www.epa.gov/25water/exotic/slide15.jpg
http://images.fws.gov/
http://www.fcsc.usgs.gov/posters/Nonindigenous/Nonindigenous_Crustaceans/nonindigenous_crustaceans.html
Developed by: Merrick, Richards
Updated: August 2003
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Stream invertebrates
 Much of the aquatic life in streams is
composed of benthic macroinvertebrates.
 The term macroinvertebrate includes clams,
crayfish, worms, and insects.
 Macroinvertebrates do not have internal
skeletons, are larger than 5 microns, and,
typically, live on a stream substrate (bottom,
woody debris, macrophyte, etc..)
photo source: North American Benthological Society
Developed by: Merrick, Richards
Updated: August 2003
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Insects
 Adaptation to life in
streams and rivers
 Introduction to
taxonomy
 General life cycle
 Introduction to
functional roles
Developed by: Merrick, Richards
Updated: August 2003
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Morphological adaptations to running water
Adaptation
Significance
Representative Groups
and Structures
Dorsoventrally
Flat
Allows crawling in
slow current
boundary layer on
substrate
Odonata – Gomphidae
Trichoptera - Glossosoma
Streamlining
Fusiform body
minimizes resistance
to current
Ephemeroptera – Baetis
Diptera - Simulium
Relatively rare body
form
Reduced
projecting
structures
Reduces resistance
to current
Ephemeroptera - Baetis
Large lateral structures
exist in some groups
Suckers
Attach to smooth
surfaces
Diptera - Blephariceridae
Rare adaptation
Friction Pads
Increased contact
reduces chances of
being dislodged
Coleoptera - Psephinus
Developed by: Merrick, Richards
Comments
Updated: August 2003
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Morphological adaptations to running water
Adaptation
Significance
Small size
Allows use of slow-current
boundary layer on top of
substrate
Silk and sticky
secretions
Attachment to stones in swift
current
Diptera – Simulium
Trichoptera - Hydropsychidae
Ballast
Cases made of large stones
Trichoptera - Goera
Attachment
claws /dorsal
processes
Stout claws aid in
attachment to plants
Ephemeroptera - Ephemerella
Reduced
power of flight
Prevents emigration from
small habitats
Plecoptera - Allocapnia
Reduces
dispersal ability
Hairy bodies
Keeps sand/soil particles
away while burrowing
Ephemeroptera - Hexagenia
Allows water flow
over body
Hooks or
Grapples
Attachment to rough areas of
substrates
Coleoptera - Elmidae
Developed by: Merrick, Richards
Representative Groups
and Structures
Comments
Stream animals
are smaller than
stillwater relatives
Updated: August 2003
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Classification of insects
Common
Name
Human
Canada Goose
Lake Darner Dragonfly
Giant water bug
Kingdom
Animalia
Animalia
Animalia
Animalia
Phylum
Chordata
Chordata
Arthropoda
Arthropoda
Class
Mammalia
Aves
Insecta
Insecta
Order
Primate
Anseriformes
Odonata
Hemiptera
Family
Hominidae
Anatidae
Aeshnidae
Belostomatidae
Genus
Homo
Branta
Aeshna
Lethocerus
species
sapiens
canadensis
eremita
americanus
Scudder
(Leidy)
Author
www.usask.ca/biology/skabugs/idclass/classify.html
Developed by: Merrick, Richards
Updated: August 2003
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Aquatic insect orders
Number of
North American
aquatic species
(estimated)
Order
Ephemeroptera
(mayflies)
Larvae
572
Odonata
(dragonflies and
damselflies)
Plecoptera
(stoneflies)
www.usask.ca/biology/skabugs/
www.usask.ca/biology/skabugs/
357
www.usask.ca/biology/skabugs/
www.usask.ca/biology/skabugs/
582
www.usask.ca/biology/skabugs/
Trichoptera
(caddisflies)
Adults
www.usask.ca/biology/skabugs/
1215+
www.usask.ca/biology/skabugs/
Developed by: Merrick, Richards
www.usask.ca/biology/skabugs/
Updated: August 2003
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Aquatic insect orders
Number of
North American
aquatic species
(estimated)
Order
Diptera (flies and
midges)
Larvae
www.usask.ca/biology/skabugs/
4662+
www.usask.ca/biology/skabugs/
Hemiptera (true
bugs)
Adults
www.usask.ca/biology/skabugs/
www.usask.ca/biology/skabugs/
www.usask.ca/biology/skabugs/
410
www.usask.ca/biology/skabugs/
Coleoptera
1842+
(beetles)
www.usask.ca/biology/skabugs/
Developed by: Merrick, Richards
Updated: August 2003
www.usask.ca/biology/skabugs/
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Aquatic insect orders
Number of
North American
aquatic species
(estimated)
Order
Megaloptera
(alderflies and
dobsonflies)
Larvae
Adults
www.usask.ca/biology/skabugs/
43
www.usask.ca/biology/skabugs/
Neuroptera
(spongilla flies)
www.usask.ca/biology/skabugs/
6
www.usask.ca/biology/skabugs/
635
Lepidoptera
(moths)
www.usask.ca/biology/skabugs/
Hymenoptera
(parasitic wasps)
55
Developed by: Merrick, Richards
Updated: August 2003
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Life cycles of aquatic Insects
Holometabolous
Hemimetabolous
 Holometabolous insects
pass through a complete
metamorphosis that
consists of four stages:
 1) Egg > immature (larva)
> Pupa > Adult
 2) During pupal stage
adult characteristics
develop
 3) Examples include;
caddisflies and dipterans
such as blackflies
fig. 14.2, p. 179 from Allan and Cushing
Developed by: Merrick, Richards
Updated: August 2003
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Life cycles of aquatic Insects
Holometabolous
Hemimetabolous
 Hemimetabolous
insects pass through
three stages in their
life cycle:
 1) Egg > Immature
(nymph) > Adult
 2) Adults are
terrestrial
 3) Examples include;
stoneflies, mayflies,
and dragonflies
fig. 14.2, p. 179 from Allan and Cushing
Developed by: Merrick, Richards
Updated: August 2003
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Hemimetabolous life cycle
www.usask.ca/biology/skabugs/lifecycle/insectlifecycle.html
Developed by: Merrick, Richards
Updated: August 2003
U1-m4-s28
Holometabolous life cycle
 Complete metamorphosis in the caddisfly
Hydropsyche sp.
 Larva
 Pupa
 Adult
www.usask.ca/biology/skabugs/lifecycle/insectlifecycle.html
www.usask.ca/biology/skabugs/lifecycle/insectlifecycle.html
Adult
www.usask.ca/biology/skabugs/lifecycle/insectlifecycle.html
Developed by: Merrick, Richards
Updated: August 2003
U1-m4-s29
Life cycle length
 Multivoltine – several
generations per year
 Univoltine – one
generation per year
 Semivoltine – one
generation every 2-3
years
www.mendozaflyshop.com/images/6_01.jpg
Developed by: Merrick, Richards
 Baetis sp., a common
mayfly is noted to be
univoltine at low
elevation and warmer
temperatures and
semivoltine at high
elevations and colder
temperatures (Allan,
1995).
Updated: August 2003
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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
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Macroinvertebrate functional roles in
organic matter processing
 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)
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
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Macroinvertebrate functional roles
 Collectors
 Dominant food
 Decompose fine particulate organic matter (FPOM)
 Feeding mechanisms
 Filterers - Detritivores
 Gatherers - Detritivores
 Representatives
 Filterers
• Hydropsychidae
• Simulidae (black flies)
A blackfly of the
family Simulidae
 Gatherers
•
•
•
•
•
Elmidae (riffle beetles)
Chironomini
Baetis
Ephemerella
Hexagenia
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
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Macroinvertebrate functional roles
 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
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-s34
Macroinvertebrate functional roles
 Predators
 Dominant food
 Living animal tissue

Feeding mechanisms
 Engulfers - Attack prey and ingest whole animals
 Piercers - Pierce tissues, suck fluids

A stonefly of the
family Perlidae
Representatives
 Engulfers
• Anisoptera (dragonflies)
• Acroneuria
• Corydalus (hellgrammites)
 Piercers
• Veliidae (water striders)
• Corixidae (water boatmen)
• Tabanidae (deerflies & horseflies)
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-s35
Other macroinvertebrates
Annelids (leeches and
aquatic worms)
http://www.usask.ca/biology/skabugs/
http://www.usask.ca/biology/skabugs/
Molluscs (clams,
mussels, and snails)
http://www.usask.ca/biology/skabugs/
http://www.usask.ca/biology/skabugs/
Crustaceans (crayfish,
amphipods, and mites)
http://www.usask.ca/biology/skabugs/
Developed by: Merrick, Richards
http://www.usask.ca/biology/skabugs/
Updated: August 2003
http://www.usask.ca/biology/skabugs/
U1-m4-s36