Stream Organisms

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Stream Organisms

• Uni1 Module 4, Lecture 4

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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.

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Stream organisms

• The slides on stream organisms are divided into
  three sections
• Autotrophs
• Invertebrates
• Fish

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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.

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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)

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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.

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Periphyton components

• Lotic phytoplankton include
• Algae
• Protozoans
• Cyanobacteria
• These are small enough to remain suspended in the
  water column and be transported by currents.

Biodidac
Hoffman Image Gallery
Hoffman Image Gallery
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Attached and benthic populations

• Many blue-green algae grow attached on the
  surface of rocks and stones (epilithic forms), 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.

Hoffman Image Gallery
Hoffman Image Gallery
University of Wisconsin Botanical Images
Collection
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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

www.urbanrivers.org/web_images/diatoms.gif
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Distribution of autotrophs Lakes vs rivers
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Algal primary productivity
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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.

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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)

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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.

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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).

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Patchy distribution of macrophytes

• Macrophyte distribution and abundance changes
  annually

www.glifwc.org/
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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.

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www.epa.gov/25water/exotic/slide15.jpg
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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
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Insects

• Adaptation to life in streams and rivers
• Introduction to taxonomy
• General life cycle
• Introduction to functional roles

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Morphological adaptations to running water
Adaptation Significance Representative Groups and Structures Comments
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
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Morphological adaptations to running water
Adaptation Significance Representative Groups and Structures Comments
Small size Allows use of slow-current boundary layer on top of substrate Stream animals are smaller than stillwater relatives
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
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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
Author Scudder (Leidy)
www.usask.ca/biology/skabugs/idclass/classify.html
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Aquatic insect orders
Order Number of North American aquatic species (estimated) Larvae Adults
Ephemeroptera (mayflies) 572
Odonata (dragonflies and damselflies) 357
Plecoptera (stoneflies) 582
Trichoptera (caddisflies) 1215
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Aquatic insect orders
Order Number of North American aquatic species (estimated) Larvae Adults
Diptera (flies and midges) 4662
Hemiptera (true bugs) 410
Coleoptera (beetles) 1842
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Aquatic insect orders
Order Number of North American aquatic species (estimated) Larvae Adults
Megaloptera (alderflies and dobsonflies) 43
Neuroptera (spongilla flies) 6
Lepidoptera (moths) 635
Hymenoptera (parasitic wasps) 55
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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 gt immature (larva) gt Pupa gt 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
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Life cycles of aquatic Insects
Holometabolous
Hemimetabolous

• Hemimetabolous insects pass through three stages
  in their life cycle
• 1) Egg gt Immature (nymph) gt Adult
• 2) Adults are terrestrial
• 3) Examples include stoneflies, mayflies, and
  dragonflies

fig. 14.2, p. 179 from Allan and Cushing
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Hemimetabolous life cycle
www.usask.ca/biology/skabugs/lifecycle/insectlifec
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Holometabolous life cycle

• Complete metamorphosis in the caddisfly
  Hydropsyche sp.
• Larva
• Pupa
• Adult

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ycle.html
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Adult
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Life cycle length

• Multivoltine several generations per year
• Univoltine one generation per year
• Semivoltine one generation every 2-3 years

• 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).

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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
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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)

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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)
• Gatherers
• Elmidae (riffle beetles)
• Chironomini
• Baetis
• Ephemerella
• Hexagenia

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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

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Macroinvertebrate functional roles

• 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)

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Other macroinvertebrates
Annelids (leeches and aquatic worms)
Molluscs (clams, mussels, and snails)
Crustaceans (crayfish, amphipods, and mites)
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