Stream Ecology
Freshwater Ecology
substrate
temperature
light
Physical
current
pH
photosynthesis
macrophytes
Biological
macroinvertebrates
Chemical
DO
Turbidity
fish
Conductivity
Macroinvertebrates
“Macro”
“Invertebrate”
Large enough to be
seen with the naked
eye
Lacking an internal
skeleton of cartilage
and bones
Invertebrates account for 70% of all known species of living organisms (microbes,
plants, and animals
If we consider just animals, invertebrates account for 96% of known species
The Importance of Macroinvertebrates
• Macroinvertebrates are an
essential component of
freshwater ecosystems
• They serve as food for other
organisms (fish, amphibians
and waterfowl)
• Are essential to the breakdown
and cycling of organic matter
and nutrients
• Macroinvertebrate diversity is
vital to a properly
functioning ecosystem
Why Study Macroinvertebrates?
• Macroinvertebrates are used to
assess the health of freshwater
environments
• Some macroinvertebrates are
sensitive to stress produced by
pollution, habitat modification, or
severe natural events
• Sampling and identifying
macroinvertebrates can reveal
whether a body of water is
healthy or unhealthy and may
reveal the cause of the problem
• Known as BIOMONITORING
Macroinvertebrate Biology
Habitat
Movement
Feeding
Breathing
Life History
Stress Tolerance
Habitat
The place where an organism lives
Running waters – lotic – seeps,
springs, brooks, branches, creeks,
streams, rivers
Standing waters – lentic – bogs,
marshes, swamps, ponds, lakes
erosional (riffles, wave action) or
depositional areas (point bars, pools)
Mineral
bedrock,
boulders, cobbles,
pebble, gravel,
sand, silt, clay
Organic
live plants, detritus
Movement
Locomotion, habits, or mode of existence
Clingers – maintain a relatively fixed position on firm substrates in current
Climbers – dwell on live aquatic plants or plant debris
Crawlers – have elongate bodies with thin legs, slowly move using legs
Sprawlers – live on the bottom consisting of fine sediments
Burrowers – dig down and reside in the soft, fine sediment
Swimmers – adapted for moving through water
Skaters – adapted to remain on the surface of water
Feeding
Macroinvertebrates are described by how they eat,
rather than what they eat
Functional Feeding Groups – categories of
macroinvertebrates based on body structures and
behavioral mechanisms that they use to acquire their
food
Shredders
Chew on intact or large pieces of plant material
• have basic mouthparts, without any special modifications
• basic mouthparts include two jaw like structures (mandibles) for cutting and
grinding and often an upper lip (labrum) and a lower lip (labium) to help
keep food in their mouths
• Material is usually >1 mm, referred to as Coarse Particulate Organic Matter
(CPOM)
Shredder-herbivores feed on living aquatic
plants that grow submerged in the water
(northern casemaker caddisflies)
Shredder-detritivores feed on detritus, or
dead plant material in a state of decay (giant
stoneflies)
Collectors
Acquire and ingest very small particles (<1 mm) of detritus,
often referred to as fine particulate organic matter (FPOM)
Collector-gatherers – eat fine detritus that has fallen out of
suspension that is lying on the bottom or mixed with
bottom sediments
• position themselves on the bottom and eat the detritus from
the top of the sediment (non-biting midges)
• burrow through the bottom and unselectively swallow the
sediment and fine detritus as they go (aquatic
earthworms)
• finger-like projections from some of the mouthparts (palps)
help them gather the fine particles of food
Collector-filterers- use special straining mechanisms to
feed on fine detritus that is suspended in the water
• spin nets from silk (netspinner caddisflies)
• have hairs on their heads (black flies)
• appendages create water current for their feeding (mussels)
Piercers
mouthparts, or sometimes their entire head, protrude as modifications to puncture
food and bring out the fluids contained inside
mouthparts are modified into one or two hard, sharp, hollow tubes that they use to
stab into their prey (water scorpions)
Piercer-herbivores – penetrate the
tissues of vascular or aquatic plants
or individual cells of filamentous
algae and suck the liquid contents
(crawling water beetles,
microcaddisflies)
Piercer-predators – subdue and kill
other animals by removing their
body fluids
Scrapers/Grazers
• Adapted to remove and consume the
thin layer of algae and bacteria that
grows tightly attached to solid
substrates in shallow waters
• Jaws of scrapers have sharp, angular
edges (function like using a putty
knife or paint scraper)
• After algae has been removed, the
material is swept into the mouth by
finger like projections from other
mouthparts
(flathead mayflies, water pennies, snails)
Engulfer-Predators
• Feed upon living animals,
either by swallowing the
entire body of small prey or
by tearing large prey into
pieces that are small enough to
consume
• Typically have large jaws with
pointed ends and sharp, tooth
like projections for attacking
and devouring their prey
e.g. (common stoneflies and hellgrammites)
Autochthonous vs. Allochthonous Inputs
Autochthonous – the relative amount of biomass
produced within the system (in stream) algae, periphyton,
macrophytes
Allochthonous – the relative amount of biomass
produced outside the system (riparian and upland) tree and
shrub leaves and needles
Light is a primary determinant of whether the food base for a given
community is live green plants growing within the aquatic
environment or decaying plant material that originated in the
terrestrial environment
River Continuum Concept
River
Continuum
Concept
Breathing
Closed Breathing System
Open Breathing System
depend upon oxygen dissolved in the
water for their breathing
obtain oxygen directly from the
atmosphere
Oxygen enters the organisms by
simple diffusion either through their
general body surface or through gills
that are specialized for this purpose,
or both
All some attach a quantity of air to
their body, called an air store, and take
it underwater to breathe from (either in
a bubble or in a thin layer)
Some have behavioral mechanisms,
such as wriggling the body, to
increase the rate of oxygen diffusion
Others breathe by pushing either
spiracles or some type of extension on
the end of their body to the surface to
reach the atmosphere (breathing tubes
or siphons)
Life History
Reproduction, growth and development of an organism
Hermaphroditic organisms – contain both male and female reproductive organs
(flatworms, aquatic earthworms, leeches, snails and mussels)
Oviparous – females lay their eggs outside of their body
Ovoviviparous – females retain their eggs and allow them to hatch within their
body and release free-living offspring
Growth is relatively simple in flatworms, aquatic earthworms and leeches because
they are not restricted by any type of external protective structures
Exoskeletons of arthropods does not grow once it has been produced, so growth of
the organism is restricted. As a result, arthropods must shed their skin (molt) in
order to increase in size (3-45 times).
Mollusks are enclosed in non-living protective covers produced by the organism,
called shells; shells are made of protein and calcium carbonate; made larger by
adding material, like a tree growth ring
Complete Metamorphosis
Incomplete Metamorphosis
Stress Tolerance
Natural
volcanoes, forest
fires, floods,
landslides
Anthropogenic
pollution, removal of water
by irrigation, dams,
deforestation, removal of
riparian vegetation
Freshwater invertebrates vary in their ability to cope with
environmental stress
Biomonitoring takes advantage of this situation by identifying
whether an aquatic environment is inhabited predominantly by stress
tolerant or stress intolerant organisms
Classification
Kingdom: Animalia
Phylum: Arthropoda (Arthropods)
Annelida (Segmented Worms)
Mollusca (Mollusks)
Group 1 Taxa
Pollution Sensitive Organisms Found In
Good Quality Water
Stoneflies
Mayflies
Water Pennies
Dobsonflies
Riffle Beetles
Mussels
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Plecoptera
“plekein” – to braid (wings of adult are folded to fit under front wings) Families: Perlidae
“ptera” – tail
Perlodidae
Leuctridae
Plecoptera: Stoneflies
• 3 pairs of segmented legs on thorax
• 2 tarsal claws
• 2 stick-like tails
• gills on thorax (often where leg joins thorax)
• long antennae
• double set of wings
• wing pads are often visible
• most are crawlers
• shredder-detritivores or engulfer-predators
Incomplete Metamorphosis
Adults:
long, thin antennae that
project from the head
Both pairs of wings are
membranous and have
many veins
Wings fold, when not is
use, so that they lie flat
over the abdomen
Ephemeroptera: Mayflies
“ephemeros” – lasts a day
“Ptera” - wings
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Ephemeroptera
Families: Baetidae
Heptageniidae
Ephemeridae
• Usually has 3 tails, although some with 2
Incomplete Metamorphosis
• single tarsal claw
• 3 pair of segmented legs on thorax
Adults have
• gills occur on abdomen (flat plates or filaments)
triangular shaped
• short antennae
wings that are held
straight up when
• have a single set of wingpads
body is at rest
• scraper/grazer or collector-gatherers
Coleoptera: Beetles
Water Penny
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Psephenidae
“koleon” – sheath hardened front wings provide protective cover
“ptera” – wing
for hind wings and abdomen
Complete Metamorphosis
• thin, flat, flexible plates to help mold body to rock shape
• single hooks at the end of legs
• jaws have thin sharp edge to scrape algae
• dense fringe of fine hairs to increase grip on rocks
• gills occur on underside of abdomen
• lotic-erosional
• clingers
• scrapers
Megaloptera: Dobsonflies
and Fishflies (Hellgramites)
“megal” – large or of giant size
“ptera” – tail
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Megaloptera
Family: Corydalidae
Complete Metamorphosis
• 6 legs
• large mandibles, projecting toothed jaws
• large elongate bodies
• head and thorax have thick, hardened skin, abdomen
thin and soft
• 8 pairs of lateral filaments from abdomen segments
• gill tufts
• no wing pads occur on thorax
• engulfer-predators
• primarily lotic-erosional
• primarily crawlers, some burrowers, sprawlers
Adults:
cylindrical bodies
soft abdomen
Wings are large,
elongate,
membranous with
many veins
wings held
slanted and roof
like over the
abdomen
Coleoptera: Beetles
Riffle Beetle
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Elmidae
“koleon” – sheath hardened front wings provide protective cover
“ptera” – wing
for hind wings and abdomen
Complete Metamorphosis
• segmented, hardened, worm-like body
• gills protrude from end of abdomen
• primarily lotic-erosional, lentic-littoral
• scrapers, collector-gatherers
• primarily clingers, also climbers
Mollusca: Mussels
“mollu” – hard or brittle external coat
“bi” – two
“valva” – hinged and movable pieces
“volvere” – to roll or wrap
• mussels and clams are mollusks that have
two shells
• often the largest invertebrates present in
freshwater environments
• live throughout lotic and lentic habitats
• collector-filterers, have tubular siphons
that create a one way current, cilia and
mucous coating on gill filaments filter
suspended particles of food
• burrowers
• have parasitic larval stage
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Group 2 Taxa
Can Exist Under a Wide Range of Water Quality
Conditions
Generally of Moderate Quality Water
Caddisflies
Damselflies
Dragonflies
Blackflies
Craneflies
Water Boatman
Backswimmers
Crayfish
Amphipods
Trichoptera: Caddisflies
“trich” – hair
“ptera” – tail
• 6 segmented legs
• worm-like bodies
• no easily visible antennae
• thick, hardened skin on head
• either live in a fixed retreat or makes a
portable case
• shredder-detritivores, shredder-herbivores,
collector-gatherers, collector-filterers,
and scrapers
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Trichoptera
Family: Hydropsychidae
Family: Limnephilidae
Family: Helicopsychidae
Complete Metamorphosis
Adults have long wings
folded back
Odonata: Dragonflies and
Damselflies
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Odonata
Families: Aeshnidae
“odon” – tooth, refers to mouthparts of the adults
Gomphidae
Libellulidae
• Wing pads are present on the thorax
Families: Calopterygidae
• Three pairs of segmented legs extend from the thorax
Coenagrionidae
• Two claws occur on the end of segmented legs
Lestidae
• No gills are found on the sides of the abdomen, but
some have three, elongate gills
Incomplete Metamorphosis
• Bodies are either long and stout or oval and somewhat flattened
• Head is narrower than the thorax and abdomen
• No gills are found on the end of the abdomen
• Three short, stiff, pointed structures occur on the end of the
abdomen, forming a pyramid-shaped valve for the opening
on the end of the abdomen
• body is elongate and slender
• head is wider than the thorax and abdomen
• three flat, elongate gills project from the rear of the abdomen
Hemiptera: True Bugs
Water Striders
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hemiptera
Family: Gerridae
“heteros” – different
Half wing near body is leathery, half is membranous
“ptera” - wing
• 3 pairs of segmented legs on thorax
• legs are skinny and long to help distribute body weight
• 2 claws on segmented legs
• only middle and hind legs touch water; front legs are held up
• piercer-predators
• skaters
• lentic-limnetic or lotic-depositional
Incomplete Metamorphosis
Hemiptera: True Bugs
Water Boatman
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hemiptera
Family: Corixidae
“heteros” – different
Half wing near body is leathery, half is membranous
“ptera” - wing
Incomplete Metamorphosis
• well developed, prominent eyes
• modified beak (blunt, triangle shaped non-segmented mouth)
• swims upright (backswimmers swim on back)
• have short front legs, much shorter than other pairs of legs
• two long claws on mid pair of legs
• swimming hairs
• 2 pair of long hind legs with swimming
• dark colored back, light colored stomach
• hind legs are oarlike with swimming hairs
• front legs with stiff setae (hairs) to be used like a rake
• surface for air; thin film of air on underside (plastron)
• collector-gatherers
• lentic-littoral and lotic-depositional habitats
Hemiptera: True Bugs
Backswimmers
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hemiptera
Family: Notonectidae
“heteros” – different
Half wing near body is leathery, half is membranous
“ptera” - wing
Incomplete Metamorphosis
• oval shaped body, dark colored stomach
• swims on back
• has short front legs
• hind pair of legs are oarlike with swimming hairs
• has narrow, segmented beak (mouth)
• uses hind legs as oars
• usually red eyes, well-developed and prominent
• dark colored stomach, light colored back
• lentic-littoral and lotic-depositional habitats
• swimmers
• piercer-predators
• hold stored air in two troughs with fringes of hair on the bottom of abdomen
Diptera: True Flies
Blackfly
“di” – two
True flies have two wings, other insects have four
“ptera” - wing
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Simulidae
Complete Metamorphosis
• worm-like with one swollen end (bowling pin)
• usually dark in color
• usually live in colonies
• have well developed, hardened head
• fan-like mouth with brushes used for eating
• proleg under head
• have disc at rear end with many small hooks to attach to rocks
• lotic-erosional
• clingers-use silk to stick to substrate
• collector-filterers
Diptera: True Flies
Crane Flies
“di” – two
True flies have two wings, other insects have four
“ptera” - wing
• fleshy, plump, segmented, worm-like body
• no legs, no wings
• usually brown, white or green in color
• head is retractable
• two spiracles on posterior used for breathing
• burrowers, sprawlers
• shredder-detritivores, collector-gatherers
• lentic-littoral; lotic-erosional, lotic-depositional
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Tipulidae
Complete Metamorphosis
Crustacea: Crustaceans
Decapoda (Crayfish)
“crusta” – hard or brittle external coat
“deka” – ten
“poda” – foot
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Family: Astacidae
Crayfish have five pairs of walking legs
Incomplete Metamorphosis
• one pair of antennae much longer than others
• 5 pairs of walking legs
• 2-3 pair of walking legs have hinged claw
• other legs have pointed tip
• 2 large, compound eyes
• live in a variety of habitats
• are mostly nocturnal
• omnivores
Crustacea: Crustaceans
Amphipods
(Scuds/Sideswimmer)
“crusta” – hard or brittle external coat
“amphi” – of both kinds
“poda” – foot
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Amphipoda
Incomplete Metamorphosis
Two kinds of appendages on bottom of body
• 7 pair of legs
• 2 pair of antennae
• head fused to thorax
• laterally flattened
• white or clear body with many segments
• swims sideways and rests in a curved position
• occur in many habitats
• omnivores, many functional feeding groups
Group 3 Taxa
Can Exist Under a Wide Range of Water Quality
Conditions, Generally are Highly Tolerant of Poor
Quality Water
Midgeflies/Chironomids
Worms
Leeches
Pouch Snails
Diptera: True Flies
Midge/Chironomid
“di” – two
True flies have two wings, other insects have four
“ptera” - wing
• small, slender, slightly curved body
• hardened head capsule (often yellow)
• sometimes has a brush like structure at rear
• occur in all types of habitats
• primarily burrowers
• primarily collector-gatherers
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Chironomidae
Complete Metamorphosis
Kingdom: Animalia
Phylum: Annelida
Class: Oligochaeta
“olig” – long
“chaite” - hair
Worms and Leeches
Incomplete Metamorphosis
• body is soft, moderately muscular,
elongate and cylindrical
• body consists of round, ring-like
segments arranged in a row
• each segment after the first has
bundles of tiny hairs (chaetae)
• no suckers or eyespots are present
• lentic-littoral, lotic-depositional
• burrowers, collector-gatherers
Kingdom: Animalia
Phylum: Annelida
Class: Hirudinia
Order: Rhynenobdella
Incomplete Metamorphosis
• flat, segmented body
• head section usually skinnier than rear
• body shape can change with movement
• ventral side is usually paler in color
• ventral suckers on both ends
• sometimes attach to and feed off other
organisms
Mollusca: Clams, Mussels,
Snails
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
“mollu” – hard or brittle external coat
“gaster” - stomach
“pod” - foot
digestive system begins in muscular foot
projecting from shell
• snails are freshwater mollusks with one shell
• divided into two major groups, based on breathing
• some breathe oxygen dissolved in water (gilled
snails)
• others obtain oxygen from air by structure that
works like a lung (lunged snails)
• lentic-littoral, lotic-depositional, lotic-erosional
• scrapers
Pollution Indices
EPT - # of EPT taxa found in stream (Ephemeroptera,
Plecoptera, Trichoptera) mayflies, stoneflies, caddisflies
% of Aquatic Worms (% of Midges) numbers of
individuals found that are midges
Pollution Sensitivity Index – Assigns Scores to Each Type
of Macroinvertebrate - sum ten indices to get a composite
score