EVPP 550 Waterscape Ecology and Management

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EVPP 550Waterscape Ecology and Management
Lecture 11

• Professor
• R. Christian Jones
• Fall 2007

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Lake Biology BenthosProfundal Benthos

• Profundal habitat can be very challenging in
  lakes
• Cold for most of the year due to summer
  stratification
• Anaerobic in mesotrophic and eutrophic lakes
• Poor food quality no resident primary producers,
  all food is imported and stale

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Lake Biology BenthosProfundal Benthos

• A few groups have been able to adapt to this
  environment
• Those which have can prosper if conditions are
  not too severe
• Examples are chironomids (midges), chaoborus
  (phantom midges) and oligochaetes

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Lake Biology BenthosProfundal Benthos

• Chironomids have been extensively studied
• Some species can maintain constant respiration
  even at low DO
• Some can withstand no oxygen for up to 4 months
  at 10oC
• Food supply of profundal chironomids is surface
  sediment particles ingested in bulk with algae
  and bacteria selectively assimilated

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Lake Biology BenthosProfundal Benthos

• Adaptations
• Hemoglobin
• Helps to bind and store limited amounts of O2
• Anaerobic glycolysis
• Can split carbohydrates to produce energy with
  using oxygen
• Similar to what happens in your muscles under
  strenuous activity
• Accumulate an oxygen debt that must later be
  satisfied
• Stop growth, become dormant

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Lake Biology Profundal Benthos

• Life History of Chironomus anthrocinus in L.
  Esrom
• Egg mass deposited at night in May on lake
  surface near shore
• Water currents spread the eggs throughout the
  lake as they sink to the bottom
• By June, hatching occurs, food is abundant and
  larvae double in size by early July
• Oxygen is depleted in summer and growth stops

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Lake Biology Profundal Benthos

• Life History of Chironomus anthrocinus in L.
  Esrom
• Fall overturn brings oxygen to the bottom
  satifying the oxygen debt and allowing fresh
  growth to occur based on food still in the water
  column
• Animals are quiescent during winter, but perk up
  again the following spring with onset of new food

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Lake Biology Profundal Benthos

• Life History of Chironomus anthrocinus in L.
  Esrom
• Some have grown large enough to emerge after one
  year, but many need a little more growth and
  emerge the second year
• Emergence occurs at the surface, mating occurs,
  eggs are laid, and adults die within a few days
• Highly synchronized popn

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Lake Biology Profundal Benthos

• Chaoborus
• Phantom midge
• Alternates between plankton and benthos
• Prey mostly on zooplankton and are preyed upon by
  fish
• Migrates daily from sediment surface to photic
  zone
• Under anaerobic conditions, may stop downward
  migration at the thermocline

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Lake Biology Profundal Benthos

• Oligochaetes
• Development is unsynchronized
• Burrow through surface sediment, digesting
  bacteria, mixing sediments, and recycling
  nutrients

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Littoral Zone

• Portion of lake where photic zone includes the
  bottom

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The Littoral Zone - Macrophytes

• Macrophytes
• Plants whose overall structure is visible to the
  naked eye
• Distribution in lakes is subject to two basic
  constraints
• Water must be shallow enough for light to reach
  the bottom ( littoral zone as we have defined)
• Physical stability sufficient to allow plants to
  grow to the bottom

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The Littoral Zone - Macrophytes

• Characteristics
• General Morphology
• 4 basic morphological types typically occupying
  zones of increasing depth
• Emergent
• Floating-leaved
• Submersed
• Unrooted

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The Littoral Zone - Macrophytes

• Emergent macrophytes
• Occupy the transition zone between land and water
• Rooted in sediment or saturated soils (anaerobic)
• Shoots and leaves extend into the air so, like
  terrestrial plants, they must be self-supporting
  get CO2 from air
• Mostly angiosperms
• Ex. cattails, wild rice

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The Littoral Zone - Macrophytes

• Floating-leaved macrophytes
• Root in sediment, leaves float on surface
• Connections are via stems or petioles
• 0.5 m lt z lt 3 m
• Need to have some standing water, but limited by
  petiole or stem length
• In case of water lilies, both root and stem are
  underwater and petioles (leaf stem) extends
  through water to surface leaves
• A patch of water lilies may actually be one plant
• Ex yellow water lily (Nuphar), white water lily
  (Nymphaea)

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The Littoral Zone - Macrophytes

• Submersed Macrophytes
• Whole plant is underwater
• 0.5 lt z lt 10 m (angio-sperms), up to 100 m for
  mosses, Chara
• No supporting tissue, rely on turgor pressure and
  buoyancy to maintain erect form
• Underwater leaves often finely dissected, but may
  be laminar
• May have heterophylly (different underwater vs.
  surface leaves)
• Ex Myriophyllum (milfoil), Potomogeton
  (pondweed), Chara (stonewort), Isoetes (water
  fern)

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The Littoral Zone - Macrophytes

• Unrooted macrophytes
• Floating
• Lemna (duckweed)
• Eichornia (water hyacinth)
• Submersed
• Ceratophyllum (coontail)

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The Littoral Zone - Macrophytes

• Taxonomy
• Charaphytes (stoneworts)
• Algal group related to green algae
• Macroscopic form
• Ex Chara, Nitella
• Bryophytes (mosses, liverworts)
• Plants with some tissue and reproductive
  specialization, but no vascular tissue (xylem,
  phloem)
• Ex Sphagnum

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The Littoral Zone - Macrophytes

• Taxonomy
• Ferns and Fern Allies
• Plants with vascular tissue, but no flowers
• Ex Isoetes (submersed macrophyte found in soft
  water)
• Ex Equisetum (horsetail) (emergent macrophyte)

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The Littoral Zone - Macrophytes

• Taxonomy
• Gymnosperms
• Vascular tissue
• Reproductive cones
• Ex Bald Cypress (emergent)
• Angiosperms
• Vascular tissue
• Flowers
• Ex Cattail (Typha)
• Ex Water Lilies (White and Yellow)
• Ex Myriophyllum (milfoil)
• Ex Hydrilla
• Ex Potamogeton (pondweed)
• Ex Vallisneria (water celery)

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Macrophytes Factors Affecting Growth

• Low oxygen levels around roots
• Sediments are usually anoxic, but roots need
  oxygen or growth will be inhibited
• Some species have vertical air tubes called
  lacunae which extend from the shoots down into
  the roots to help aerate
• Root cells may be able to withstand oxygen debt

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Macrophytes Factors Affecting Growth

• Inorganic carbon supply
• Low rate of diffusion of CO2 through bulky
  macrophyte tissue could lead to carbon shortage
• Plants can also use CO2 and in very soft water,
  uptake can occur through roots

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Macrophytes Factors Affecting Growth

• Depth Pressure
• Vascular macrophytes do not grow to a depth of
  more than 10 m (representing 1 extra atmosphere
  of pressure)
• This seems to be related to the effect of this
  extra pressure on the xylem and phloem
• However, mosses have been found at up to 165 m
  and Chara to 64 m in Lake Tahoe, for example

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Macrophytes Factors Affecting Growth

• Depth - Light
• Two effects Light Pressure
• Water transparency is highly correlated with
  depth to which macrophytes can grow
• Note that maximum depth of colonization is less
  than photic zone depth which is about double
  Secchi disc depth

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Macrophytes Factors Affecting Growth

• Depth - Light
• One way that macrophyte communities respond to
  potential light limitation is to favor species
  that develop a canopy as opposed to those the
  grow near the sediment surface (rosettes)

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Macrophytes Factors Affecting Growth

• Nutrients
• NP can be taken up by roots and shoots
• Relative importance of root vs. shoot uptake
  depends on sediment vs. water concentrations
• Ex Lake Wingra, WI
• 73 of P by roots
• 27 of P by shoots
• Root uptake is then translocated to shoots to
  fuel growth

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Macrophytes Factors Affecting Growth

• Sediment Stability
• Texture is important
• Need fine particles fine sand, silt or clay
• Course sand, cobble, boulders are not good
  rooting medium
• Stability is also important
• If sand is moving, like on a beach plants will
  not become established

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Macrophytes Patterns of Abundance Production

• Seasonal
• In temperate areas, macrophytes are very seasonal
  in their growth
• Maximum development in late summer
• However, some dieback over much of the year
• In fact, plants create and shed shoots
  continuously

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Macrophytes Factors Affecting Growth

• Productivity determination
• Maximum standing crop
• But this ignores biomass that was shed building
  up to maximum
• C-14 approach
• Measure C-14 uptake by actively photosynthesizing
  parts of plant
• Cohort analysis
• See previous page

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Macrophytes Spatial Patterns

• Within lake
• Macrophytes generally cover only those parts of
  the right habitat (light, substrate, etc.)
• Between lakes
• Great differences between lakes

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Littoral Zone - Periphyton

• Characteristics
• General Morphology
• Algae unicells, filaments, colonies
• 2 general types of attachment
• Adnate cells in close contact with substrate,
  hard to dislodge
• Loose cells only loosely attached, easily
  dislodged
• Taxonomy
• All groups of algae represented, esp
• Cyanobacteria, diatoms, greens

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Littoral Zone - Periphyton

• Factors affecting development
• Substrate Availability
• The amount of surface habitat obviously
  influences the abundance of periphyton
• Could be fairly static like bottom area in photic
  zone or very dynamic like annual plant surfaces
• Light
• Have a very similar photosynthesis-light
  relationship as phytoplankton

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Littoral Zone - Periphyton

• Factors affecting development
• Nutrients
• Can periphyton get nutrients from their host
  substrate?
• Results seem to suggest this is not a major
  factor
• Label P in sediments, grow macrophytes, less than
  5 of P in epiphytes comes from sediment
• High correlation with lake water P

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Littoral Zone - Periphyton

• Patterns of Abundance and Productivity
• Epiphytic periphyton vary both with depth and
  seasonally
• These variations are a combination of
• Changes in the density of epiphytes on the
  macrophyte
• Changes in the amount of macrophyte substrate
  available at different depths and times

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Littoral Zone - Periphyton

• Productivity would also need to take into account
  variations in light and P-I response

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Littoral Zone - Periphyton

• Resulting productivity could vary seasonally and
  from one year to the next
• Note day-to-day variation in production (light
  driven)
• Note different seasonal pattern (substrate
  availability driven)
• Note rough equivalence of 10 mg C produced per mg
  Chl a present per day

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Littoral Zone Littoral Invertebrates

• Characteristics
• Include a much larger suite of organisms than
  found in the profundal benthos
• Some of the dominant groups include
• Flatworms
• Oligochaetes
• Molluscs
• Snails
• Bivalves
• Arthropods
• Crustaceans
• Insects

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Littoral Zone Littoral Invertebrates

• Characteristics
• A wide variety of feeding strategies including
• Grazers/herbivores (due to presence of primary
  producers in the littoral zone)
• Detritivores
• Predators
• Littoral grazers tend to focus on periphyton as
  it is much more digestable
• Macrophyte production tends to get utilized as
  detritus

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Littoral Zone Littoral Invertebrates

• Characteristics
• Type of predators
• Lurking
• Dragonflies
• Sit in a concealed position
• Attack prey as they come by
• Concealed, but dependent on prey movement
• Hunting
• Water bugs
• Actively search for prey
• Often well-armoured, taste bad, and move quicky
  to avoid predators
• Can capture both moving and stationary prey

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Littoral Zone Littoral Invertebrates

• Characteristics
• Littoral zone can be an area of great physical
  and chemical complexity
• Allows a very high diversity, but also presents
  some significant sampling problems
• Heterogeneous distribution
• Difficulties in capturing organisms within
  vegetation, rocks, logs, etc.

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Littoral Invertebrates Patterns of Abundance

• Seasonal and spatial patterns
• Examine results from a study of littoral
  invertebrates in the tidal freshwater Potomac
  River
• Organisms captured by dropping nets over 0.5 m2
  of weedbed
• Nets closed by diver at bottom and brought to
  surface where organisms were removed from
  vegetation and preserved
• Study design
• 3 bed types open water, Hydrilla, mixed
• 2 months (July, August)
• 5 replicates each

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Littoral Zone Littoral Invertebrates

• Results
• Macrophytes harbored much higher abundance of
  macroinvertebrates than open water
• Taxa list was similar at all sites, but relative
  abundance differed both with plant type and month

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Littoral Zone Littoral Invertebrates

• Cluster analysis
• Confirmed differences between veg and open water
• Suggested that variation between months was more
  important that variation between plant types

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Littoral Zone Littoral Invertebrates

• PCA
• Reinforced importance of plants
• And the effect of month over plant type

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