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EVPP 550 Waterscape Ecology and Management – Lecture 11 Professor R. Christian Jones Fall 2007 Lake Biology – Benthos Profundal 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

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lake biology benthos profundal benthos
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”
lake biology benthos profundal benthos3
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
lake biology benthos profundal benthos4
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
lake biology benthos profundal benthos5
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
lake biology profundal benthos
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
lake biology profundal benthos7
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
lake biology profundal benthos8
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 pop’n
lake biology profundal benthos9
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
lake biology profundal benthos10
Lake Biology –Profundal Benthos
  • Oligochaetes
    • Development is unsynchronized
    • Burrow through surface sediment, digesting bacteria, mixing sediments, and recycling nutrients
littoral zone
Littoral Zone
  • Portion of lake where photic zone includes the bottom
the littoral zone macrophytes
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
the littoral zone macrophytes13
The Littoral Zone - Macrophytes
  • Characteristics
    • General Morphology
      • 4 basic morphological types typically occupying “zones” of increasing depth
      • Emergent
      • Floating-leaved
      • Submersed
      • Unrooted
the littoral zone macrophytes14
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
the littoral zone macrophytes15
The Littoral Zone - Macrophytes
  • Floating-leaved macrophytes
    • Root in sediment, leaves float on surface
    • Connections are via stems or petioles
    • 0.5 m < z < 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)
the littoral zone macrophytes16
The Littoral Zone - Macrophytes
  • Submersed Macrophytes
    • Whole plant is underwater
    • 0.5 < z < 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)
the littoral zone macrophytes17
The Littoral Zone - Macrophytes
  • Unrooted macrophytes
    • Floating
      • Lemna (duckweed)
      • Eichornia (water hyacinth)
    • Submersed
      • Ceratophyllum (coontail)
the littoral zone macrophytes18
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
the littoral zone macrophytes19
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)
the littoral zone macrophytes20
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)
macrophytes factors affecting growth
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
macrophytes factors affecting growth22
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
macrophytes factors affecting growth23
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
macrophytes factors affecting growth24
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
macrophytes factors affecting growth25
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)
macrophytes factors affecting growth26
Macrophytes – Factors Affecting Growth
  • Nutrients
    • N&P 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
macrophytes factors affecting growth27
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
macrophytes patterns of abundance production
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
macrophytes factors affecting growth29
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
macrophytes spatial patterns
Macrophytes – Spatial Patterns
  • Within lake
    • Macrophytes generally cover only those parts of the right habitat (light, substrate, etc.)
  • Between lakes
    • Great differences between lakes
littoral zone periphyton
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
littoral zone periphyton32
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
littoral zone periphyton33
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
littoral zone periphyton34
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
littoral zone periphyton35
Littoral Zone - Periphyton
  • Productivity would also need to take into account variations in light and P-I response
littoral zone periphyton36
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
littoral zone littoral invertebrates
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
littoral zone littoral invertebrates38
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
littoral zone littoral invertebrates39
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
littoral zone littoral invertebrates40
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.
littoral invertebrates patterns of abundance
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
littoral zone littoral invertebrates42
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
littoral zone littoral invertebrates43
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
littoral zone littoral invertebrates44
Littoral Zone – Littoral Invertebrates
  • PCA
    • Reinforced importance of plants
    • And the effect of month over plant type