1 / 46

EVPP 550 Waterscape Ecology and Management – Lecture 11

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

Lucy
Download Presentation

EVPP 550 Waterscape Ecology and Management – Lecture 11

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. EVPP 550Waterscape Ecology and Management – Lecture 11 Professor R. Christian Jones Fall 2007

  2. 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”

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. Lake Biology –Profundal Benthos • Oligochaetes • Development is unsynchronized • Burrow through surface sediment, digesting bacteria, mixing sediments, and recycling nutrients

  11. Littoral Zone • Portion of lake where photic zone includes the bottom

  12. 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

  13. The Littoral Zone - Macrophytes • Characteristics • General Morphology • 4 basic morphological types typically occupying “zones” of increasing depth • Emergent • Floating-leaved • Submersed • Unrooted

  14. 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

  15. 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)

  16. 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)

  17. The Littoral Zone - Macrophytes • Unrooted macrophytes • Floating • Lemna (duckweed) • Eichornia (water hyacinth) • Submersed • Ceratophyllum (coontail)

  18. 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

  19. 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)

  20. 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)

  21. 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

  22. 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

  23. 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

  24. 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

  25. 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)

  26. 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

  27. 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

  28. 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

  29. 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

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

  31. 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

  32. 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

  33. 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

  34. 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

  35. Littoral Zone - Periphyton • Productivity would also need to take into account variations in light and P-I response

  36. 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

  37. 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

  38. 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

  39. 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

  40. 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.

  41. 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

  42. 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

  43. 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

  44. Littoral Zone – Littoral Invertebrates • PCA • Reinforced importance of plants • And the effect of month over plant type

More Related