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154 Cards in this Set
- Front
- Back
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Difference between introduced species and invasive species
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Invasive species cause harm
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Difference in extinction rate between freshwater and terrestrial fauna in North America
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Extinction rate of freshwater fauna is five times faster than terrestrial fauna
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Term for the ecosystem of a lake
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Lentic ecosystem
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3 geological types of lakes (depression in bedrock)
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Glacial scour
Volcanic - Crater lakes Tectonic - Rift lakes |
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Characteristics of geologically formed lakes
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Often large and deep
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2 types of lakes formed by depressions in sediment
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Glacial sediments (e.g. Lake district tams)
Fluvial sediments (e.g. Oxbow lakes) |
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Characteristics of lakes formed by depressions in sediment
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Short lived and shallow
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Formation of barrier lakes
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Lakes formed by land slides, lava flows, ice barriers and glacial moraine
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3 Lake thermal stratifications
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Epilimnion
Metalimnion (thermocline) Hypolimnion |
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Determinants of thermocline depth
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Wave size (transfer of heat)
Water clarity (depth of penetration) Duration of calm conditions (heating time) |
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Monomictic lake
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Single period of stratification and mixing (warm temperate)
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Polymictic lake
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Stratified by day, mixed at night (shallow tropical)
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Oligomictic lake
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Stable statification, rare mixing by storms (Deep tropical)
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Seiche
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Oscillation of water in a lake
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Littoral zone
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Part of a sea, lake or river that is close to the shore
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Dimictic lake
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A lake that mixes from top to bottom during two mixing periods each year
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Characteristics of rivers which decrease as you move downstream
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Gradient: Steep > Level
Turbulence: Turbulent > Smooth Substrate size: Rock > gravel > sand > Silt Less erosion of new material |
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3 River zones
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Erosion zone
Sediment transport zone Sediment deposition zone |
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Characteristics of a river erosive zone
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Steep slope
Large substrate Turbulent flow |
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Characteristics of a river sediment transport zone
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Reduced gradient
Deposition balanced by erosion Gravel and sand substrate Smoother flow |
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Characteristics of a river sediment deposition zone
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Sediment deposited
Little erosion of new material Silty substrate |
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Characteristics of a river riffle
(riffle-pool sequence) |
Fast flow,
shallow, large substrate, steep gradient |
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Characteristics of a river pool
(riffle-pool sequence) |
Slow flow
Deep finer substrate Lower gradient |
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Characteristic taxa of a riffle
(riffle-pool sequence) |
Ephemeroptera (Mayflies)
Plecoptera (stoneflies) Simulidae (black fly) |
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Characteristic taxa of a pool
(riffle-pool sequence) |
Odonata (dragonflies/damselflies)
Diptera (Flies) Coleoptera (Beetles) |
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River flood refugia
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Flood plain (out)
Hyporheic zone (down) Within channel (stay and hide) |
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Nitrate Ion
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Nitrite Ion
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Ammonia
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Biological nitrogen fixation formula
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Organisms capable of nitrogen fixation
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Free living bacteria
Symbiotic bacteria in legumes/clover Cyanobacteria |
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Enzyme involved in nitrogen fixation
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Nitrogenase
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Important nitrogenase cofactors
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Molybdenum
Iron |
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Environment where Nitrogen fixation takes place and why
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Nitrogen fixation occurs in specialised cells or anaerobic microzones
- Nitrogen fixation is inhibited by Oxygen |
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Why N fixation is limited in a marine compared to a freshwater environment
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Competition between sulphate and molybdate inhibits Mo uptake
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Ideal Nitrogen/Phosphorus ratio
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16:1
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Nutrient conditions of a freshwater system where cyanobacteria are favoured over green algae
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Nitrogen/Phosphorus ratio <16
(Nitrogen limited) |
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Nitrification formula
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Conditions which inhibit nitrification
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Low O2
Low pH (nitrification creates H+) |
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Examples of Dissolved Inorganic Nitrogen (DIN)
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NO3- (Nitrate)
NO2- (Nitrite) NH4+ (Ammonium) |
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Example of Dissolved Organic Nitrogen (DON)
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Amino Acids
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Denitrification formula
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Inhibitor of denitrification
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Oxygen
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Ammonification formula
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Organic matter (urine, faeces, dead organisms) --> NH3
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Eutrophication
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Over-fertilization of lakes with nutrients and the changes that occur as a result
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Primary producers in lotic (flowing) systems
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Attached algae and macrophytes (aquatic plants)
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Primary producers in lentic (standing) systems
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Phytoplankton (unless very shallow or very eutrophic)
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Inorganic forms of Phosphorus
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Biological uses for Phosphorus
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Nucleic acids
ATP/NADP Phospholipids Bones and teeth |
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Sources of Phosphorus
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Apatite (primary mineral rock)
Phosphorite (sedimentary rock) Organic Matter |
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Carbon dioxide + Water ->
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Carbonic acid
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Weathering caused by carbonic acid
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Carbonation weathering
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How weathered Orthophosphate may be lost
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Lost in runoff
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How weathered Orthophosphate may be occluded
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Locked in Fe and Al oxides
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How weathered Orthophosphate may be nonoccluded
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Held on soil particles
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How weathered Orthophosphate may be used biologically
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Taken up by plant roots/phytoplankton
Assimilated by soil microbes |
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How microbes and plant roots may increase weathering to liberate phosphates
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Secretion of organic acids
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pH at which phosphorus is most biologically available
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7
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Fate of phosphorus in a low pH environment
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Bound to Fe and Al oxides
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Fate of phosphorus in a high pH environment
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Bound to Ca minerals
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Affect of oxygen on Phosphorus availability
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Affect of salinity on Phosphorus availability
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pH of rivers and why
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Slightly acidic due to high concentrations of CO2 and humic material
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pH of the ocean
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~8
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Circular disk used to measure water transparency in oceans and lakes
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Secchi disk
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inertia and viscosity
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Anatomical adaptations to resist flow
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Production of silk or sticky secretions
Suckers or hooks Body streamlined or flattened |
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Influence of depth on velocity of flowing water
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3 classifications of drift
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Constant
Catastrophic Behavioural |
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Time of day when behavioural drift by macro-invertebrates increases in freshwater
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Higher at night - less visual predation
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Aquatic marginal wetlands
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Wetland fed from a parent water body
(Fringe or flood) |
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Fringe wetland
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Aquatic marginal wetland with a continuous or very frequent connection with a parent water body
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Flood wetland
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Aquatic marginal wetland only connected with a parent water body during high water
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Mire wetland
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Wetland which persists independently of a parent water body
(Fen or Bog) |
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Fen wetland
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Valley mire wetland which receive water from groundwater and runoff
Generally nutrient rich |
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Bog wetland
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Mire wetland fed solely by rainwater and aerial deposition
Generally nutrient poor |
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Diffusion of Oxygen in water compared to air
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Oxygen diffuses 10,000 times slower in water compared to air
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Why waterlogged soil tends to be deficient in nitrate
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Anaerobic conditions promotes bacterial denitrification
NO3- --> N2 |
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Why wetlands tend to contain increased toxic chemical species
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Absence of oxygen creates reduced forms of metal ions which are more chemically reactive
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Examples of reduced toxic chemical species found in wetlands
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Aerenchyma
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Air channel in the roots of some plants, which allows exchange of gases between the shoot and the root
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Paraphyletic group and a genus of bacteria which fix nitrogen
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paraphyletic group: Rhizobia
Genus: Frankia |
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plants characterized by their ability to form a symbiosis with the nitrogen fixing actinobacteria Frankia
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Actinorhizal plant
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Example of an actinorhizal plant
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Alder (Alnus glutinosa)
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Delay in development in response to regularly and recurring periods of adverse environmental conditions
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Diapause
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Non-living particulate organic material; typically including the bodies or fragments of dead organisms and fecal material
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Detritus
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A genus of between 151 and 350 species of mosses commonly called peat moss
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Sphagnum moss
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Why biomonitoring is preferable to chemical monitoring
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Organisms respond to intermittent pollution,
Organisms are sensitive to low levels of pollution, Organisms may be sensitive to new or unexpected pollutants Organisms reflect the impacts of multiple pollutants. |
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Disadvantages to detecting pollution by monitoring a single species
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Abundance of species may be affected by variables other than pollution
e.g. Seasonal variation habitat availability weather temperature |
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Bioaccumulation
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Low levels of pollutants magnified within organism
Useful for biomonitoring |
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Examples of species which exhibit bioaccumulation useful for biomonitoring
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High trophic level species
Bryophytes, Molluscs, Fish |
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Why communities are generally used for biomonitoring
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Wide range of tolerances
Sensitive to different pollutants Loss of particularly sensitive species registers subtle effects |
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Species extremely sensitive to sewerage pollution but immune to acidification
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Stoneflys
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Characteristics of a species suitable for biomonitoring
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Presence/absence related to water quality, not other factors
Integration of conditions over time, not just current situation Not too mobile - Reflection of sampling site, not elsewhere Easy to identify |
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Advantages of using bacteria for biomonitoring
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Huge populations
Widely distributed |
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Disadvantage of using bacteria for biomonitoring
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Not easily identified
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Advantage of using algae for biomonitoring
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Sensitive to nutrient enrichment
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Disadvantages of using algae for biomonitoring
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Seasonal changes in abundance
Lots of samples required |
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Advantages of using macrophytes for biomonitoring
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Easy to identify
Good indicator of nutrient levels |
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Disadvantages of using macrophytes for biomonitoring
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Seasonal changes in abundance
Obtain nutrients from both water and sediment |
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Advantages of using fish for biomonitoring
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Easy to identify
Reflect changes lower in food chain |
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Disadvantages of using fish for biomonitoring
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Highly mobile
Difficult and expensive to sample |
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Advantages of using macro-invertebrates for biomonitoring
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Widely distributed
Broad spectrum of tolerances Relatively sedentary Relatively long lifespan - present most of year Easy to sample and ID |
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Disadvantages of using macro-invertebrates for biomonitoring
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Seasonal variation in community
Vary with other factors (habitat) Aggregated – lots of samples needed |
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Scale used to categorise the particle size of a substrate
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Wentworth scale
- Negative log2 of smallest diameter (mm) |
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Examples of living organic substrates in freshwaters
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Biofilms
Algal mats Macrophytes |
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Examples of dead organic substrates in freshwaters
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– Coarse woody debris (CWD) >8cm
– CPOM (>1mm) (leaves etc.) – FPOM (<1mm, > 0.5μm) – DOM (> 0.5 μm) |
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Examples of freshwater rock taxa (lithophilous)
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Water penny (Psephenidae) – underside of rocks
Freshwater sponges (Spongillidae) – large stable rocks |
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Adaptations of freshwater sand taxa (Psammophilous)
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Lestinogomphus africanus Dragonfly - Syphon, hairy (prevents sand particles penetrating joints)
Meiofauna (<0.5mm) |
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Example of a freshwater species which processes large woody debris (Xylophilous)
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Riffle beetles (Elmidae) - Large claws to hold on
-Rare due to removal of wood from rivers |
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Characteristic fauna living on plants (Phytophilous)
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Moss: caseless caddis
Macrophytes: More complex plant = higher diversity and abundance |
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Effect of temperature on maximum oxygen concentration in freshwater
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Cold water can hold more oxygen
Halves between 0 - 30C Rivers near saturation (turbulence) |
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Freshwater organisms with gills
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fish, Ephemeroptera, Trichoptera
Diffuses across concentration gradient Dependent on flow to replenish water |
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Freshwater organisms with lungs
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lungfish, amphibians, pulmonate snails
Dependent on access to surface |
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Freshwater organisms which use air bubbles
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water beetles, water spiders
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Physical gills
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structure common among some types of aquatic insects, which holds atmospheric oxygen in an area with small openings called spiracles. The structure (often called a plastron) typically consists of dense patches of hydrophobic setae on the body, which prevent water entry into the spiracles.
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Adapted to a narrow temperature range
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Stenothermic
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Adapted to a wide temperature range
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Eurythermic
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Term used to indicate the number of generations per year
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voltinism
Univoltine - 1 gen/year Bivoltine - 2 gen/year Multivoltine > 2 gen/year Semivoltine < 1 gen/year |
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Examples of behavioural adaptations to increase flow of water over respiratory structures
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Plecoptera (stoneflies) – do ‘press-ups’ to increase water flow
Ephemerella (mayfly) – beats its gill plates |
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How temperature generally affects voltinism
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Autochthonous energy in freshwater systems
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Energy sourced from primary production by photosynthesis by Phytoplankton, biofilm and macrophytes
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Allochthonous energy in freshwater systems
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Energy imported from elsewhere: Detritus
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CPOM
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Coarse Particulate Organic Matter
>1mm |
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FPOM
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Fine Particulate Organic Matter
0.5μm - 1mm |
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DOM
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Dissolved Organic Matter
<0.5μm |
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Periphyton
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A complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus that is attached to submerged surfaces in most aquatic ecosystems
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River continuum concept
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Conceptual model which predicts changes in river energy sources and function with increasing stream order
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River Continuum Concept predictions concerning low-order streams
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Shaded - High detrital inputs
Shredders predominate Low Productivity/Respiration ratio Low FPOM/CPOM ratio |
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River Continuum Concept predictions concerning high-order streams
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No shading - detritus unimportant
Macrophytes abundant Collector-filterers dominate Low Productivity/Respiration ratio High FPOM/CPOM ratio |
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River Continuum Concept predictions concerning mid-order streams
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Less shading - lower detritus
Abundant periphyton and FPOM Grazers dominate Highest Productivity/Respiration ratio |
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Ontogenetic diet shift
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Changing of feeding strategy throughout development
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Example of a species with an ontogenetic diet shift
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Stonefly - shift from eating plant material to carnivory
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Five functional feeding groups exhibited by freshwater macro-invertebrates
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Scrapers/Grazers
Shredders Predators Collector-gatherers Collector-filterers |
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Examples of freshwater scrapers/gathers
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Snails (Gastropoda)
Fish (Pisces) Mayflies (Ephemeroptera) |
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Examples of freshwater shredders
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Amphipods
Isopods Caddisflies (Trichoptera) Stoneflies (Plecoptera) |
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Examples of engulfing freshwater predators
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Dragonflies (Odonata)
Stoneflies (Plecoptera) Fish (Pisces) |
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Examples of freshwater collector-gatherers
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Mayflies (Ephemeroptera)
Caddisflies (Trichoptera) True flies (Diptera) |
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Examples of freshwater collector-filterers
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Caddisflies (Trichoptera)
True flies (Diptera) Zooplankton (Copepoda) |
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Gape limited predator
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Size of prey limited by size of predator's mouth
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Example of a piercing freshwater predatory taxa
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True bugs (Hemiptera)
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Methods of passive filter feeding
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simple sieves
• Net-spinning caddis larvae • Size of particles restricted by size of sieve • Small organisms – difficult to sieve water due to high viscosity sticky screens • Individual fibres of appendage sticky • Can capture particles smaller than aperture of sieve • Simulium (Diptera) – blackfly larva with fans on head |
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Method of active filter feeding
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Scan and trap
• Zooplankton – copepods • Generate current using appendages • Active detection of particles – chemicals in surrounding water • Open and close feeding appendages as particle passes |
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Alternative stable states of shallow lakes
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Evidence for 'alternative stable states' in shallow lakes
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Buffer mechanism which resists the change of a shallow lake from plant dominated to algal dominated
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Plants provide refuges for grazing zooplankton from fish predation
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Buffer mechanism which resists the change of a shallow lake from algal dominated to plant dominated
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Phytoplankton outcompete plants for nutrients preventing establishment
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Events which trigger shallow lakes to switch from plant dominated to algal dominated
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Destruction of plants:
- For boating - Herbicide application or runoff Alteration of food web structure: – Loss of zooplankton (insecticides) – Decrease in piscivorous fish (fishing) |
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Likely state of a shallow lake with a high phosphorus concentration
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Phytoplankton / Algal dominated
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Likely state of a shallow lake with a low phosphorus concentration
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Plant / Macrophyte dominated
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Bottom-up solutions to remediate a eutrophicated lake
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Reduce nutrient inputs (cut off source)
Take out sediment (contains lots of P) |
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Top-down solution to remediate a eutrophicated lake
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Biomanipulation – manipulation of the food web to increase grazing of algae via a trophic cascade
– Removal of all fish – Removal of zooplanktivores – Increased stocking of piscivores |
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Phytoplankton seasonality in lake ecosystems / Temperate lake succession
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SPRING peak of Diatoms - Mixing
SUMMER decline: Stratification - nutrient limitation, grazing by crustaceans / zooplankton AUTUMN peak - breakdown of thermocline, change in species: cyanobacteria WINTER: Mixing, low production despite nutrients |
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Experimental addition of phosphorus to a lake
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Huge growth of phytoplankton
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