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Aquatic Ecology > Lecs 1-3 > Flashcards

Lecs 1-3 Flashcards

1
Q

What is Limnology

A

the study of inland waters

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2
Q

What are the evidences of climate change seen at Lake Geneva

A

-increased hypolimnetic temperatures
-changes in stratification and mixing
shifts in the spawning dates of some species

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3
Q

What are the types of inland waters?

A

-lentic environments
-lotic environments

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4
Q

What is a lentic environment?

A

-standing or very slow flowing waters
-ex. lake, ponds, reservoirs, wetlands

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5
Q

What is a lotic environment?

A

-flowing water
-ex. springs, streams rivers

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6
Q

Describe a Lake

A

-relatively large body of water
-deeper than 3 meters with an area greater than about 1-10ha
-often shows thermal stratification

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7
Q

Describe a Reservoir

A

-artificial pond or lake
-created by placing a dam in a valley or depression
-morphology and hydrology is different from natural ponds/lakes

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8
Q

Describe a Pond

A

-a relatively small body of water
-area of less than 1-10 ha
-shallow enough to be easily mixed by light wind

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9
Q

Describe a Wetland

A

-land area saturated with water, permanently or seasonally
-vegetation of aquatic plants adapted to the unique hydric soil
-4 kinds: marsh, swamp, bog, fen

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10
Q

Molecular Shape of water

A

Water molecules have a bent shape with one oxygen atom connected to two hydrogen atoms.
Impact: This shape makes water a polar molecule, which means it can dissolve many other substances. This is essential for processes like carrying nutrients in our bodies and supporting chemical reactions in nature.

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11
Q

Polarity of water

A

Water molecules have a partial negative charge near the oxygen atom and a partial positive charge near the hydrogen atoms.
Impact:
Solvent Ability: Water can dissolve many substances, which is crucial for everything from cellular functions in living organisms to chemical reactions in industries.
Adhesion and Capillary Action: Water can stick to other surfaces and move up narrow spaces against gravity. This is important for processes like water transport in plants.

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12
Q

Hydrogen bonding of water

A

Hydrogen atoms in one water molecule can weakly bond with oxygen atoms in another water molecule.
These bonds create several unique properties:
-High specific heat
-Cohesion and surface tension
-Ice floating

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13
Q

Elaborate how hydrogen bonding create unique properties of water

A

High Specific Heat: Water can absorb a lot of heat before it gets hot, helping regulate temperature in environments and organisms.
Cohesion and Surface Tension: Water molecules stick together, leading to phenomena like water droplets forming and insects walking on water.
Ice Floating: Water expands and becomes less dense when it freezes, causing ice to float on liquid water, which helps protect aquatic life in cold climates.

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14
Q

Maximum density of pure water is at what temperature?

A

4 °C

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15
Q

What happens to water below 4 °C

A

hydrogen bonding of ice starts to develop and continues until crystal formation at 0 °C

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16
Q

What happens to water at 4 °C

A

liquid water molecules pack together more closely, this increases the density of the water

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17
Q

What happens to water above 4 °C

A

hydrogen bonding declines, molecules gain energy and move farther apart; making the water less dense

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18
Q

T/F Density difference with temperature affects energy required to mix layers

A

True;
eg. the amount of work to mix layers between 29-30 ◦C is 40x that needed to mix layers between 4-5 ◦C.

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19
Q

What would be the consequence if ice was denser than water?

A

-ice will sink and will kill organisms in the water

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20
Q

Describe Salinity

A

-the amount of dissolved ions in an aquatic ecosystem

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21
Q

How does Salinity influence water density?

A

-as salinity increases, density increases
-salt water is denser

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22
Q

What is viscosity and what is its disadvantage?

A

-a measure of a liquid’s resistance to flow
-Disadvantage: organisms must expend large amounts of energy to move through water

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23
Q

T/F Viscosity is directly proportional to water temperature

A

False; Viscosity is inversely proportional to water temperature
-in H2O, viscosity decreases with increasing temperature

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24
Q

What is Specific Heat?

A

-the amount of heat needed to raise or lower the temperature of 1 g of substance by 1°C at 15°C

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25
Q

Is the specific heat of water high or low?

A

-remarkably high = 4.19 joules

26
Q

Why is the specific heat of water high?

A

-Large amounts of energy are required to disrupt hydrogen bonds between liquid water molecules
-Conversely, large amounts of energy have to be removed to freeze water (formation of hydrogen bonds in a lattice)

27
Q

How is water as a solvent?

A

-dipolar moment makes water an excellent solvent for ionic (electrically charged) compounds
-H2O molecules “stick” to other polar molecules and ions
-dissolves more things than anything else; but not everything, e.g., grease, oil

28
Q

How is pH affected by temperature?

A

-increasing temperature can decrease pH

29
Q

________ corresponds to the excess of cations compared with strong anions

A

Total alkalinity

30
Q

Define alkalinity

A

-water body’s ability to absorb hydrogen ions when acid solutions are added
-Acid Neutralizing Capacity
-If water can absorb a lot of hydrogen ions without changing pH, the water is well buffered

31
Q

Define water hardness

A

-the amount of dissolved calcium and magnesium in the water

32
Q

What is redox potential?

A

the tendency of a chemical species to acquire electrons and thereby be reduced

33
Q

T/F Redox processes will alter alkalinity

A

True

34
Q

Describe solubility of gases in water

A

-Only a relatively few gasses are dissolved in natural waters under normal conditions
-Higher the temperature, the less gas is dissolved

35
Q

What is Thermal Stratification?

A

it occurs when the water in a lake forms distinct layers through heating from the sun

36
Q

What are the different Thermal Gradients?

A

Epilimnion -upper mixed layer; warmer water (less dense)
Metalimnion -middle layer; where temperature changes
Thermocline is a steep temperature gradient; the plane where dT/dz is maximum
Hypolimnion - lowest layer; cooler water (more dense)

37
Q

Stability of Thermal Stratification

A

-The ability of a lake to mix through wind turbulence
-Stratification becomes increasingly stable with heating from the sun
-The larger the difference in temperature (and density) between the epilimnion and the hypolimnion, the more stable the thermal stratification.

38
Q

What factors influence thermal stratification and mixing?

A

Time of year
Lake depth
Topography
Solutes
Wind fetch (Longer the distance wind travels, increased mixing)

39
Q

What are the different mixing patterns of lakes?

A

-Holomictic (monomictic, dimictic, polymictic)
-Amictic
-Meromictic

40
Q

Describe Holomictic Lakes

A

-Lakes that mix from top to bottom at least once a year
-Most lakes are holomictic
-Monomictic, Dimictic, Polymictic

41
Q

What are Monomictic Lakes?

A

mix from top to bottom during one mixing period each year.

42
Q

Describe Cold Monomictic Lakes

A

-during brief summer polar lakes mix; do not reach above 4 °C
-inversely stratified most of the year
-do not stratify in the summer
-usually high latitude or altitude

43
Q

Describe Warm Monomictic Lakes

A

-mix in winter due to cooler temperatures
-lakes do not freeze
-thermally stratified throughout much of the year

44
Q

What are Dimictic Lakes?

A

-mix from the surface to bottom twice each year.
-during winter, they are covered by ice
-during summer, they are thermally stratified
-lakes in temperate regions incl. Ontario
-lake turnover in spring and fall

45
Q

What are Polymictic Lakes?

A

-typically small or shallow lakes
-too shallow to develop thermal stratification
-waters mix from top to bottom throughout the ice-free period

46
Q

What are Cold polymictic lakes?

A

-those that are ice-covered in winter
-4 degrees top to bottom
-stratify briefly in summer

47
Q

What are Warm polymictic lakes?

A

-no ice-cover in winter
-stratification breaks down often

48
Q

Describe Amictic lakes

A

-No mixing
-Perennially sealed off by ice; permanently frozen lake
-Exhibit inverse cold water stratification

49
Q

Describe Meromictic lakes

A

-deep layers do not intermix with upper layers due to a strong density gradient caused by dissolved solute gradient or lake morphometry
-can remain unmixed for years, decades, or centuries

50
Q

Describe Stratification of a Meromictic lakes

A

-Usually divided into three layers:
Mixolimnion: top layer of lake and essentially behaves like a holomictic lake.
Chemocline (chemical gradient): area in between monolimnion and mixolimnion creates a pycnocline
Monimolimnion: bottom layer of lake circulates little, and generally hypoxic and saltier than the rest of the lake.

51
Q

What are the 2 Types of Oxygen Profiles in Dimictic Lakes

A

Positive heterograde
Negative heterograde

52
Q

Describe Positive heterograde

A

-caused by a metalimnetic O2 maximum usually due to high concentration of photosynthesizers at metalimnion.

53
Q

Describe Negative heterograde

A

-caused by a metalimnetic O2 minimum
-typically due to accumulation of detritus caught at the density boundary
respiration of bacteria, algae, zooplankton

54
Q

Orthograde profile

A

-Oligotrophic lakes are characterized by low nutrients and low productivity
-Little decomposition to use up O2, therefore usually high O2 in the hypolimnion.
-Usually lower O2 at the surface due to warmer temperatures

55
Q

Clinograde profile

A

-Eutrophic lakes (high nutrients) have high primary and secondary productivity
-When algae and other organisms die, can result in high respiration and decomposition rates throughout water column, but especially at the lake bottom where detrital biomass sinks to
-Benthic animals and bacteria use up O2 during respiration, making the hypolimnion anoxic (anaerobic)
-Clinograde profile develops soon after stratification in eutrophic lakes

56
Q

Explain the process of winter fish kill

A
  1. Ice forms a barrier between pond water and the atmosphere preventing the circulation of oxygen
  2. Heavy snowfall covers the pond and blocks sunlight, which stops the oxygen-creating process of photosynthesis
  3. Vegetation begins to die and uses the limited oxygen supply in the decomposition process
  4. Oxygen depletion becomes critical and fish begins to suffocate, resulting in a winterkill
57
Q

What is Photic zone?

A

-Depth at 1% incident light penetration in a lake
-Determines the extent of plant and algae distribution
-Also known as euphotic zone

58
Q

What is Aphotic zone?

A

Below photic zone; is the portion of a lake where there is little or no sunlight (<1%)

59
Q

What is PAR (Photosynthetically Active Radiation)?

A

-the amount of light available for photosynthesis, which is light in the 400 to 700 nanometer wavelength range.
-PAR changes seasonally and varies depending on the latitude and time of day.

60
Q

What is Compensation depth?

A

-This is the depth at which photosynthesis = respiration of plants and algae
-Below this depth plants and algae do not persist.

61
Q

In eutrophic lakes, where does most photosynthesis occurs?

A

in the epilimnion

62
Q

In oligotrophic lakes, where does most photosynthesis occurs?

A

below the thermocline

Aquatic Ecology (6 decks)

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