Lecture 6 - RH

Question 1

What makes water life different to terrestrial life?

Answer 1

Low oxygen conditions under water

Pressure at depth

Animals are suspended in the medium rather than being on the ground

Easier dispersal of eggs/offspring than terrestrial ecosystems

Animals are surrounded by food and just have to strain the medium

Aquatic habitat is more diverse than the terrestrial habitat

Primary producers are smaller and more mobile in aquatic habitats compared to terrestrial

More sessile invertebrate animals in aquatic habitats

More complex food webs in aquatic habitats

Question 2

What is water cycling like over land?

Answer 2

Precipitation > Evaporation and so excess precipitation is carried into the oceans by ground-water runoff.

Most precipitation over land comes from evaporation of ocean.

Evapotranspiration is more than evaporation of surface water highlighting the importance of plants for water balance

Question 3

What has human activity done to the water balance and distribution?

Answer 3

Altered river flows by dams

Land clearing and changes in drainage patters

Redirection of water for irrigation, consumption, and industry

Exploitation of ground water reserves

Anthropogenic climate change, regional alterations of precipitation and evaporation

Question 4

What is limnology?

Answer 4

The study of lakes, rivers, and wetlands.

OR

The study of the structural and functional relationships of inland waters and organisms as they are affected by their physical , chemical, and biotic environments.

Question 5

What are lotic systems?

Answer 5

Flowing-water systems

Question 6

What are lentic systems?

Answer 6

Standing-water systems

Question 7

What are wetland systems?

Answer 7

Transition zone between terrestrial and aquatic systems. Soil is waterlogged or submerged at least part of the year typically having at least some rooted aquatic vegetation.

Question 8

What is a catchment?

Answer 8

Area of land drained by a river system

Also known as a watershed or drainage basin

Question 9

How does water move through a catchment?

Answer 9

Can run as surface runoff into a water body.

Different zones underground

Question 10

What is an aquifer?

Answer 10

Subterranian body of water that is flowing

Question 11

How long ago was Australia’s Great Artesian aquifer deposited?

Answer 11

300k years ago

Question 12

What has the Great Artesian Basin used for?

Answer 12

Water extracted is used for irrigation, drinking, and industry. (100 times the volume of Sydney)

Question 13

Why is it important to preserve confined aquifers?

Answer 13

Confined aquifers contain very old water that is non-renewable and is not part of the active hydrological cycle

Question 14

What is the lag time in regards to river flow through a catchment?

Answer 14

Time taken for surface water to move into the stream moving towards the catchment

Question 15

What does the absence of riparian vegetation do to the rate of water accumulation in streams moving towards catchments?

Answer 15

Water moves more freely with less riparian vegetation presence and so it accumulates quicker after heavy rains.

Rivers return to base flow more quickly

Question 16

What does the presence of riparian vegetation do to the flow of water in streams?

Answer 16

Vegetation promotes infiltration of water under the soil via entrapment under litter and root channels in soil

Stabilizes soil and reduces erosion

Produces a way for water to evaporate again via transpiration reducing run off

Question 17

What does forest clearcutting do to catchments?

Answer 17

Removes barrier to ultraviolet light

prevents the moderation of heating and cooling of the ground

Nutrient uptake from soil is diminished (nutrients are flushed out by water into catchment)

Question 18

What are the zones found in lakes?

Answer 18

Littoral which is near the entry into the lake

Limnetic which is the surface layer of water where photosynthesis is possible

Profundal layer is deep under the limnetic zone and is dark and photosynthesis is not possible

Question 19

What are the subdivisions of the limnetic and profundal zone of water?

Answer 19

Limnetic layer contains:

Epilimnion: surface layer that is mixed by wind - or temperature - driven currents

Profundal layer contains:

Metalimnion: Region of thermocline transition between epilimnion and the hypolimnion

Hypolimnion: the lowest layer of water where it is dark, cold, and relatively stagnant

Question 20

What are pellagic and benthic organisms?

Answer 20

Pellagic: live suspended in the water

Benthic: Live on the floor of the ocean/lake

Question 21

Where is the water’s maximum density?

Answer 21

4 the grease

Question 22

What happens to waters density with salt concentration?

Answer 22

The more salty it is the more dense it is

Question 23

Where is the thermocline located?

Answer 23

Under the point where wind mixing is taking place

Question 24

What is the difference between holomixis and meromixis?

Answer 24

Holomixis refers to complete mixing to the bottom

Meromixis refers to incomplete mixing not reaching to the bottom

Question 25

What is seasonal overturn?

Answer 25

Changes in temperature alter the density of different parts of the water. In Spring, ice melts and surface water warms up. As a result, the water sinks mixing the water and creating an isothermal water column. In Autumn, the surface water cools and stratification breaks down and surface water cools towards 4 degrees becoming more dense.

Question 26

Why is seasonal overturn important?

Answer 26

It stimulates plankton growth by injecting nutrients back into surface water. Amount and timing of biological production and decomposition is influenced by circulation regime

Question 27

What does "dimictic cycle" refer to?

Answer 27

Semi-annual overturn

Question 28

What happens in a warm monomictic lake?

Answer 28

water undergoes holomixis only once and is usually found in warm temperate climates. This happens because water never goes to 4 degrees or below meaning the water doesn't need to warm back up to undergo another seasonal overturn.

Question 29

Where can warm monomictic lakes be found?

Answer 29

Warm temperate locations

Question 30

What causes some lakes and rivers look brown?

Answer 30

Humic substances (dissolved organic material from plant matter)

Question 31

How much light is absorbed in the top 1 m normally?

Answer 31

50% of light

Question 32

What does light penetration depend on?

Answer 32

Silt, detritus, minerals, and dissolved organic matter

Question 33

How is water clarity (light penetration) measured?

Answer 33

Using a secchi disk

Question 34

What are the seasonal trends seen in secchi depth affected by?

Answer 34

Plankton production Silt input Mixing

Question 35

What are the interannual trends seen in secchi depth affected by?

Answer 35

Climate fluctuations

Question 36

What are the long-term trends seen in secchi depth affected by?

Answer 36

degraded water quality

Question 37

What is freshwater system pH affected by?

Answer 37

Chemistry and human impacts *oceans are more constant

Question 38

How is water temperature and O2 solubility related?

Answer 38

O2 solubility inversely related tow temperature

Question 39

What does dissolved oxygen depend on in the epilimnion?

Answer 39

temperature

Question 40

What does dissolved oxygen depend on in the hypolimnion?

Answer 40

microbial respiration and mixing

Question 41

What are the most important macronutrients for biological growth?

Answer 41

Phosphorus and Nitrogen

Question 42

What is the limiting nutient in most freshwater systems?

Answer 42

Phosphorus

Question 43

What is the limiting nutient in most oceans?

Answer 43

Nitrogen

Question 44

Why is phosphorus so important in freshwater systems?

Answer 44

To produce chlorophyll

Question 45

What does oligotrophic refert to?

Answer 45

Low production associated with low phosphorus and nitrogen

Question 46

What does eutrophic refert to?

Answer 46

High production associated with high phosphorus and nitrogen

Question 47

What does acidotrophic refert to?

Answer 47

Low producion associated with acidity and low phosphorus and nitrogen

Question 48

What does alkalitrophic refert to?

Answer 48

Low production associated with high calcium

Question 49

What does argillotrophic refert to?

Answer 49

Low prodcution associated with clay turbidity

Question 50

What does siderotrophic refer to?

Answer 50

Low productivity associated with high iron content

Question 51

What does dystrophic refert to?

Answer 51

Low production associated with high humic content

Question 52

What is eutrophication?

Answer 52

Enrichment of a body of water with nutrients leading to excessive primary production, organic matter, hypoxia, and anoxia

Question 53

Where is eutrophication most commonly found?

Answer 53

Polluted waters (runoff, sewage, etc) Shallow water bodies

Question 54

How does eutrophication affect oxygen in water?

Answer 54

causes oxygen depletion

Question 55

What is organic matter produced within a system called?

Answer 55

Autochthonous organic matter

Question 56

What is organic matter produced outside the system called?

Answer 56

Allochthonous organic matter

Question 57

What are pleustons?

Answer 57

Organisms at the air-water interface

Question 58

What are neustons?

Answer 58

Microscopic organisms in the pleuston

Question 59

What species of organisms dominate eutrophic waters?

Answer 59

Cyanobacteria

Question 60

What type of environmental gradients are present in lotic systems?

Answer 60

horizontal gradients (In contrast with lentic systems which are vertical)

Question 61

What are some features of lotic systems?

Answer 61

Unidirectional, horizontal flow Flow rate fluctuations Substratum unstable Environmental gradients along down stream axis Shallow water High oxygen content High turbidity Organic matter and energy sources are mostly allochthonous Temperature fluctuates greatly Thermal stratification rare Solute content highly influenced by nearby rocks and soil Calcium ionsa re dominant from limestone rocks (Na+ dominates in many parts of Australia) Organic matter and nutrient concentrations increase with distance downstream

Question 62

What type of flora do lotic systems have?

Answer 62

benthic producers or microscopic growth in biofilms on the surface

Question 63

What type of adaptations do benthic invertebrates have in torrential regions?

Answer 63

preference for microhabitats such as under debris or stones, in pits, or in highly exposed positions Require high oxygen content Adaptations to remain attached to substratum and do not release free-swimming larvae Feeding modes such as detritus shredders, filter feeders, biofilm grazers, and predators Shelled animals depend on Ca++ ions

Question 64

What are stenothermal species and where are they found?

Answer 64

Species that live within a very narrow range of temperatures. they live in torrential regions

Question 65

What are eurythermal species and where are they found?

Answer 65

Species that can survive a wide range of temperatures, they live in depositional regions

Question 66

What happens when stream slows down?

Answer 66

It starts to act more like a lentic system. (More contribution of primary productivity from phytoplankton and autochronous organic matter)

Question 67

Why are nutrients higher in flowing systems?

Answer 67

Due to runoff

Question 68

What is the difference between a bog and a fen?

Answer 68

Bog is a peat-accumulating wetland dominated by mosses. Bogwater is acidic and nutrient poor Fens have more nutrients and higher alkalinity from groundwater dominated by sedges and has marsh-like vegetation

Question 69

What is a marsh?

Answer 69

Permanently or periodically inundated wetland characterized by nutrient -rich water and subject to seasonal fluctuations

Question 70

What is a mire?

Answer 70

Any peat-accumulating wetland