Chapter 8: Aquatic Ecosystems

Question 1

What is the littoral zone?

Answer 1

shallow, well-lit areas around the shore extending to where rooted vegetation stops, lots of organisms

Question 2

What is the limnetic zone?

Answer 2

open sunlit waters beyond the littoral zone down to depths where photosynthesis is no longer significant

Question 3

What is the profundal zone?

Answer 3

deep ocean water below the depth of effective light penetration

Question 4

What is the benthic zone?

Answer 4

bottoms of lakes and ponds, which contains sediments rich in organic matter

Question 5

Define limnology.

Answer 5

the study of freshwater ecosystems

Question 6

Define lentic.

Answer 6

standing water habitats

Question 7

Define lotic.

Answer 7

running water habitats

Question 8

Define plankton.

Answer 8

suspended organisms found in aquatic ecosystems

Question 9

Define nekton.

Answer 9

free-swimming organisms found in aquatic ecosystems

Question 10

Define neuston.

Answer 10

small organisms that live on top or just below the surface film

Question 11

Define phytoplankton.

Answer 11

photosynthetic organisms that are the base of aquatic food chains

Question 12

Define zooplankton.

Answer 12

small animals that eat phytoplankton

Question 13

Define benthos.

Answer 13

decomposing anerobic bacteria and other organisms that live in the benthic zone

Question 14

Characterize the epilimnion.

Answer 14

upper warmer portion of a stratified lake, continuously supplied with oxygen from air and photosynthetic organisms

Question 15

Characterize the hypolimnion.

Answer 15

cold, dark region of a stratified lake completely cut off from the surface air, continuous contact with bottom mud and nutrients

Question 16

Characterize the metalimnion.

Answer 16

the middle layer in a stratified lake, characterized by thermocline

Question 17

What is the thermocline?

Answer 17

steep temperature gradient in lakes dropping about 1 degree Celsius each meter

Question 18

What is the relationship between Biological Oxygen Demand (BOD) and the productivity of a lake? Why?

Answer 18

As productivity increases, BOD increases. This is because there are more organisms that require oxygen and there is more dead matter to be decomposed.

Question 19

What is an Oligotrophic lake and what types of fish can be found there?

Answer 19

nutrient poor lakes, low productivity, more dissolved oxygen, clear, cold and deep
-trout and other fish sensitive to low dissolved oxygen

Question 20

What is a eutrophic lake and what types of fish can be found there?

Answer 20

nutrient rich, high productivity, turbid, warmer and often shallow
-fish that can tolerate low dissolved oxygen

Question 21

Describe the relationship between the redox-potential of lake sediments and nutrient availability.

Answer 21

Redox potential is whether the sediments in contact with the water are oxidized or reduced. If oxygen is present many nutrients are bound to the oxidized mud and are unavailable for use. Nutrients in reduced muds are dissolved and available.

Question 22

Describe the events occurring during the fall and spring turnover in temperate lakes.

Answer 22

The thermocline disappears and the lake becomes evenly mixed. This brings up all the nutrients from the bottom, prompting blooms of phytoplankton.

Question 23

Describe the process of stratification that occurs in temperate lakes during the winter.

Answer 23

The coldest water (0 degrees Celsius) will be just beneath the ice and the warmest water (4 degrees Celsius) near the bottom because that is the temperature water is most dense.

Question 24

Characterize riffles in a swiftly flowing stream.

Answer 24

shallow turbulent stretches where water flows swiftly over a rough bottom of sand and rock where most of the primary productivity happens.

Question 25

Characterize pools in a swiftly flowing stream.

Answer 25

deep water flowing slowly over a smooth sand, gravel or mud bottom, found above and below riffles

Question 26

Characterize runs in a swiftly flowing stream.

Answer 26

fast-flowing stretches of streams that flow over bedrock or rock and sand with smooth surface water.

Question 27

What is meant by the aufwuchs, or periphyton?

Answer 27

an extensive mat of photosynthetic organisms (diatoms, algae, mosses, etc) that has the most primary productivity in the steam; found in riffles

Question 28

How does the nature of a stream-bottom influence the productivity in the stream?

Answer 28

sandy bottoms are least productive because there is little surface for organisms to grip. Gravel and rubble bottoms are most productive because it has the most surface area for organisms to attach, and nooks and crannies for larvae.

Question 29

Describe the abiotic and biotic changes that occur as current decreases in slow water streams.

Answer 29

Dead organic matter accumulates on the bottom, detritus from upstream is the main source of energy, fish become more compact to swim through all the plants, crustaceans, mollusks, and insect larvae live in the silt on the bottom.

Question 30

How do regulated rivers and streams differ from free-flowing ones.

Answer 30

Regulated rivers have been dammed, channelized, or otherwise modified. Free-flowing ones are the ones left as made by nature.

Question 31

Contrast the effects of releasing water from the epilimnion and hypolimnion of a reservoir on the receiving stream.

Answer 31

If it is released from the epilimnion, the effect of the flow is similar to a natural lake; receives warm nutrient-rich, well-oxygenated water, creates favorable conditions. If it is released from the hypolimnion, it receives cold, oxygen-poor water carrying iron and other minerals and high concentrations of organic material.

Question 32

List two ways in which the effects of hypolimnial release on a receiving stream can be reduced.

Answer 32

Gated withdrawl structures or artificial circulation.

Question 33

Characterize basin wetlands.

Answer 33

develop in shallow basins ranging from upland topographic depressions to filled-in lakes and ponds

Question 34

Characterize riverine wetlands.

Answer 34

found along shallow and periodically flooded banks of rivers and streams

Question 35

Characterize fringe wetlands.

Answer 35

occur along costal areas of large lakes or at the edge of marine estuaries.

Question 36

Distinguish between swamps and marshes.

Answer 36

Marshes are wetlands dominated by herbaceous (non-woody) vegetation. Swamps are wetlands dominated by woody vegetation.

Question 37

Describe the problem of wetland depletion in North America.

Answer 37

87% loss due to conversion to farmland

8% loss annually to urban development

Question 38

In addition to being areas of high productivity, give three useful functions performed by wetlands.

Answer 38

• overflow areas for flood control
• nurseries and prime habitat for fish, waterfowl and lots of other wildlife
• cleaning and filtering water, removing sediments, nutrients and toxins

Question 39

Distinguish between the pelagic and benthic regions of marine ecosystems.

Answer 39

Pelagic region is the open ocean, the whole body of water.

Benthic region is the bottom sediments.

Question 40

Where does most productivity occur in marine ecosystems?

Answer 40

shallow, sunlit waters where phytoplankton form the base of the food chain.

Question 41

Under what conditions are areas of open-ocean very productive.

Answer 41

regions where upwelling currents bring nutrients to the surface layers.

Question 42

Characterize the supralittoral fringe of the rocky intertidal zone.

Answer 42

salt water comes every once in a while on highest tides or salt sprays, experiences wide temperature fluctuations, intense solar radiation, long periods of dessiccation

Question 43

Characterize the littoral area of the rocky intertidal zone.

Answer 43

covered and uncovered daily by tides; algae, barnacles and various gastropods live here

Question 44

Characterize the infralittoral fringe of the rocky intertidal zone.

Answer 44

lowest part, may only be uncovered during lowest tides

Question 45

Contrast life on sandy shores and mudflats with that on rocky shores.

Answer 45

Sandy shores and mudflats are difficult, no source of attachment, most organisms stay buried in the sand/mud.
Rocky shores create tide pools that boom with marine life; subjected to sudden wide fluctuations in temperature and salinity.

Question 46

Describe the feeding styles of animals inhabiting sandy shores and mudflats.

Answer 46

deposit feeders, they ingest organic matter from the mud/sand

Question 47

In what type of waters are coral reefs found?

Answer 47

warm, nutrient poor waters

Question 48

Describe the relationship between the zooxanthellae and the coral polyps

Answer 48

It is a mutualistic relationship.
During the day the photosynthetic zooxanthellae directly transfer organic material to the coral and help deposit calcium carbonate for exoskeleton.
At night the coral feeds on zooplankton; gets phosphates, nutrients, and other nutrients needed for it and zooxantellae

Question 49

Why are coral reefs restricted to well-sunlit waters?

Answer 49

so it can provide necessary sunlight for zooxanthellae, coral zonxantellae

Question 50

What are estuaries and how would you characterize their productivities.

Answer 50

partly ecnlosed costal ecosystems that occur where oceans meet the land and seawater and freshwater mix creating a nutrient-rich, very productive ecosystem

Question 51

Where are salt marshes found?

Answer 51

on the alluvial plains around the margins of the estuaries or in the shelter of offshore islands and sand bars.

Question 52

Characterize a mangroove swamp.

Answer 52

on tidal flats in tropical regions, dominated by salt-tolerant woody plants with shallow, widely spreading roots that come from the trunk and branches
-can for an extensive chain of islands in shallow bays

Question 53

What is the function of the pneumatophores possessed by many mangrove trees?

Answer 53

they are root extensions to take in more oxygen for the roots