Chapter 8: Aquatic Ecosystems Flashcards
What is the littoral zone?
shallow, well-lit areas around the shore extending to where rooted vegetation stops, lots of organisms
What is the limnetic zone?
open sunlit waters beyond the littoral zone down to depths where photosynthesis is no longer significant
What is the profundal zone?
deep ocean water below the depth of effective light penetration
What is the benthic zone?
bottoms of lakes and ponds, which contains sediments rich in organic matter
Define limnology.
the study of freshwater ecosystems
Define lentic.
standing water habitats
Define lotic.
running water habitats
Define plankton.
suspended organisms found in aquatic ecosystems
Define nekton.
free-swimming organisms found in aquatic ecosystems
Define neuston.
small organisms that live on top or just below the surface film
Define phytoplankton.
photosynthetic organisms that are the base of aquatic food chains
Define zooplankton.
small animals that eat phytoplankton
Define benthos.
decomposing anerobic bacteria and other organisms that live in the benthic zone
Characterize the epilimnion.
upper warmer portion of a stratified lake, continuously supplied with oxygen from air and photosynthetic organisms
Characterize the hypolimnion.
cold, dark region of a stratified lake completely cut off from the surface air, continuous contact with bottom mud and nutrients
Characterize the metalimnion.
the middle layer in a stratified lake, characterized by thermocline
What is the thermocline?
steep temperature gradient in lakes dropping about 1 degree Celsius each meter
What is the relationship between Biological Oxygen Demand (BOD) and the productivity of a lake? Why?
As productivity increases, BOD increases. This is because there are more organisms that require oxygen and there is more dead matter to be decomposed.
What is an Oligotrophic lake and what types of fish can be found there?
nutrient poor lakes, low productivity, more dissolved oxygen, clear, cold and deep
-trout and other fish sensitive to low dissolved oxygen
What is a eutrophic lake and what types of fish can be found there?
nutrient rich, high productivity, turbid, warmer and often shallow
-fish that can tolerate low dissolved oxygen
Describe the relationship between the redox-potential of lake sediments and nutrient availability.
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.
Describe the events occurring during the fall and spring turnover in temperate lakes.
The thermocline disappears and the lake becomes evenly mixed. This brings up all the nutrients from the bottom, prompting blooms of phytoplankton.
Describe the process of stratification that occurs in temperate lakes during the winter.
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.
Characterize riffles in a swiftly flowing stream.
shallow turbulent stretches where water flows swiftly over a rough bottom of sand and rock where most of the primary productivity happens.
Characterize pools in a swiftly flowing stream.
deep water flowing slowly over a smooth sand, gravel or mud bottom, found above and below riffles
Characterize runs in a swiftly flowing stream.
fast-flowing stretches of streams that flow over bedrock or rock and sand with smooth surface water.
What is meant by the aufwuchs, or periphyton?
an extensive mat of photosynthetic organisms (diatoms, algae, mosses, etc) that has the most primary productivity in the steam; found in riffles
How does the nature of a stream-bottom influence the productivity in the stream?
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.
Describe the abiotic and biotic changes that occur as current decreases in slow water streams.
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.
How do regulated rivers and streams differ from free-flowing ones.
Regulated rivers have been dammed, channelized, or otherwise modified. Free-flowing ones are the ones left as made by nature.
Contrast the effects of releasing water from the epilimnion and hypolimnion of a reservoir on the receiving stream.
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.
List two ways in which the effects of hypolimnial release on a receiving stream can be reduced.
Gated withdrawl structures or artificial circulation.
Characterize basin wetlands.
develop in shallow basins ranging from upland topographic depressions to filled-in lakes and ponds
Characterize riverine wetlands.
found along shallow and periodically flooded banks of rivers and streams
Characterize fringe wetlands.
occur along costal areas of large lakes or at the edge of marine estuaries.
Distinguish between swamps and marshes.
Marshes are wetlands dominated by herbaceous (non-woody) vegetation. Swamps are wetlands dominated by woody vegetation.
Describe the problem of wetland depletion in North America.
87% loss due to conversion to farmland
8% loss annually to urban development
In addition to being areas of high productivity, give three useful functions performed by wetlands.
- 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
Distinguish between the pelagic and benthic regions of marine ecosystems.
Pelagic region is the open ocean, the whole body of water.
Benthic region is the bottom sediments.
Where does most productivity occur in marine ecosystems?
shallow, sunlit waters where phytoplankton form the base of the food chain.
Under what conditions are areas of open-ocean very productive.
regions where upwelling currents bring nutrients to the surface layers.
Characterize the supralittoral fringe of the rocky intertidal zone.
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
Characterize the littoral area of the rocky intertidal zone.
covered and uncovered daily by tides; algae, barnacles and various gastropods live here
Characterize the infralittoral fringe of the rocky intertidal zone.
lowest part, may only be uncovered during lowest tides
Contrast life on sandy shores and mudflats with that on rocky shores.
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.
Describe the feeding styles of animals inhabiting sandy shores and mudflats.
deposit feeders, they ingest organic matter from the mud/sand
In what type of waters are coral reefs found?
warm, nutrient poor waters
Describe the relationship between the zooxanthellae and the coral polyps
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
Why are coral reefs restricted to well-sunlit waters?
so it can provide necessary sunlight for zooxanthellae, coral zonxantellae
What are estuaries and how would you characterize their productivities.
partly ecnlosed costal ecosystems that occur where oceans meet the land and seawater and freshwater mix creating a nutrient-rich, very productive ecosystem
Where are salt marshes found?
on the alluvial plains around the margins of the estuaries or in the shelter of offshore islands and sand bars.
Characterize a mangroove swamp.
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
What is the function of the pneumatophores possessed by many mangrove trees?
they are root extensions to take in more oxygen for the roots
