Chapter 7 – Aquatic Ecology
I.
What are the two major types of aquatic life zones?
A. Saltwater or marine
B. Freshwater
II.
What are the main kinds of organisms in aquatic life zones?
A. Plankton – free floating organisms
1. Phytoplankton – microscopic, photosynthetic, cyanobacteria, and many types of
algae; producers that support most aquatic food chains and webs
2. Nanoplankton – newly discovered and poorly understood
3. Zooplankton – non-photosynthetic primary consumers of phytoplankton or
secondary consumers of other zooplankton
B. Nekton – strong-swimming organisms such as fish, turtles, and whales
C. Benthos – bottom dwelling creatures such as oysters, barnacles, and lobsters
D. Decomposers – break down organic compounds, dead bodies, and wastes of aquatic
organisms into simple nutrient compounds for use by producers
III.
How do water’s unique properties affect aquatic life?
A. Buoyancy provides physical support
B. Limited temperature fluctuations
C. Nutrients are dissolved and readily available
D. Potentially toxic metabolic wastes are diluted and dispersed
IV.
What factors limit life at different depths in aquatic life zones?
A. Temperature
B. Access to sunlight for photosynthesis
C. Dissolved oxygen content
D. Availability of nutrients, such as carbon, nitrogen, and phosphorus
V.
Why are the oceans important?
A. Cover 71% of the earth’s surface
B. Regulate earth’s climate
C. Regulates temperature of troposphere
D. Provides habitat for marine plants and animals
E. Human produced wastes flow or are dumped into the ocean and are dispersed by
currents and often diluted to less harmful levels
F. Oceans have two major life zones
1. Coastal zone – warm nutrient rich shallow water that extends from high tide
mark on land to the edge of the continental shelf (submerged part of the
continent)
2. Open sea – the part of the ocean beyond the continental shelf
VI.
What are estuaries and tidal ecosystems?
A.
Estuary partially encloses area of coastal water where sea water mixes with fresh
water and nutrients from rivers, streams, and runoff from land
B.
Constant water movement stirs up the nutrient-rich silt, making it available to the
producers
C.
Temperature and salinity vary
1. After heavy rainfall, streams and river deposit huge amounts of fresh water in
to an estuary, raising the temperature and reducing the salinity
2. During high tides, large volumes of cold, salty water flow into an estuary and
then flow out during low tides
VII.
What are coastal wetlands?
A. Areas of coastal land that are covered all or part of the year with salt water
B. Made up of bays, lagoons, salt flats, mud flats, and salt marshes
C. Serve as nurseries and habitats for shrimp and other aquatic animals
VIII.
What are mangrove swamps?
A. Dominated by mangrove trees that can live partially submerged in saltwater
B. Found on coastlines in warm, tropical climates
C. Provide breeding, nursery, and feeding grounds
IX.
What are rocky and sandy shores?
A. The intertidal zone is the area of shoreline between low and high tides
1. Organisms in this stressful zone must be able to avoid being swept away or
crushed by waves
B. Some coasts have steep rocky shores pounded by waves
1. Variety of organisms found in numerous pools and other niches in the rocks in
the intertidal zone
C. Other coasts have sloping barrier beaches or sandy shores
1. Organisms such as crabs, lugworms, clams, ghost shrimp, sand dollars, and
flounder survive by burrowing, tunneling, or digging in the sand
2. Shorebirds feed on these organisms
3. Natural sand dunes, held in place by the roots of grasses, serve as defense against
sea
a. Often destroyed by human activities and development
X.
What are barrier islands?
A. Long, thin, low offshore islands of sediment that run parallel to shore
B. Help protect the mainland, estuaries, lagoons, and coastal wetlands
C. Beaches are constantly shifting
D. Gentle waves build the islands up and storm waves flatten and erode them
1. Longshore currents, which run parallel to beaches, take sand from one area and
deposit it in another
E. Structures built by humans on low-lying barrier islands are damaged or destroyed by
flooding, severe beach erosion, or major storms, including hurricanes
XI.
What are coral reefs?
A. Form in clear, warm coastal water of trpics and subtropics
B. Most biologically diverse life zones
C. Ecologically complex
XII.
What impact do humans have on coastal zones?
A. Two-thirds of world’s population live along coasts or within 100 miles
B. Since 1900 world has lost half of coastal wetlands to development
1. In 200 years in U.S., 55% of estuaries and coastal wetlands have been destroyed
or damaged
2. California has lost 91%
3. Florida has lost largest area
C. Coastal ecosystems are vulnerable to toxic contamination because they trap
pesticides, heavy metal, and other pollutants (sewage treatment plants, septic tank
systems, and urban runoff)
D. Humans have caused death of 10% of world’s coral reefs especially in S.E. Asia and
Carribbean
1. 300 coral reefs in 65 countries are protected as reserves or parks
2. Protected reefs can often recover
3. Protection is expensive
E. More than half of coastal mangrove forests have been lost to industrial logging,
conversion for raising fish, rice fields, and urban development
XIII.
What can be done about beach erosion?
A. Serious problem along most gently sloping beaches of barrier islands and mainland
shores
1. 30% of U.S. shoreline experiencing significant erosion
2. Main cause is sea level has been gradually rising for past 12,000 years
B. Engineers have tried several methods to halt or reduce erosion
C. Coastal zone ecologists call for banning or limiting coastal development
D. U.S. government spend $150 million a year on beach replenishment
XIV.
What biological zones are found in the open sea?
A. The open sea is the part of the ocean beyond the continental shelf
B. Divided into 3 zones based on penetration of sunlight
C. Euphotic zone – upper zone where photosynthesis occurs
a. makes of 90% of ocean surface
b. produces only about 10% of world’s commercial fish
1. Bathyal zone – dimly lit
2. Abyssal zone – dark
a. water is very cold and has little dissolved oxygen
D. Dead and decaying organisms fall to the ocean floor to feed microscopic decomposes
and scavengers, such as crabs and sea urchins
1. Deposit feeders, such as worms, take mud into their guts and extract nutrients
from it
2. Filter feeders, such as oysters and mussels, pass water through or over their
bodies and extract nutrients from it
XV.
What are freshwater life zones?
A. Aquatic zones where water with dissolved salt concentration of less than 1% by
volume and accumulates on or flows through the surfaces of terrestrial biomes
B. Lakes, ponds, and inland wetlands are standing (lentic)
C. Flowing (lotic) systems are streams and rivers
D. Cover 1% of the earth’s surface
E. 41% of world’s know fish species live in freshwater
XVI.
What life zones are found in freshwater lakes?
A. Lakes are large natural bodies of standing fresh water formed when precipitation,
runoff, or groundwater seepage fill depressions in the earth’s surface
B. These depressions are caused by
1. glaciation
2. crustal displacement accompanied by or causing earthquakes
3. volcanic activity
C. Lakes consist of four zones Littoral zone – shallow area near shore to the depth
where rooted plants stop growing
a. most productive zone
b. high biological diversity
c. high number of decomposers
1. Limnetic zone – open sunlit surface water layer away from the shore that extends
to the depth penetrated by sunlight
a. contains phytoplankton, zooplankton, and fish
2. Profundal zone – deep open water where it is too dark for photosynthesis
3. Benthic zone – bottom of a lake inhabited by decomposers, detritus feeding
clams, wormlike insect larvae, and catfish
XVII. How do plant nutrients affect lakes?
A. Classified according to nutrient content and primary productivity
B. Oligotrophic (poorly nourished) lake
1. newly formed and has small supply of plant nutrients
2. deep with steep banks
3. low net productivity
4. usually has crystal-clear blue or green water
5. small populations of phytoplankton and fish
C. Eutrophic (well-nourished) lake
1. contains large or excessive supply of nutrients
2. typically shallow
3. water is generally murky green or brown
4. high net productivity
a. large population of phytoplankton, many zooplankton, and diverse
population of fish
5. depleted of dissolved oxygen in warm summer months
D. Mesotrophic lakes fall between two extremes of nutrient enrichment
XVIII. What seasonal changes occur in temperate lakes?
A. Water is densest as a liquid at 4 degrees C which is why ice at 0 degrees C floats on
water
B. This unusual property causes thermal stratification of deep lakes in northern areas
1. During summer, lakes are stratified into different temperature layers that resist
mixing
2. Summer sunlight warms surface water making it less dense
C. These lakes have three layers
1. Epiliminon – upper layer of warm water with high levels of dissolved oxygen
2. Thermocline – middle layer where the water temperature changes rapidly with
increased depth
a. acts as a barrier to the transfer of nutrients and dissolved oxygen from upper
to lower layers
3. Hypoliminon – lower layer of colder, denser water with lower concentration of
dissolved oxygen because it’s not exposed to the atmosphere
D. When temperatures begin to drop in the fall, the surface layer becomes more dense
1. It sinks to the bottom when it cools to 4 degrees C
2. The thermocline disappears
3. This mixing, fall overturn, brings nutrients from bottom sediments to the surface
4. Sends dissolved oxygen from surface to the bottom
E. The ice melts in spring and lake’s surface water warms to 4 degrees C
1. It sinks through and below the cooler, less dense water
2. Winds blowing across lake’s surface cause strong vertical currents that mix
surface and bottom water
a. brings dissolved oxygen from the surface to the bottom
b. brings nutrients from bottom to surface
3. During this spring overturn the lake’s temperature and dissolved oxygen levels
are roughly the same at all depths
XIX.
What are the zones in freshwater streams and rivers?
A. Surface water is precipitation that doesn’t sink into the ground or evaporate
B. Surface water becomes runoff when it flows into streams and eventually to the ocean
as part of the hydrologic cycle
C. A watershed, or drainage basin, is the entire land area which delivers water,
sediment, and dissolved substances via small streams to a larger stream or river, and
finally to the sea
D. Downward flow of surface water and groundwater from mountain highlands to the
sea takes place in three zones of a river system
E. The source zone is a narrow zone of headwater or mountain highland streams of cold,
clear water rushing over waterfalls and rapids
a. dissolves large amounts of oxygen from the air
b. algae and moss attach to rocks
c. few phytoplankton
d. fish have compact flattened bodies so they can hide under rocks
1. The transition zone is where headwater streams merge to form wider deeper
streams that flow down gentler slopes
a. warmer water
b. support phytoplankton and wider variety of fish with lower oxygen
requirements
2. In the flood plain zone streams join into wider deeper rivers that meander across
broad, flat valleys
a. water has higher temperatures and less dissolved oxygen
b. supports a large population of algae and cyannobacteria
c. water is often muddy and contains large concentrations of silt
d. fish in river channels are different from ones present in the backwaters of the
river
e. the meandering rivers are sometimes straightened, deepened, and widened by
humans to improve navigation and to help reduce flooding and bank erosion
(1) this stream channelization is controversial
f. at its mouth the river may divide into many channels as it flows through
coastal wetlands and estuaries
3. Streams and rivers shape the land around them
4. To protect a stream or river from excessive pollutants, the watershed must be
protected
XX.
Why are freshwater inland wetlands important?
A. Inland wetlands are lands away from the coast that is covered all or part of the time
with fresh water
1. Some, such as, prairie potholes, swamps, and floodplains are seasonal wetlands
2. Other inland wetlands include marshes, mud flats, bogs (rain fed, peat-rich
areas), wet meadows, and wet arctic tundra in summer
B. Inland wetlands play important ecological and economic roles
C.
D.
E.
F.
XXI.
1. Provide food and habitats for fish, migratory waterfowl, and other wildlife
2. Are called nature’s kidney because they improve water quality by filtering,
diluting, and degrading toxic wastes, excess nutrients, sediment, and other
pollutants
3. Floodplain wetlands near rivers reduce flooding and erosion by absorbing stormwater and releasing it slowly
Inland wetlands help replenish groundwater supplies
Play significant roles in global carbon, nitrogen, sulfur, and water cycles
Provide recreation
Used to grow crops such as blueberries, rice, and cranberries
What impact do humans have on inland wetlands?
A. Many inland wetlands are drained, dredged, filled in, or covered over
B. In U.S., 183 sq. miles are lost each year
1. 80% to agriculture
2. 20% to mining, forestry, oil and gas extraction, highways, or urban development
C. U.S. requires federal permit to fill wetlands or deposit dredged or fill material in
them
1. These requirements have cut wetland loss by 75% since 1969
2. Only 8% of remaining inland wetlands are under federal protection
D. Federal policy, called mitigation banking, does allow destruction of existing wetlands
if an equal area of same type of wetland is created or restored
1. Half of attempts to create new wetlands fail to replace lost ones
2. Created wetlands bear little resemblance to natural ones
3. Restoring and creating wetlands is expensive
E. Best and cheapest coarse of action is prevention of destruction
1. Environmentalists call for comprehensive land-use planning where government
work together to steer developers away from wetlands
2. Consider mitigation banking as a last resort and require creation and evaluation
of new wetlands before old ones are destroyed
XXII. How sustainable are aquatic ecosystems?
A. Requires understanding connections of how human activities affect energy and
nutrient flow, trophic relationships, and biodiversity
B. Aquatic ecosystems are directly connected to everything upstream and anything that
occurs in their watersheds
C. Aquatic ecosystems are constantly renewed but only work if they are not overloaded
with pollutants and excessive nutrients and are not over-fished