What is something that farmers do that causes eutrophication, leading to dead zones?
Over-fertilize
100
In which century was a decline in oxygen first observed?
20th century (specifically 1950s for most ecosystems)
100
What do aquatic organisms do when they first experience declining oxygen levels?
Leave to areas of higher oxygen levels.
100
Which of the Great Lakes has become a dead zone?
Lake Erie
200
Absence or total depletion of oxygen.
Anoxia
200
Which two nutrients are the primary cause of eutrophication?
Nitrogen and Phosphorus
200
Considering that most ecosystems started showing declines in oxygen levels in 1950s, in which decade did they finally become hypoxic?
1970s
200
What kinds of aquatic organisms are most likely to die from hypoxia?
Aquatic organisms that cannot escape fast enough or at all.
200
What colour indicates the occurrence of eutrophication?
Green
300
Coastal waters too low in oxygen to sustain life.
Dead Zones
300
How has the number of dead zones increased per decade? a) doubled b) tripled c) quadrupled d) no change
a) doubled
300
What is the largest dead zone?
Baltic Sea
300
Which season is hypoxia most likely to occur?
Summer
300
Name two of three ways nutrients are deposited in coastal waters.
Over-fertilization, burning of fossil fuels, or emissions from vehicles.
400
Excessive richness of nutrients in a lake or other body of water, which causes a dense growth of plant life and death of animal life from lack of oxygen.
Eutrophication
400
What percentage of fertilizer do soils absorb? a) 0% b) ~20% c) ~40% d) ~60%
b) ~20%
400
What is the second largest dead zone?
Gulf of Mexico
400
Which of the following aquatic organisms are least likely to survive low oxygen levels?
a) corals
b) crustaceans
c) demersal/bottom-dwelling fish
d) all of the above
400
Name two of three ways nutrients are deposited in coastal waters.
Over-fertilization, burning of fossil fuels, emissions from vehicles ...
500
Rapid increase in the population of algae in an aquatic system.
Algae Blooms
500
Which is most hypoxia-tolerant?
a) oysters
b) corals
c) jellyfish
d) striped bass
c) jellyfish
500
The Baltic Sea showed earlier declines of oxygen levels than most ecosystems. In which decade did the Baltic Sea start showing declines of oxygen levels?
1930s
500
Does hypoxia make deeper, cooler water MORE or LESS available in the summer?
Less Available
500
Name one of the two rivers that discharge at least 1.6 million metric tons of nitrogen and 100,000 metric tons of phosphorus into the Gulf of Mexico annually.