K.Etheredge – Marine Science
PRACTICE TEST: Estuaries, Salinity & Osmoregulation, Marine Plants
Choose the correct response for each question. Write all answers on a separate sheet of paper.
PLEASE DO NOT WRITE ON THIS TEST.
1. The process of salt sticking to fine
sediments or particles in the ocean:
a. increases salinity levels of the area
b. adds more salt into the ocean
c. causes the salt to sink to the bottom
d. does not affect the salinity level
2. How do hydrothermal vents impact the
ocean’s salinity?
a. they add salts as the hot water
dissolves the Earth’s crust
b. they remove salts that react with
basalt (volcanic) rock
c. all of the above
3. When seawater reaches the poles and
freezes, what happens to the salinity of
the water surrounding the ice?
a. it remains the same
b. it decreases
c. it increases
4. Choose the correct statement.
a. the amount of salt in the ocean is
decreasing
b. the amount of salt added to the
ocean is balanced by the amount
removed
c. the amount of salt in the ocean is
increasing
5. Estuaries that have high rates of
evaporation and little runoff:
a. are called brackish estuaries
b. do not exist
c. are called negative estuaries
6. Which of the following causes the water
to become saltier?
a. evaporation
b. runoff
c. melting sea ice
d. precipitation
7. Salt wedges:
a. form when saltwater floats at the
surface of an estuary
b. move back and forth in an estuary
with the daily tides
c. result in an evenly mixed estuary
d. all of the above
8. Due to osmosis in a marine environment,
water tends to flow from the
___________ to the ___________.
a. surrounding seawater; marine
organism
b. marine organism; surrounding
seawater
9. When in seawater, what would happen
to a marine organism’s cells (that are
less salty than the seawater) if it is not
adapted to cope with osmosis?
a. the cells would swell and could
burst
b. the cells would shrink and could
collapse
c. the cells would stay the same
10. Some marine organisms keep their
internal salt and water concentrations at
a level that is different than that of the
surrounding environment. This type of
animal is called an
a. osmoregulator
b. osmoconformer
11. Cartilaginous fish (sharks and rays) cope
with osmosis by:
a. storing urea in their bodies
b. matching the surrounding salt
concentrations so water doesn’t
flow in any net direction
c. excreting excess salt with their
rectal gland
d. all of the above
12. True/False. The bull shark is an
exception to cartilaginous fish in that it
can survive in freshwater.
a. true
b. false
13. Which of the following is NOT an
adaptation that marine animals might
have to cope with osmosis in saltwater?
a. having efficient kidneys
b. producing diluted urine
c. excreting salt through a salt gland
14. Burrowing, digging, and closing of the
animal’s shell:
a. are adaptations often found in
benthic estuary animals
b. help shield the animal from changes
in the salinity of the water
c. are adaptations found in
osmoconformers
d. all of the above
15. Some marine fish, like salmon, migrate
to spawn in estuaries and freshwater
rivers where the surrounding water is
less salty than the fish’s cells. What is
the tendency of water to move?
a. water will flow in both directions
but with no net gain or loss in the
cell
b. water will tend to flow into the
fish’s cells
c. water will tend to flow out of the
fish’s cells
16. In the previous question, what are
adaptations of these types of fish that
allow them to survive in freshwater?
a. they excrete excess salt through
their gills
b. they drink the surrounding water
c. they excrete large amounts of
dilute urine
17. The following are characteristics of
estuaries EXCEPT:
a. have a high biodiversity
b. are places where oceans meet
rivers
c. are very much influenced by tides
d. have stable salinity levels
18. What is the impact of estuaries on fish
populations?
a. They protect a large portion of
commercial fish species during their
juvenile stage.
b. They have caused over 90% of the
large fish population to disappear.
c. They protect older fish.
d. They are responsible for harmful
algae blooms, which kills or
displaces many fish populations.
19. How do estuaries affect the seafood
industry?
a. They are minor sources of seafood.
b. They are not used for the purpose
of seafood harvesting.
c. They reduce local economies and
jobs pertaining to the seafood
industry.
d. They provide more than two-thirds
of the seafood that humans eat,
directly and indirectly.
20. How do estuary environments affect
water quality?
a. They contaminate the water from
land as it passes to the ocean by
releasing pollutants stored in the
plant roots.
b. They clean the water from land as
it moves through by trapping
pollutants and sediments in the
plant roots.
c. They increase the amount of soils
and sediments that reaches nearby
ocean environments.
d. They prevent saltwater from mixing
with freshwater.
21. If an estuary were removed for
development, what would be the most
likely result?
a. Strong storms would be greatly
slowed down.
b. A hurricane would cause less
damage to the area.
c. Flooding would reach a much
higher amount than before.
d. The seafood industry would benefit.
22. Estuaries _____________ erosion.
a. increase
b. decrease
c. have no impact on
23. The reason for the impact in the
previous two questions is mainly due to:
a. the man-made strengthening of
estuaries by developing cities on
them
b. the amount of salt that is found in
estuaries
c. the high diversity of estuary life
d. the roots of estuary plants
24. How do dams affect estuaries?
a. they increase the mixing of salt and
freshwater
b. they cause the freshwater supply to
be cut off from estuaries
c. they help wildlife
d. they keep the balance of fresh and
saltwater healthy for estuary life
25. How does controlling certain types of
invasive species, such as the rodent
nutria, help restore estuaries and
wetlands?
a. it decreases the amount of
sediments in estuaries
b. it increases the vegetation that is
responsible for holding soil
together
c. it increases erosion
d. it restores the balance of
freshwater and saltwater
26. True/False. Seawater contains only
pure water and dissolved salts.
a. true
b. false
27. What portion of seawater is made of
dissolved salts?
a. 1%
b. 35%
c. 3.5%
d. 96.5%
28. The ions that make up most of the salt in
seawater are:
a. magnesium and potassium
b. sodium and chloride
c. potassium and chloride
d. potassium and sulfate
29. A water sample’s salinity level is 25 ppt.
What does this mean?
a. it is pure freshwater
b. it is a high salinity level that would
be difficult for many organisms to
survive
c. it is most likely found in a brackish
estuary
d. there are 2.5 parts of salt per
thousand parts of water
30. How is salt removed from the ocean?
a. precipitation
b. rock erosion
c. shell-making mollusks such as clams
d. volcanoes
31. If a person was stranded at sea,
drinking the seawater would:
a. be useless since it does not hydrate
us or dehydrate us
b. be fine since our kidneys can
excrete excess salt
c. be deadly since our kidneys would
attempt to get rid of the salt by
excreting urine but would fail
32. Stomata:
a. are internal air canals used to
extract oxygen from seawater
b. are snorkel-like tubes which carry
oxygen below the surface
c. are pores in the leaves that allow
oxygen into the leaf
d. are salt glands on the leaves and
stem that excrete excess salt
33. Some marine plants survive in salty
environments by storing or concentrating
salt in their roots. Why is this an
effective adaptation?
a. Water flows into the roots
b. Water flows out of the roots
c. The water flows in both directions
but with no net gain or loss in the
cell
34. Which plant is NOT found in warm,
tropical regions?
a. mangroves
b. seagrasses
c. salt marsh grasses
35. A sacrificial leaf:
a. breaks down pollutants
b. is an adaptation for obtaining
oxygen
c. contains salts and drops off of the
plant to remove excess salt
d. is found in salt marsh grasses
36. Pneumatophores are:
a. found in salt marsh grasses
b. for the purpose of excreting excess
salt
c. prop roots that hold mangroves up
d. snorkel-like tubes that allow
oxygen to enter the plant
37. Which is NOT true of prop roots?
a. they increase the amount of
nutrients and pollutants that reach
nearby coral reefs
b. they help the mangrove obtain
oxygen
c. they stabilize the plant in unstable
mud
d. they trap sediments (sand and mud)
with their roots which helps them
expand
38. Which is an example of a submergent
marine plant?
a. mangrove trees
b. seagrasses
c. salt marsh grasses
39. Seagrasses keep their internal salinities
________ the salinity of the surrounding
seawater, which would cause water to
___________ by osmosis.
a. the same as; have no net
movement
b. lower than; flow inward
c. higher than; flow outward
40. What is the role of mangrove trees and
salt marsh grasses in estuary food
webs?
a. They are not ever eaten or used by
estuary animals.
b. They are eaten directly by many
estuary animals.
c. They are important sources of food
for manatees.
d. They are used as nutrients once the
leaves have fallen into the water
and begin to decompose