Deck 16: Continental Shelves and Neritic Zone

Question 1

How do waves and currents affect the types of benthic organisms found on the continental shelf?

Answer 1

The frequency and force of movement of the water on continental shelves controls many aspects of the benthic communities. Organisms strive for stable environments, even if those environments have strong movement of water. For organisms that withstand wave shock, their body size and shape is adapted to those forces. During storms however, waves create an unstable environment for those same, and all other, organisms, and can be responsible for mortality (especially where sediment is unusually disturbed). Currents are also important for the survival of species, as some rely on the movement of water to transport organisms, their gametes, and their larvae. The lack of water movement is also important to some communities that rely on the nutrients that fall from above; these communities also rely on the lack of current to maintain their hold on the bottom.

Question 2

Diagram a simple food web for the continental shelf.

Answer 2

A simple food web of the continental shelf begins with plankton, which are food for deposit feeders and some burrowers.

Question 3

Why do disturbances such as landslides have a greater impact on invertebrate populations than on algal populations?

Answer 3

Invertebrate populations that live on the bottom of the continental seas rely on specific types of substrate for shelter and feeding. When a landslide occurs the burrowers are buried in new sediments that are not oxygenated, thus suffocating those that are buried. Other burrowers are displaced either deeper where the sediments are anoxic, or up to the surface where they are unprotected. Landslides also effect epifauna in the same way as those that burrow; they are buried or displaced and often killed. Those that survive may not be able to move to more suitable sediment, or may be exposed to sediment floating in the water column; both situations easily lead to death. Algae populations, on the other hand, have less stringent habitat requirements, and more easily survive a landslide because of their substrate needs, physiology, and reproduction habits. Algae live in hard substrate areas. Where calcareous algae live, a landslide removes invertebrates and makes that space available for the new growth of more algae. Many species of algae are able to photosynthesize with minimal light, similar to the conditions of clarity after a landslide. Algae are very elastic and can withstand the higher current energy produced by a landslide. They also have "floats" as part of their anatomy, and can continue to grow when uprooted.

Question 4

Describe the process of succession that occurs in soft-bottom communities that are disturbed.

Question 5

Although representing only 10% of the ocean, coastal seas provide 90% of the world's commercial catch. The high level of productivity found in coastal seas supports large populations of fish and shellfish, far more than the open ocean.

Question 6

What are two ecological roles for plankton in the neritic zone?

Question 7

The uneven distribution of bottom organisms and sediment type on the continental shelf is referred to as
a. reticulation
b. patchiness
c. diversity
d. sediment selection
e. benthic orientation

Question 8

Name two important functions of bottom currents in benthic communities.

Question 9

Coastal waters receive nutrient runoff from the land and upwellings bring nutrients from deeper water to the surface. The heavy concentration of nutrients combined with large amounts of sunlight support large populations of phytoplankton which in turn support large numbers of zooplankton and fish.

Question 10

In colder waters, ___ dominate the phytoplankton.
a. krill
b. copepods
c. diatoms
d. dinoflagellates
e. kelp

Question 11

Match the following organisms with the appropriate description.

Question 12

Explain how the types of bottom sediments influence the diversity of life on the floor of the continental shelf.

Question 13

Most of the world's harvest of commercial fish comes from
a. estuaries
b. bays
c. coastal seas
d. the open ocean
e. benthic regions

Question 14

The most abundant members of the zooplankton are
a. krill
b. copepods
c. jellyfish
d. diatoms
e. dinoflagellates

Question 15

What are the main sources of nutrient input into coastal seas?

Question 16

List three explanations for the patchy distribution of organisms in soft-bottom communities.

Question 17

Currently there is concern about climate change caused by the greenhouse effect. How might this affect the productivity of coastal seas?

Question 18

Nutrients produced by bacteria in the bottom sediments are returned to the surface waters by
a. gyres
b. upwellings
c. thermoclines
d. Eckman spirals
e. the Coriolis effect

Question 19

Hard bottom sediments such as rock support seaweeds and a variety of sessile and sedentary filter feeders. Soft bottom sediments such as sand and mud support many burrowing organisms.

Question 20

Explain how decreases in the size of lobster and cod populations have affected North Atlantic kelp beds.

Question 21

Burrowing organisms would more likely be found where
a. sediments are predominantly gravel
b. the sediments are sand, and the water currents are fast
c. the sediments are silt, and the water currents are slow
d. the sediments are silt, and the water currents are fast
e. landslides frequently disrupt the bottom

Question 22

In soft-bottom communities, suspension feeders and deposit feeders are usually not found in the same areas because
a. they compete with each other for food
b. they compete with each other for space
c. deposit feeders prey on suspension feeders
d. the suspended silt in regions inhabited by deposit feeders clogs the feeding structures of suspension feeders
e. the type of sediments inhabited by deposit feeders will not support suspension feeders

Question 23

What factors affect the size of plankton populations?

Question 24

Why are kelp beds frequently compared to terrestrial rainforests?

Question 25

Why do so many species of small fish found in coastal seas travel in large schools?

Question 26

The world's most productive upwelling area is located off the coast of
a. California
b. Peru
c. China
d. South Africa
e. Europe

Question 27

Kelp communities are important because they provide a complex three-dimensional habitat for hundreds of species as well as a food source for many species.

Question 28

Why is the neritic zone such a productive area?

Question 29

Sedentary and sessile filter feeders and suspension feeders are better adapted to
a. hard bottoms
b. soft bottoms

Question 30

The dominant alga in southern California kelp forests is
a. Fucus
b. Laminaria
c. Eisenia
d. Sargassum
e. Macrocystis