1. Chapter 16: Continental Shelves and Neritic Zone

2. Continental Shelves Average of 67km wide
Descends gradually from the shore to 130m
Can be broad or narrow

3. Benthic Communities Variety found on continental shelf
Bottom composed of rock
Food supply is major limiting factor (ex: detritus)
Types of organisms depends on the stability of the environment

4. Role of sediments: Continental shelf with current flow
Bottom composed of course sediments (sand, gravel rock)
Bottom constantly shifting
Not good for infauna (animals that burrow in sediment) and interstitial animals (live in spaces between sediment particles)

5. Water flow carries large supply of food
Epifauna: animals that live on surface sediments
Sedentary or sessile filter feeders and suspension feeders
Ex: sponges, sea anemones, cnidarians

6. Weak bottom currents
Bottom composed of fine sediments (silt)
More stable
Infauna with permanent burrows
Ex: polychaete worms, amphipods, clams
Deposit feeders

7. Hard-Bottom Communities
Large sediments (rock, clam shells) that cannot be pushed apart
Found off rocky coasts
Sessile organisms

8. Epibenthic Organisms
Live on surface of bottom sediments, on hard bottoms, not evenly distributed
Uneven distribution of benthic organisms
Called patchiness
Factors affecting patchiness
Exposure to sunlight
Disturbance

9. Kelp Communities Brown algae
Requires rocky bottom, cold water, and continuous supply of nutrients
High level of photosynthetic activity
Most kelp beds less than 20m deep (66 ft.)

10. Kelp Beds Like underwater forests
Canopy  shades smaller algal species
Understory  home to many animal species

11. Macrocystis
Giant kelp (world’ s largest algae)
In Pacific and southern Atlantic
20-40m long
Gas-filled floats at base of each blade
Perennial (live 3-7 years)
Laminaria
North Atlantic
Closely packed
New tissue added at base
Constantly growing and eroding

12. Kelp Communities Used for food, shelter, or both
Favorite food of sea urchins

13. Soft-Bottom Communities
Sediments are sand, mud, or both
Strong currents (sand)  suspension feeders
Weaker currents (mud)  deposit feeders
Patchiness causes organism distribution
Changes in bottom sediments, bottom currents, patterns of larval settlement
Detritus is primary source of food

14. Neritic Zone
Coastal seas along edges of continents and above continental shelves
Large numbers of phytoplankton
Green in color  high productivity
Produces 90% of world’s annual harvest of fish and shellfish

15. Receives freshwater runoff from land
Provides nutrients for:
Microphytoplankton ( micrometers)
Nanophytoplankton (less than 20 micrometers)
Productivity  most productive in upwelling zones
Ecological importance of plankton
Supply food for animals
Area for larval development