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Chapter 16: Continental Shelves and Neritic Zone

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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


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