1. Chapter 15 Animals of the Benthic Environment
Coral Reef
Deep Sea
Rocky and sandy shores

2. Animals of the Benthic Environment-Overview
Benthic communities include a variety of habitats.
Corals need specific environmental conditions.
Hydrothermal vents support diverse communities that rely on chemosynthesis.

3. Distribution of Benthic Organisms
More than 98% of 250,000 known marine species live in or on ocean floor
Benthic organisms live mainly on continental shelves.
Their distribution is affected by surface ocean currents.

4. Distribution of Benthic Organisms
Benthic biomass matches surface chlorophyll distribution.

5. What Communities exist along Rocky Shores?
Epifauna
Attached to substrate (e.g., marine algae)
Move over sea floor (e.g., crabs, snails)
Moderate diversity of species
Greatest animal diversity at tropical latitudes
Greatest algae diversity at mid-latitudes

6. Intertidal Zonation
The physical and biological conditions cause horizontal bands of organisms to form in the intertidal waters.
Physical conditions determine the organisms found in the upper bands
Biological conditions determine the organisms found in the lower bands.

7. Zonation Spray zone – above spring tide zone Intertidal zone
area between
high and low
tide.

8. Intertidal Zonation Intertidal zone High tide zone – relatively dry
Middle tide zone – covered by all high tides & exposed by all low tides
Low tide zone – usually wet

9. Spray Zone Spray zone = Supratidal zone Organisms Avoid drying out
Many animals have shells
Few species of marine algae
Periwinkles
Limpets
Rock louse

10. High Tide Zone Animals have shells to avoid drying out.
Marine algae—rock weeds with thick cell walls
Rock weeds colonize first
Sessile animals establish later
Barnacles
Rock weed

11. Middle Tide Zone More types of marine algae Soft-bodied animals
Acorn Barnacles and mussels
Acorn Barnacles
Mussels

12. Middle Tide Zone Tidal pools are common
Sea anemones are inhabitants of the tidal pools.
Stinging nematocysts on tentacles poison prey

13. Middle Tide Mussel Bed and Sea Star
Carnivorous snails and starfish will move into this area to feed
Sea stars love to feed on mussels

14. Middle Tide Zone Also find other inhabitants in the middle tidal zone
Hermit crabs
Sea urchins

15. Low Tide Zone Abundant algae and surf grass
Many animals hidden by seaweed and sea grass

16. Low Tide Zone
Various shore crabs
Scavengers

18. Physical Environment of Sediment-Covered Shores
Sediment size related to wave and current strength
Greater the wave and current strength the larger the sediment
Course boulder beaches
Sand beaches
Salt marshes
Mud flats
High energy
Low energy

19. Intertidal Zonation and Common Organisms

20. What Communities Exist along Sediment-Covered Shores?
Infauna – burrowing animals
No stable, fixed surface
Burrowing provides more stable environment
Less risk of temperature extremes and drying out
Same marine worm (Annelida) in two pictures

21. Sandy Beach Organisms and Adaptations
Bivalve mollusks
Soft body, hard shell
Example: clams and mussels
Greatest number in low tide regions
Annelid worms

22. Sandy Beach Organisms and Adaptations
Crustaceans
Segmented body, hard exoskeleton, paired jointed limbs
Sand crabs common

23. Sandy Beach Organisms and Adaptations
Echinoderms
Spiny skin
Five tapered legs
Example: starfish and heart urchin

24. Sandy Beach Organisms and Adaptations
Meiofauna (interstitial organisms)
Live in spaces between sediment particles
Small, feed on bacteria
Polychaetes, mollusks, arthropods, nematodes

25. Mud Flats Eelgrass and turtle grass common Bivalves and other mollusks
Fiddler crabs

26. What Communities Exist on the Shallow Offshore Ocean Floor of a Rocky Coast?
Subtidal zone – zone below the tides
Rocky bottom Organisms
Kelp
Attaches to rocky bottoms with strong holdfast
Stipes and blades supported by pneumatocysts (gas filled floats)

27. Shallow Offshore Ocean Floor Communities
Kelp forests – beds of giant brown bladder kelp and bull kelp
Fast growing
Highly productive ecosystems
Shelter for variety of organisms

28. Kelp Distribution

29. Rocky Bottom Shallow Offshore Ocean Floor Communities
Lobsters
Large, spiny antennae
Live in water deeper than 20 meters (65 feet)
Scavengers
Also feed on live animals

30. Rocky Bottom Shallow Offshore Ocean Floor Communities
Oysters
Sessile bivalve mollusks
Thick shell
Food for sea stars, fish, crabs, and snails
Oyster beds – empty shells with living generation on top