1. Chapter 11
Between the Tides

3. Location
Narrow fringe along the shoreline that lies between the highest high tide and the lowest low tide

4. Easy to study

5. A unique environment Organisms are regularly exposed to air
Emersion – being out of water and exposed to air
Immersion – being submerged

6. Bottom Type (Varies) Sand, mud, rock Substrate – material on or in
which organisms live

7. Types of Communities

8. Rocky Shore Communities
Organisms are attached to rocks
Sessile – permanently attached
Epifauna – live on the surface of the substrate

9. Challenges of the Environment
Exposure at low tide – can lead to desiccation (drying out), temperature changes, salinity change
Adaptations: clam up, run and hide (tide pool or crevice), tolerate it
High tide – wave shock, restrictions on feeding
Adaptations: flexible, low profile, strong anchors (muscular foot, holdfast, byssal threads), thick shell, compact shape

15. Plentiful Resources Plenty of nutrients, light and food
High tides bring plankton and detritus (decaying organic matter)

16. The Battle for Space

17. Limiting Resources
There is not enough space – all areas are occupied – competition for space

19. Vertical Zonation

20. The rocky intertidal community is usually divided into distinct bands or zones at characteristic heights in the intertidal
Vertical zonation - A given species is only found in a particular vertical range

21. Zonation is Caused by:
Complex interaction of physical and biological factors
Upper limit determined by physical factors
Lower limit determined by biological factors

23. Soft-Bottom Intertidal Communites

24. Substrate: Sand or mud
Organisms are buried in the sand or mud (substrate)
Infauna – live in the sediment

25. Challenges of the environment
Size of particles determines many physical characteristics of the habitat

27. Problems for Sandy Bottoms
Sediments are constantly shifting – nowhere to attach
Water drains quickly
Can have a lot of water motion

28. Problems for Muddy Bottoms
More organic matter to decay and use up oxygen
Flow of water that brings in new oxygen is reduced
Except for the upper few centimeters of mud the interstitial water (water between the grains) is deficient of oxygen

29. Anoxic – sediments with absolutely no oxygen
Anaerobic bacteria can break down organic matter without oxygen – hydrogen sulfide is produced as a byproduct
H2S – smells like rotten eggs and turns things black