1. An Introduction to Zonation

2. What is Zonation? The patterning of ecosystems in parallel bands .
Occurs as a result of tides (intertidal zones), altitude (changing biomes as you go up a mountain), latitude (biomes), changing soil moisture (around the edge of a pond).
Caused by varying environmental conditions.

6. Classic Case: Rocky Intertidal Ecology
Rocky - hard substrate (rock)
Intertidal - area between high tide and low tide marks
Ecology - the study of the interactions that determine the distribution and abundance of organisms. * Interactions can be between organisms or between organisms and their environment

7. Intertidal zone
This area is is exposed to the air usually twice a day as the tides ebb and flood
Tides create a partly aquatic and partly aerial environment
Locally the tidal range is about 3 meters
Rocky, sand, estuaries, mangroves, coral reefs, etc.
Patterns are similar worldwide

8. Tidal Zones on a Rocky Ocean Shore
Splash Fringe Level
High Tide Level
Mid Tide Level
Low Tide Level
Low Fringe Level

9. Mostly shelled orgs
Spray or Splash Zone
High Tide Zone
Middle Tide Zone
Many soft bodied orgs and algae
Low Tide Zone

10. Big Island

11. Vertical zonation
Banding pattern on the rocky shore as a result of the rise and fall of the tides
The distribution of organisms is in horizontal bands
Upper, middle and low zones
Caused by differing tolerances of organisms to stresses, both biotic and abiotic

12. Limits of organisms Upper limits are set by abiotic factors.
Lower limits are set by biotic factors.

13. Abiotic factors

14. 1. Desiccation = water loss; drying out
Occurs at low tide due to air exposure
Can increase with wind
Some species are more tolerant to being in the air (e.g. limpets, Fucus, Porphyra) and can live higher in the intertidal zone
Adaptations: - close up e.g. barnacles, mussels - lose water then rehydrate e.g. Fucus

15. 2. Temperature
Water temperature varies only slightly over the year (7-12°C)
Air temperature, however, can vary drastically (0-30°C)
Organisms out of the water are subject to greater variations in temperature
Adaptations:
Evaporative cooling by mussels
Eurythermal enzymes

16. 3. Salinity
Salinity can increase with evaporation or decrease with fresh water input (e.g. rain)
Euryhaline - tolerant to wide variations in salinity e.g. mussels, barnacles
Stenohaline - can only tolerate a narrow range of salinities e.g. sea stars
Adaptations:
Close up e.g. barnacles, mussels
Ion pumps e.g. crabs

17. 4. Food & oxygen availability
Many marine organisms get their food from the water (as plankton!) they can only feed when underwater
Also, many marine organisms obtain oxygen from the water
Organisms living high in the intertidal zone have a limited time in which they can feed and acquire oxygen
Adaptations: - scaleless fish e.g. clingfish - feed whole time they are underwater

18. 5. UV light Marine organisms can get sunburns too
Especially when out of the water
Adaptations:
Sun screen - natural compounds that absorb UV
Protective shell

19. Biotic factors

20. 1. Competition
= use or defense of a resource that reduces its availability to other individuals (food, space, cover, water, sunlight, etc.)
Interspecific – Competition for resources between species.
Intraspecific – Competition between individuals of the same species.
HOW?
Interference – Direct. Aggressive behavior that prevents other individuals from foraging, reproduction, etc.
Exploitative – Indirect. Use of a common resource.
Apparent – Indirect. 2 species have the same predator. An increase in species A increases the prevalence of the predator decreasing species B.

21. 2. Predation Animals eating other animals
Predators can be generalists (eat a wide range of food) or specialists (eat a single prey type)
Refuges from predation:
Size e.g. some mussels are too big to be eaten by Pisaster
Space e.g. limpets living on vertical surfaces to avoid predation by birds
Height in the intertidal e.g. Pisaster / mussel interactions (Paine experiments)

22. 3. Herbivory Animals eating plants Similar to predation interactions
Refuges from herbivory:
Chemical defenses e.g. sulphuric acid in Desmarestia, bromine in Prionitis
Physical defenses e.g. calcium carbonate in coralline algae
Height in the intertidal e.g. Ulva and Porphyra live very high to avoid being eaten

23. Review: In the Intertidal Zone...
Upper limits are set by abiotic factors such as desiccation, temperature, salinity, food and oxygen availability, light
Lower limits are set by biotic factors such as competition, predation, herbivory