1. Life on the Continental Shelf
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Life on the Continental Shelf

2. Continental Shelf:
shallow submerged extension of the continent

3. THE CONTINENTAL SHELVES
Average width – 75 km, narrower in areas with strong current;
Average slope – 0o07’;
Average depth flattest portion– 60 m;
Average depth where greatest change of slope – 130 m;
Hills of 20 m or more and depression of 20 m or more

4. slope continental shelf rise abyssal plain abyssal hills ridge
Notice the narrow shelf by Florida
Transform faults- fractures along which the lithosphere slides horizontally past one another
ridge
transform fault

5. (low tide to shelf break))
Photic 100m
(low tide to shelf break))
(Tidal zone)

6. Also known as the sublitoral zone
SUBTIDAL ECOSYSTEM
Marine areas that are never exposed during low tide i.e. always submerged.
Also known as the sublitoral zone

7. SUBTIDAL ABIOTIC FACTORS
rich in nutrients (brought in from river discharges), i.e., sediment runoff)
Lithogenous sediments are formed by the weathering process and are made up of small particles of weathered rocks and oceanic volcanoes. They are often formed together when metal and silicate ions bond. There are two types of lithogenous sediments; terrigenous and “red clay” and they are different because of the process behind their existences. For instance, terrigenous sediments are produced as a result of the weathering process of rocks above the water. These eroded particles are carried by the wind and other natural means to the oceans and are deposited at the bottom. Although it can be easily found in river beds, not much of this finds its way to the deep ocean. Red clay lithogenous sediment, on the other hand, is plentiful in the ocean. It is reddish-brown (hence the name) and is a combination of terrigenous material and volcanic ash. It is transported to the oceans by currents and wind and it settles in deep places along the ocean floor.
Biogenous sediments are formed from the insoluble remains of past life forms and parts such as bones and teeth. In many areas where the water is shallow, a majority of these sediments are the remains of shells or fragments from shelled sea creatures as well as corals. In the deep sea where there is no such a high concentration of these life forms, biogenous sediment is made from the microscopic shells that are deposited by tiny plants, animals, and plankton that live on the water’s surface and eventually make their way down to the ocean floor.
Nile River Delta
Mississippi Delta

8. SUBTIDAL ABIOTIC FACTORS
Influenced by sedimentation processes (especially shallow areas)
- lithogenic sediments (physical and chemical weathering of rocks (turbidities, volcanic ash, red clay))
- biogenic sediments (shells and skeletons of marine organisms)
Lithogenous sediments are formed by the weathering process and are made up of small particles of weathered rocks and oceanic volcanoes. They are often formed together when metal and silicate ions bond. There are two types of lithogenous sediments; terrigenous and “red clay” and they are different because of the process behind their existences. For instance, terrigenous sediments are produced as a result of the weathering process of rocks above the water. These eroded particles are carried by the wind and other natural means to the oceans and are deposited at the bottom. Although it can be easily found in river beds, not much of this finds its way to the deep ocean. Red clay lithogenous sediment, on the other hand, is plentiful in the ocean. It is reddish-brown (hence the name) and is a combination of terrigenous material and volcanic ash. It is transported to the oceans by currents and wind and it settles in deep places along the ocean floor.
Biogenous sediments are formed from the insoluble remains of past life forms and parts such as bones and teeth. In many areas where the water is shallow, a majority of these sediments are the remains of shells or fragments from shelled sea creatures as well as corals. In the deep sea where there is no such a high concentration of these life forms, biogenous sediment is made from the microscopic shells that are deposited by tiny plants, animals, and plankton that live on the water’s surface and eventually make their way down to the ocean floor.

9. Pelagic SUBTIDAL ORGANISMS Benthic (on/in bottom sediment)
Plankton (suspended in water column)
Nekton (able to swim against current)
Benthic (on/in bottom sediment)
Demersal
Epifauna
Infauna

10. Distribution of marine life
Pelagic
Benthic

11. SUBTIDAL COMMUNITIES Soft-bottom Subtidal Communities
Hard-bottom Subtidal Communities
Muddy shoresMuddy shores develop on places where clay and silt (particles finer than sand) are deposited by river currents or by tidal action. In places where the velocity of the water is low enough the fine particles will sink to the bottom where bottom organisms will fixate them. In temperate regions this is the place of mud-flats with saltmarshes higher up the coast. In tropics these muddy shores are mostly covered by mangroves. If the visibility is high enough there is a chance that sea-grass communities occure in deeper water.

12. SOFT-BOTTOM SUBTIDAL COMMUNITIES
Made up of :
Muddy substrate
Sandy substrate

13. SOFT-BOTTOM SUBTIDAL COMMUNITIES
Influenced by:
1. Particle size distribution
2. Sediment stability
3. light
4. salinity
5. temperature

14. CHARACTERISTICS OF SOFT-BOTTOM SUBTIDAL COMMUNITIES
Type of dominant substrate i.e. sand, mud etc.
Mainly infauna, some epifauna and almost no sessile organisms

15. SOFT-BOTTOM SUBTIDAL ORGANISMS
1. infauna
Benthic organisms that bury themselves in the sediment
2. epifauna
Organisms that inhabit the surface of the bottom sediment
No. of subtidal sp. > intertidal (more stable, no desiccation)
Distribution of organisms influenced by particle size (mud or sand)

16. Infauna

17. Epifauna

18. Soft-bottom subtidal communities
Epibionts

19. Soft-bottom subtidal communities
Infauna: 
live within the sediment, mostly soft bottom; 
mostly clams and worms (polychaetes) 
burrow tubes for food scavenging and oxygen supply
Primary producers: algae, mostly benthic diatoms and dinoflagellates
cyanobacteria mats on mudflats
mud more productive than sand
macro- and meiobenthos, often detrivores, living of deposits from seagrasses and marshes
birds important grazers

20. Soft-bottom subtidal communities

21. Soft-bottom subtidal communities
Examples of meiofauna in sand

22. Soft bottom subtidal communities
32,000 polychaetes in sand/m2 vs
earth worms in soil/m2
Ecological Role:
clean sediments
aerate soil

23. Carnivore feeders
Fish, crabs and birds
Hawaiian Stilt

24. Herbivore feeders

25. Deposit-feeders

26. Suspension-feeders

27. HARD-BOTTOM SUBTIDAL COMMUNITIES
Rocky shore
Coral reefs
Most important organisms are the sea weeds (able to settle on rocks/hard substrate

28. PRODUCERS Most important communities - seaweeds Strong competition
Amount of light influence distribution of seaweeds
Seaweeds found in these areas have higher chlorophyll concentration

29. grazers
Invertebrates that move slowly: sea urchin, limpets, chitons, abalone
Algal defense against predators
- By having food that are not tasty
- Fast regeneration
- Calcification (formation of calcium)

30. Hard-bottom subtidal communities
Generalized food web
Detritus

31. Hard-bottom subtidal communities
Examples of N. Atlantic Kelp

32. Hard-bottom subtidal communities
Geographic Distribution of Kelp

33. Air sack
holdfast

34. Recap Muddy shores Deposition of silt by tide or river
Temperate: intertidal- mud flat communities
subtidal- muddy bottom or seagrass communities
Tropic: intertidal- mangroves
Sandy shores
Deposition of sand by wave action
Temperate: intertidal- beach communities
Tropic: intertidal- beach communities
subtidal- sandy bottom or seagrass communities
Rocky shores
Little deposition
Temperate: intertidal- barnacles, seaweeds, mussels
subtidal- kelp beds or forests
Tropic: intertidal- algae and corals
subtidal- coral reefs

35. Inquiry What is the sublittoral zone? What is meiofauna (infauna)?
How do organisms survive living in a soft bottom community?
What food source are soft-bottom communities are based on?
Why don’t we see anemones and sea slugs in the high tide zone?