continental shelf region
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The continental shelf is an underwater landmass which extends from a continent, resulting in an area of relatively shallow water known as a shelf sea. Much of the shelves were exposed during glacial periods and interglacial periods
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continental shelf region
- 1. Life on the Continental Shelf 013
- 2. Continental Shelf: • shallow submerged extension of the continent
- 3. THE CONTINENTAL SHELVESTHE CONTINENTAL SHELVES • Average width – 75 km, narrower in areas with strong current; • Average slope – 0o 07’; • 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. continental shelf slope rise abyssal plain abyssal hills ridge transform fault
- 5. (Tidal zone) (low tide to shelf break)) Photic 100m
- 6. SUBTIDAL ECOSYSTEMSUBTIDAL ECOSYSTEM • Marine areas that are never exposed during low tide i.e. always submerged. • Also known as the sublitoral zone
- 7. SUBTIDAL ABIOTIC FACTORSSUBTIDAL ABIOTIC FACTORS • rich in nutrients (brought in from river discharges), i.e., sediment runoff) Mississippi Delta Nile River Delta
- 8. SUBTIDAL ABIOTIC FACTORSSUBTIDAL 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)
- 9. SUBTIDAL ORGANISMSSUBTIDAL ORGANISMS • Plankton (suspended in water column) • Nekton (able to swim against current) Benthic (on/in bottom sediment) • Demersal • Epifauna • Infauna Pelagic
- 10. Distribution of marine life Pelagic Benthic
- 11. SUBTIDAL COMMUNITIESSUBTIDAL COMMUNITIES Soft-bottom Subtidal Communities Hard-bottom Subtidal Communities
- 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
- 19. 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 Soft-bottom subtidal communities
- 22. 32,000 polychaetes in sand/m2 vs 50-500 earth worms in soil/m2 Ecological Role: • clean sediments • aerate soil Soft bottom subtidal communities
- 25. Deposit-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
- 34. Muddy shores • Deposition of silt by tide or river Temperate: intertidal- mud flat communities subtidal- muddy bottom or seagrass communities Tropic: intertidal- mangroves subtidal- muddy bottom or seagrass communities Sandy shores • Deposition of sand by wave action Temperate: intertidal- beach communities subtidal- muddy bottom or seagrass 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 Recap
- 35. Inquiry 1. What is the sublittoral zone? 2. What is meiofauna (infauna)? 3. How do organisms survive living in a soft bottom community? 4. What food source are soft-bottom communities are based on? 5. Why don’t we see anemones and sea slugs in the high tide zone?
Editor's Notes
- Notice the narrow shelf by Florida Transform faults- fractures along which the lithosphere slides horizontally past one another
- 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.
- 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.
- 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.