Life on the Continental Shelf - Marine Biology - Lecture Slides, Slides for Biology. Central University of Kerala
maalolan
maalolan19 January 2013

Life on the Continental Shelf - Marine Biology - Lecture Slides, Slides for Biology. Central University of Kerala

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These are the lecture slides of Marine Biology. Key important points are: Life on the Continental Shelf, Continental Shelf, Extension of the Continent, Continental Shelves, Subtidal Ecosystem, Subtidal Abiotic Factors, S...
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Life on the Continental Shelf

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Continental Shelf: • shallow submerged extension of

the continent

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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

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(Tidal zone)

(low tide to shelf break))

Photic 100m

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SUBTIDAL ECOSYSTEM

• Marine areas that are never exposed during low tide i.e. always submerged.

• Also known as the sublitoral zone

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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)

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SUBTIDAL ORGANISMS

Plankton (suspended in water column) • Nekton (able to swim against current)

Benthic (on/in bottom sediment) • Demersal Epifauna Infauna

Pelagic

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Distribution of marine life

Pelagic

Benthic

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SUBTIDAL COMMUNITIES

 Soft-bottom Subtidal Communities

 Hard-bottom Subtidal Communities

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SOFT-BOTTOM SUBTIDAL COMMUNITIES

Made up of : • Muddy substrate • Sandy substrate

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SOFT-BOTTOM SUBTIDAL COMMUNITIES

Influenced by: 1. Particle size distribution 2. Sediment stability 3. light 4. salinity 5. temperature

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CHARACTERISTICS OF SOFT- BOTTOM SUBTIDAL

COMMUNITIES

• Type of dominant substrate i.e. sand, mud etc.

• Mainly infauna, some epifauna and almost no sessile organisms

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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)

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Soft-bottom subtidal communities Epibionts

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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

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Soft-bottom subtidal communities

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Soft-bottom subtidal communities Examples of meiofauna in sand

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32,000 polychaetes in sand/m2 vs 50-500 earth worms in soil/m2 Ecological Role:

• clean sediments • aerate soil

Soft bottom subtidal communities

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Deposit-feeders

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Suspension-feeders

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HARD-BOTTOM SUBTIDAL COMMUNITIES

• Rocky shore

• Coral reefs

• Most important organisms are the sea weeds (able to settle on rocks/hard substrate

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PRODUCERS • Most important communities -

seaweeds

• Strong competition

• Amount of light influence distribution of seaweeds

• Seaweeds found in these areas have higher chlorophyll concentration

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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)

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Hard-bottom subtidal communities Generalized food web

Detritus

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Hard-bottom subtidal communities Examples of N. Atlantic Kelp

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