subtidal lecture
TRANSCRIPT
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SUBTIDAL SUBTIDAL ECOSYSTEM ECOSYSTEM
BAT 213
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SUBTIDAL ECOSYSTEMSUBTIDAL ECOSYSTEM
Marine areas that are never exposed during low tide ie always submerged
Also known as sublittoral zone
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Marine Zonation
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SUBTIDAL ABIOTIC FACTORSSUBTIDAL ABIOTIC FACTORS
i) temperature fluctuates from one area to another especially with depth
ii) 1 atm increase in pressure with 10 m depth
iii) strong influence of currents and waves especially those in the shallow depths
iv) turbulence may prevent stratification
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SUBTIDAL ABIOTIC FACTORSSUBTIDAL ABIOTIC FACTORS
v) rich in nutrients (brought in from river discharges)
vi) influenced by sedimentation processes (especially shallow areas)
- lithogenic sediments (physical and chemical weathering of rocks)
- biogenic sediments (shells and skeletons of marine organisms)
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SUBTIDAL ORGANISMSSUBTIDAL ORGANISMS
Plankton (suspended in water column)
Nekton (able to swim against current)
Benthos (on/in bottom sediment)
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SUBTIDAL ORGANISMS
Factors that may influence subtidal organisms:
1. Water depth
2. Distance from land.
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Distribution of Marine Life
A. Pelagic
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Distribution of marine life
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Distribution of Marine Life
A. Pelagic B. Benthos
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Distribution of marine life
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Distribution of Marine Life
A. Pelagic B. Benthos
1. Demersal
2. Epifauna
3. Infauna
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Epifauna
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Infauna
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SUBTIDAL COMMUNITIESSUBTIDAL COMMUNITIES
A. Soft-bottom Subtidal Communities
B. Hard-bottom Subtidal Communities
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SOFT-BOTTOM SUBTIDAL COMMUNITIES
Made up of :
A. Muddy substrate
B. Sandy substrate
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SOFT-BOTTOM SUBTIDAL COMMUNITIES
Influenced by:1. Particle size distribution2. Sediment stability3. light4. salinity5. temperature
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CHARACTERISTICS OF SOFT-BOTTOM SUBTIDAL COMMUNITIES
Type of dominant substrate ie sand, mud etc.
Most infauna, some epifauna and almost no sessile organisms
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SOFT-BOTTOM SUBTIDAL COMMUNITIES
More abundant than soft-bottom intertidal communities
Less abiotic problems :1. No problem with desication2. Temperature and salinity more stable
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DISTRIBUTION OF ORGANISMS
Particle size influence distribution of infauna (?)
Particle size distribution (depending on depth)
Easier for organisms to borrow in sand compared to mud (water drainage better in sand)
Patchy sediment type – patchy distribution of organisms
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DISTRIBUTION OF ORGANISMS
Some larvae choose substrate before undergoing metamorphosis
Some larvae can detect adults and settle close by
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SOFT-BOTTOM SUBTIDAL ORGANISMS
1. infauna Benthic organisms that bury
themselves in the sediment2. epifauna
Organisms that inhabit the surface of the bottom sediment
No. of subtidal sp. > intertidal (more stable, no dessication)Distribution of organisms influenced by particle size (mud or
sand)
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PRODUCTIVITY
Minimum productivity(by diatoms and other microalgae)
Most communities based on ditritus
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DEPOSIT FEEDERS
1. Polychaetes : accumulation using tentacles or by ingestion of sediment
2. Sand dollars : use mucus to bring food to mouth
3. Bent nosed clam : collect sediment using siphon
4. Brittle stars : collect detritus using tube-feet
5. Peanut worms, sea cucumber, ghost shrimp
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Proboscis
Gills
Tube feeding by polycheate, Arenicola Marina. Black arrows show water flow and open arrows show sediment flow. Sediment brought to anoxic area, digested and deposited at upper region of shaft
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SUSPENSION/ FILTER FEEDERS Cockles : water intake via siphon Polychaetes and amphipods Brittle star : traps particles using tube feet Sea pens : traps particle from water column
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Scavenger dan Predator Shrimps and large crustaceans (scavenger) Whelks dan moon snail : feed on other bivalves Sea stars and crabs (can act as scavenger or
predator) Rays and skates Flounder, halibut and sole
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Soft Bottom Communities
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Soft Bottom Benthic Communities
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HARD-BOTTOM SUBTIDAL COMMUNITIES
Small subtidal communities
Some time they may be in the form of coral reefs
Hard substrate may include organisms that produce calcium carbonate
Rich in epifauna but less as infauna
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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 sea weeds
Weeds that live in deep ocean. Sea weeds established themselves.
Weeds found in area have higher chlorophyll concentration
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grazers Invertebrates that move slowly. : sea urchin,
limpets, chitons, abalone
Algal defence against predators- By having food that are not tasty- Fast regenaration- Calcification (formation of calcium)
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Epipelagic
From surface to about 200 m depth (euphotic zone)
Most inhabited depth of the Ocean
Presence of light - photosynthesis
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Mesopelagic From about 200 m to 1000 m depth ‘twilight’ or disphotic zone Available light mainly blue Seasonal and diurnal vertical
migration (search for food) Vertical migration can be up to 600 m
Fish (lanternfish – myctophids), zooplankton (particularly crustaceans)
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Lantern fish: Myctophidmost abundant fish in deep ocean
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Myctophiid: Diaphus holti. About 7 cm long Found at depth 40 – 275 night 225 – 650 day
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Bathypelagic From1000 to 3000 m depth Zone of eternal darkness (aphotic
zone) Abundance and diversity of organisms
sharply reduced (mainly due to lack of food)
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Abyssopelagic From 3000 m to deepest part of Ocean Zone of eternal darkness (aphotic
zone) Organisms usually colourless Animals normally without eyes but
have ‘flashing’ organs that help them catch food
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Angler fish: Cryptopsaras couesi (18 in long)
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Anoplogaster cornuta: Commonly calle ‘fangtooth’
Found at around 16,000 feet depth