The Corals

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• Possibly the most bio-diverse ecosystems in the world.

• Total coral reef area: 285,000 km2 = 0.09% of ocean area.

• Small oasis of densely packed life in the vast ocean.

Remember which classes of Cnidarians will be found as corals?

Anthozoa Hydrozoa

Lack a medusa phase Most alternate life stages between medusa and a polyp

ANTHOZOA ARE THE CORALS!!!!!!!!!

3 Classes of Cnidarians

Anthozoa Scyphozoa• Alternate between

polyp and medusa stage

• Medusa stage usually larger and more developed than the polyp

• The familiar jellyfish

• Small in size, usually mistaken for algae

• Most alternate life stages between medusa and a polyp

• Often form colonies

• true corals, anemones, sea pens, sea fans

• Lack a medusa phase, remain polyps throughout life cycle

Remember your mnemonic

Hydrozoa

Hydrozoan vs. Anthozoan Life cycles

What is missing in the Anthozoan (anemones, sea pens, sea fans) life cycle????

Sperm and Egg released simultaneously into the ocean

What corals eat. Some general strategies.

• Omnivores. • Use Nematocysts to capture prey. • Photosynthetic energy.• Scavengers. • Sessile and motile.• Filter feeders.

Coral reefs

• Tropical waters where coral reefs found are typically very nutrient limited.

• How can such rich communities grow in such an unproductive environment?

zooxanthellae

• Green algae (photosynthetic)

It’s just a fun word to say!

Zooxanthellae inside a sea slug

zooxanthellae

• Many Cnidarians live in symbiosis with zooxanthellae.

• They can be nearly completely dependant on them for energy.

Zooxanthellae and corals

• Most reef-building corals contain zooxanthellae• Mutually beneficial symbiotic relationship

Zooxanthellae and coralsYou tell me what they each gain?

Zooxanthellae• Protected environment• Compounds needed for

photosynthesis– Nitrogen– Phosphorus– Carbon dioxide

corals• Oxygen• Help remove waste • Most importantly

zooxanthellae supply the coral with glucose, glycerol, and amino acids, which are the products of photosynthesis. The coral uses these products to make proteins, fats, and carbohydrates, and produce calcium carbonate

Zooxanthellae and corals

• As much as 90 percent of the organic material photosynthetically produced by the zooxanthellae is transferred to the host coral tissue (Sumich, 1996). This is the driving force behind the growth and productivity of coral reefs (Barnes, 1987; Levinton, 1995).

• This is why reefs are where they are. Shallow warm water.

Light in the water column and zooxanthellae photosynthesis

What can we infer about the habitat of zooxanthellae from these two graphs?

Notice that their photosynthetic activity is lower in the blue green spectrum.

Zooxanthellae major role determining the locations of corals

• Water must be:

• Shallow (< 30 m)• Warm (at least 23o C)• Within limited salinity range (26-46 ppm)• Clean and clear

Distribution of corals• Limited distribution in latitude (30oN – 30oS) and depth

(< 30 m)

Why? Light and temperature

Video

• ..\..\..\Lesson Videos\Biology 11\Zooxanthellae Diversity.flv

• Why such a high diversity in zooxanthellae?

Hard corals vs. Soft corals

Hard corals• Reef builders. • Rigid skeleton made of calcium

carbonate (CaCO3)• Secrete calcium cabonate

Soft corals• No skeleton• No calcium carbonate secretions

Reef Building

• Reefs are made from the CaCO3 skeletons of dead hard corals.• Most established reefs are 5000-10,000 years old.

Coral Bleaching

Reading (coral bleaching)

• What are the corals doing to become “bleached”?

• Why are they doing this?• What is the effect of temperature?

Coral bleaching

Coral bleaching

Corals expel zooxanthellaeand turn white

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Regional summer SST anomaly temperature (oC)

No. cells reporting bleaching

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Strong linkwithtemperature

McWilliams, Côté et al. 2005 Ecology

Bleaching Video

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Mass Coral Bleaching (Great Barrier Reef Marine Park Authority).flv

STOP HERE

Giant Green AnemoneAnthopleura xanthogrammica

http://www.flickr.com/photos/chayshots/235067851/

Whose been surfing Tofino?

Whose seen these?

Which class of Cnidarian is this?

Cluehttp://www.google.com/imgres?q=anemone+life+cycle&hl=en&client=firefox-a&hs=8lP&rls=org.mozilla:en-US:official&biw=979&bih=477&tbm=isch&tbnid=gb9Yzw-nz9wYCM:&imgrefurl=http://www.uas.alaska.edu/arts_sciences/naturalsciences/biology/Tamone/catalog/urticina_crassicornis/life_history.htm&docid=x4yuABN6sZvKbM&imgurl=http://www.uas.alaska.edu/arts_sciences/naturalsciences/biology/Tamone/catalog/urticina_crassicornis/images/urticina_crassicornis9.jpg&w=512&h=365&ei=jSP-TqORMKzZiQLy96y1Cg&zoom=1&iact=rc&dur=169&sig=101830522278361665895&page=1&tbnh=97&tbnw=136&start=0&ndsp=12&ved=1t:429,r:0,s:0&tx=83&ty=22

3 Classes of Cnidarians

Anthozoa Scyphozoa• Alternate between

polyp and medusa stage

• Medusa stage usually larger and more developed than the polyp

• The familiar jellyfish

• Small in size, usually mistaken for algae

• Most alternate life stages between medusa and a polyp

• Often form colonies

• true corals, anemones, sea pens, sea fans

• Lack a medusa phase.

Remember your mnemonic

Hydrozoa

Anthozoa (means “Flower like”)

Giant Green Anemone• Largest green anemone in the world• Giant green anemones that live in sunlight are

a vivid green• Specimens in caves are paler, nearly white.• Why?• Zooxanthellae

Sessile but………

• The Giant Green anemone can move on its pedal.

Reading

• Discussion • Fill out examination worksheets

Range and Habitat• Range: Low to mid intertidal zones of the Pacific Ocean, ranging

continuously from Unalaska to Point Conception. It also occurs in areas of cold upwelling, possibly as far south as Panama.

• Habitat: • Exposed coastlines, bays and harbors, on seawalls, rocks, tidepools, and

pilings. • From above low tide line, to about 50 ft. (15 m) depth. • Each Giant green anemone is solitary, but is often in tentacle-tip contact

with others in favorable tidepools and conditions, and can be found in densities of up to 14 per m².

• Although their habitat can become crowded, they do not display aggressive behaviors, seen in their smaller relative, A. elegan-tissima.

• A. xanthogrammica is restricted to the lowest tide zones, where surf and currents continually provide a fresh supply of water, and cannot survive where there is industrial pollution, sewage, or sludgy water.

Also occurs here in cold water upwelling zones.

FeedingCapture prey with stinging nematocysts in their tentacles.

Cause no harm to humans.

To prevent from desiccation, giant green anemones will retract their tentacles and close, during low tides.

Desiccation?????

Drying up

Video: http://www.montereybayaquarium.org/videos/Video.aspx?enc=0ZZ+8rD1FkZFMg4UwjaBnQ==

Omnivore, Photosynthetic, Scavenger, Sessile suspension feeder

Why do Giant Green Anemones live on rocky shores??? You tell me.

• Crashing waves bring foods into the tentacles of the anemone

Predator-Prey relationships

Predators

• Nudibranch’s and Snails feed on the tentacles, and column .

• Sea slugs eat anemones, including the stinging cells, but they don’t get stung. The slugs use the anemones stingers for defense against predators, by moving them onto their own bodies.

Prey

• Prey:mussels, sea urchins, small fish, and crabs.

Feeding Behavior• The larvae preferentially settle in mussel beds, in anticipation of this future food source. • Later, they migrate downward to take up their characteristic position, in the pools and

channels below the musssel bed, where they wait for food to drop down from above. • Prey are paralyzed and captured after coming into contact with the anemones stinging

tentacles. Once the prey has been paralyzed, A. xanthogrammi-ca pulls these animals into its mouth, located in the center of its crown.

• When digestion is finished, it excretes the waste through the same opening. • The epidermis and tissues lining the gut of A. xanthogrammica contain living photosynthetic

algae zooxanthellae. These symbiotic protists can produce organic nutrients through photosynthesis that may also contribute to the nutritional needs of the anemone.

• Mussels and snails are washed into anemones waiting tentacles, as the wave’s crash against the shore. The anemone eats the animals, then spits out the clean shells. Empty snail shells, may become homes for hermit crabs.

• The hermit crab Pagarus samu-elis often walks up and down the column of the anemone, even walking through and stroking the tentacles and probing the mouth opening, all without being stung. It is possible that the hermit crab becomes so coated with mucus from the anemone that the anemone responds as if the crab were its own tissue.

• Hermit crabs which are not previously associated with the anemone may be eaten, or simply taken into the gastro vascular cavity and then later released.

The hermit crab can have the same relationship to the Giant Green Anemone as these clownfish do with this anemone.

Reproduction• Giant green anemones

release sperm and brownish eggs in late spring and summer, producing pelagic, planktotrophic larvae. (Open ocean, plankton eating, larvae)

• Larval development has not been closely followed, but the larvae swim or float freely for some time, and become widely dispersed.

What are the two major reproductive strategies of Cnidarians????

Sexual and Asexual. The Giant green anemone does not reproduce asexually.

What does this picture have to do with the Giant Green Anemone?

• Anthopleura xanthogrammica has been the source of several medical studies.

• “Contained within its tissues is a cardiotonic agent that has been associated with favorable stimulatory effects when introduced to the vertebrate heart.”

Adaptations to currents• 2 species of anemone M.

farcimen and A. xanthogrammica

• M. farcimen lives in deeper waters not exposed to strong wave action.

• A. xanthogrammica are exposed to strong wave action.

• What adaptations do you notice in the Giant Green Anemone to the strong wave action?

Different body types will exist among individuals within the species A. xanthogrammica

• Which part of this shore will experience greater wave action?

• What differences do you notice in body type?

• Smaller diameter and smaller stem in higher wave areas

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Drawing assignment

• worksheet