so you think you are alone corals

More Learnin’

So You Think You Are Alone

Microbes Are Smallest Forms of Life

From American Museum of Natural History

Big Humans

Big Animals

Tallest Trees

• Giant Sequoia, California

• 115 meter, 385 feet

Largest Plants

• Quaking Aspen

– Populus tremuloides

• aspen clone growing near Salt Lake City, Utah,

– weighs more than 6,000 tons

– 43 hectares

– 47,000 individual stems.

Largest Organisms

• Fungi - Oregon

• Honey Mushroom

– Armillaria ostoyae

• 2,200 acres (890 hectares)

• at least 2,400 years old

Tallest Buildings

Great Wall of China

8,851.8 kilometers (5,500 miles)

Great Barrier Reef

• stretches over 2,600 kilometers (1,600 mi)

• area of approximately 344,400 square kilometers (133,000 sq mi).[

Great Barrier Reef From Space

Barrier Reefs

Thickest reef almost 1 mile thick.

Coral reefs are largest biogenic structures on Earth

• What does this have to do with microbes?

Coral Reefs

• Thick layer of calcium carbonate covered by thin layer of living organisms

– Built up over long periods of time

Cnidarians

Phylum Cnidaria

Cnidarian Morphology

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Coral Polyps

Coral Polyps

Coral Feeding

Scleractinian Corals (reef building corals)

• secrete CaCO3

• external skeletons secreted by epidermis

Coral Skeleton

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Hard Corals

Corals are animals, so why do we care about coral reefs in this class?

• Cool

• Incredibly diverse

• Very important economically

• http://www.underseaproductions.com/demo_reels/marine_life_behaviour_video_footage.html

Energetics and Ecosystems

• Energy is required to do work

– Biological work

• Maintaining concentration gradients across membranes– Active transport

• Biosynthesis– Breaking down and building up bio molecules

• Movement– Cilia

– Muscles

First Law of Thermodynamics

• Energy can not be created or destroyed

– It can only be converted from one form to another

– Forms of energy

• Electromagnetic

• Kinetic

• Nuclear

• Potential

Photosynthesis

• The most important energetic process taking place for life on earth

– Converts electromagnetic energy from the sun (released by fusion reactions in the sun) to potential energy stored in the chemical bonds of glucose

Cellular Respiration

• Energy stored in the chemical bonds of glucose is converted into energy stored in the chemical bonds of ATP

• ATP releases that energy

– Used to do biological work

Energy Flow Through Ecosystem

• Sun

• Plants– Primary producers

• Herbivores– Primary consumers

• Carnivores– Secondary consumers

• Decomposers

• Energy lost as heat to environment

Flow of Energy From One Trophic Level to the Next is Inefficient

• Only about 10% of energy captured by plants is passed on to primary consumers

• About 10% of energy captured by primary consumers is passed on to secondary consumers

Energy Pyramid

Biomass Pyramid

Forests

Prairies

Deserts

Coral Reef Video

• Schooling Fish

• http://www.underseaproductions.com/demo_reels/schooling_fish_video_footage.html

Coral Reef Video

• http://www.underseaproductions.com/demo_reels/seascapes_video_footage.html

• How many plants do you see on this video?

Coral Reefs

• Do not see many aquatic plants (algae) on coral reefs

• Yet coral reefs are teeming with life and are one of the most diverse communities on the planet

• How can this be?????

The Mystery of the “Inverted Energy Pyramid”

Missing Primary Producers

• Two possibilities

1) Maybe plants are photosynthesizing but the plant material is eaten by herbivores as fast as it is produced.

- Therefore we don’t see a build up of plants

Lots of Herbivores Living or Coral Reefs

Biogenic Sand

Long-spined Urchin (Diadema antillarum)

Results of Overfishing and Diadema Die-off

Missing Primary Producers

• In undisturbed reefs, primary productivity of algae is rapidly removed by the herbivores

• But calculations of rate of photosynthesis by algae was not enough to explain the energy and biomass at higher tropic levels

Missing Primary Producers

• Not looking in the right place.

• Scientists (and the video we just saw) looked all over the coral reef for primary producers

– Needed to look “inside” of corals

Symbiotic Zooxanthellae

CORAL REEFS - ZOOXANTHELLAE

--- Are group of algae called dinoflagellates (also form red tides).Symbiodinium spp.)

--- Are different colors; brown, green, yellow.

--- Dinoflagellates mutualistic with other groups; sea slugs, giant clams, tunicates.

--- Can live outside host

Classification of Life

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

• King Phillip Chooses Only Fancy Green Sox

• 5 Kingdom system– Animals

– Plants

– Fungi

– Protistans

– Monerans

Classification of Life3 Domains

From the University of California Museum of Paleontology

Domain- Archaea

• 2 distinct groups of Prokaryotes based on DNA

• Those "bacteria" that lived at high temperatures or produced methane clustered together as a group well away from the usual bacteria and the eukaryotes.

• Divided prokaryotes into two Domains

Archaea

• Archaeans include inhabitants of some of the most extreme environments on the planet. – rift vents in the deep sea at temperatures well over

100 degrees Centigrade.

– hot springs

– in extremely alkaline or acid waters

– inside the digestive tracts of cows, termites, and marine life where they produce methane

– in the anoxic muds of marshes and at the bottom of the ocean, and even thrive in petroleum deposits deep underground.

Domain- Bacteria

Domain-Eukaryota

• Five Kingdoms

– CHROMISTA (Kelps, diatoms, haptophytes)

– FUNGI (Fungi)

– METAZOA (Animals)

– PLANTAE (Plants)

– PROTISTA (Protists)

Kingdom Protista

• ALVEOLATES---Apicomplexa (Apicomplexans) ---Ciliata (Ciliates) ---Dinoflagellata (Dinoflagellates) ---Foraminifera (Forams)

• Chlorophyta (Green algae) • Choanoflagellata• CHROMISTA (Stramenopiles) • Diplomonadida• Euglenida• Kinetoplastida (Bodonids and trypanosomes) • Myxomycota (Slime molds) • Parabasalia• Pelobionta (Pelomyxa) • Radiolaria (Radiolarians) • Rhodophyta (Red algae) • Testaceafilosea (Testate Amoebae

Dinoflagellates

• Diverse unicellular protists

• Many are photosynthetic

• Some species are capable of producing their own light through bioluminescence

Mutualistic Relationship Between Corals Polyps and Zooxanthellae

• Mutualistic interaction

– Interaction between two species in which both species benefit

– Examples???

Green polyp tissue, red zooxanthellae

Coral – Zooxanthellae Mutualism

• Zooxanthellae provide corals:– Energy (photosynthesis

products) and as a by-product ability to grow and reproduce fast enough to produce reefs.

– Zooxanthellae can provide up to 90% of a coral’s energy requirements

• Corals provide zooxanthellae with:– Protection from predators

via Cnidarian nematocysts.

– Removal of dissolved organic material from water column (to keep water clear)

– Waste products useful for algal photosynthesis (nitrogen and phosphorous)

• )

Coral-Zooxanthellae Mutualism

• Explains one aspect of the distribution of coral reefs

• Coral Reefs are found

– Shallow water

– Near continents

– Tropical

– Eastern sides of continents

Distribution of Corals

Coral reefs limited to the “photic zone”

• Zooxanthellae require light for photosynthesis

– Corals limited to relatively shallow water

Photic Zone

Coral Reef Zonation

• There are consistent patterns of zonationon coral reefs with increasing depth– Water absorbs light so

there is less light as depth increases• Thus, ability of

zooxanthellae to provide corals with energy decreases with depth

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Coral Species Change Growth Form at DepthPlating in Star Coral (Monastrea)

More Sponges and Fewer Corals at Greater Depths

Mutualisms

• Important for the two participant species to be able to find each other

• How do they do this?

Maternally passed from parent to offspring

-vertical transmission

Transmission of Zooxanthellae

Coral Life Cycle

• Corals can reproduce sexually or asexually– Zooxanthellae easily

passed from parent to offspring in asexual reproduction

• Corals also reproduce sexually– Egg and sperm– Mothers can place

zooxanthellae in eggs

Sexual Reproduction in Corals

• Some species of corals release both eggs and sperm in the water– Fertilization occurs in the water column

• Spawners

• Other species hold the eggs but release the sperm in the water– Fertilization occurs in the Mom, later release larvae

• brooders

– Maternal transmission of zooxanthellae occurs more often in brooders than spawners

Transmission of Zooxanthellae

- Environmental transmission each new generation

- Free-living Zooxanthellae enter new corals each generation

• This is very important for some of the issues we will talk about later

Benefits of Coral ReefsFisheries

Benefits of Coral Reefs Protect Shore

Benefits of Coral ReefsTourism

Benefits of Coral ReefsBiodiversity

Decline of Caribbean Coral Reefs

Threats to Coral ReefsStorm Damage

Threats to Coral ReefsCrown of Thorns Starfish

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Threats to Coral ReefsSiltation

Threats to Coral ReefsAlgal Blooms

Threats to Coral ReefsDynamite fishing

Threats to Coral ReefsCoral Bleaching

Coral Bleaching

Coral Bleaching

Coral Bleaching

• Environmental stress puts a strain on the symbiotic relationship

– fresh water dilution

– sedimentation

– subaerial exposure

– solar irradiance

– temperature

Coral Bleaching

• Fresh water dilution and sedimentation are local conditions so coral bleaching due to these factors is limited to certain small areas.

• Solar irradiance and especially temperature are stressors that cause coral bleaching on a global scale

– Potentially a much bigger problem

Coral Bleaching

Coral Bleaching

• Polyps can live for a while without the zooxanthellae, but growth rate is greatly reduced

– If stress is eliminated the zooxanthellae may return to the polyps and the coral recovers

– If stress continue for too long, then the polyps will die

New Guinea

Temperature and Coral Bleaching

• Coral reefs are vulnerable to increased temperature, which causes corals to lose their symbiotic algae in a process called coral bleaching.

• Small increase in water temperature is enough to trigger bleaching

• Over the last 30 years, average ocean temperatures have increased 0.3 to 0.4 degrees Celsius.– Mass coral bleaching episodes have increased

dramatically over the last 2-3 decades.

Temperature and Coral Bleaching

• El Nino events can change the pattern of ocean currents and bring warmer water to reefs

– 16 % of the world’s coral reefs experienced bleaching in 1997-1998

• mortality approaching 90% in some places

– about half of damaged reefs have not recovered.

Mechanisms of Coral Bleaching

• Not well understood

• Often talk about polyps “expelling zooxanthellae”

– This may or may not be an accurate word choice

• This discussion might benefit from a better knowledge of about theories of mutualisms

Mechanisms of Coral Bleaching

• Zooxanthellae may be lost from polyps “unintentionally”

• Cell Adhesion Dysfunction

– High temperature shock could result in cell adhesion dysfunction between the cnidarianendodermal cells and the zooxanthellae cells.

• Cell adhesion dysfunction would cause the detachment and loss of zooxanthellae from the coral.

Mutualisms

• Mutualisms are interactions between two species in which both species benefit

– Often think of species behaving altruistically

• Probably more complicated then that.

Mutualisms

• Species are involved in mutualisticrelationships because the benefits of interacting with the other species are larger than the costs of that interaction

– If something happens to alter the benefits and costs then species might “reconsider” whether or not they want to be involved in the relationship

• Whether or not they can do anything about it can vary from system to system

Zooxanthellae may “choose” to leave the polyps

Stressed corals may give provide zooxanthellaefewer nutrients for photosynthesis

- less benefit to the mutualism

If the fitness of algae living independently is greater than the fitness of algae living in polyps then the algae may “decide” to leave the polyp and exist independently.

Polyps may “Expell” Zooxanthellae

• Coral polyps might “decide” to end the relationship with the zooxanthellae if

– The costs of hosting zooxanthellae increase

– The benefits received from the zooxanthellaedecrease

Polyps may “Expell” Zooxanthellae

• Stress might alter the physiology of the zooxanthellae and cause them to release compounds that are harmful to polyps (perhaps free oxygen radicals)

• Polyps will release the zooxanthellae rather than suffer the effects of the toxins.

Polyps may “Expell” Zooxanthellae

• Adaptation Mechanism

– If certain strains of zooxanthellae cannot function when stressed, the polyps expell these zooxanthellae to leave their tissues open to be recolonized by a different strain of zooxanthellaethat are better adapted to the current environment

Coral Diseases

• Coral diseases are another threat to coral reefs

• Coral diseases were first identified in the 1970s and their prevalence has increased since then

Black-band Disease

• Black-band disease is characterized by a blackish concentric or crescent-shaped band, 1 to 30 mm wide and up to 2 m long, that “consumes” live coral tissue as it passes over the colony surface, leaving behind bare skeleton.

Black-band Disease

• The disease is caused primarily by a cyanobacteria– sulfide-oxidizing

bacteria, sulfur- reducing bacteria, other bacteria and nematodes, ciliate protozoans, flatworms and fungal filaments also are present.

• The photosynthetic pigments of the dominant cyanobacteriagives the band its maroon to black color

Black-band Disease

• The dead skeleton will be attacked by boring algae, boring sponges, boring clams, and parrot fish which will gnaw away the skeleton

– remove about 1 cm per year.

• This means that in 100 years, a 1-meter high coral head will be completely consumed and converted to sediment.

White-band Disease

• White-band disease was first identified in 1977 on reefs surrounding St. Croix. It is now known to occur throughout the Caribbean where it is believed to only affect staghorn and elkhorncorals.

• This disease is characterized by tissue that peels or sloughs off the coral skeleton in a uniform band, generally beginning at the base of the colony and working its way up to branch tips

• The band ranges from a few millimeters up to 10 cm wide, and tissue is lost at a rate of about 5 mm per day

White-band Disease

• The cause of White-band Disease is unknown.

– unusual aggregates of rod-shaped bacteria were found in the tissue of corals affected by White-band Disease

• scientists have not determined the role of this microorganism

White-band Disease

• Since the 1980s, Acroporacervicornis has been virtually eliminated from reef environments throughout the Caribbean.

• In the U.S. Virgin Islands, populations of Acropora palmata declined from 85 percent cover to 5 percent within 10 years

• White-band disease currently is the only coral disease known to cause major changes in the composition and structure of reefs

Yellow Blotch Disease

• Affects only star corals in the genus Montastraea and the brain coral Colpophyllia natans

• First identified in 1994 in the lower Florida Keys. It is now known to occur throughout the Caribbean

Yellow Blotch Disease

• Yellow blotch disease begins as pale, circular blotches of translucent tissue or as a narrow band of pale tissue at the colony margin, with affected areas being surrounded by normal, fully pigmented tissue.

• As the disease progresses, the tissue first affected in the center of the patch dies, and exposed skeleton is colonized by algae . The area of affected tissue progressively radiates outward, slowly killing the coral.

Yellow Blotch Disease

• The rate of tissue loss by corals afflicted with YBD averages 5 t 11 cm per year, which is less than that of other coral diseases.

• However, corals can be affected for many years, and the disease can affect multiple locations on a colony.

• Though the cause of Yellow Blotch Disease remains unknown

Red-band Disease

• Red-band disease consists of a narrow band of filamentous cyanobacteria that advances slowly across the surface of a coral, killing living tissue as it progresses.

• Affects massive and plating stony corals, and also sea fans throughout the wider Caribbean. – exposed skeletal surfaces are

rapidly colonized by algae and other competing organisms.

Sea Fan Aspergillosis

• Caused by the pathenogenic fungus Aspergillus sydowii.

Why has the prevalence of coral diseases increased so much in the last

40 years?

• One theory is that anthropogenic stresses on the environment have made corals more susceptible to infection by coral diseases

Dust Hypothesis

• Changes in global climate and land use in Africa resulted in severe droughts in the Sahara and Sahel of Africa starting in the 1970s.

Dust Hypothesis

• Hundreds of millions of tons of African dust are transported annually from the Sahara and Sahel to the Caribbean and southeastern U.S.

• A similar dust system in Asia carries dust from the Gobi and Takli Makan deserts across Korea, Japan, and the northern Pacific to the Hawaiian Islands, the western U.S., and as far eastward as Europe.

I’ve cleaned this dust off of boats in the Caribbean.

Dust Hypothesis

• African and Asian dust air masses transport nutrients (iron, nitrates, other nutrients), pollutants, and viable microorganisms that may adversely affect human health and downwind ecosystems such as coral reefs.

Dust Hypothesis- Mechanisms

• interfere with a coral's immune system, making it more susceptible to disease pathogens.

• induce pathogenicity in a microorganism in the reef environment.

• trigger a rapid increase in the number of pathogenic microorganisms.

• fuel macroalgae or phytoplankton growth– has been shown for Red tides in the Gulf of Mexico

• directly deposit pathogenic microorganisms.

Lots of topics for future research about the role of microbes in coral reef

ecosystems