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Reef Ecology Introduction
Atlantic and Gulf Rapid Reef Assessment Reef Ecology Introduction University of Miami, RSMAS Dr. Robert Ginsburg
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A healthy coral reef stony corals crustose stony corals coralline
algae Slide 11 reef fishes © H. Moody
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Stony corals have soft polyps above a stony (calcareous skeleton).
They expand to feed on plankton mostly at night. © R. McCall Meandrina meandrites
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Colonies are formed when the polyps divide asexually.
Tentacle Mouth Skeleton Colony Single Polyp Diagram from P.Humann
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Large corals continue to grow via asexual division (reproduction) throughout their lives.
Background name: Deep_Blue.tif Porites porites © K. Desai
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Adult corals also reproduce sexually.
Species that grow large engage in mass spawning once, or several times, a year. © E. Hickerson © G.P. Schmahl Close-up Montastraea franksi Colpophyllia natans
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Recruits allow reefs to recover after disasters.
Larvae that settle and become recruits often attach to crustose coralline algae. Recruits allow reefs to recover after disasters. © R. Steneck Porites astreoides
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Zooxanthellae (zooxs.)–tiny, yellow-brown algae inside the cells of stony reef corals.
Zooxs. photosynthesize and pass some organic molecules to coral host. The zooxs. gain shelter, plus access to carbon dioxide and inorganic nutrients needed for photosynthesis. © J. Reichman Close-up
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Bleaching occurs when polyps lose their yellow- brown colour
Bleaching occurs when polyps lose their yellow- brown colour. Bleached polyps are still alive. Close-up Bleaching occurs because most of the “zooxs” are gone, and/or have lost their yellow-brown pigments. © L. Benvenuti Porites
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Some bleached corals glow pale purple, pink or blue!
© R. Ginsburg Siderastrea siderea
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Bleaching occurs in response to stressors like unusually high or low temperatures, high or low salinities, or too much sedimentation. Mass bleaching when too warm during warm months. © L. Benvenuti Montastraea faveolata
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Corals are not killed by temporary bleaching.
They will die if the stress lasts for an extended period of time, or is very severe. Bleaching events are occurring more often as the oceans warm. not bleached completely bleached partially bleached © L. Williams © S. Zea C.natans D. labyrinthiformis Montastraea
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Pale–polyps that have either just started to bleach or are recovering from bleaching.
Close-up pale bleached © P. Dustan Montastraea faveolata
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Partial Mortality–when parts of a coral die, the white skeleton below is exposed.
© P. Dustan Close-up white skeleton = recent death live Mycetophyllia
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When coral polyps have just been killed, the freshly exposed, white skeleton may look bleached.
turf algae recently dead live © J. Lang Colpophyllia natans
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Montastraea cavernosa
Bleached, not dead– Polyps are translucent (nearly colorless) and distort the appearance of the skeleton below. Close-up Corals with large, thick polyps are conspicuous, even when they are bleached. © J. Lang Montastraea cavernosa
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After they have bleached, small, thin polyps are hard to see.
Sometimes a fluorescent rim (not present here) is visible around the mouths of M. annularis, M. faveolata, and M. franksi. Close-up © E. Peters Partially bleached Montastraea faveolata
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Montastraea cavernosa
What else kills stony corals? Pathogens Outbreaks of disease have also increased in frequency and severity in recent decades. Background name: Deep_Blue.tif © L. Benveuti Montastraea cavernosa
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Montastrara faveolata
Black-Band Disease A discrete, dark reddish-brown or black mat at the interface between live polyps and recently exposed coral skeleton. Close-up Don’t confuse the exposed skeleton with bleaching! © P. Dustan Montastrara faveolata
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What’s going on here? Bleaching + recent death from black-band disease
Background name: Deep_Blue.tif © L. Benvenuti Colpophyllia natans
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Yellow-band (blotch) Disease
Tissues are pale (even bleached) before dying. Mostly in Montastraea and brain corals. later stage; algal turfs in dead area early stage; no dead polyps © A. Bruckner Montastraea faveolata © A. Bruckner
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Because the polyps initially are pale, yellow-band disease is easily confused with bleaching, especially in the early stages of the disease. © J. Lang Close-up, early stage © E. Peters More advanced stage Montastraea faveolata
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Yellow-band Disease Coral polyps may die so slowly that recently
exposed, white skeleton is rarely seen. A colorless-yellow rim develops along the margins of the live polyps © R. Ginsburg Montastraea faveolata
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White plague No “band” at the interface between polyps and recently dead skeleton. Polyps die relatively quickly. Most common in head corals. © G. Schmahl, FKNMS © P. Dustan Close-up Colpophyllia natans Dichocoenia stokesi
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Montastraea faveolata
White plague outbreaks occurred after the mass bleaching events in 1998 and 2005. . BVI, Jan. 2006 © C. Aldridge Montastraea faveolata
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Stephanocoenia intersepta
Dark Spots Disease Blotchy discolorations. Polyps die slowly, or sometimes recover. Most common in S. siderea and S. intersepta. © A. Bruckner © A. Bruckner Siderastrea siderea Stephanocoenia intersepta
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Corallivores (coral predators)
Some fishes and invertebrates eat stony corals. parrotfish bites Background name: Deep_Blue.tif damselfish algal gardens © B. Kakuk © B. Kakuk Montastraea annularis Montastraea faveolata Corallivore densities can be extremely high if their own predators are overfished.
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deep bites at the edge of a C. natans
Stoplight (Sparisoma viride) and certain other parrotfishes bite or scrape coral polyps, removing the underlying skeleton. © A. Bruckner © A. Bruckner Close-up spot bites in a Montastraea deep bites at the edge of a C. natans
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Parrotfish bites sometimes merge to form huge lesions that can be over 25 cm long on M. annularis lobes. © A. Bruckner © A. Bruckner Montastraea annularis stoplight parrotfish (Sparisoma viride) biting Montastraea annularis
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damselfish bites in Montastraea
Small, circular (<1cm diameter) lesions in live coral are created by threespots and some other damselfish. © P. Humann © B. Kakuk Stegastes planifrons (threespot damselfish) damselfish bites in Montastraea
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Damselfish Algal Gardens
The damselfish cultivate tiny algal turfs that settle on the exposed skeletons for food and shelter for their offspring. Close-up © B. Kakuk © J. Lang Montastraea annularis Porites astreoides
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Predation–Hermodice carunculata
Scars on branch tips or small bumps on head corals. Usually feed at night. feeding scar © A. Bruckner © P. Dustan Close-up WP H. carunculata on A. palmata H. carunculata on M.?faveolata with white plague
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Macroalgae (Seaweeds)/Algal Turfs
Sea weeds and algal turfs are kinds of benthic algae that can compete with corals for space on the bottom. Background name: Deep_Blue.tif © B. Kakuk
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Black sea urchins and herbivorous fishes grow large enough to dislodge seaweeds.
Background name: Deep_Blue.tif © R. Steneck © M. Moe Diadema antillarum (black sea urchin) Sparisome viride (stoplight parrotfish)
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Dying Diadema, 1983 © B. Causey Black sea urchin populations have not yet fully recovered.
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1960’s 1990’s © M.J. Hugenholtz Overfishing spearing © C. van Dongen
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Overfishing small mesh traps 2000’s 1990’s
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On reefs with few large herbivores, seaweeds or algal turfs are now overgrowing stony corals and preventing larval settlement. © J. Bruno
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