AGRRA: Introduction to Coral Reefs Revision: Judith Lang

The following images are Copyright © by New World Publications and by other photographers. Permission is granted to use the photographs and slides in this presentation with the AGRRA Program and, with attribution, for other valid educational purposes. All other uses are strictly prohibited. For permission to use their images, special thanks to: L. Benvenuti, A. Bruckner, J. Bruno, K. Desai, P. Dustan, P. Edmunds, M. Gerber, E. Hickerson, H. Hudson, P. Humann, L. Ilyes, B. Kakuk, J.-P. Maréchal, K. Marks, R. McCall, M. Moe, H. Moody, A. Moulding, M. Nugues, J. Reichman, C. Rogers, A. St. Gelais, G. Schmahl, R. Steneck, C. van Dongen, E. Weil, L. Williams

Stony corals are the major framework constructors of coral reefs. Their soft polyps overlie stony (calcareous) skeletons. Meandrina jacksoni The polyps expand to feed on plankton, usually at night.

Colonies are formed when the polyps divide asexually. Diagram from P. Humann Tentacle Mouth Single Polyp Skeleton Colony

reproduction) throughout their Colonial corals continue to grow via asexual division (reproduction) throughout their lives. Porites porites and Millepora complanata

Adult corals also reproduce sexually. Species that grow large engage in mass spawning of gametes once, or several times, a year. Montastraea franksi Colpophyllia natans

Recruits give reefs a chance of recovering after disasters have killed adult corals. Coral larvae need to settle on solid surfaces like dead corals or crustose coralline algae. Porites astreoides

are Zooxanthellae (‘zoox’) are tiny, yellow-brown algae in some cells of reef-building corals. Zoox gain shelter, access to carbon dioxide for photosynthesis and inorganic wastes (= nutrients for growth) from their host coral.

Zoox contribute organic compounds to their coral host (= support its health, growth, and calcification). Montastraea cavernosa recruit with zoox Clades are genetically distinct populatons of zoox that characterize certain reef habitats, and/or coral species and/or location on a coral.

Bleached Bleached corals are still alive! Bleaching occurs when most of the zoox are gone, and/or remain but have lost most of their yellow-brown photosynthetic pigments. Corals are not killed by temporary bleaching. Bleached Porites

Bleaching occurs in response to unusually high or low temperatures, unusually high or low salinities, or too much sediment. Partially bleached Montastraea annularis

varies by: Severity of bleaching varies by: the coral’s species or colony identity the cladal identity of its zoox its location on the reef with respect to depth, currents, shading, etc. C. natans D. labyrinthiformis M. meandrites

occurs, sexual reproduction When mass bleaching occurs, sea water temperature is above warm season averages.* Polyps die and/or, at least temporarily, are more susceptible to disease and/or their future growth or sexual reproduction is redu ce d. Montastraea faveolata * Increases of ~1 o C for ~4 weeks, or ~3-4 o C for 1-2 days

Montastraea annularis Major Mass Bleaching Events 1998: Bahamas and Mesoamerica 2005: Eastern and NE Caribbean

(biological disease causing agents). Corals are also killed by pathogens (biological disease causing agents). Montastraea faveolata with Yellow Band disease (YB)

Large Large outbreaks of disease are common when corals start to “recover” from severe bleaching. Formerly bleached Montastraea faveolata now with White Plague (WP)

Corallivores (coral predators) include some invertebrates (below) and fishes. Snail feeding on a staghorn coral, Acropora cervicornis Fireworm on a Montastraea faveolata already infected with White Plague (WP)

Threespot damselfish, Stegastes planifrons like the t Damselfish like the threespot (Stegastes planifrons) create small lesions in live corals to cultivate algal gardens for food and to use as a nursery for their young. Montastraea annularis with threespot bites

Stoplight (Sparisoma viride) and some other parrotfishes kill coral polyps and excavate their skeletons. Stoplight parrotfish (S. viride) biting Montastraea annularis Lesions from merged stoplight bites can be > 30 cm/12 in long!

when parts of a coral die, the white skeleton Partial Mortality: when parts of a coral die, the white skeleton below is exposed, superficially resembling bleaching. Mycetophyllia with new mortality

a When large predators are rare, corallivores may be very common and kill many corals. Black grouper, Mycteroperca bonaci

competing Corals may lose when competing for space on the substratum with cyanobacteria, thick/dense turf algae, macroalgae, and some invertebrates.

(long-spined sea urchin) and large (≥ 30 cm) Feeding by Diadema antillarum (long-spined sea urchin) and large (≥ 30 cm) parrotfishes dislodges the basal holdfasts of benthic algae. Stoplight parrotfish, Sparisoma viride Having been decimated by disease, Diadema are now rare on many reefs.

When large herbivores are rare, turf algae and macroalgae (seaweeds) may colonize dead corals, becoming so abundant that they prevent coral larvae from settling. These algae can also overgrow live corals.

in Overfishing in the wider Caribbean has already depleted many populations of shark, large- and small-sized bony fish, queen conch and spiny lobster.

Rapidly assess key structural and functional attributes of tropical Western Atlantic reefs. And provide fishery- independent estimates of fishing intensity. AGRRA Program Primary Goals:

S. siderea encrusting/nodular platy/bifacial © R. Steneck © M. Nugues Common AGRRA Corals by shape and size flower (phaceloid flower (phaceloid) branching massive

turf algae AGRRA Benthic Algal Groups macroalgae cyanobacteria crustose coralline algae

© L. Ilyes Common AGRRA Fish Groups ornamentals herbivores predators