12 Nov 08 OCN 628 – Benthic Biology

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  • 1.Coral Reefs What is a coral reef? Habitat forming scleractinians Different types of reef Symbiosis Biogeography Controls on Biogeography The value of reefs 29 April 2008OCN 621 – Biological Oceanography
  • 2.What is a coral reef? “Reef” Feature lying beneath the surface of the water with which a boat could get stuck on Typically diverse assemblage of habitat forming scleractinians Mainly Shallow But……not always…… Important engineers Biodiversity “Rain forests of the ocean” Cover less than 1/10% of ocean floor Habitat for 25% of all marine species
  • 3.Scleractinians (primarily) Other organisms also produce calcium carbonate structures Forminifera, cocolithophores, pteropods, halimeda, red algae, soft coral spicules, sponge spicules Reef structure is cemented together by calcareous red algae or by lithification Organisms creating non-carbonate skeletons Chitin, silica, gorgonin Octocorals, sponges What is a coral reef?
  • 4.Coral Reefs of the World Great Barrier Reef, Australia Largest coral reef in the world, 2600km Belize Barrier Reef Second largest in the world New Caledonia Barrier Reef Second longest double barrier reef – 1500km Andros Barrier Reef 3rd largest barrier reef, 167km long and 64km wide Red Sea Coral Reef Egypt & Saudi Arabia Pulley Ridge Florida, Deepest photosynthetic coral reef, 60m deep
  • 5.Scleractinian morphology Branching Often fast growing Plate-like Often found in deeper environments Massive/lobed Generally slower growing, k-selected Encrusting Sometimes parasitic
  • 6.Branching
  • 7.Plate Like
  • 8.Massive, Lobed
  • 9.Encrusting
  • 10.Types of Reef 4 Main types of reef Fringing, Barrier, Patch and Atoll Also – Apron, Bank, Ribbon & Table Fringing reef a reef that is directly attached to a shore or borders it with an intervening shallow channel or lagoon Bora Bora, French Polynesia
  • 11.Bora Bora
  • 12.Types of Reef Barrier Reef a reef separated from a mainland or island shore by a deep lagoon Great Barrier Reef - Australia
  • 13.Great Barrier Reef, Australia
  • 14.Types of Reef Patch Reef an isolated, often circular reef, usually within a lagoon or embayment Outer edge of each patch reef is surrounded by a halo of sand that extends out to adjacent seagrass beds. The width of this ring of sand is determined by the distance that herbivorous fish feel is within safe foraging range from the reef. Florida
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  • 16.Types of Reef Atoll Reef a more or less circular or continuous barrier reef extending all the way around a lagoon without a central island Midway, Hawaiian Islands
  • 17.Midway Maldives
  • 18.Island erosion Island sinking Reef accretion Atoll Formation
  • 19.Spur and groove formation Reef Zones
  • 20.Symbiosis Photosynthetic algal endosymbionts Dinoflagellates Algae located in gastrodermis Carbohydrates and lipids excreted by the algae Protection and nitrogenous waste provided by host Other marine taxa also engage in similar symbiosis Sea anemones, jellyfish, sponges, clams, forams Can provide up to 90% of corals energy
  • 21.Symbiosis
  • 22.Symbiosis Genus Symbiodinium Different species live in different corals Controversial Ingested by corals But not digested Reproduce by budding 3 Life Stages Vegatative Cyst Motile
  • 23.Shallow water coral biogeography Warm tropical climates Low latitudes (30ºN to 30ºS) High solar insolation Warm water currents Clear shallow waters good light penetration ~30m low sedimentation and turbidity Oligotrophic waters nutrient poor but not exclusively Hard substrata
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  • 26.Annual Pattern of Daily Solar Insolation
  • 27.Biogeography
  • 28.Biogeography What limits shallow coral reefs? High latitude and depth Temperature, chronic low temperature stress Light irradiance, insufficient solar insolation Aragonite (CaCO3) saturation state Competition with temperate fauna Kleypas, 1999, Grigg, 2006
  • 29.Biogeography Distinct fauna between Atlantic and Indo-Pacific Lower diversity in the Atlantic Younger, smaller ocean basin with less thermal capacity North-south mountain ranges did not impede glacial advances during ice ages More extinction events But older coral genera ~60 mya ?
  • 30.Modified from Spalding, M. et al. 2001 Biogeography
  • 31.Biogeography Higher diversity in the Indo-Pacific Older ocean basin with more stability through geological time Larger body of water with more thermal capacity East-west mountain ranges limited glacial advances during ice ages But younger coral genera ~30 mya ? Center of diversity in the Indo-Australian Archipelago (IAA) Diversity gradient as radial distance from center increases
  • 32.Veron, 1995 Biogeography
  • 33.Reef $$ Value Found in over 100 countries Over 500 million people worldwide rely on coral reefs Major source of food Poorer countries Fish and invertebrates Conch, bivalves, octopus, squid…. Food for pelagic fish species Limestone Building materials, breakwaters, cement Jewelry Aquarium trade Tourists $6-10billion US tourist industry Beach protection Wave breaks
  • 34.Conclusions Majority of coral reefs are shallow, warm tropical, made from carbonate accreting species Majority have photosynthetic algae A reef can be in many different forms Limited in latitude and depth Higher diversity in the Indo Pacific Reefs are worth $$s