coral reef communities l.
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 15 PowerPoint Presentation
Download Presentation
Chapter 15

Loading in 2 Seconds...

play fullscreen
1 / 85

Chapter 15 - PowerPoint PPT Presentation

  • Uploaded on

Coral Reef Communities. Chapter 15. Key Concepts. Coral reefs are primarily found in tropical clear water, usually at depths of 60 meters or less. The three major types of coral reefs are fringing reefs, barrier reefs, and atolls.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Chapter 15' - konane

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
key concepts
Key Concepts
  • Coral reefs are primarily found in tropical clear water, usually at depths of 60 meters or less.
  • The three major types of coral reefs are fringing reefs, barrier reefs, and atolls.
  • Both physical and biological factors determine the distribution of organisms on a reef.
key concepts3
Key Concepts
  • Stony corals are responsible for the large colonial masses that make up the bulk of a coral reef.
  • Reef-forming corals rely on symbiotic dinoflagellates called “zooxanthellae” to supply nutrients and to produce an environment suitable for formation of the coral skeleton.
  • Coral reefs are constantly forming and breaking down.
key concepts4
Key Concepts
  • The most important primary producers on coral reefs are symbiotic zooxanthellae and turf algae.
  • Coral reefs are oases of high productivity in nutrient-poor tropical seas. Nutrients are stored in reef biomass and efficiently recycled.
key concepts5
Key Concepts
  • Inhabitants of coral reefs display many adaptations that help them to avoid predation or to be more efficient predators.
  • Coral reefs are huge, interactive complexes full of intricate interdependencies.
world of coral reefs
World of Coral Reefs
  • Coral reefs are highly productive, but occur in nutrient-poor waters
  • This is made possible by the symbiotic relationship between coral animals and zooxanthellae
  • These symbionts + algae form the basis of the community; other reef animals depend on these organisms
coral animals
Coral Animals
  • Stony (true) corals deposit massive amounts of CaCO3 that compose most of the structure of coral reefs
  • Hermatypic—coral species that produce reefs, found in shallow, tropical waters
coral animals9
Coral Animals
  • Ahermatypic—corals that do not build reefs, which can grow in deeper water from the tropics to polar seas
    • most do not harbor zooxanthellae
coral animals13
Coral Animals
  • Coral colonies
    • large colonies of small coral polyps, each of which secretes a corallite
    • a planula larva settles and attaches
    • a polyp develops, and reproduces by budding to form a growing colony
    • polyps’ gastrovascular cavities remain interconnected
    • a thin, usually colorful epidermis overlies the colony surface
coral animals15
Coral Animals
  • Sexual reproduction in coral
    • mostly broadcast spawners—release both sperm and eggs into the surrounding seawater
    • some are brooders—broadcast sperm, but retain eggs in the gastrovascular cavity
    • spawning is usually synchronous among Pacific reef species, but nonsynchronous among Caribbean species
coral animals16
Coral Animals
  • Reproduction by fragmentation
    • some branching corals are fragile and tend to break during storms
    • if they survive the storm, fragments can attach and grow into new colonies
    • fragmentation is a common form of asexual reproduction for branching corals
coral animals17
Coral Animals
  • Coral nutrition
    • symbiotic zooxanthellae
      • supply 90% of nutritional needs of stony coral
      • zooxanthella provide glucose, glycerol and amino acids
      • coral polyp provides a suitable habitat and nutrients, absorbed directly through the animal’s tissues
      • zooxanthellae remove CO2 and produce O2
      • need of zooxanthellae for sunlight limits depths to which stony corals can grow
coral animals19
Coral Animals
  • Coral nutrition (continued)
    • corals as predators
      • small animals paralyzed by the nematocysts are passed into the digestive cavity
coral animals21
Coral Animals
  • Coral nutrition (continued)
    • other sources of nutrition
      • corals can feed off bacteria living in their tissues, which feed on dissolved organic matter directly from the water
      • mesenteric filaments (coiled tubes attached to the gut wall) can be extruded from the mouth to digest and absorb food outside the body
reef formation
Reef Formation
  • Involves both constructive and destructive phases
  • Bioerosion—the destructive phase of reef formation
    • boring clams or sponges attack exposed surfaces on the undersides of large corals
    • the coral stand weakens, then topples in a storm or ocean surge
    • debris smothers boring organisms, cracks are filled with CaCO2 sediments, and coralline algae cement it together
coral reef types
Coral Reef Types
  • Fringing reefs border islands or continental landmasses
coral reef types28
Coral Reef Types
  • Barrier reefs are similar to fringing reefs but separated from the landmass and fringing reef by lagoons or deepwater channels
coral reef types31
Coral Reef Types
  • Atolls, usually elliptical, arise out of deep water and have a centrally-located lagoon
coral reef types33
Coral Reef Types
  • In addition, patch reefs can occur within lagoons associated with atolls and barrier reefs
  • Darwin’s theory of atoll formation:
    • corals colonize shallow areas around newly-formed volcanic islands to form a fringing reef
    • the island sinks and erodes, and a barrier reef is formed about the island
    • the island sinks completely, leaving an atoll
reef structure
Reef Structure
  • Reef front or forereef—portion of the reef that rises from the lower depths of the ocean to a level just at or just below the surface of the water, on the seaward side
    • drop-off—a steep reef-front that forms a vertical wall
    • spur-and-groove formation or buttress zone—finger-like projections of the reef front that protrude seaward; disperses wave energy and helps prevent damage
reef structure39
Reef Structure
  • Reef crest—the highest point on the reef and the part that receives the full impact of wave energy
    • where wave impact is very strong, it may consist of an algal ridge of encrusting coralline algae, lacking other organisms, and penetrated by surge channels—grooves of the buttress zone
  • Reef flat or back reef—portion behind the reef crest
coral reef distribution
Coral Reef Distribution
  • Major factors influencing distribution:
    • temperature – corals do best at 23-25o C
    • light availability – photosynthetic zooxanthellae need light
    • sediment accumulation – can reduce light and clog feeding structures
    • salinity
    • wave action – moderate wave action brings in oxygenated seawater, removes sediment that could smother coral polyps
    • duration of air exposure – can be deadly
comparison of atlantic and indo pacific reefs
Comparison of Atlantic and Indo-Pacific Reefs
  • Pacific reefs are older and have a greater depth of reef carbonates
  • Buttress zone is deeper on Atlantic reefs and coral growth may extend to 100 m down
    • Pacific coral growth rarely exceeds 60 m
  • Algal ridges more common in the Pacific because of wind and waves
comparison of atlantic and indo pacific reefs47
Comparison of Atlantic and Indo-Pacific Reefs
  • Hydrozoan Millipora complanata (fire coral) is dominant on Atlantic reefs
    • Similar species never dominate in the Pacific
  • Gorgonians more abundant in the Atlantic
  • Soft corals (subclass Alcyonaria) more abundant in the Pacific
  • Atlantic corals nocturnal; Pacific corals diurnal
comparison of atlantic and indo pacific reefs48
Comparison of Atlantic and Indo-Pacific Reefs
  • Atlantic corals often reproduce by fragmentation; Pacific corals by sexual reproduction
  • Coral diversity is far greater in the Indo-Pacific than the Atlantic
  • Greater sponge biomass in the Atlantic
  • Pacific has giant clams and sea stars that prey on corals
reef productivity
Reef Productivity
  • Source of nutrients
    • land runoff for reefs close to land
    • source for atolls unclear
    • possible explanations:
      • nutrients accumulated over time are efficiently recycled
      • reef bacteria and filter feeders capitalize on nutrients from dissolved/particulate organic matter
    • nutrients brought from other communities
reef productivity52
Reef Productivity
  • Reef photosynthesis
    • photosynthetic organisms: zooxanthellae, benthic algae, turf algae, sand algae, phytoplankton, seagrasses
    • more dense than tropical ocean, with greater biomass than reef animals
    • associations of producers with other organisms assist in efficient recycling
    • turf algae process the most organic carbon
reef productivity54
Reef Productivity
  • Reef succession
    • ratio of primary production to community respiration = P-R ratio
      • P = gross photosynthesis
      • C = community respiration
    • P-R ratio used to measure state of development of a biological community
reef productivity55
Reef Productivity
  • Reef succession (continued)
    • P-R ratio > 1 = primary production exceeds respiratory needs
      • biomass increases, excess biomass available for growth or harvesting
    • P-R ratio = 1 = steady state
      • little biomass remains available for growth
    • P-R ratios for coral reefs are typically close to 1
      • high productivity balanced by high respiration
reef productivity56
Reef Productivity
  • Reef succession (continued)
    • increases in productivity are often the result of eutrophication
      • eutrophication—nutrient enrichment
    • eutrophication typically manifested as a dramatic proliferation of algae
      • if grazing doesn’t increase, algae can grow over and smother corals
coral reef ecology
Coral Reef Ecology
  • Coral provides:
    • foundation for reef food webs
    • shelter for resident organisms
  • Reefs form a complex 3-dimensional habitat for many beautiful and strange creatures
coral reef community
Coral Reef Community
  • Sponges and cnidarians
    • sessile organisms, though anemones can move if necessary
    • filter feed; anemones also paralyze and consume small fishes and crustaceans
  • Annelids
    • sessile filter feeders include featherduster and Christmas tree worms
    • fireworms are mobile predators
    • palolo worms burrow through and weaken coral and usually deposit feed
coral reef community60
Coral Reef Community
  • Crustaceans
    • shrimps, crabs and lobsters
    • vary from parasites to active hunters
  • Molluscs
    • gastropods eat algae from coral surfaces
    • giant clams are filter feeders, but also host symbiotic zooxanthellae
    • octopus and squid are active predators
coral reef community62
Coral Reef Community
  • Echinoderms
    • feather stars, sea urchins, brittle stars, sea stars, and sea cucumbers
    • filter feed, scavenge, or eat sediment
  • Reef fishes
    • most prominent and diverse inhabitant
    • diverse food sources, including detritus, algae, sponges, coral, invertebrates, other fish
species interactions on coral reefs
Species Interactions on Coral Reefs
  • Competition among corals
    • fast-growing, branching corals grow over slower-growing, encrusting or massive corals and deny them light
    • slower-growing corals extend stinging filaments from their digestive cavity to kill faster-growing corals
    • fast-growing corals can also sting and kill using long sweeper tentacles with powerful nematocysts
species interactions on coral reefs64
Species Interactions on Coral Reefs
  • Competition among corals (continued)
    • slower-growing corals are more tolerant of shade, and can grow at greater depths
    • as a result…
      • fast-growing, branching corals on many reefs dominate upper, shallower portions
      • larger, slower-growing corals dominate deeper portions
species interactions on coral reefs65
Species Interactions on Coral Reefs
  • Competition between corals and other reef organisms
    • sponges, soft corals and algae can overgrow stony corals and smother them
    • algae outcompete corals at shallow depths unless grazers control the algae growth
  • Other competitive interactions
    • hydrozoans overgrow gorgonians
    • fast-growing colonial invertebrates on coral surfaces overgrow many species
species interactions on coral reefs66
Species Interactions on Coral Reefs
  • Effect of grazing
    • grazing of larger, fleshier seaweeds permits competitively inferior filamentous forms or coralline algae to persist
    • herbivory decreases with depth
    • damselfish form territories where they exclude grazers and permit abundant algal growth
      • provides habitat for small invertebrates
      • overgrows corals; fast-growing, branching corals are most successful near damselfish
species interactions on coral reefs67
Species Interactions on Coral Reefs
  • Effect of predation
    • predation of sponges, soft corals and gorgonians provides space for competitively inferior reef corals
    • species that feed on fast-growing coral assist slower-growing species to remain
    • corallivores seldom destroy reefs
    • small invertebrates are almost all well hidden or camouflaged, indicating the prevalence of predation in the reef
coral reef ecology68
Coral Reef Ecology
  • Coral reefs - marine habitats with greatest diversity/abundance of fishes
  • Seems to defy competitive exclusion principle, which suggests that no 2 species can occupy the same niche
    • 60-70% of reef fishes are general carnivores
    • about 15% are coral algae grazers or omnivorous
coral reef ecology69
Coral Reef Ecology
  • Hypotheses proposed to explain this:
    • competition model—factors such as time of day or night, size of prey, position in the water column, etc. provide each species with a unique niche (hence, no competition)
    • predation disturbance model—assumes competition, but suggests that the effect of predation or other causes of death keep populations low enough to prevent competitive exclusion
coral reef ecology70
Coral Reef Ecology
  • Hypotheses proposed to explain this:
    • lottery model—assumes competition occurs, but suggests that chance determines which species of larvae setting from the plankton colonize a particular area of the reef
    • resource limitation model—suggest that available larvae are limited and that limitation prevents fish population from ever reaching the carrying capacity of the habitat
threats to coral reefs
Threats to Coral Reefs
  • Effect of physical changes on the health of coral reefs
    • hurricanes and typhoons topple and remove coral formations
    • El Niño Southern Oscillation (ENSO)
      • changes winds, ocean currents, temperatures, rainfall and atmospheric pressure over large areas of tropical and subtropical areas
      • can cause massive storms
threats to coral reefs72
Threats to Coral Reefs
  • Coral bleaching
    • a phenomenon by which corals expel their symbiotic zooxanthellae
    • most often associated with warming of the ocean water by ENSO or global warming
    • if the stress is not too severe, corals may regain zooxanthellae and recover
    • if the stress is prolonged, corals may fail to regain zooxanthellae and die
threats to coral reefs73
Threats to Coral Reefs
  • Coral diseases
    • black band disease—a distinct dark band of bacteria migrates across the living coral tissue, leaving behind a bare white skeleton
threats to coral reefs75
Threats to Coral Reefs
  • Coral diseases
    • white pox—characterized by white lesions and caused by Serratia marcescens
    • other coral diseases:
      • white band disease
      • white plague
      • yellow blotch disease
threats to coral reefs77
Threats to Coral Reefs
  • Human impact on coral reefs
    • overfishing may occur
    • human-sewage bacteria cause white pox
    • nutrient-rich runoff (eutrophication) increases algal growth, which covers and smothers corals
      • e.g. Kane’ohe Bay in Hawaii
evolutionary adaptations of reef dwellers
Evolutionary Adaptations of Reef Dwellers
  • Protective body covering
    • tough, defensive exteriors help animals avoid predation, but can limit mobility and growth
  • Protective behaviors
    • producing a poisonous coating of mucus
    • burying the body in sand to hide
    • inflating to appear larger
    • hiding at night when nocturnal predators are active
evolutionary adaptations of reef dwellers82
Evolutionary Adaptations of Reef Dwellers
  • Role of color in reef organisms
    • color for concealment and protection
      • countershading
      • disruptive coloration
      • camouflage (bright colors in reef environment)
evolutionary adaptations of reef dwellers84
Evolutionary Adaptations of Reef Dwellers
  • Role of color in reef organisms
    • other types of camouflage
      • body shape
    • warning coloration
    • other roles of color
      • defending territories
      • mating rituals
evolutionary adaptations of reef dwellers85
Evolutionary Adaptations of Reef Dwellers
  • Symbiotic relationships on coral reefs
    • cleaning symbioses
      • cleaner wrasses, gobies, etc. feed on parasites of larger fishes
      • cleaning organisms set up a cleaning station
    • Other symbiotic relationships
      • clownfishes and anemones
      • conchfish and the queen conch
      • gobies and snapping shrimp
      • crustaceans and anemones