Today’s Class Outline

1. Today’s Class Outline • Coastal Ecosystems – why they are awesome • Coral reefs • Basic biology • Threats

2. An abundance of life in coastal ecosystems! All of the factors foster extreme productivity and biodiversity – coastal systems are dynamic ecosystems! What do I mean by this? Lots of primary production! Lots of species diversity Why? Dynamic spatial ‘gradients’ (rapid changes over space) of important controls on ocean life: • Salinity • Temperature • Light • Nutrients • Sediment types (sandy vs. muddy) • Water levels (tides)

3. Many different types of coastal ecosystems, depending on climate, type of coastline (rocky vs. gradual slope) Underwater (sub-tidal) habitat type examples • Coral reefs • Seagrass meadows • Kelp forests Inter-tidal habitat types examples • Mangrove forests (tropics/sub-tropics) • Salt marshes (temperate/boreal/polar latitudes) Estuaries – larger regions of where ocean meets rivers (‘Bays’)

4. What is a coral? • A plant • An animal • A type of rock structure • An algae

5. What is a coral? A coral is an animal – a type of Cnidarian (yes, like a jellyfish) Colonial organisms - clonal colonies composed of many physically connected, interdependent individuals Individual animals known as “polyps”. Few mm in diameter Polyps grow together to produce calcium carbonate, which form the hard stony coral ‘reefs’ over time

6. Coral reefs – where do these proliferate? • Warm water (>18°C, ideally 23-25°C) so 30°N to 30°S • Shallow (<70 m depth, usually<25m) • Fully saline (marine, near 33 ppt) • Low sediment supplies because need clear water • Very limited exposure to air (<1 hr per day)

7. Coral anatomy • Each polyp has a stomach that opens at only one end - the mouth, which is surrounded by a circle of tentacles • Tentacles for defense, capture small animals for food, clear away debris • Food goes into polyp through mouth, waste also comes out mouth! • Most corals feed at night • Corals have nematocysts (stinging cells, similar to jellyfish), located in tentacles and outer tissues - delivering powerful toxins to capture prey • Coral eat tiny zooplankton and even small fish (depends on size). Can also collect organic particles in mucous film and strands

8. Why are corals so colorful? Zooxanthellae!!

9. Mutualistic relationship with phytoplankton Corals contain photosynthetic algae, called zooxanthellae. Both corals and algae benefit from this relationship. Zooxanthellae live in coral’s tissues – coral provides algae with protected environment and compounds needed for photosynthesis Algae produces oxygen and organic carbon (glucose, glycerol, and amino acids) that coral needs, and remove wastes Tight recycling of nutrients in nutrient-poor tropical waters! Driving force behind growth & productivity of corals >90% of organic material photosynthetically produced by zooxanthellae transferred to the host coral

10. Individual polyps combine to form stony reefs Over the course of many years, stony coral polyps create massive reef structures Reefs form b/c polyps secrete calcium carbonate (CaCO3) Polyps will lift off its base and secrete a new basal plate above the old one, creating a small chamber in the skeleton. While the colony is alive, CaCO3 is deposited, adding partitions and elevating the coral. Polyps are small (1 to 3 mm in diameter) but entire colonies can grow large & weigh several tons Growth rate: 2 mm to 10 cm per year

11. Coral overview

12. Coral Reproduction Corals do both sexual and asexual reproduction - Asexual reproduction important for increasing size of colony. Sexual reproduction increases genetic diversity Asexual reproduction – fragmentation (pieces broken off and attach elsewhere to develop new colonies). Done early on and throughout life. Sexual reproduction –Takes 7-10 yrs to sexually reproduce Two types of sexual reproduction: • Broadcast spawning - external fertilization. By far most common • brooding – internal fertilization. https://oceanservice.noaa.gov/education/kits/corals/media/supp_coral03h.html

13. Broadcast spawning – a “blizzard” of gametes! Most corals (~75%) are hermaphroditic (polyps produce both male and female gametes) Once a year (based on cues from moon, sun, and water temp) entire colonies of coral reefs simultaneously release eggs and sperm (gametes) at the same time – mass synchronized spawning Gametes are visible to naked eye - billions of colorful flakes Bundles of gametes rise to surface for fertilization, break open and release egg and sperm to join together to form larva (“planula”). Creates sheen on water with distinct odor Planulae float for days or weeks before settling on floor. Then zooxanthellae settle

14. Coral spawning

15. The other type of sexual reproduction: brooding Internal fertilization Far less common (~1/4 of sexual reproduction) Coral release larvae (not eggs or sperm) Extended reproductive season (few months to sometimes continuous) http://coral.aims.gov.au/info/reproduction-sexual.jsp

16. Many types of corals(Don’t memorize these for the exam) • Branching • Pillar (no secondary branches) • Table • Elkhorn – thick, fast growing, high wave action • Folaise – great habitat • Encrusting – slow growing • Massive – slow growing • Mushroom - solidary

17. Deep Sea Coral

18. What types of organisms live on coral reefs? Mobile invertebrates (crustaceans, echinoderms, polychaetes, mollusks) and sessile (non-moving) invertebrates (corals themselves, sponges) Algae Fish! So many fish! Organisms at every stage on tropic cascade, from primary producers to higher order consumers As a result, corals have highest biodiversity in world. ~1/4 all ocean species depend on coral reefs for survival

19. Animals that live on Coal Reefs