Lecture 8 cards Flashcards
Acropora
Species of coral–150 spp in pacific, 3 spp in atlantic
Most significant environmental factors
Temperature, light, salinity, turbidity/sedimentation, wave energy
Temperature
About 20C, max range 18-40C, cold upwellings prevent health, cooler water favors algal growth rather than coral growth, so competition could be what prevents coral success
Light
Photosynthesis is essential for dinoflagellates (zooxanthellae) that are essential for rapid calcification. Compensation depth for coral growth 15-20% of surface light intensity
Salinity
Open-ocean salinity is required
Turbidity/sedimentation
Can inhibit coral growth, decreased light attenuation decreases photosynthesis, sediments can foul the surfaces and smother animals, some animals produce mucus sheets in response
Wave energy
Corals strive with strong water movements. Prevents sedimentation, high oxygen content, skeletons resistant to shock, cannot withstand aerial exposure
Subsidence Theory
Corals fringing land masses or volcanoes are the result of crust subsiding, allowing reefs to grow upward and outward. Making 3 stages of reef development fringing-barrier-atoll
Glacial control theory
Change in sea level caused by formation and melting of glaciers allowed corals to grow into very high structures
Why is the productivity so high in coral reefs?
Favorable light conditions, high temperatures, constant water movements to replenish nutrients and enhance diffusion rates, tight recycling of nutrients
Primary producers
Dinoflagellates (zooxanthellae, 70% of tissue weight of corals), filamentous/encrusting algal mats, calcareous algae (reds, greens), N-fixing cyanobacteria, phytoplankton
Corallite
Cup-shaped skeleton in 6 compartments
Planula
Ciliated larva of stony corals
Hermatypic
When corals have zooxanthellae. Promotes calcification.
Acanthaster
Crown-of-thorns echinoderms, attack coral reefs, outbreaks occur in cycles possibly by removal of top predator or by weather
Mutualisms in coral reefs
Zooxanthellae in many reef organisms, cleaning relationships, burrowing shrimp and gobiid fish, clown fish and anemones
Allelochemicals
Toxic chemicals that can harm or prevent the growth of other coral species
Reefs are built by
Scleractinian hermatypic corals (stony corals) and crustose coralline algae
Main causes of coral loss
Predatory starfish, infectious diseases, destructive fishing techniques, poor land use practices, coral bleaching
Epifauna
Orgs that live on the sediments
Infauna
Orgs than live in the sediments
Controlling factor of benthic orgs
Substratum type–hard vs. soft, rocks, skeletons, wood, etc
Soft sediment parameters
Grain size, sorting/angularity, vertical distribution of sediment properties
Grain size
Indicates current velocity
Sorting/angularity
Sorting is the measure of the range of particle sizes. More sorted = narrow range of particle size. Angularity = roughness
Bioturbation
Sorting due to the action of organisms
RPD
Redox potential discontinuity, depth below which oxidation processes are replaced by reduction processes. Measured by the property Eh, aka redox potential
Bio factors that cause benthic organisms to be aggregated
Food availability and feeding activity, predation effects, reproductive effects on dispersal and settlement, behavioral effects–induced movement and aggregation
