Marine Ecology
Coral reefs
Global distribution of coral reefs
Productivity and diversity
Structure of coral
Coral anatomy
Coral anatomy Zooxanthellae are within the gastrodermal
layer lining the gastrovascular cavity.
What does the coral animal provide to the zooxanthellae?
Nutrients, especially nitrogen and phosphorus-containing compounds
Carbon dioxide Location in the photic zone Protection
What do the zooxanthellae provide to the coral? Organic molecules
(carbohydrates, proteins, other organic molecules)
End products of photosynthesis Radiolabelled C-14 experiments verify
this transfer of organic molecules 98% of a coral’s nutrition comes from
the zooxanthellae Oxygen Aids in calcification
Calcification
Active transport of calcium from seawater into epidermal cells of coral occurs.
At peak of calcium deposition, a cell must transport 50-100 times its own volume.
Calcium carbonate deposition is 14X greater in light than in dark, so role of zooxanthellae proposed to be important
Highest deposition on sunny days at noon. Mechanism of coupling not well-understood.
Calcified coral skeleton
Other coral basics
Feeding Shape vs. depth
Role of coral in food web
Primary producers Primary consumers Secondary consumers, and
up Detritovores?
Factors affecting reef growth
Temperature Depth Salinity Sediment Wave action Nutrients
Paradox: low nutrients, high productivity
Hypotheses Efficient coupling between coral and its
symbionts High flow rate of water over reef; integrated
amount that flows over the reef is relatively high
Nitrogen fixation by cyanobacteria creates a source of nitrate
Nutrients in particulates are relatively high, and are efficiently sequestered by reef organisms.
Reef structure
Reef building Reef breakdown
Types of coral reefs
Fringing Barrier Atoll (Darwin’s other theory…)
Pacific vs. Atlantic reefs Differences in diversity Differences in species
composition Hypotheses to explain these
differences
Key threats to coral reefs The scope of the problem Major threats (explained in
some detail)Coral bleachingOverfishingSewage and other pollutantsStorms
Implications of reef loss
