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