Coral Reefs Flashcards
What are the limiting factors to coral reef growth?
Temperature Depth Sedimentation Salinity Wave Action Air exposure
What is the optimum temperature for healthy coral growth?
23-29 degrees Celsius
What is the minimum temperature for coral growth
18 degrees Celsius
Why do coral need to grow in shallow water?
Corals need to grow in shallow water where sunlight can reach them. Corals depend on the zooxanthellae (algae) that grow inside of them for oxygen and other things, and since these algae needs sunlight to survive, corals also need sunlight to survive. Corals rarely develop in water deeper than 165 feet (50 meters).
Where is the worlds longest reef?
The great barrier reef off the coast of Queensland, Australia, it stretches for 1,429 miles over an area of approximately 133,000 square miles
Why do corals grow in shallow, clear water?
Corals need to grow in shallow water where sunlight can reach them. Corals depend on the zooxanthellae (algae) that grow inside of them for oxygen and other things, and since these algae needs sunlight to survive, corals also need sunlight to survive. Corals rarely develop in water deeper than 50 meters. Corals also need clear water that lets sunlight through; they don’t thrive well when the water is opaque. Sediment and plankton can cloud water, which decreases the amount of sunlight that reaches the zooxanthellae.
What types of reef are there? Describe them.
Fringing reef: grows near the coastline around islands and continents. They are separated from the shore by narrow, shallow lagoons. Fringing reefs are the most common type of reef that we see.
Barrier reef: also parallel the coastline but are separated by deeper, wider lagoons.
Atoll: ring-shaped, arising from deeper water and has a central lagoon
What is Darwin’s Subsidence Theory (1842)?
The subsidence theory proposed by Charles Darwin was formulated to describe coral reef development. It envisaged that fringing reefs, barrier reefs, and atolls represent successive stages as a result of vertical growth of reefs on subsiding basements in an evolutionary sequence.
Why are coral reefs so productive?
Coral reefs’ high productivity has been attributed mainly to photosymbioses between the coral animal and algae of the family Symbiodiniaceae, with recognition that the host can increase algal photosynthesis by concentrating nutrients and enhancing the efficiency of light absorption. (add to this)
What are the benefits of the Zooxanthellae symbiont to corals?
-Removal of excretory products (N, P, etc.)
-Provide O2 via photosynthesis
-Corals uptake carbohydrates made by algae (aids growth - carbon supply)
-Algae promote calcification rates, Ca uptake greater in light than dark, Algae act as CO2 sink • Shift Carbonate-Bicarbonate-CO2
interaction, increased CO2 in atmosphere may hinder this (ocean acidification)!
-Provide protection from UV, Zooxanthellae contain mycosporine-like amino acids, Act as sunscreen for corals, Bleaching makes them more susceptible to damage
What are corals?
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps.
Why is there such high diversity on coral reefs?
- Structural Complexity -> More complexity=more niches=more fish & species
- Narrow niches -> Coral fish evolved to have very specific requirements, narrower niches, fit more species in (e.g. Luckhurst & Luckhurst, 1978)
- ‘Lottery’ Hypothesis (Sale, 1980)
Coral fish produce many larvae that settle on the reef. This creates competition for vacant space where the chance of a species colonising a space is seen as a lottery. “First come first served”. Large turnover of species in any one place hence overall high diversity on reef at any one time
