Coral Reefs: Importance, Structure, and Threats

Coral Reefs

Massive structures formed by coral organisms.

Geological Importance

Significant physical structures in marine environments.

Biological Importance

High biodiversity and complex ecosystems.

Economic Importance

Supports fishing, tourism, and shoreline protection.

Coral Composition

Assemblages of skeletons and sediments from organisms.

Reef-Building Corals

Belong to Scleractinia; secrete calcium carbonate.

Zooxanthellae

Endosymbiotic algae aiding coral nutrition.

Scleractinia

Order of corals responsible for reef formation.

Polyps

Individual coral organisms forming colonies.

Asexual Reproduction

Polyps can reproduce without sexual processes.

Corallite Cups

Structures housing individual coral polyps.

Cenosarc

Tissue connecting polyps in a coral colony.

Mutualism

Coral and zooxanthellae benefit each other.

Heterotrophic Feeding

Corals supplement energy from captured prey.

Nematocysts

Stinging cells in coral for capturing prey.

Dinoflagellates

Single-celled organisms, including zooxanthellae.

Symbiodinium microadriaticum

Formerly a single species of zooxanthellae.

Genetic Diversity

At least 10 distinct taxa of zooxanthellae.

Symbiosome

Vacuole containing the endosymbiotic algae.

Clade A

Shallow-water zooxanthellae species.

Clades B-D

Deeper-water zooxanthellae species.

Endodermal Tissues

Coral tissues housing zooxanthellae.

Cell Density

Up to 1 million zooxanthellae cells/cm².

Zooxanthellae

Symbiotic algae providing nutrients to corals.

Glucose

Simple sugar produced by zooxanthellae for corals.

Amino acids

Organic compounds used for coral protein synthesis.

Coral respiration

Process of oxygen consumption by corals.

Calcification

Calcium carbonate deposition enhanced by zooxanthellae.

Hermatypic corals

Reef-building corals with high calcification rates.

Ahermatypic corals

Non-reef building corals with low calcification.

Branching corals

Grow rapidly, up to 10 cm per year.

Massive corals

Produce calcium carbonate slowly, about 1 cm per year.

Morphological plasticity

Variable growth in response to environmental conditions.

DNA sequencing

Modern method for identifying coral species.

Coral reef distribution

More abundant on eastern continental margins.

Salinity requirement

Average salinity of about 35 ppt for corals.

Sea surface temperature

Minimum of 20°C for coral growth.

Bioerosion

Process of coral reef degradation by organisms.

Coral reef types

Includes shelf, fringing, barrier reefs, and atolls.

Fragmentation

Asexual reproduction method in corals.

Open marine salinities

Corals thrive in typical ocean salinity levels.

Turbidity

Corals poorly develop in high sediment areas.

Wave action

Strong currents influence coral reef growth.

Budding Off

Asexual reproduction method in corals.

Sexual Reproduction

Involves spawning gametes externally.

Brooding

Fertilized eggs retained by the parent.

Hermaphroditic

Organisms possessing both male and female reproductive organs.

Dioecious

Species having distinct male and female individuals.

Mass Spawning

Synchronous release of gametes by corals.

Planktonic Gametes

Free-floating reproductive cells in the water.

Great Barrier Reef

Location where many corals spawn synchronously.

Coral Zonation

Distribution of coral species at varying depths.

Coralline Algal Ridge

Structure that withstands high wave action.

Decline of Coral Reefs

Over 50% of corals perished last century.

Climate Change Threats

Includes ocean acidification and rising temperatures.

Crown-of-Thorns Starfish

Predator causing significant coral mortality.

Catastrophic Mortality

Mass mortality events from natural disturbances.

Anthropogenic Disturbances

Human activities causing coral reef damage.

Overfishing

Decline of herbivores leading to algal overgrowth.

Fishing Statistics

Global reef fish catches peaked in 2002.

Catch-per-Unit-Effort (CPUE)

Measure of fish abundance relative to fishing effort.

Coral Bleaching

Expulsion of zooxanthellae due to stress.

Zooxanthellae

Symbiotic algae crucial for coral health.

Ocean Warming

Natural temperature variations affecting marine ecosystems.

Acropora palmata

Caribbean elkhorn coral species, vital for reefs.

2016 Bleaching Event

Massive coral die-off in Great Barrier Reef.

Coral Cover

Percentage of reef area occupied by live corals.

Fish Diversity

Coral reefs host the most diverse fish communities.

Nurse Shark

Large shark species feeding on seafloor invertebrates.

Caribbean Reef Shark

Predatory shark species found in Caribbean reefs.

Predation and Grazing

Processes affecting coral health and survival.

Acanthaster planci

Crown-of-thorns starfish, major coral predator.

Coral Diseases

Infections harming coral health, like black band disease.

Coral Bleaching

Loss of color in corals due to stress.

Overfishing

Depletion of fish stocks impacting reef ecosystems.

Nutrient Loading

Excess nutrients from runoff affecting coral health.

Crown-of-thorns Outbreaks

Increased populations damaging coral reefs since 1960s.

Hurricanes and Typhoons

Natural disasters causing catastrophic coral mortality.

Sedimentation

Accumulation of particles harming coral growth.

Giant Triton

Predator of crown-of-thorns, helps control populations.

Harlequin Shrimp

Eats crown-of-thorns, aiding coral reef recovery.

Coral Habitat

Diverse environments supporting various marine species.

Diurnal Feeding

Daytime feeding behavior of certain reef predators.

Nutrification

Enrichment of water with nutrients, harmful to corals.

White Band Disease

Specific coral disease leading to tissue loss.