Yellow-band disease is a disease that attacks colonies of coral at a time when coral is already under stress from pollution

Pollution

Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

, overfishing

Overfishing

Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....

, and climate change

Climate change

Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

. It is characterized by large blotches or patches of bleached, yellowed tissue on Caribbean

Caribbean

The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

 scleractinia

Scleractinia

Scleractinia, also called stony corals, are exclusively marine animals; they are very similar to sea anemones but generate a hard skeleton. They first appeared in the Middle Triassic and replaced tabulate and rugose corals that went extinct at the end of the Permian...

n corals.

Yellow-band disease is a bacterial infection that spreads over coral, causing the discolored bands of pale-yellow or white lesions along the surface of an infected coral colony. The lesions are the locations where the bacteria have killed the coral’s symbiotic

Symbiosis

Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...

 photosynthetic

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 algae

Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

, called zooxanthellae which are a major energy source for the coral. This cellular damage and the loss of its major energy source cause the coral to starve, and usually cause coral death. There is evidence that global warming

Global warming

Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...

 is causing the spread of this disease.

Mechanism of action

Coral provides a stable environment for marine organism which is destroyed by Yellow-band disease (or yellow blotch disease). The bacteria produces the characteristic pale yellow lesions and eventually kills the zooxanthellae by impairing its mitosis

Mitosis

Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...

 and its ability to carry out photosynthesis

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

. Yellow-band disease is found on coral reefs in the Caribbean

Caribbean

The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

.

Impact

Yellow-band disease has severely affected reef building corals in the Caribbean. Compared to the late 1990s, current data suggests that the disease remains a severe epidemic. In one study, 10 meter belt transects were taken at various depths, sampling coral colonies in the Lesser Antilles

Lesser Antilles

The Lesser Antilles are a long, partly volcanic island arc in the Western Hemisphere. Most of its islands form the eastern boundary of the Caribbean Sea with the Atlantic Ocean, with the remainder located in the southern Caribbean just north of South America...

. At a depth of 5 m, yellow band rings and lesions were found on 79% of the colonies per transect

Transect

A transect is a path along which one records and counts occurrences of the phenomena of study .It requires an observer to move along a fixed path and to count occurrences along the path and, at the same time, obtain the distance of the object from the path...

, and only 21% of the colonies in this depth range appeared healthy.

Recent research indicates that yellow-band disease continues to be in an infectious phases in the Caribbean. It has been
found to cause infection in Pacific coral as well.