User:Rlucia98/lobophyllia

Lobophyllia hemprichii colony in waters near Koh Phangan, Thailand.

Lobophyllia - "Brain Coral"

Background

Lobophyllia is a genus of marine stony corals characterized by a spherical shape and deep grooves found all over the polyp membrane, resembling the human brain. Their exoskeleton containing deep grooves is made of calcium carbonate and protects the living tissue and symbiotic zooxanthellae living within the coral. Lobophyllia, like all stony corals, form colonies by secreting calcium carbonate, which acts as cement to attach neighboring polyps. Brain coral form large reefs in most shallow warm waters, including the Atlantic, Pacific, Caribbean and surrounding regions, and are also commonly found in aquariums. They are able to grow 6 feet tall and can live to 900 years in ideal conditions.

Close-up of Grooved Brain Coral (Diplora labyrinthiformis).

Classification

Brain Coral Classification

Taxa	Classfication
Kingdom	Animalia
Phylum	Cnidaria
Class	Anthozoa
Subclass	Hexacorallia
Order	Scleractinia
Family	Lobophylliidae
Genus	Lobophyllia

Lobophyllia is a genus of the Anthozoa class in the Cnidaria phylum.

Growth and Reproduction

Growth

Brain coral grows slowly but serves as foundations for coral reefs and organisms living within due to their strong structure and large size. Individual brain coral polyp tissues are not separated from others by skeletal structures like most corals, resulting in highly associated and advanced polyp colonies. Because their tissues are closely positioned, polyps are able to communicate and share nutrients, increasing productivity of the colony. Close integration also allows for corals to detect damage in other polyps and send nutrients to those polyps to help injured portions of the colony.

Within corals live symbiotic zooxanthellae, which provide nutrients to the coral and receive shelter and protection from the coral. Zooxanthellae provide up to 90% of their produced organic materials to the corals. In addition to zooxanthellae nutrients, corals filter feed on zooplankton, bacterioplankton, and other microscopic food particles in the water column.

Brain coral broadcast spawning.

Reproduction

Lobophyllia reproduce both asexually and sexually, and are hermaphroditic--meaning they contain both male and female gametes. Although they have the ability to produce asexually, they are more apt to reproduce sexually.

Asexual reproduction in corals consists of budding and fragmentation. During budding, a new polyp grows from the existing coral and breaks off of the parent once it matures to start a new colony. Fragmentation occurs when a portion of the coral colony breaks off during a storm or other damaging events. The broken piece of coral begins a new colony once it settles in a new area with favorable conditions.

Corals reproduce sexually in variety of manners, including broadcast spawning and brooding. Lobophyllia are specifically known to reproduce through broadcast spawning, in which sperm are released in the water column to fertilize an egg within the colony. Once the sperm fertilizes the egg, the fertilized egg develops within a polyp and is released into the water column once it hatches as larva. The larva then sinks to the ocean floor or reef surface and forms a new colony. Broadcast spawning allows for higher genetic diversity and expansion to further locations.

Brain coral exhibiting fluorescence in the deep sea.

Biofluorescence

A few species of Lobophyllia exhibit fluorescence, in which corals absorb incoming light and reflect it at a different wavelength, resulting in bright colors that glow in the dark blue sea. The specific function of fluorescence in corals is yet to be determined, but there are hypotheses on why it may be useful.
In shallow water corals, the fluorescence may be used as a type of sunscreen to protect the zooxanthellae living within by emitting a light that is less damaging. In deep water corals, the fluorescence may be absorbed by the phytoplankton to be used for photosynthesis. Blue light travels deep into the ocean, but it cannot travel through the solid coral exterior to reach phytoplankton living inside. The fluorescence can act as a substitute for light penetrating the water so zooxanthellae can remain inside the coral and still receive light for photosynthesis.

Fluorescence in corals is used in research today to help determine the health of colonies. In healthy corals, fluorescence is displayed in particular patterns in colors. However, in diseased corals, the fluorescence is scattered and the colors change. Scientists today are investigating which diseases cause certain fluorescent displays and results can be used to evaluate the health of coral reefs in the future and determine which diseases they are suffering from.

Mechanism

Biofluorescence is the reemission of light, not to be confused with bioluminescence, which is the production of light through biochemical processes and enzymes. First, radiation from sunlight at one wavelength is absorbed by the coral. Then, the coral reemits the the radiation at a longer and lower wavelength. As a result, the color reflected by the coral is different than the one it receives and appears to glow. Corals often emit colors of green, red and orange, but there are also reports of pink and purple.

Coral Bleaching

A bleached brain coral has lost its vibrant color.

Causes

Coral bleaching is often the result of rising sea temperatures brought by global warming and climate change. When water temperatures increase, symbiotic zooxanthellae living within coral are ejected from the coral. As a result, corals lose their bright colors brought by the photosynthetic zooxanthellae and a hard, white coral skeleton remains. Without zooxanthellae, corals are more at risk of mortality.

Furthermore, Lobophyllia are at risk of bleaching due to disease. Brain corals are advanced in the sense that their tissues are closely-positioned to share nutrients. However, close proximity and lack of skeletal structures separating tissues allows pathogens to travel to different polyps without barriers, causing disease to spread rapidly.

Today, are many cases of bleached brain corals around the world. In the Red Sea, many different corals, including Lobophyllia, are bleaching due to Skeletal Eroding Band disease (SEB). SEB is caused by Halofolliculina corallasia, a colonial cilliate protozoan. SEB attacks the polyps along with other areas of the corals, preventing growth and the mutual symbiosis between zooxanthellae and the coral. SEB is present in major coral reef locations, including the Caribbean and the Great Barrier Reef, and can have devastating effects on communities.

Bleached coral in The Great Barrier Reef.

Effects

Coral reefs serve as feeding grounds for large predators, sanctuaries for small fish, and nurseries for juveniles. As corals bleach, small fish search elsewhere to lay eggs and find a source of nutrients. Over time, a decreasing amount of fish are born in reefs and there is less prey for larger fish. Eventually, all organisms must search elsewhere for sanctuary and nutrients, resulting in a barren coral reef with minimal biodiversity.

Not only are coral reefs the core to a fluid ecosystem, but they are also a source of economic prosperity. Areas around the world depend on tourism for economic success, including parts of Australia, Caribbean Islands, and Hawaii. Additionally, the bleaching of corals decreases the overall amount of fish that many countries use to sustain their economies.