Aquaviews - SCUBA Blog » Coral

The Fascinating Phenomenon of Coral Fluorescence

Nevin — Mon, 28 Jun 2010 17:12:04 +0000

Coral reefs are remarkable to look at during the day, and most of you who have scuba dived, have probably done a night dive on the reef where coral reefs appear even more interesting under the glare of the dive light. However, it’s time to look at coral with a “new light”. If you wish to experience a reef come alive in a kaleidoscope of psychedelic colors, try diving with UV dive lights to witness the spectacular phenomenon of coral fluorescence.

What is coral fluorescence? Well under certain light wavelengths some species of corals exhibit a phenomenon known as fluorescence where the coral itself appears to glow in shades of green, red or blue. Corals that normally appear dull brown in the daytime or under white light can take on vivid rainbow hues. Corals fluorescence when certain pigments inside them react to strong light absorbing the cooler blue end of the spectrum and reflecting back greens or reds.

The phenomenon of Coral Fluorescence is still full of mystery and the reasons why certain coral fluoresce are to this date unknown. Strangely enough not all corals fluoresce, and only a few species possesses this unique property which further complicates the search for the reason why corals glow in the first place.

There are several theories provided by scientist, and perhaps the most likely reason is that it acts as a kind of “sun block” for the coral protecting the zooxanthallae inside the coral from the harmful rays of the sun . Marine Biologists say that this property could perhaps protect shallow coral from bleaching or provide deeper coral the ability to absorb the UV light from the sun and reflect it back to the zooxanthallae allowing them to photosynthesize in the absence of sufficient sunlight.

Other fluorescence theories claim that fluorescence is an indicator of the health of coral, or is somehow used to signal coral spawning. Some scientists have also suggested that the light is used by coral to ward off predators.

Whatever the reason, for divers and underwater photographers, fluorescence is simply another unique dive experience and photo op. In order to observe this phenomenon, you will require “black light” or UV dive lights as well as your ordinary white lights to help you get around. UV lights alone are highly ineffective to navigate by, and you may end up bumping into things so use your ordinary lights till you get to the reef and then turn off the lights allowing your eyes to adjust to the darkness, while using your UV light to illuminate the coral. The process is pretty much hit and miss as not all coral pops out in vivid color. But when it does the results are simply striking. For underwater photographers coral fluorescence photography has become a whole new fascinating sub-set of the hobby, with some photographers switching exclusively to capturing coral under UV light.

photos from flickr.com by shadowfall, Chris_Moody, Johnson Cameraface, Storm Crypt

Coral Identification: Types Of Coral (Part 1- Hard Coral)

Noreen — Tue, 08 Jun 2010 17:40:39 +0000

Knowing and being able to identify different types of marine life, fish and coral makes scuba diving all the more exciting and enjoyable. When it comes to Coral Identification the sheer number of and different types of coral make it hard to come up with an extensive, all encompassing list. However, as part of our series of posts on marine life identification, we’ve put together a list of some common types of coral you are likely to spot when reef diving.

Sometimes mistaken for and referred to as plants or rocks, corals are actually made up of small marine invertebrate animals known as Coral Polyps and their exoskeleton structure that acts as a home. That is we see as the hard chalky structures that join together to form coral reefs. There are two main types of coral- Hard Coral and Soft Coral.
Above photo by flickkerphotos on flickr

HARD CORAL
Hard corals are made of a rigid calcium carbonate (limestone) and appear very much like rocks. Each polyp secretes a hard exoskeleton made up of calcium carbonate and a chalky internal skeleton that stays in place even after they die. As each generation of polyps dies and their exoskeleton remains, the coral grows a bit larger and because each polyp is so small, hard corals grow at a very very slow rate. Hard corals are scientifically known as “scleractinians”.

Types of Hard Coral

Staghorn Coral

photo by Nick Hobgood on flickr

Staghorn coral (Acropora cervicornis): Staghorn coral is a branching coral with cylindrical branches ranging from a few centimeters to over 6.5 feet (2 m) in length.This coral exhibits the fastest growth of all known western Atlantic corals, with branches increasing in length by 4-8 inches (10-20 cm) per year and is one of the three most important Caribbean corals in terms of its contribution to reef growth and fish habitat.

Pillar Coral

photo by nashworld on flickr

Pillar corals (Dendrogyra cylindricus): This type of coral grows up from the sea floor, but without any secondary branching. They can grow to be up to 2.5 m (8 ft) tall. They can grow on both flat and sloping sea floors at a depth of between 1 and 20 m (65 ft). They are one of the few types of hard coral whose polyps can commonly be seen feeding during the day.

Table Coral

photo by doug.deep on flickr

Table Coral (Acropora):Table Coral is the same branching type of coral as Staghorn coral, however it grow as flat plates. The shape of table coral is ideal to expose as much of their surface as possible to sunlight. The usual color of table coral is a dull brown or green, but it is brightened up by the numerous reef fish that shelter under and around its plates.

Brain Coral

photo by bob.bachand on flickr

Brain coral (family- Faviidae): Named because of this corals spheroid shape and grooved surface which resembles an animal brain. The life span of the largest brain corals is 900 years. Colonies can grow as large as 6 or more feet (1.8 m) high.

Blue Coral

photo by Mindful One on flickr

Blue coral (Heliopora coerulea): Blue corals is named for their distinctive, permanently blue skeleton, which is generally hidden by greenish-grey or blue polyps. Blue corals occur in tropical waters, on intertidal reef flats and upper reef slopes.

Great Star Coral

photo by richard ling on flickr

Great star coral (Montastraea cavernosa): This type of coral is a colonial stony coral found in the Caribbean seas. It forms into massive boulders and sometimes develops into plates. It’s Polyps are the size of a person’s thumb and can be seen fully extend at night.

Tube Coral

photo by Nick Hobgood on flickr

Tube Coral (Tubastraea): Tube Coral is a large polyp stony coral, and is found in a variety of colors and forms depending upon species. The tubastraea faulkneri is known as the Orange Cup or Sun Coral, pictured above.

Elkhorn Coral

photo by diver_meg on flickr

Elkhorn coral (Acropora palmata): This coral is considered to be one of the most important reef-building corals in the Caribbean. This species of coral is structurally complex with many large branches. The coral structure closely resembles that of elk antlers. A popular choice as a home for lobsters, parrot-fish, snappers and other reef fish. Elkhorn coral colonies are incredibly fast growing with an average growth rate of 5 to 10 centimetres (2.0 to 3.9 in) per year and can eventually grow up to 3.7 metres (12 ft) in diameter.

Soft Corals continued in Coral Identification: Types Of Coral (Part 1)

Coral Identification: Types Of Coral (Part 2- Soft Coral)

Noreen — Mon, 07 Jun 2010 17:33:14 +0000

If you missed our first past on Hard Corals and Types of Hard Coral- CLICK HERE

SOFT CORAL
Soft corals are also composed of some rigid calcium carbonate, but it is blended with protein so it is less rigid than hard corals. These corals are “rooted,” but because they have no exoskeletons, they sway back and forth with the currents, appearing to be more like plants blowing in the breeze.

Types of Soft Coral

Gorgonian (a.k.a Sea Fans)

*photos by Skinned Mink, PacificKlaus, JennyHuang on flickr

Gorgonian: This family of soft coral is also called sea whips or sea fans. Individual tiny polyps form colonies that are normally erect, flattened, branching, and reminiscent of a fan. Others may be whiplike, bushy or even encrusting. A colony can be several feet high and across but only a few inches thick. They may be brightly colured, often purple, red, or yellow. Gorgonians are found primarily in shallow waters, though some have been found at depths of several thousand feet.[1][3] The size, shape, and appearance of the gorgonians are highly correlated with their location. The more fan-shaped and flexible gorgonians tend to populate shallower areas with strong currents, while the taller, thinner, and stiffer gorgonians can be found in deeper, calmer waters.

Carnation Coral

photo by Nemo’s great uncle on flickr

Carnation Coral (Dendronephthya): Easily one of the most beautiful soft corals in the ocean the carnation coral comes in a spectacular range of colors and flourish below underhangs and caves. They are found mostly in Indo-Pacific – Islands of the Indopacific including Fiji, Tonga, Solomon Islands and the Great Barrier Reef. Unfortunately this specimen of soft coral is extremely sensitive to changes in water chemistry and is on the decline.

Toadstool Coral

photo by Paul J. Thompson on flickr

Toadstool Coral (Sarcophyton): Also known by a host of other names like Leather Coral, Mushroom Leather Coral and Trough Coral Sacrophyton corals are found in various shades of brown, with white or gold polyps. It is difficult to identify many species because they all have the similar appearance of a mushroom or toadstool, each with a distinct stalk and capitulum (cap). As they grow older, they develop a folded appearance.

Tree Corals

photo by sarsifa on flickr

Tree Corals (family-Nephtheidae): These flowery soft corals are commonly seen on many of our shores. They are usually attached to hard surfaces including boulders, jetty pilings and coral rubble. These soft corals look like bushes. The common tissue is generally rubbery but rough to the touch. A thick ‘main trunk’ attaches to a hard surface on one end, with many small branches on the other end which is why they are referred to as Tree Coral. The Carnation Coral Dendronephthya belong to this family of soft corals.

Sea Pens

photo by CW Ye on flickr

Sea Pens (cnidarians belonging to the order Pennatulacea): Sea pens are grouped with the octocorals (“soft corals”), together with sea whips and gorgonians. They were named after their feather-like appearance reminiscent of antique quill pens. Sea pens may rise up to 2 metres (6.6 ft) in some species, such as the tall sea pen (Funiculina quadrangularis) and are sometimes brightly colored. Rarely found above depths of 10 metres (33 ft), sea pens prefer deeper waters where turbulence is less likely to uproot them.

Bubble Coral

photo by CybersamX on flickr

Bubble Coral (Plerogyra sinuosa): Bubble corals have large water filled bubbles (vesicles) covering the large sharp sepia. Found in the Pacific Ocean and parts of the Red Sea, bubble coral can be seen in varying species, colors and forms. They maintain their egg-like or rather grape like appearance during the sunlit hours, then deflate at dark, manifesting finger-tentacles that feed on plankton, etc. This type of coral is sometimes referred to as Grape or Pearl Coral and also as Bladder Coral.

Sea Pens- Not The Underwater Writing Kind

Noreen — Wed, 26 May 2010 10:13:03 +0000

A stunning creature of the seas, the sea pen a species of soft coral gets it’s name as it resembles a plump, old-fashioned quill pen.

Similar to anemone, sea pens are colonial marine cnidarians belonging to the order Pennatulacea, in other words they are a colony of polyps working together for the survival of the whole. The primary polyp loses its tentacles and becomes the stalk of the sea pen, with a bulb at its base—the bulb anchors the sea pen in the muddy or sandy bottom. The various secondary polyps form the sea pen’s “branches” and have specialized functions. The Sea Pen may grow up to 2 meters (6.6 ft) in some species, such as the tall sea pen (Funiculina quadrangularis) and are sometimes brightly colored. Rarely found above depths of 10 meters (33 ft), sea pens prefer deeper waters where turbulence is less likely to uproot them.

The Sea Pens primary source of nutrition and food is plankton. Though they don’t move around often, they are able relocate and re-anchor themselves if need be. They tend to position themselves favorably in the path of currents, ensuring a steady flow of plankton. Their primary predator and as unlikely predators as they seem are nudibranchs and sea stars some of which feed exclusively on sea pens.

Some sea pens when touched emit a bright greenish light, known as bioluminescence. They may also force water out of themselves as a defensive act, deflating and retreating into their peduncle. So the next time you’re diving keep a look out for these beautiful marine creatures in tropical and temperate waters worldwide.

*Photo Credits: photos by CW Ye, doug.deep, zlatkarp, Nick Hobgood on flickr

Coral to be Cryogenically Frozen for the Future

Nevin — Wed, 28 Oct 2009 07:47:15 +0000

Corals from tropical oceans around the world are being placed in deep freeze at a British Zoo to preserve them against extinction for future generations owing to the rapid destruction of coral due to increase in greenhouse gas emission levels.

Research has shown that by 2040 almost all of the worlds coral reefs will be dead, wiped out by the rising oceans temperature and increasing acidity levels caused by rising CO2 levels in the atmosphere. The ZSL or the Zoological Society of London is planning the world’s first “Coral Cryobank” where thousands of samples of coral of every species will be cryogenically frozen at -200 degrees centigrade in liquid nitrogen.

Whipsnade Zoo in Bedfordshire has been identified for the new location of the Global Coral Cryobank, where an attempt to store samples of every species of coral on earth is to be made. There are currently over 1800 known tropical corals and around 3,350 cold water species. A Recent scientific breakthrough in regenerating coral from frozen samples is what led to the creation of the Cryobank.

In the wake of rising concerns over the destruction of reefs across the world, and studies made by scientists by observing the effects of the rising CO2 levels on the Great Barrier Reef in Australia, have led many to believe that the gradual destruction of reefs across the world is inevitable. This month 120 legislators from across 16 countries will meet in Copenhagen to discuss how to prevent the destruction of reefs and marine ecosystems and preserve marine ecosystems. The move by the ZSL in the creation of the new coral cryobank is a ground-breaking effort to preserve coral reefs and an example that will be followed by many others. The Smithsonian Institute in Washington is already considering a similar preserve for coral along the same lines as the ZSL, in order to protect coral reefs for future generations.

* Photo credits: Photos by only_point_five, utnapistim on flickr

Playing With Fire Underwater: Fire Coral Demystified

Nevin — Sat, 19 Sep 2009 14:46:19 +0000

What is Fire Coral?

Most Scuba divers who have dived in tropical or sub-tropical reefs will have been cautioned about getting stung by the notorious Fire Coral, and will have filed away the information as just one of the many things that can sting or harm you underwater.

Fire Coral also known as Stinging or Red Sea Coral belongs to the Milleporina order of species and contrary to popular belief isn’t really a coral at all. Fire corals are marine organisms that form colonies that look just like real coral; they are actually closely related to the jellyfish family and other stinging anemones. The Fire Coral gets its name from the painful burning sting that it inflicts on the unwary diver that brushes against it.

How does it look? How can I identify Fire Coral?

Fire Coral is unfortunately rather polymorphic and can appear in several physical forms. Sometimes it appears heavily branched and delicate in appearance, other times it is more, fan-blade shaped and massive. Most common forms it appears is either branched, plated, or encrusted. It is believed to have close to 50 varieties of Fire Coral species making it rather hard to describe. Most of the time Fire corals have a bright yellow-green and brown skeletal covering fading to a whitish hue at the tips, and will be soft and hairy and rounded up close.

Where does it exist?

Fire Coral are widely distributed in tropical and subtropical waters. Primarily occurs in the Indian and Pacific Oceans.

Fire corals form extensive outcrops on projecting parts of the reef where the tidal currents are strong. They are also abundant on upper reef slopes and in lagoons, and occur down to depths of 40 meters.

What does it Do?

Fire Coral belongs to the family of Milleporina, Millepora means ‘many pores’. Upon close inspection, the coral appears to have long fine hairs that protrude from the skeleton. The hairs possess clusters of stinging cells (nematocysts) that inflict the stings on human skin. These hairs capture prey, and help feed the coral.

Divers often mistake fire coral for sea weed or normal coral and may brush against it or lean on it for support. Upon contact the very small nematocysts on the corals hairs release toxins while the sharp calcified exo-skeleton cuts the divers’ skin. A fire Coral sting can cause intense pain and can be felt from two days to up to two weeks. The degree of pain varies on the duration of contact and the number of nematocysts that entered the wound.

Prevention

The best method of prevention is to practice and master Buoyancy control and avoid unnecessary contact with any coral. Wearing full wetsuits & diving gloves is a good way to ensure you don’t accidentally get in contact with Fire Coral.

What do I do if I get stung?

The first step is to rinse the wound or affected area with salt water, as fresh water will increase the pain. Secondly use vinegar (acetic acid) or Isopropyl Alcohol to kill any remaining stinging cells clinging to your skin and help break down the toxin. Use tweezers to put out any stinging hairs. Immobilize the affected limb to prevent spreading and Finally, apply hydrocortisone cream as necessary to reduce inflammation. It is also critical to watch the wound for infection, which will have to be treated with antibiotics by a doctor.

If the diver displays symptoms like shortness of breath and swelling of the tongue, neck and face, he has probably developed an allergic reaction to the sting and should be treated for allergy and rushed to a hospital.

Photos by: Nick Hobgood, Tim Sheerman-Chase, Scary Cow, welshcathy, Paul and Jill, Craig Grobler

5 Stunning Coral Reefs of the World

Noreen — Tue, 11 Aug 2009 07:01:13 +0000

Coral Reefs are huge Scuba Diving attractions. Brilliant colors like pinks, purples, yellows and reds stand out against the hues of blue. Shoals of brightly colored fish dart in and out of the different type of coral, sea anemones, sea urchins and sponges.These ecosystems are the forest of the Oceans and 25% of all marine life reside in these reefs. The rich colorful environment of coral reefs, along with it’s wealth of marine life make it the most popular type of diving destination to explore and discover. Here’s a take of the most stunning Coral Reefs and Reef areas in the World-

1. The Great Barrier Reef: The most popular and largest reef in the world, the Great Barrier Reef is situated off the coast of Queensland, Australia. Contrary to belief it is not one big coral reef but is composed of over 2,900 individual reefs and 900 islands that stretches over 3,000 kilometres (1,600 miles) over an area of approximately 344,400 square kilometres (133,000 sq miles). Seen from space and rated on of the 7 wonders of the World, its no wonder it’s a Top Dive destination.
The Barrier reef displays over 30 species of whales, dolphins and porpoises . Turtles, dugongs, sea snakes and sharks among over 1,500 species of fish and 400 species of coral have made these reefs their home.

* Photos by In Veritas Lux on flickr (top) Eulinky on flickr(bottom)

2. Belize Barrier Reef: The second largest coral reef system and almost as popular as the Great Barrier Reef is the Belize Barrier Reef. Roughly 300 meters (1,000 ft) offshore in the north and 40 kilometers (25 miles) in the south of Belize is the Coral Reef stretching 900 kilometers (560 miles) long. The Belize Reefs attract close to 130,000 visitors to the Country of which scuba diving an snorkeling are very popular.

Part of these reefs is the ever famous Belize Great Blue Hole, a large underwater sinkhole almost perfectly circular in shape, over 300 meters (984 ft) across and 125 meters (410 ft) deep. It’s rated one of the Top 10 Dive Sites in the World and a Must Dive on most diver’s list of dive destinations.

* Photo by Lauretta Burke, World Resources Institute Staff on flickr

3. New Caledonia Barrier Reef: Located in New Caledonia in the South Pacific is the second longest reef after the Great Barrier but isn’t as popular as the Belize Barrier Reef. Reaching a length of 1,500 kilometers (930 miles), the reef encloses a lagoon of 24,000 square kilometers (9,300 sq miles). The average depth of the reefs are about 25 meters (82 ft).

Much of the enormous 1,000 odd species diversity in New Caledonia is yet unclassified as new species of fish and invertebrates.The reefs provide one of the main nesting sites for the Green turtle and is a popular place to spot the rare dugong.

4. Andros, Bahamas: Affectionately known by Bahamians as the “Big Yard”, the largest island in the Bahamas, Andros is home to the third largest Barrier Reef in the World. The Reef extends over 140 miles (230kms) long.

The Island offers some exciting diving of a different kind.Wall diving and Blue hole diving. The island sits on the edge of the steep oceanic trench called the Tongue of the Ocean. This means that when you dive off one side of the island you don’t see a long low reef, but an underwater wall which goes down and down to 6000 feet. The island’s blue holes are water filled cave systems which are very popular dive sites. They attract cave divers from all over the world to dive sites such as ‘Stargate’, ‘The Guardian’ and ‘Little Frenchman’.

* image- fundensity.com

5. Red Sea Coral Reef: Located off the coast of Israel, Egypt and Saudi Arabia, the Red Sea features extensive shallow shelves, noted for their marine life and corals. The fringing reefs are said to be 5000-7000 years old and are largely formed of stony acropora and porites corals.

The reef stretches 2,000 km (1,240 miles) along the coastline and have a rich and diverse ecosystem found nowhere else. 10% of it’s 1,200 species of fish are found only here. Sharks are a common sighting and over 44 species are recorded in the Red Sea. The Dahab Blue Hole is part of this Coral Reef and a very popular dive site.