Ancient Black Coral in the Gulf of Mexico

Black corals are a group of deep water, tree-like corals related to sea anemones. Though black coral's living tissue is brilliantly colored, it takes its name from the distinctive black or dark brown color of its skeleton. For the first time, scientists have been able to validate the age of deep-sea black corals in the Gulf of Mexico. They found the Gulf is home to 2,000 year-old deep-sea black corals, many of which are only a few feet tall. These slow-growing, long-living animals thrive in very deep waters—300 meters (984 feet) and deeper—yet scientists say they are sensitive to what is happening in the surface ocean as well as on the sea floor.


"The fact that the animals live continuously for thousands of years amazes me,”� said Dr. Nancy Prouty of the U.S. Geological Survey Pacific Coastal and Marine Science Center, who analyzed the coral samples that were collected by the USGS and colleagues as part of several ongoing deep-sea coral ecosystem studies between 2003 and 2009. “Despite living at 300 meters and deeper, these animals are sensitive to what is going on in the surface ocean because they are feeding on organic matter that rapidly sinks to the sea floor. Since longevity is a key factor for population maintenance, recovery from a disturbance to these ecosystems, natural or man made, may take decades to centuries."

Reliably age dating the corals, as done in the recent study, is a critical step in using them as natural archives of environmental change.

Like shallow-water coral reefs, deep-sea coral-reef ecosystems are among the most diverse and productive communities on Earth, providing shelter and feeding grounds for commercial and non-commercial fish species and their prey, as well as breeding and nursery areas. Activities that affect both the seafloor and the surface ocean, such as certain methods of petroleum exploration and commercial fishing, can impact these ecosystems.

The skeletons that these animals secrete continuously over hundreds to thousands of years offer an unprecedented window into past environmental conditions. Age dating used in combination with emerging technologies, such as sampling skeletal material with a laser to determine its chemical composition, enables scientists to reconstruct environmental conditions in time slices smaller than a decade over the last 1,000 to 2,000 years.

Black corals grow in tree- or bush-like forms. Scientists confirmed that black corals are the slowest growing deep-sea corals. They grow 8 to 22 micrometers per year as compared to the shallow-water reef-building coral, typically found in tropical areas like Hawaii, which grows about 1 mm per year, or 65 times as fast as black coral. Human fingernails grow about 3 mm per year, or 200 times faster than black coral.

Black corals can capture and record in their skeletons the history of changing concentrations of carbon in surface waters and the atmosphere. Unlike the skeletons of most shallow-water corals, which consist of calcium carbonate, black coral skeletons are composed mainly of organic matter: successive layers of protein and chitin (a long molecule containing carbon, oxygen, hydrogen, and nitrogen) glued together by a cement layer. These skeletons are very similar to insect cuticles in that they are quite flexible and can thus bend in water currents.

Like trees, black corals exhibit radial growth, with the oldest skeletal material found in the center and successfully younger material building out toward the edge. Viewed in a horizontal cross section, the black coral’s growth bands resemble tree rings.

In 2008 some black coral off the coast of Hawaii was found to be as old as 4000 years. Located on the floor of the Pacific Ocean, off Hawaii, the 3 meters tall, (extremely) long-lived "black coral" could yield some valuable clues about past incidents of climate change; specifically, it could better scientists' understanding of how oceans draw down carbon dioxide - and of ocean acidification in general. Brendan Roark of Texas A&M University, had led a research expedition in 2006 to study the corals' climate records.

A full copy of the present study can be found online in the Feb. 10, 2011, edition of “Marine Ecology Progress Series.”

Source: www.enn.com

Coral Reef Ecosystems - Learn and Act

What is Coral?


Corals are composed of thin plates, or layers, of calcium carbonate secreted over time by hundreds of soft bodied animals called coral polyps. Polyps range in size from a pinhead to a foot in length. Each polyp lives in a symbiotic relationship with a host zooxanthellae that gives the coral its color. Zooxanthellae take in carbon dioxide, process it through photosynthesis, and give off oxygen and other important nutrients that are then used by the host polyp. As in all photosynthesizing organisms, this means that corals must be exposed to a sufficient amount of sunlight. This confines most corals to shallow waters that are clean and clear.

There are two kinds of corals: hard and soft. Hard corals (Scleractinia), such as brain, star, staghorn, elkhorn and pillar corals have rigid exoskeletons, or corallites, that protect their soft delicate bodies. Soft corals (Gorgonians), such as sea fans, sea whips, and sea rods, sway with the currents and lack an exoskeleton.


What is a coral reef?

Coral reefs are one of the most biologically diverse ecosystems on earth, rivaled only by tropical rain forests. They are made up not only of hard and soft corals, but also sponges, crustaceans, mollusks, fish, sea turtles, sharks, dolphins and much more. Competition for resources such as food, space and sunlight are some of the primary factors in determining the abundances and diversity of organisms on a reef. Each component of a coral reef is dependent upon and interconnected with countless other plants, animals and organisms. This means that fluctuations in the abundance of one species can drastically alter both the diversity and abundances of others. While natural causes such as hurricanes and other large storm events can be the stimulus for such alterations, it is more commonly anthropological forces that effect these types of shifts in the ecosystem.

For example, overfishing of herbivorous fish often results in increased growth of algae and sea grasses. This generally results in an increase in other herbivorous marine life, such as sea urchins. Over time all ecosystems will naturally establish these types of balances between predators and prey and organisms in competition for similar resources. The question is how long those balances take to establish and what other reef relationships they affect.


What is the coral reef ecosystem?

The health, abundance and diversity of the organisms that make up a coral reef is directly linked to the surrounding terrestrial and marine environments. Mangrove forests and seagrass beds are two of the most important facets of the greater coral reef ecosystem. Mangroves are salt-tolerant trees that grow along tropical and sub-tropical coasts. Their complex root systems help stabilize the shore line, while filtering pollutants and producing nutrients. Their submerged roots and detritus provide nursery, breeding, and feeding grounds for invertebrates, fish, birds, and other marine life. Many of the animals raised in mangroves migrate to coral reefs for food, spawning and habitat.

Seagrasses are flowering plants that often form meadows between mangrove habitats and coral reefs. They form the foundation of many food webs, providing nutrients for everything from sea urchins and snails to sea turtles and manatees. Seagrass also provides protection and shelter for commercially valuable species such as stone crabs, snappers and lobsters. Additionally, they filter the water column, prevent seabed erosion, and release oxygen essential for most marine life.

The ecosystem services of mangroves and seagrass are vital to the long term health of coral reefs.

Source: http://reefrelief.org/


There is another very important element of the reef ecosystem that is often over looked: the land. Pollutants, nutrients and litter enter near shore waters through rivers, streams, underground seepage, waste water and storm water runnoff. Even areas hundreds of miles from the coast can effect the clarity and quality of water flowing to the reef. It does not matter how far removed a pollutant may seem, it all flows down stream and it can all impact our marine environment and our reefs.