Staghorn coral (Acropora cervicornis), a threatened species

by B. N. Sullivan

When we think of endangered or threatened species in the ocean, we usually think of sea turtles, or whales, or certain kinds of fishes.  Unfortunately, populations of some coral species also have been seriously depleted, and some are at risk for extinction.

According to the language of the Endangered Species Act of 1973 (ESA), a species is considered to be 'endangered' if it is in danger of extinction throughout all or a significant portion of its range.  A species is considered 'threatened' if it is likely to become an endangered species within the foreseeable future.

The pretty Staghorn coral (Acropora cervicornis) in the center of the photo above is officially classified as a 'threatened' species.  Acroporid corals like this one are important reef-building corals, and they provide a habitat for fishes and invertebrates..

In the United States, this species is found in the Florida Keys, and along the Atlantic coast of Florida as far north as Boca Raton, but it is absent from U.S. waters in the Gulf of Mexico, according to the National Oceanic and Atmospheric Administration (NOAA).  A. cervicornis does occur in the western Gulf of Mexico, and also in the Bahamas, the Caribbean islands, and Venezuela.

In a few places (very few)  it is still possible to see large stands of this antler-shaped coral, but more often these days, the species exists only as small colonies, like the one in the photo above.  In fact, reef surveys have shown that, since 1980, populations of A. cervicornis have collapsed, declining by up to 98% throughout the range.

So, what is responsible for such a marked decline?  The number one threat to Acroporid corals is White-band Disease, a devastating, rapidly spreading disease that destroys the tissues of the coral.  The cause of White-band Disease is poorly understood, but the results are devastating.

A. cervicornis is "particularly susceptible to damage from sedimentation and is sensitive to temperature and salinity variation," according to NOAA. In addition, NOAA lists hurricanes, increased predation, bleaching, algae overgrowth, and human impacts among the factors that threaten Acroporid corals.

Fortunately, conservation efforts have been initiated to manage and protect what remains of the A. cervicornis population.  In some areas -- such the U.S. Virgin Islands, Puerto Rico, and the Florida Keys National Marine Sanctuary (FKNMS) -- restoration activities also have been undertaken following hurricanes, ship groundings, and the like.  Nevertheless, restoration efforts, such as re-attachment of broken coral fragments and attempts to culture and settle coral larvae, are painstaking and have had limited success.

What you can do:

• When you snorkel, dive, or go to the beach, NEVER stand on or touch coral.
• Do not collect coral, dead or alive.  (Federal and State regulations prohibit collection of all soft and hard corals.)
• Divers should maintain proper buoyancy, be careful not to kick corals when swimming over them, and keep gear items such as hoses, gauges, etc. secured so that they do not drag across the coral.
• Boaters should use mooring buoys wherever they are available.  If you must anchor, avoid doing so near coral; instead of throwing your anchor, swim it down and place it on sand.

The above rules apply to all corals, of course, not just Acroporid corals.

More information: NOAA Fact Sheet: Atlantic Acropora corals - 2-page 'pdf' file

Stingrays: Dangerous or Not?

by B. N. Sullivan

Our previous pictorial post about a dive site in the Cayman Islands called Stingray City generated a lot of interest, and quite a few questions about stingrays. We decided to tell our readers some more about these interesting marine animals.

Stingrays are found in warmer waters around the world. Stingrays are Elasmobranchs - a classification of fishes that include sharks and other kinds of rays, like Mantas and Eagle Rays. Elasmobranchs differ from other fishes in that their skeletons are made of cartilage rather than bone.

There are many species of stingray. The species pictured on this page, and in our photo essay about Stingray City, is the Southern Stingray (Dasyatis americana). It can be found in the warmer latitudes of the Western Atlantic, and throughout the Caribbean and the Gulf of Mexico. They are found most often in relatively shallow waters where there are sandy bottoms, because that is where they find their food.

The diet of these creatures consists of small animals that live in the sand - mostly shellfish, small crustaceans and worms. The stingray feeds by hovering directly over the sand and fluttering the wing-like edges of its body disc to clear away the top level of sand. This exposes the little creatures that live just under the sand, and the stingray plops on top of them and eats them.

The photos in an earlier post on The Right Blue shows a Southern Stingray hunting for its dinner on a sand flat in the Turks and Caicos Islands.

The stingray's mouth and gill slits are on the underside of the body. You can see the mouth and gill slits clearly in the second photo of our post about Stingray City. The stingray's eyes are on the top of its body, as you can see in the photos on this page. When stingrays lie on the sand, they flutter their 'wings' a bit to cover themselves with sand until only their eyes and the end of their tail are visible.

But what about the 'stinger' that gives the stingray its common name?

The 'stinger' actually is a barbed spine that is located at the base of the stingray's tail. The barb contains a venom and is the stingray's defensive weapon. It does not use the barb on prey.

Stingrays spend a lot of time swimming just over the surface of sandy bottoms, looking for food. When they feed, and sometimes when they rest, they settle onto the bottom and lie flat. Thus, whether resting or hunting, they are subject to predation from above. If they are disturbed from above while they are on the sand, they quickly erect the barbed spine at the base of their tail as a defense.

The stingray's tail does not have a 'stinger' at the end of it, and they do not sting divers or prey by whipping their tails around. Most people who have had nasty encounters with stingrays have been divers and waders who accidentally stepped on a ray, or swam closely over one that was half-buried in the sand.

Many people will recall that Steve Irwin, the well-known Australian environmentalist and television personality, met his death after an unfortunate encounter with a stingray in 2006. Ironically, Steve was filming an underwater documentary about the ocean's deadliest creatures at the time of the incident.

Apparently Steve Irwin either laid down on top of a stingray, or swam just a few inches above where one was buried in the sand. The stingray did what stingrays do when some creature threatens them from above: it quickly raised the barbed spine at the base of its tail. Unfortunately, the barb pierced Steve Irwin's chest.

Irwin's death was sobering to divers and especially to underwater photographers. I think it is safe to say that every underwater photographer or videographer in the world has spent a considerable amount of time lying or kneeling on the sand to take pictures. Steve Irwin's death was a dramatic reminder to look carefully at the surface of the sand for evidence of a partially buried stingray before settling there.

So, are stingrays dangerous? In certain circumstances, yes; in most cases, no.

Here are some earlier posts on The Right Blue that feature stories and photos of stingrays:

• Stingray City, Grand Cayman Island - photos of a Southern Stingrays interacting with divers
• Picture this! - photos of a Southern Stingray hunting with a Bar Jack (Caranx ruber)
• The 'eyes' have it - features close-up images of a Blue-spotted Stingray (Taeniura lymma)
• Blue Spotted Stingray at Pulau Sipadan - photo only
• On a collision course with critters in the sea - story and photo of a large deep-dwelling stingray species in Hawaii (at the bottom of the page)

Loggerhead sea turtles need further protection

Over our lifetime of diving and being around the ocean, we have had close encounters with many sea turtles. We like sharing our sea turtle stories and photos, and we know that readers of The Right Blue like them, too. We've told our readers about Green sea turtles (Chelonia mydas) in Hawaii (including a special Green sea turtle named Myrtle), and yesterday we featured a Hawksbill turtle (Eretmochelys imbricata) that we had encountered in the Red Sea. Today we'd like to introduce you to another species of sea turtle.

Meet the Loggerhead (Caretta caretta). While there are populations of Loggerhead turtles around the world, the North Atlantic Loggerheads are genetically distinct from other populations. They are an important part of the marine ecosystem along the coasts of the southeastern United States, yet many marine scientists believe that they are on the brink of extinction.

In the past, Loggerheads were actively hunted for their meat, and their eggs were gathered as food. Today the species is protected internationally, although major threats to their survival remain. Loggerheads are most at risk from commercial fishing activities, and from degradation of their nesting grounds.

Loggerhead sea turtles become entangled in gill nets, and get caught in trawls and scallop dredges. Like all sea turtles, Loggerheads are air breathers, so they must surface from time to time in order to breathe. Entanglement in fishing gear prevents them from surfacing, so they drown. Turtles that do not drown outright often are injured in the process of struggling to escape fishing gear.

Fisheries that employ long-lines -- gear that consists of hundreds of baited hooks on a single line to catch fish -- also inadvertently catch Loggerheads. Long-line fishing is efficient, and is probably less ecologically damaging than trawling or dredging (in terms of 'by-catch'). Nevertheless, no one has yet discovered a method to eliminate the danger of long-lining to the sea turtles who are attracted to the bait, and who end up swallowing large steel fishing hooks along with that bait.

In the United States, there are Loggerhead nesting beaches along the Atlantic coast, particularly in North and South Carolina, Georgia, and Florida. Loggerheads also nest on beaches of States bordering the Gulf of Mexico, from Florida to Texas. Sadly, the number of nests on these beaches is declining, and in the case of Florida, the number of Loggerhead nests has declined by about 50% over the past decade -- a startling figure!

An explosion of beachfront development is partly to blame. Some coastal areas are simply being eliminated as nesting grounds as housing and commercial activities encroach on them. Other nesting areas are being damaged by pollution, and disturbed by human and motor vehicle traffic. Turtles swimming in populated areas also are more at risk from collisions with boats.

Today two conservation organizations, Oceana and the Center for Biological Diversity, have petitioned the Federal government of the United States to strengthen protection for North Atlantic Loggerhead turtles. They are urging the National Marine Fisheries Service, the agency responsible for protecting Loggerheads in ocean waters, and the U.S. Fish and Wildlife Service, the agency responsible for protecting turtles on land, to change the designation of these Loggerheads from "threatened" to "endangered" under the U.S. Endangered Species Act.

In addition to the threats from commercial fishing and degradation of nesting areas mentioned above, these conservationists also believe that climate change is now impacting the survival of Loggerheads. As summarized in a press release issued by Oceana and the Center for Biological Diversity:

Many marine biologists fear climate change will stress loggerhead sea turtle populations even further. Climate change can cause severe storms, erosion and sea level rise, all of which can affect sea turtle nesting on beaches. Rising temperatures caused by climate change may alter the timing or location of nesting or may increase the number of female turtles, because the sex of the hatchlings is temperature dependent. Climate change may also affect sea turtles by altering ocean currents and migration routes. Finally, ocean acidification caused by rising carbon dioxide levels breaks down the shells of preferred turtle prey, such as mollusks and crustaceans, and could alter turtles' food supply.

We decided to tell our readers about Loggerhead sea turtles today in support of this effort by Oceana and the Center for Biological Diversity to recruit greater protection for these magnificent animals. For more information, please visit the Sea Turtle pages on the Oceana website.

We have crossed paths with very few Loggerheads over the years. As a result, we had no photos of Loggerheads in our personal collection to use for this article. All of the photos accompanying today's post came from external sources. The nice Loggerhead portrait near the top of the page came from Wikimedia Commons, and the photos of the Loggerhead with the fishing hook in its mouth were supplied by Oceana. We thank the donors of these photos for allowing us to publish them on The Right Blue.

Some of the factual information in this article was derived from Oceana's report, Climate Change and Commerical Fishing: A One-Two Punch for Sea Turtles (12 page 'pdf' file), and the Loggerhead Sea Turtle 5-year Review, published in August of 2007 by the U.S. National Marine Fisheries Service, and the U.S. Fish and Wildlife Service. (67 page 'pdf' file)