11 September 2009
Rare Algae Saves Caribbean Coral
A rare opportunity has allowed a team of scientists to evaluate corals--and the essential, photosynthetic algae that live inside their cells--before, during, and after a period in 2005 when global warming caused sea-surface temperatures in the Caribbean to rise.The team, led by Penn State biologist Todd LaJeunesse, found that a rare species of algae that is tolerant of stressful environmental conditions proliferated in corals at a time when more sensitive algae that usually dwell within the corals were being expelled.
Certain species of algae have evolved over millions of years to live in symbiotic relationships with species of corals. These photosynthetic algae provide the corals with nutrients and energy, while the corals provide the algae with a place to live.
"There is a fine balance between giving and taking in these symbiotic relationships," said LaJeunesse.
Symbiodinium trenchi is normally a rare species of algae in the Caribbean, according to LaJeunesse. "Because the species is apparently tolerant of high or fluctuating temperatures, it was able to take advantage of a 2005 warming event and become more prolific."
Symbiodinium trenchi appears to have saved certain colonies of coral from the damaging effects of unusually warm water.
"As ocean temperatures rise as a result of global warming, we can expect this species to become more common and persistent," said LaJeunesse. "However, since it is not normally associated with corals in the Caribbean, we don't know if its increased presence will benefit or harm corals in the long term."
If Symbiodinium trenchi takes from the corals more than it gives back, over time the corals' health will decline.
In 2005, sea surface temperatures in the Caribbean rose by up to two degrees Celsius above normal for a period of three to four months, high enough and long enough to severely stress corals.
The process of damaged or dying algae being expelled from the cells of corals is known as bleaching because it leaves behind bone-white coral skeletons that soon will die without their symbiotic partners.
Although Symbiodinium trenchi saved some corals from dying in 2005, LaJeunesse is concerned that the species might not be good for the corals if warming trends continue and Symbiodinium trenchi becomes more common.
"Because Symbiodinium trenchi does not appear to have successfully co-evolved with Caribbean coral species, it may not provide the corals with adequate nutrition," he said.
The research was published in the online version of the journal Proceedings of the Royal Society B on September 9, 2009.
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Labels: Caribbean, coral, environment, marine biology, research, SCUBA News
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6 May 2009
Caribbean Big Fish Disappearing
Sharks, barracuda and other large predatory fishes disappear on Caribbean coral reefs as human populations rise, endangering the region's marine food web and ultimately its reefs and fisheries, according to a study published today in the journal PLoS One.While other scientists working in the Caribbean have observed the declines of large predators for decades, the new study by Chris Stallings documents the ominous patterns geographically in much more detail than other research to date.
“I examined 20 species of predators, including sharks, groupers, snappers, jacks, trumpetfish and barracuda, from 22 Caribbean nations,” said Stallings, a postdoctoral associate at the FSU Coastal and Marine Laboratory. “I found that nations with more people have reefs with far fewer large fish because as the number of people increases, so does demand for seafood. Fishermen typically go after the biggest fish first, but shift to smaller species once the bigger ones become depleted. In some areas with large human populations, my study revealed that only a few small predatory fish remain.”
Stallings said that although several factors — including loss of coral reef habitats — contributed to the general patterns, careful examination of the data suggests overfishing as the most likely reason for the disappearance of large predatory fishes across the region. He pointed to the Nassau grouper as a prime example. Once abundant throughout the Caribbean, Nassau grouper have virtually disappeared from many Caribbean nearshore areas and are endangered throughout their range.
“Large predatory fish such as groupers and sharks are vitally important in marine food webs,” Stallings said. “However, predicting the consequence of their loss is difficult because of the complexity of predator-prey interactions. You can't replace a 10-foot shark with a one-foot grouper and expect there to be no effect on reef communities. Shifts in abundance to smaller predators could therefore have surprising and unanticipated effects. One such effect may be the ability of non-native species to invade Caribbean reefs.”
A case in point, said Stallings, is the ongoing invasion by Pacific lionfish, which were introduced by aquarium releases.
“Lionfish are minor players on their native Pacific reefs, yet they are undergoing a population explosion and overeating small fishes in the greater Caribbean region,” said Professor Mark Hixon of Oregon State University, Stallings' doctoral advisor at OSU. “Preliminary evidence suggests that lionfish are less invasive where large predatory native fishes are abundant, such as in marine reserves,” Hixon said.
The study also demonstrates the power of volunteer and community research efforts by non-scientists. Stallings used data from the Reef Environmental Education Foundation's (REEF) online database, which contains fish sightings documented by trained volunteer SCUBA divers, including more than 38,000 surveys spanning a 15-year period.
Further Reading:
Fish predators of the Caribbean: the curse of too many people, Florida State University
Fishery-Independent Data Reveal Negative Effect of Human Population Density on Caribbean Predatory Fish Communities, PLoS One
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Labels: Caribbean, research, SCUBA News, sharks
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7 May 2008
Dominica’s Dive Fest celebrates 15 years
Dominica’s Dive Fest, the Caribbean’s longest running scuba diving festival, encourages visitors to discover the beautiful landscapes and colourful marine life within the island’s waters. Would-be divers and snorkellers as young as eight can participate in pool- or ocean-based introductory sessions to teach them the basics, with some trial sessions even offered completely free of charge. The annual event takes place in Dominica from 11th – 20th July 2008. To mark this special 15th anniversary year, many local dive centres are offering group travel packages whereby one diver goes free with every seven that book.
“Dive Fest was established to showcase the incredible marine environment of Dominica to both visitors and residents and is now one of the island’s staple events” comments Steve Bornn, director of tourism at the Discover Dominica Authority.
More information on the Dive Fest can be found at can be found at www.dominicawatersports.com. For more on diving Dominica see SCUBA Travel: Dominica
Labels: Caribbean, dive destination, Dominica, SCUBA diving, SCUBA Travel
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24 June 2007
Caribbean Corals in Danger of Extinction
The study found that 10 percent of the Caribbean’s 62 reef-building corals were under threat, including staghorn and elkhorn corals. These used to be the most prominent species but are now candidates to be listed as Critically Endangered on the IUCN Red List of Threatened Species.
A gathering of 23 scientists in Dominica analysed data on Western Tropical Atlantic corals, seagrasses, mangroves and algae, which are fundamental components of marine ecosystems providing food and shelter for numerous other organisms and local communities.
The threats to corals and other marine species include coastal pollution and human development; increased sedimentation in run-off water; thermal stress and heightened severity of hurricanes from climate change; and shifts in species dynamics due to over-fishing, according to the study. Scientists explained that the Caribbean has undergone the longest and most sustained impacts from human development since the colonization of the Americas.
Next to corals, mangroves appear to be the hardest hit. Mangrove cover in the region has declined by 42% over the past 25 years, with two of the eight mangrove species now considered Vulnerable to extinction and two more in Near Threatened status.
“Mangroves protect shorelines, shelter fish, and filter pollution,” said Aaron Ellison of Harvard University. “The Caribbean was blessed with an abundance of these useful plants, but the consensus of this workshop is that mangroves are in trouble everywhere and need to be protected and restored,” he added. Mangrove forests are being cut down to make way for coastal housing, tourism, and aquaculture development.
The scientists noted that some healthy Caribbean coral reefs still exist in well-managed marine protected areas such as Bonaire Marine Park in the Netherlands Antilles. Direct human impacts are reduced in these areas allowing most corals to thrive; however, thermal stress from global warming affects all corals in the Caribbean and must be reversed if these refuges of Caribbean beauty are to survive, they added.
Further Reading: Conservation International
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Labels: Caribbean, coral, environment, SCUBA Travel
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25 May 2007
Review: On-Line Coral Reef Course
Coral Reef Ecosystem & Food Web Course
$59.55
http://www.beautifuloceans.com/
This new course for divers discusses the coral reef ecosystem and food web. It illustrates its points using animals and plants found in and around coral reefs. For instance, the Caribbean Reef Shark is discussed as a top-level, active, predator. The authors manage to pack loads of information on their example species into a small space, without the prose becoming uninteresting. And even when I thought I knew lots about a subject they managed to surprise me. For instance, did you know that sponges may be able to live to over 1000 years old?
Although much of the information applies to coral reefs throughout the world, the example species are found in the Caribbean.
By the end of the course its authors hope that you will have learnt to appreciate all life on coral reefs from the tiniest phytoplankton to the shark. You will also have learnt how each creature is interconnected with the others.
The course is available on-line, where you work through at your own pace at your computer. It includes videos of animal behaviour and interactive quizzes. You can also take the course at selected dive schools in the Caribbean.
The course materials are well written, with many interesting asides. The Manual, in pdf format, is 119 pages long. It has a comprehensive index and is lavishly illustrated with a high-quality photograph or diagram on nearly every page.
We are delighted to be able to offer our newsletter subscribers the chance to win the course. Subscribe at http://www.scubatravel.co.uk/news.html then send us an e-mail with "Beautiful Oceans" as the subject line. Closing date is 11 June. Your e-mail entries will not be passed to any other company unless you win, in which case Beautiful Oceans will be in touch with you.
For more information visit http://www.beautifuloceans.com/
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Labels: Caribbean, coral, environment, marine biology, sealife
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4 May 2007
The Seahorse is Creature of the Month
Seahorses are delightful to spot, curling onto sponges, coral or sea grass. They range in size from the tiny Hippocampus denise which is just 16 mm, to the 35 cm (1 foot) Pacific seahorse.
Seahorses are not easily seen as they blend in with their surroundings. They can change skin colour to match their environment and even grow skin filaments to imitate seaweed or sea grass growths.
The seahorse is remarkable as the male becomes pregnant. The female seahorse deposits her eggs into the male's pouch where they are fertilised. The eggs remain in the male's pouch until they hatch, when the male gives birth to tiny seahorses. The time to hatching takes between 10 days and four weeks, depending on the species and water temperature. Male seahorses are often pregnant for as many as 7 months in the year. The natural lifespan of seahorses is not known, but believed to be from one year for small species to five years for a larger species.
Seahorses are opportunistic predators, sitting and waiting until prey come close enough and then sucking them rapidly from the water with their long snouts. Their eyes move independently of each other, maximizing their search area. They will eat anything small enough to fit into their mouths
The name hippocampus comes from the ancient Greek, loosely hippos meaning horse and campus meaning sea monster. Hippocampi refer to the mythical creatures on which the sea gods rode. Early zoologists initially classified seahorses as insects not fish.
All seahorses for which data is available are listed on the IUCN Red List of Threatened Species as either Vulnerable or Endangered. This means they are facing a high risk of extinction in the wild. There are many reasons for their vulnerability. Seahorses are exploited for traditional medicines and the aquarium trade. Male brooding means that young depend on parental survival for far longer than in most fish. Many species are monogamous so widowed animals don't reproduce until they have found a new partner. Their low population density and low mobility means that this can take some time. Habitat degradation is also a real threat to populations as they mainly inhabit shallow, coastal areas, which are highly influenced by human activities.
Further Reading
IUCN 2006. 2006 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 20 April 2007.
Project Seahorse - http://seahorse.fisheries.ubc.ca/
Seahorse photo taken in Dominica, copyright Harald Jahn.
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Labels: Caribbean, Dominica, fish, seahorse, sealife
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2 May 2007
Dominica - "the Nature Island" - Supports Whaling
Ironically, the Caribbean island markets itself as the "Nature Island", with whale watching being one of its attractions.
As a response to the financial input from Japan, a British peer, Lord Ashcroft, has commissioned an unprecedented television advertising campaign which he hopes will persuade the inhabitants of Dominica and five other West Indies nations not to support Japan's plan to overturn the ban on commercial whale hunting.
The campaign is being mounted in conjunction with the UK- and US-based Environmental Investigation Agency (EIA).
In recent years, the Japanese government, recognising the importance of national votes at the IWC, has been actively recruiting support from some of the world's smaller nations, trading financial assistance for pro-whaling votes at IWC meetings. The governments of six island nations in the eastern Caribbean, with a combined population of about half a million people, have succumbed to such overtures. Along with Dominica they are Antigua & Barbuda; Grenada; Saint Kitts and Nevis; Saint Lucia; Saint Vincent & the Grenadines. In every case, the Japanese have provided these nations with financial support in the form of fisheries aid.
Dominica joined the IWC in 1981 then left 1983 without voting on the ban on whaling in 1982. It rejoined the IWC in 1992, mostly taking a pro-whaling position, but often abstaining on key votes, including the vote to establish the Southern Ocean Sanctuary. However since 1997 Dominica has voted almost exactly in line with Japan, with 95 out of 98 votes cast mirroring Japan’s vote.
Lord Ashcroft, who has a home in Belize, said, "Amongst the sightings of which I have the most vivid and fond memories are of humpback whales in the Southern Ocean, close to Antarctica. To watch these huge and extraordinary creatures 'breach' - launching themselves head first right out of the water and then crashing back down - is in my view amongst the great wonders of the world. It is entirely beyond my comprehension that the Japanese now plan to harpoon fifty humpback whales next year in the Southern Ocean Whale Sanctuary itself. We must persuade our Caribbean friends to resist the Japanese bribery, and to vote in favour of the whales and a continuation of the ban."
The 59th annual meeting of the IWC takes place in Anchorage, Alaska, from 28th to 31st May 2007. In the run up to this meeting, the TV ad will be showing on prime time television in all six Caribbean countries that vote with Japan.
The Caribbean Whale Friends web site, funded by Lord Ashcroft, is asking people to e-mail the government departments of Dominica and the other nations, urging them to oppose commercial whaling. Contact details are at http://www.caribbeanwhalefriends.org/country_2.htm
The television commercial can be downloaded from the following link:
Username: ftp017 / password: whalepass
ftp://ftp.rushes.co.uk/
You can also view it at http://www.caribbeanwhalefriends.org/
More information:
Environmental Investigation Agency
Caribbean Whale Friends
SCUBA Diving in Dominica
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Labels: Caribbean, Dominica, environment, whale and dolphins
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15 December 2006
Splendid Toadfish - Creature of the Month
Toadfish are found on the sand and mud bottoms of coastal waters worldwide. They usually have broad heads and drab colours, and look something like toads. The Splendid Toadfish, though, is different.
Splendid Toadfish is attractively patterned in purple.
Most of its fins are edged in yellow with the pelvic fin
being entirely yellow. It also has a yellow mouth.
Also known as the Coral Toadfish, Sanopus splendidus
generally lives on sand under crevices or coral heads
in clear water, 10-25 m. It hunts at night, preying on
small fishes, snails and polychaete worms.
The Splendid Toadfish was thought to be only found in
Cozumel (Mexico) but sightings have also been reported
in Belize. However, it is not widespread and is
classified as vulnerable by the IUCN Red List of
Threatened Species (www.iucnredlist.org). This means
that although it is not Critically Endangered or
Endangered it is facing a high risk of extinction
in the wild in the medium-term future.
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