August 31, 2011
Prior to beginning our research at Little Inagua, we knew there was some “weather” occurring in the eastern Caribbean that we had to keep our eyes on. At first, we thought we could leave one day early, transit back to Nassau, and avoid the storm. However, when we awoke the morning of August 22nd, Captain Steve informed us that the questionable weather off to the east was blowing up into a Tropical Storm… known as Irene.
The path of Hurricane Irene
August 30, 2011
From August 19th-22nd, we experienced nothing but great wall diving around Little Inagua, which is always a diver’s delight. The island of Little Inagua is five miles to the northeast of Great Inagua, and hosts a large Land and Sea Park. The island is 30 square miles and home only to herds of feral donkeys and goats, descendants of stock introduced by the French. A protective reef surrounds Little Inagua on all sides, beginning at 14m depth and dropping nearly vertically to the ocean floor.
Nearly vertical wall off Little Inagua
The winds come from the southeast in the summertime creating 4-6 foot swells and making scuba surveys on the south and east facing coastlines nearly impossible. Charts show the north and south ends of the island as sheer drop-offs with reefs almost exclusively on the east and west coasts. This layout combined with the windy weather limited our research capabilities around Little Inagua to mostly the north and west sides.
August 18, 2011
Throughout most of the Caribbean, there are species of coral that are common and easily spotted on a dive, and those that are rare and difficult to locate. Experienced divers can usually characterize a reef fairly quickly based on the types of corals growing there. Some common corals that are generally easy to find include star corals (Montastrea sp.), starlet corals (Siderastrea sp.) and brain corals (Diploria sp.). On the other hand, pillar corals (Dendrogyra cylindrus) and staghorn corals (Acropora cervicornis) are generally quite rare. The corals of Hogsty Reef and Great Inagua have so far not followed this formula. Living Oceans Foundation researchers have seen an unusually high number of rare corals. Specifically, pillar corals appear to be thriving on the reefs here and staghorn corals are demonstrating remarkable resilience.
Pillar coral (Dendrogyra cylindrus) is not a rare find around the Inaguas
August 17, 2011
Ten days ago scientists and crew from the Golden Shadow deployed a piece of equipment known as a Recording Doppler Current Profiler (RDCP). Today, team members collected it from the waters off the western side of Great Inagua. The RDCP, a type of acoustic Doppler profiler, has been suspended over the sea floor collecting data at regular intervals to provide the expedition with some critical information that would be difficult, if not impossible, to collect manually. The RDCP measures how fast water is moving as it passes over a set point from the sea floor to the surface; a vertical span is known as the water column. A secured RDCP can measure the speed of the current at regular intervals from its anchorage to the surface. The RDCP uses acoustic (sound) waves to measure water currents. Like a dolphin using echolocation, the device sends out a series of pings. These waves of sound bounce off of the surrounding environment and return to the instrument where any change in pitch is recorded.
The Recording Doppler Current Profiler (RDCP) suspended in the water column
August 16, 2011
Have you ever wondered if reef fish communicate, sleep or defend a territory? Scientific divers, Ken Marks and Dave Grenda, are on our team to survey and observe Caribbean reef fish in a quest to better understand how they contribute to reef health. Ken and Dave have been participating in the Global Reef Expedition as our onboard fish experts. Their assignment on each dive is to record a number of attributes about the fish populations in the Inaguas and Hogsty Reef. To achieve this objective, on each dive they reel out a 30-meter measuring tape, while swimming along holding a T-shaped meter stick used to estimate fish size and distance. This process is repeated a few times during each dive. The diver records the species, sizes, and abundance of fishes encountered along the transect line. This type of survey is known as a ‘belt transect’ and gives researchers a sample of reef fish density and biomass in a specific location.
Conducting a belt transect with a T-shaped meter stick off of Great Inagua, Bahamas
August 15, 2011
Although no one knows for certain how they came to be in the Caribbean Sea, lionfish are probably here to stay. Living Oceans Foundation research divers have noted lionfish on every dive in Great Inagua and Hogsty Reef so far. Atlantic and Gulf Rapid Reef Assessment (AGRRA) surveys first detected lionfish around Andros Island, Bahamas in 2007, although they may have been present prior to that date. Since then, their numbers have been steadily rising, as has the size of the individual lionfish observed during survey dives. Today, lionfish are present throughout the Caribbean. In fact, lionfish have been spotted in the Western Atlantic Ocean as far north as Rhode Island, and as far south as Colombia.
Lionfish photographed on the reefs around Great Inagua, Bahamas
August 14, 2011
Like jumping feet first into the rabbit hole made famous in “Alice in Wonderland” by Lewis Carroll, the deeper you dive on a reef, the more things change in interesting ways. “Curiouser and curiouser,” mused Alice as she delved into her subterranean world. A diver passing through a deep coral reef might well think the same thing. This morning, CAPT Phil Renaud, Executive Director of the Khaled bin Sultan’s Living Oceans Foundation and Dr. Bernhard Riegl of the National Coral Research Institute based out of Nova Southeastern University in Florida (supported by the Dive Safety Officer and Videographer), had a rare opportunity to experience the deep reef first-hand. The purpose of their excursion into the depths was to compare a small portion of the deep reef around Great Inagua with the shallow reefs we have been surveying thus far on the expedition.
A sheer drop-off to deeper water on the reef around Great Inagua
The divers immediately noticed that the hemi-spherical shapes many coral species adopt in the shallows morphed into a flat, plate-like formation at depth. This growth pattern is caused by lower amounts of sunlight penetrating the water as depth increases. To maximize growth rates and, in turn, the amount of sunlight being received by their zooxanthellae algae [zoo-zan-thel-ee], corals adopt a flat morphology at depth. Individual coral animals, known as polyps, house a multitude of microscopic zooxanthellae in their tissues. Thousands of specks of the minute algae photosynthesize, using carbon dioxide released by the coral as it metabolizes. This process also provides the polyps with oxygen and organic nutrients. The coral-zooxanthellae partnership is known as a symbiotic relationship. In this case, because both parties benefit from their interactions, scientists refer to it as mutualism.
Deep-water corals exhibiting a flat plate-like morphology to maximize their ability to harvest available sunlight
August 13, 2011
Over the past few decades there has been a rapid decline in the health of shallow water scleractinian corals (stony or hard corals). Simultaneously, there has been a steady increase in the number of coral diseases being reported. Many of these diseases have been identified by field characteristics – the color of the affected tissue, the shape of exposed skeleton, advancing patterns of tissue loss, or the presence of unusual structural features – rather than by the agent causing the disease. For this reason, coral diseases have acquired names like black-band disease, red-band disease, dark spots, white pox disease and white plague. Unfortunately, there have been relatively few scientific studies that have conclusively described the structural and cellular (morphological) changes underlying these different syndromes, or even the causes of the various changes.
Agaricia agaricites showing dark spots disease on the reef around Great Inagua
August 12, 2011
The Golden Shadow is back on the western shore of Great Inagua and the day has been packed with activity, as team members leave and arrive, new research projects are launched, and scientific surveys around Great Inagua continue. Early this morning we bid farewell to our Bahamian friends who have been on board since the beginning of the expedition helping with scientific surveys of Great Inagua and Hogsty Reef. Two new team members joined us today, Alannah Vellacott, a student at College of The Bahamas, and Tavares Thompson, Park Warden with the Bahamas National Trust.
One research team in particular is excited to begin following-up on previous research projects from the Cay Sal expedition (26 April to 18 May 2011). Team Parrotfish is studying herbivorous reef fish, and is made up of Dr. Sonia Bejarano, a Living Oceans Foundation Fellow, and Christian Clark, the current North American Rolex Scholar. Dr. Bejarano has been studying herbivorous reef fish internationally. In the Bahamas, these are usually species of parrotfish and surgeonfish. She is attempting to understand how many herbivorous fish live in an area (their abundance) and how much they feed in and around the coral reefs. During the Cay Sal expedition, Dr. Bejarano used fish counts and underwater video cameras to record herbivorous reef fish abundance and feeding behavior respectively.
The Princess Parrotfish (Scarus taeniopterus) is a common herbivore on the reefs around Great Inagua
Read the rest of How Does Wave Action Impact Grazing Reef Fish? »
August 11, 2011
In 1997-1998, the marine equivalent of a massive and destructive forest fire overwhelmed numerous coral reefs around the world. Caribbean coral biologists still speak of the bleaching event of 1998 in reverential tones. A powerful El Niño season was a factor in generating extreme tropical sea surface temperatures. As a consequence, over-stressed corals everywhere released their symbiotic algae known as zooxanthellae [zoh-zan-thel-ee]. This phenomenon is known as coral bleaching.
Millions of microscopic zooxanthellae play a critical role in a coral colony’s ability to both metabolize, and process waste. The tiny algae also give corals their color. When zooxanthellae are released into the water column, the remaining coral head appears as white as its underlying calcium carbonate skeleton. A coral colony can survive for a limited time without zooxanthellae, as long as environmental conditions return to normal. Slowly, new zooxanthellae will reappear in the coral tissues, and the corals, although susceptible to disease and algal overgrowth, having a fighting chance of recovery. However, in 1998, conditions did not level out and an estimated 16% of the world’s corals died (Wilkinson 2000). In some regions, the rate of mortality was probably much higher, and the relatively shallow western Caribbean and Bahamas were likely hit especially hard.
A bleached brain coral becoming overgrown with algae. Photo: NOAA
To understand our initial observations taken at eight study sites on Hogsty Reef, thirteen years after the 1998 massive bleaching event, let’s return now to the forest fire analogy. Imagine large, healthy coral heads on a reef as the old growth trees of a forest. When a raging fire burns through a forest, it destroys almost all of the young seedlings and saplings, leaving behind only a few of the strongest old-growth trees. However, any remaining live trees are weakened and damaged by the fire and are susceptible to diseases and parasites. The surviving trees are also responsible for reseeding the forest with the next generation of seedlings.
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