SCUBA Travel News

Researchers from Florida State University have found that Red Grouper (Epinephelus morio) dig out and maintain complex structures at the bottom of the sea. They remove sand, exposing hard rocks that are crucial to corals and sponges and the animals that rely on them. The work demonstrates that Red Groupers modify their environment, much as beavers do, creating habitat for many other animals including lobster and commercially important fish.

"Watching these fish dig holes was amazing enough,” says Felicia Coleman, lead researcher, “but then we realised that the sites served to attract mates, beneficial species such as cleaner shrimp that pick parasites and food scraps off the resident fish and a variety of prey species for the Red Grouper. So it's no surprise that the fish are remarkably sedentary. Why move if everything you need comes to you?”

“The research is incredibly valuable because it demonstrates how interconnected species are in the sea,” says Dr. Susan Williams, a professor at the University of California, Davis. “Red Groupers are the 'Frank Lloyd Wrights' of the sea floor because they are critical habitat architects. The species that associate with them include commercially valuable species- such as vermilion snapper, black grouper, and lobsters. If the groupers are overfished, the suite of species that depends on them is likely to suffer.”

Working along the West Florida Shelf, the authors observed the excavating behaviour of the Red Grouper during both their juvenile stage in inshore waters as their adult stage at depths of 100 m. The study serves to document this behaviour and its apparent impact on the biological diversity of the ocean. Their article on the study, “Benthic Habitat Modification through Excavation by Red Grouper, Epinephelus morio, in the Northeastern Gulf of Mexico,” is published in the most recent issue of the journal The Open Fish Science Journal.

Red Grouper (Epinephelus morio) is an economically important species in the reef fish community of the southeastern United States, and especially the Gulf of Mexico. It is relatively common in karst regions of the Gulf.

As juveniles, Red Grouper excavate the limestone bottom of Florida Bay and elsewhere, exposing “solution holes” formed thousands of years ago when sea level was lower, and freshwater dissolved holes in the rock surface. When sea level rose to its present state, these solution holes filled with sediment. By removing the sediment from these holes, Red Grouper restructure the flat bottom into a three dimensional matrix.

Spiny lobsters are among the many species that occupy these excavations, especially during the day when they need refuge from roving predators.

“What are the consequence of overfishing these habitat engineers?” asks co-author Koenig. “You can't remove an animal that can dig a hole five meters across and several meters deep to reveal the rocky substrate and expect there to be no effect on reef communities. The juveniles of a species closely associated with these pits, vermilion snapper, are extremely abundant around the offshore excavations. It is possible that the engineered habitat is significant as a nursery for this species, which other big fish rely on as food. One could anticipate a domino effect in lost diversity resulting from the loss of Red Grouper-engineered habitat.”

Red Grouper clearly remove sufficient sediment to transform an otherwise two-dimensional area into a three-dimensional structure below the seafloor, providing refuge for themselves and for other organisms. In the process, they expose hard substrate, thus creating settlement sites for corals, sponges, and anemones, allowing the creation of three-dimensional structure above the seafloor as well. Addition of these roles to their contribution as resident top predators suggests that they might have a disproportionately large per capita influence on the ecosystem within which they live.

Red Grouper have been harvested in the United States since the 1880s and are currently the most common grouper species landed in both commercial and recreational fisheries of the Gulf of Mexico.

Excessive fishery removals can and often do have cascading effects in marine communities that ultimately result in the loss of many species. This situation arises when the captured species has a disproportionately large influence on the system within which it lives. The Red Grouper has been shown to be one such species.

Further Reading:
Benthic Habitat Modification through Excavation by Red Grouper, Epinephelus morio, in the Northeastern Gulf of Mexico
pp.1-15 (15) Authors: Felicia C. Coleman, Christopher C. Koenig, Kathryn M. Scanlon, Scott Heppell, Selina Heppell, Margaret W. Miller
doi: 10.2174/1874401X01003010001
Florida State University

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Labels: America, coral, fish, marine biology, research, SCUBA News

Flower Garden Banks National Marine Sanctuary is among the healthiest coral reef ecosystems in the US Caribbean and Gulf of Mexico, according to a new NOAA report.

Sanctuary managers will use the report to track and monitor changes in the marine ecosystem located 70 to 115 miles off the coasts of Texas and Louisiana.

“We found that 50 percent of the area surveyed for this report is covered by live coral,” said Chris Caldow, a NOAA marine biologist and lead author on the report. “This is significant because such high coral cover is a real rarity and provides critical habitat for many different types of fish and other animals that live in these underwater systems.”

The sanctuary also is unusual in that it is dominated by top-level predators, including large grouper, jacks, and snappers that are virtually absent throughout the U.S. Caribbean. Researchers looked at the relationship between physical measures of the sanctuary’s habitat such as depth, slope and geographic location, and the nature of the fish community in each location.

The report cautions that despite the sanctuary’s relatively healthy condition, it may be more susceptible to environmental impacts than previously thought. For example, scientists observed high levels of coral bleaching and corals severely impacted from hurricane activity.

NOAA predicts changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and conserves and manages the US coastal and marine resources.

For more on Flower Garden Banks see the NOOA site.

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Labels: America, coral reef, environment, SCUBA News

Researchers at Portsmouth University and the US Coast Guard are working together to develop a computer model that will predict how long someone will survive when lost at sea.

The Search and Rescue Survival Model has been designed to take the pressure off rescuers making difficult decisions about when a search and rescue mission should be stopped.

“Using this new computer model will take pressure off humans making very emotional and sensitive decisions about when to end a search,” said Professor Mike Tipton, human and applied physiologist, from the University of Portsmouth.

“When the model predicts that a victim can no longer survive, the search and rescue team can stop or redeploy the search.

“It will ensure that Coast Guard personnel are not exposed to the high risks associated with search and rescue operations any longer than necessary and will also help to save time and resources,” he said.

The US Coast Guard currently uses a software system known as SAROPS (Search and Rescue Optimal Planning System) to calculate how far a person will have drifted and how large the search area should be.

Data such as wind speed, sea state and water temperature is entered into SAROPS along with information about the victim’s sex, height, weight and what they were wearing to determine exactly how the search should be conducted.

“Calculating survival time will add another layer to SAROPS; it will be able to predict not only where a search should be conducted but when it should be stopped,” said Professor Tipton.

“The University of Portsmouth has been able to tap into and analyze data held by the Institute of Naval Medicine and the Royal National Lifeboats Institution, both critical to the development of this survival model. To our knowledge no other similar repository of this information exists - even in the US.

“The development of this technology is very exciting. It will be trialled in American waters in late 2009 and once thoroughly tested, the aim is to roll it out to the whole of the US,” he said.

Labels: America, research, SCUBA diving, USA

The NOAA National Marine Sanctuary Program has developed a colourful new printed guide and Web page for scuba divers, about diving in America's 13 national marine sanctuaries.

“NOAA’s national marine sanctuaries have something to offer every diver, from the most experienced to the newly certified,” said Daniel J. Basta, sanctuary program director. “We hope that all divers visiting our sanctuaries will want to join efforts to help preserve and protect these special places for future generations.”

The new diving guide describes the world beneath the sea at each of the national marine sanctuaries, from the shipwrecks and nutrient-rich waters of Stellwagen Bank off Massachusetts to the pristine coral reefs of Fagatele Bay in American Samoa. The brochure also offers tips on how to be a more responsible diver by mastering buoyancy control, respecting marine wildlife, and how to volunteer for habitat monitoring activities in your local marine sanctuary.

Available in PDF format at http://sanctuaries.noaa.gov/visit/diving.html, a short version of the new guide can be downloaded and customised for use by dive operators and tourism companies to give their customers.

NOAA is the National Oceanic and Atmospheric Administration of the United States Department of Commerce.

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Labels: America, dive destination