Archive for 09/13/2011

mlive –

Michigan waters have more than 500 shipwrecks officially logged. Local divers are determined to find more.    

“The history is certainly a big draw for divers in Michigan, because there’s so much history on the bottom of the lake,” says Chuck Larsen, owner of Ocean Sands Scuba in Holland. “Everything from glacier remains to boulder fields to wrecks. There’s billions of dollars of commerce just littering the bottom of Lake Michigan.”  

While Michigan divers are quick to compliment the cold waters they venture into, novices could easily be confused by the desire to plunge into one of the Great Lakes’ 40 degree depths. But this cold water is part of what makes these dives unique.

“Some of these wrecks you see, these ships went down hundreds of years ago,” says Ken Engelsman, co-owner of Michigan Diving Center in Spring Lake. “But in this cool, dark water they look like they just went down a few weeks ago. It’s just amazing how well fresh water preserves everything.”

The preservation, not to mention the abundance of wrecks in Michigan waters, is what lures divers and keeps bringing them in for more.

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Science Daily –

The Academy of Natural Sciences has announced the discovery of a new species of large predatory fish that prowled ancient North American waterways during the Devonian Period, before backboned animals existed on land.

Drs. Edward “Ted” Daeschler and Jason Downs of the Academy and colleagues from the University of Chicago and Harvard University describe the new denizen of the Devonian they named Laccognathus embryi in the current issue of the Journal of Vertebrate Paleontology.

The 375-million-year-old beast was discovered by the same group of researchers who discovered Tiktaalik roseae, the important transitional animal considered “a missing link” between fish and the earliest limbed animals. The fossil remains of the new species were found at the same site as Tiktaalik, on Ellesmere Island in the remote Nunavut Territory of Arctic Canada.

The Devonian Period (415 to 360 million years ago) is often described as the Age of Fishes because of the rich variety of aquatic forms that populated the ancient seas, lagoons and streams. Laccognathus embryi is a lobe-finned fish whose closest living relative is the lungfish. The creature probably grew to about 5 or 6 feet long and had a wide head with small eyes and

robust jaws lined with large piercing teeth. “I wouldn’t want to be wading or swimming in waters where this animal lurked,” said Daeschler, co-author of the paper and the Academy’s curator of vertebrate zoology. “Clearly these Late Devonian ecosystems were vicious places, and Laccognathus filled the niche of a large, bottom-dwelling, sit-and-wait predator with a powerful bite.”

The researchers named the new species in honor of Dr. Ashton Embry, a Canadian geologist whose work in the Arctic islands paved the way for the authors’ paleontological explorations.

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Nadine Lymn –

Earth’s coral reefs have not been faring well in recent decades, facing multiple threats from pollution, disease, elevated water temperatures, and overfishing. Often referred to as the “rainforests of the Sea,” coral reefs support a wide variety of marine life, help protect shorelines, and contribute significantly to tourism and the fishing industry. A new study looks at a rare but catastrophic impact on reefs: the damage caused by natural disasters such as an earthquakes.

In May of 2009, a powerful, magnitude-7.3 earthquake shook the western Caribbean, causing lagoonal reefs in Belize, 213 kilometers (132 miles) from the epicenter, to avalanche and slide into deeper water. As reported in a preprint article of Ecology, a journal of the Ecological Society of America, Richard Aronson of the Florida Institute of Technology and colleagues analyzed data that suggest how the history of the reef will influence its recovery.

During the quarter-century before the earthquake struck, the reefs had gone through mass mortalities of two sequentially dominant coral species. Novel events in their own right, these mass mortalities were instantly “rendered moot” on half the reefs, which were destroyed when the earthquake hit.

Aronson and colleagues’ work focused on a 375-square-kilometer (144-square-mile) area of the Belizean Barrier Reef, which they monitored from 1986 to 2009. The group revisited 21 sites in 2010 to determine the impacts of the earthquake. They found that approximately half the reef slopes had slabbed off and slid into deeper water. Only sediment and the skeletal debris of corals remained.

Beginning in 1986, a bacterial infection called white-band disease killed virtually all the then-dominant staghorn coral (Acropora cervicornis) in the study area. By 1995, lettuce coral (Agaricia tenuifolia) had taken over the number-one spot. But when high temperatures from the 1998 El Nino–Southern Oscillation, which were aggravated by global climate change, caused mass coral bleaching, lettuce coral disappeared. An encrusting sponge (Chondrilla caribensis) colonized its skeletal remains, along with seaweed.

What’s astonishing about this series of events, say the authors, is that—as evidenced by radiocarbon-dating of reef cores—staghorn coral had dominated the reefs for nearly 4,000 years.

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