The net slowly was brought back up to the surface, all quiet on board the Commonwealth Scientific and Industrial Research Organisation (CSIRO)’s research vessel Investigator as they waited to see what would be brought up. This would be the first biodiversity survey at the new Cocos (Keeling) Islands Marine Park located off Western Australia, and all were anxious to see what would be pulled up.
Museums Victoria Research Institute senior collections officer Dianne Bray, who was onboard, said the net from their final trawl at first looked disappointing: “When we put these nets down hoping to get animals, we are surveying biodiversity. So initially we thought it was just full of sediment and manganese nodules. Then we started going through it and one of my colleagues spent at least an hour just going through it picking shark teeth. It was amazing, it really was!”
Megalodon ancestor tooth and other shark teeth collected from seafloor near Cocos (Keeling) Islands … [+]
More than 750 teeth were extracted from ocean floor near Muirfield Sea Mountain, south west of the Cocos (Keeling) Islands. One of the teeth that were found was identified as a megalodon shark, or its closest ancestor. “The teeth look to come from modern sharks, such as mako and white sharks, but also from ancient sharks including the immediate ancestor of the giant megalodon shark,” said Western Australian Museum Curator of Fishes Dr. Glenn Moore. “This shark evolved into the megalodon, which was the largest of all sharks but died out about 3.5 million years ago.”
This, along with teeth belonging to the mako shark and two great white shark relatives, was astounding to the scientists onboard. “We’ve also found a few mako and white shark teeth during the underway voyage but nothing like the numbers found during the previous voyage. It’s incredible to think we’ve collected all these teeth in a net from the seafloor some 4 to 5 km below the ocean surface,” Moore said, who went on to say it was fascinating that such a large number of teeth were collected from a relatively small area on the seafloor. Moore told ABC News that he doesn’t know of any obvious explanation of why they might all be together other than perhaps it was a low point in the ocean floor, so they would eventually make their way down. “I have never seen anything like this, or heard of anything like that, it’s a unique opportunity to have an almost complete collection from one spot. And when the palaeontologist get their hands on them I’m sure they’ll be very happy.”
Scientist Helen O’Neill from CSIRO with the undescribed striped hornshark found in this voyage.
It’s not only the palaentologists that are happy. Shark expert Dr. Will White from CSIRO’s Australian National Fish Collection said the voyage was not only success because they discovered this graveyard – it was the collection of new specimens! Dr. John Keesing from CSIRO, who is Chief Scientist on the voyage, agreed and said the discovery of new species was quite common on these sort of biodiversity surveys. “It’s been estimated that around a third of the species collected on recent biodiversity survey voyages on RV Investigator may be new to science,” Dr Keesing. “The discoveries we make aren’t just limited to new species. These voyages give us the opportunity to learn more about marine ecosystems, as well as species range, abundance and behaviour.”
White was especially excited about the collection of a specimen of a new species of shark! “Early in the voyage, we collected a striking small, stripey hornshark,” said Dr White. “This species is unique to Australia, but it hasn’t yet been described and named. The specimen we collected will be incredibly important to science because we’ll use it to describe the species.” Hornsharks belong to the family Heterodontidae (also known as bullhead sharks), known for their blunt heads, curved snouts, long mouths, and sharp spines on their dorsal fins. In Australia, the most well-known species is the Port Jackson shark (Heterodontus portusjacksoni) found in the southern waters of the continent. Predominantly seen in shallow habitats and a well-studied shark, it’s a stark contrast to this new species which lives in water over 492 feet (150 meters) deep and we know nothing about its behavior. “Australia has a truly enormous marine estate that’s home to some of the most diverse marine life on the planet but we still know very little about what lives beneath the waves,” White said in a CSIRO press release. “From the very first survey on this voyage, we’ve been making new discoveries and collecting data that will be vital in helping to protect and conserve the life in our oceans.”
CSIRO research vessel (RV) Investigator continues to make discoveries throughout December.
Discoveries such as these demonstrate the importance of marine biodiversity surveys and the valuable contribution they make to understanding ocean life. “From small, new, bottom-dwelling sharks, to massive ancient mega-sharks that once roamed the oceans, these biodiversity surveys give us vital insights into the life in our oceans,” Keesing said. Parks Australia Head of Division, Jason Mundy, agrees and adds that the learnings will aid Parks Australia in managing remote marine parks. “It shows there is more to learn about our 60 Australian Marine Parks, especially those in deep and difficult to access environments. This is made possible through partnerships with research organisations and universities,” Mr. Mundy said.
The RV Investigator will continue to survey the Gascoyne Marine Park, as well as the nearby Carnarvon Canyon Marine Park, until mid-December and then end its voyage in Fremantle, Western Australia.
