Welcome to this week’s marine science briefing, which starts with a sad tail of fickle fishes, before the main course on getting about underwater. In this we see three adaptations by marine vertebrates to propulsion, including how whale design can improve underwater turbines, and what the fastest sharks would be wearing at the 2012 Olympics in London!

Marine science

Ladies don’t like loosers: Female fish are likely to swim out on males who get sand kicked (finned?) in their faces. La plus çla;a change… ScienceDaily (Nov. 24, 2010)

Stopping that sinking feeling: Whale sharks (Rhincodon typus) are slightly negatively buoyant, but have a body shaped like an aerofoil so that slight forward motion will keep them at a constant depth. ScienceDaily (Nov. 27, 2010)

Swim skin: Sharks might have the ultimate swim suits in their denticle covered skins (denticle means ‘small tooth’ – sharks are covered with teeth rather than the scales bony fish have). Latest analysis shows that the denticles are patterned over the surface of the shark, with very flexible denticles occurring where the shark bends when it is powering through the water. This flexibility is not, however, to make it easier for the shark to bend, instead it is to prevent flow separation, which occurs when the boundary layer of water in contact with the shark’s skin peels away creating energy-sapping vortices. I’ve tried to draw what might be happening in the picture (above right), which shows how a smooth surface is, paradoxically, not the most energy efficient solution for a flexing surface in water. Instead a surface with small plates that can move to either smooth out undulations, or increase the surface energy to stick the water tight to the skin (I’m not sure which mechanism is correct) actually works out best… Based on: ScienceDaily (Nov. 24, 2010)

Whale design: The bumps of the hump-backed whale’s flippers may be more than just decoration. Adding them to turbine blades for use generating electricity underwater, where the blades are turning very slowly, results in improved stall characteristics and better hydrodynamic performance. ScienceDaily (Nov. 27, 2010)

Life at the margins: We know a lot about the marine life in the shallow waters of the continental shelf, and have glimpses of life in the deeps around ocean ridges, but much of the rest of the ocean is unknown to us. This study looks at existing information in the literature and museum collections to try and piece together a picture of life at the continental margins, where the sea-bottom slopes down to the abyssal plain. The continental margin is rather more interesting than I had imagined, with deep canyons and gulleys as well as gentle slopes. In addition, eddies from marginal currents (such as the gulf stream), means that the waters are not uniform in temperature or productivity. This leads to a patchwork of different habitats, with different faunal communities, which the authors acknowledge have been too little studied for them to be able to develop a comprehensive picture of life in these habitats. This is most evident in the graphs, which show that the number of species known to exist in each habitat is directly proportional to the number of occasions the habitat has been surveyed…
Kelly NE, Shea EK, Metaxas A, Haedrich RL, Auster PJ (2010) Biodiversity of the Deep-Sea Continental Margin Bordering the Gulf of Maine (NW Atlantic): Relationships among Sub-Regions and to Shelf Systems. PLoS ONE 5(11): e13832. doi:10.1371/journal.pone.0013832

Sea salt from space: Salinity is one fo the key physical measurements in the marine ecosystem, along with temperature it allows oceanographers to follow water masses, and work out circulation patterns. A new satellite Aquarius/SAC-D, built in collaboration between NASA and Argentina’s space agency, is designed to measure salinity of surface waters from space. The satellite is now entering its final preparation stages before launch, which is planned in spring 2011. ScienceDaily (Nov. 28, 2010)

Conservation

Winter hide-out: The northern bottlenose whale Hyperoodon ampullatus, hunted into the 1970’s for dog food, is one of the less-encountered whale species, spending a most of its time in deep dives after prey. A small population of 160 individuals off Nova Scotia has now been monitored over a complete annual cycle, and shown not to be migratory. ScienceDaily (Nov. 21, 2010)

Fisheries and exploitation

Tuna tank: Juvenile Atlantic bluefin tuna (Thunnus thynnus) have been adapted to life in a tank by scientists in Spain. Tuna do not readily make this adaptation, being used to a world without walls. The work is an essential first stage to captive breeding of the species. ScienceDaily (Nov. 26, 2010)

Hunky marine biologist flogs togs: There are so many ways you can read this – perhaps as a ray of hope for graduating marine biologists: There is a (glamorous) career out there, with the sea still in shot (if no longer in focus)… Deep Sea News, November 26th 2010.

Bonefish low: Bonefish (Albula vulpes) have been adopted as an indicator of ecosystem health in the Florida Keys because they are highly mobile, and feed on a wide range of small animals towards the base of the marine food chain. This year the numbers of the fish are very low, and this is possibly associated with deaths of young bonefish in an unusually cold January in 2009, though conditions for collecting data this year have also been bad. ScienceDaily (Nov. 22, 2010)

Dinner bell: This study looks at how dolphins identify species of fish by their sonar reflections. Simple experiments with geometric shapes had previously shown that dolphins can discriminate between them by sonar alone, but can they discriminate between real fish with complex profiles, and aligned at random? To evaluate this the researchers looked at three species of fish, and analysed the spectrum of sound returned from them when they were illuminated by a synthesised dolphin sonar signal. The researchers conclude that both dolphins and porpoises can discriminate between prey species by sound alone.
Yovel Y, Au WWL (2010) How Can Dolphins Recognize Fish According to Their Echoes? A Statistical Analysis of Fish Echoes. PLoS ONE 5(11): e14054. doi:10.1371/journal.pone.0014054

Pollution

Slick Sunday: Dr BIK at Deep-Sea News is promising a weekly roundup of news from the Gulf Oil Spill, for those of you interested in what happens after the slick leaves the front page. There are a number of things to look out for – damage to deep sea reef and other benthic communities, oil in the food-chain, so keep an eye on this… The first Sunday release was dated 14th November 2010, latest updates from 28th November are here, and include BP’s risk culture, is seafood safe? On-going Beach cleans, holiday rental booms and busts.

Now look after it: In the aftermath of the Gulf of Mexico oil spill are coming calls for continuous oceanographic monitoring, plus facilities for sharing data more rapidy between interested parties. ScienceDaily (Nov. 21, 2010)

Regulation trap: Telling commentary that shows that people in the Minerals and Mining Service (MMS) didn’t think they had the expertise to understand the technology the oil industry was employing in the Gulf of Mexico. In these circumstances it will be nigh-on impossible to regulate the industry! Deep Sea News, November 23rd, 2010

Climate change

UN COnvention on climate change: The Cancun round is kicking off, with very low expectations from all cocerned after the disappointing meeting in Copenhagen (COP15) in 2009. The wise money is on some emolient phrases (“countries will endeavour to…” etc.), and a return to business as usual with another meeting in 2011. It is disheartening, but working through the UN is the only way we can build a global consensus that might solve this problem; we need a sustainable future that offers peace and prosperity for everyone, not just those of us lucky enough to have been born in the industrialised west. COP16, November 29th-December 10th 2010, Cancun, Mexico.

CO₂ hits new highs: Scientists are predicting that carbon dioxide production will hit record highs this year, with a 3% increase over 2009 levels. The results are despite cuts by some countries and a global recession, and improvements in forest management that have seen reduced CO₂ emissions from tropical forest loss. The simple fact is that we need to see very much larger cuts in emissions before the actual atmospheric concentration will start to come down… ScienceDaily (Nov. 21, 2010)