Climate Change, Acidification, & the Oceans, Marine Conservation & Sustainable Management, Marine Life

News from the life aquatic

There are three great open access papers out this week that I want to share. Three! But which to share? Well why not all three. Here’s a quick round-up of some of the latest research in ocean science. Best served with a nice slice of your favourite treat.

Can you tell what (species) it is yet?
Every time we explore life in the deep sea we find more and more creatures that bioluminensce. Around 80% of all eukaryotic life in waters below 200 meters are thought to have this ability. In this study by Matthew Davis of The University of Kansas (USA) and fellow researchers, it emerges that diversity of species (species richness) in deep sea fish groups may be influenced by photophores – light emitting cells on the body of fish. The researchers work found that some lineages of the lanternfishes (Myctophidae) – which are made up of over 250 species – have photophores with species-specific patterns. This means species can clearly be identified from one another. This diversification seems to have happened after the evolution of the lanternfishes photophores some 73 – 104 million years ago. As diversification of photophores occurred, so too did speciation.  http://dx.doi/10.1007/s00227-014-2406-x

 

Where the young turtles swim
We watch baby turtles hatch and make their way into the open ocean. We watch them when they show up in coastal waters years later as ‘teenagers;. But where do they go when they are growing up? That is what Kate Mansfield of the University of Central Florida and fellow researchers set about to discover for loggerhead turtles (Caretta caretta) . 17 young turtles – all between 3.5 and 9 months old and reaching a maximum length of just 18 cm were tagged with small solar-powered satellite transmitters. And what an adventure these guys had. Staying mostly at the surface, these critters were found enjoying a wide area of the ocean past the continental shelf, – with one turtle travelling up to 2,672 miles! What was particularly surprising for the researchers was that they didn’t just hang out in gyre-associated currents – sometimes they went off exploring
http://dx.doi10.1098/rspb.2013.3039

 

I’m sure there used to be people living there
With changing climate comes changing sea levels. And for many areas that means a sea level rise. In this study by Ben Marzeion from the University of Innsbruck (Austria) and Anders Levermann from Potsdam University (Germany), looked at all 720 UNESCO World Heritage Sites to see what increasing sea levels would mean for them. The researchers decided to take a not-too unrealistic prediction of 3 degrees Celsius above pre-industrial levels in the next 2000 years. Under this scenario, their models indicated that 136 sites (19%) would be impacted by sea level rise. Doesn’t sound too bad, on the grand scheme of things but those sites do include key heritage areas like the Sydney Opera House, the Tower of London, and Independence Hall. Check out some visualisations from The Weather Channel, created using ‘Drown your Town’. But the researchers didn’t stop there. They also looked at how much of the current human population would be impacted by sea level rise. The same scenario indicated that 7% of the world’s population is living on land that will be undersea within 2000 years. Around 60% of those affected live in just 5 countries – China, India, Bangladesh, Vietnam, and Indonesia. Sobering thoughts for the future.  http://dx.doi:10.1088/1748-9326/9/3/034001

 

Image: ‘Drown your Town’ used on Cape Town, South Africa (50m rise – possibly a little extreme!). Credit: Drown your Town

Marine Conservation & Sustainable Management

Plastics are a sea turtle’s not so tasty treat

Well it seems its the season for posting about plastic pollution in our oceans.  Following on from my recent posts on pelagic fish consuming plastics and the ‘plastisphere‘ I bring you yet another impact of plastic pollution…this time on sea turtles.

Tommaso Campani from the University of Siena, Italy and colleagues have been busy looking at deceased  loggerhead turtle (Caretta caretta ) stranded along the Tuscany coasts.  What they found was disturbing, but perhaps not unsurprising.  71% of the turtles  were found to have a total of 483  items of debris in their intestine, stomach, or oesophagus.  441 of those items were plastic, and primarily sheet-like plastic (think plastic bags).  Looking through the eyes of a loggerhead turtle, its perhaps easy to suggest that the high level of sheet-like plastic is likely to arise from the similarity of the plastic with jellyfish – a major prey item of the species.  Even the colour of plastic didn’t seem to deter these unfussy critters consuming the plastic.

Although the sample size was small (just 31 turtles), and ingestion of debris – particularly plastic – cannot be directly linked to their death, it does raise some questions about the disposal of litter…or rather lack thereof.

The paper has been published in the journal  ‘Marine Pollution Bulletin’.  Unfortunately it is not open access so you’ll need journal access (or to pay for access) to read it.

Image: Wondering what it is?  Yup… a plastic bag.  Credit Patrick Kelley Worldwide Photographer/Marine Photobank

Fisheries, Aquaculture, & Sustainable Seafood

UV LED lights reduce sea turtle bycatch

Bycatch – the accidental capture (and often mortality) of any species – or even a subset of a species (like juveniles) – in fishing does not make for a good fishing trip.  It takes up valuable space in your net, it can damage your gear, and it can cause population declines of species accidentally caught.  New ways to reduce bycatch are being tried out (some more successfully than others) more and more regularly.

When it comes to gillnets, bycatch of turtles is a big problem.  It doesn’t take much for a wayward turtle to find itself tangled up and unable to get out by itself.  For fishers, cutting the net to release them is often the only solution.  Enter Dr John Wang from the University of Hawaii.  He came up with an interesting proposal….what if turtles were better able to see the net, but the targeted fish couldn’t?

In this newly published piece of research, John demonstrates that by simply attaching UV LED lights to the gillnet floatlines (a line at the top of the net has floats on it which keeps it upright in the water), Green sea turtle (Chelonia mydas) bycatch declined by some 40%, but both the target catch size and the value of the catch didn’t decrease.

It all comes down to vision. The turtles are really quite good at detecting UV light…the fish not so much (in this study there was a variety of target species – mainly flounders – members of the family Pleuronectidae).  Clever stuff.  But John isn’t planning on stopping there.  He notes that different turtle and different fish species may react to different colours of UV light.  Watch this space for news on how that goes.

The paper is open access – talk a look at it here http://rsbl.royalsocietypublishing.org/content/9/5/20130383

Image: Green sea turtles entangled in a n abandoned small-scale net.  Credit Projeto Tamar Brazil/Marine Photobank