Faltering Ice – The Crack in Larsen C

There is currently a great deal of collective breath-holding surrounding the fate of a portion of the Larsen C ice shelf. Reports since December have been narrating the changes in a widening crack along its face, as the rift has increased in length by 20 miles. Only a 12 mile stretch of intact ice keeps the shelf tenuously anchored. As USA Today notes, you can literally bet on when it will give way.

The Larsen ice shelf is a region of chaos along the Antarctic Peninsula which curves towards the toe of Chile. The region is named after whaling captain and explorer Carl Anton Larsen, who experienced an Antarctic winter stranding with his men, not unlike that of Ernest Shackleton. Much of the shelf has already been lost previously due to catastrophic collapse events. 1995 saw the crumbling of Larsen A. Seven years later, Larsen B disintegrated over the course of 2-3 months. Its epic demise was cataloged by watching satellites.

The sheering off of these massive stretches of ice are not without effect. Ice shelves are comparable to sea ice, and their liberation does not directly contribute to changes in sea level. However, they often fortify nearby glaciers, and once absent, glacial movement can speed up significantly. Glacial ice, in contrast, can contribute to changing sea levels. It is thought that global warming trends have contributed to many ice sheet de-stabilization events around Greenland and Antarctica. Because ice is a cooling influence on climate due to its reflective nature (called albedo), ice loss is part of a positive feedback loop. Warming trends reduce both ice cover and albedo which leads to further warming.

This NASA photo released December 1, 2016 shows what scientists on NASA's IceBridge mission photographed in a view of a massive
View of the Larsen C ice shelf fissure in Nov 2015 as documented by the NASA Icebridge Mission.

On perhaps a lighter note however, the calving of ice also has also led to unexpected discoveries. After the break up of Larsen B, scientists discovered an intricate chemotrophic ecosystem a half mile below the ocean’s surface.  Chemotrophic organisms create their own energy through chemical pathways rather than relying on photosynthesis. The system below Larsen B was populated by cold seep clams and mats of microbes, examples of tenacious organisms that have adapted to get by with little access to sunlight or the growth of the phytoplankton food source it supports. This along with findings like vast microbial communities found within subglacial lakes in Antarctica adds to our collective evidence that life finds ways to subsist in the most extreme of environments.

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Speck of Science 2/7/17 – Shark Find in Belize

FIU researcher Demian Chapman and a possible new species of Bonnethead. Source: FIU 

A new species of Bonnethead has been described in Belize by FIU researcher Demian Chapman, thus the scenario of a single widespread species in that region now becomes the story of one or more species with overlapping ranges. The discovery was made after analyzing a snippet of the shark’s genome.

DNA analysis has allowed a much more nuanced perspective on species-level differences beyond the physical characteristics that were once the focus of classically-trained taxonomists. Now scientists are able to classify variance on a genetic level and have refined the technique. Now researchers use a method called DNA barcoding, which needs to examine just a small portion of an animal’s genomic sequence, and is often compared to scanning groceries at your supermarket’s checkout line. Large-scale efforts to catalog and archive these genetic identifiers, such as Barcode of Life, make this data widely accessible.


In addition, this finding was part of a larger initiative, called Finprint, focused on filling in data gaps concerning sharks, fins, and rays – all of which constitute a group of cartilaginous fish known as elasmobranchs. Finprint uses baited remote underwater video (BRUV) as one of their primary tools for studying these creatures. Much of their work appears to be focused on their spatial distribution, identifying regions that could lead to conflict with other uses such as fishing or areas that can be marked as candidates for protection.

 

Discovery from the Otter Side

While this is an amazing story, the urge to not post all the otter jokes is a fight I may lose.

Sherlotter Holmes and John Beaverson

All joking (briefly) aside, the Journal of Systematic Palaeontology just published findings about the otter species Siamogale melilutra as described by Wang et al. Skeletal pieces from three individuals were recovered in western China and used to characterize the ancient otter who outguns the giant river otter of today in size (approximately 50 kg to the giant otter’s 34).

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Giant River Otter. Photo Credit: Ernane Junior, Your Shot, National Geographic

While the specimens had elements reminiscent of both otters and badgers, a few distinctive features allowed researchers to place the animals firmly in subfamily Lutrinae, home to 13 current day otter species. However the paper notes the mixture of characteristics, described in some other genera as well, lead to some interesting questions about the ways in which the two may be related.

On the tail of this amazing find, I share an interesting otter fact which upon learning some years ago, quickly escalated their status in my heart: sea otters have loose folds of skin under their arms they use as pockets for storing food and rocks to use as tools.

I will close with the following video as it would be an otter shame not to:

Speck of Science 1/24/16 – Bees of the Seas

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Many of nature’s means of doing business on land has aquatic parallels. Seagrasses produce seeds and pollen the same way as terrestrial grasses do. However, there are certainly some differences. The pollen grains of seagrasses dwarf their land-based counterparts at almost 50 times larger, and the physics of the water in which pollination occurs certainly follows rules vastly different than those air currents.

Scientists have been postulating for some time about how marine plants get the job done in such a different environment, evident in this 1976 abstract for a submission in Letters to Nature.  Many aquatic plants may reproduce by variations of self-cloning where a sexual partner is not needed to give rise to new individuals. Sea grasses often dabble in a little of both worlds, as both have their evolutionary advantages. Cloning, often referred to more specifically as vegetative propagation in plants, allows underwater flora to quickly take up real estate without expending as many resources.  However, sexual reproduction confers the benefits of genetic variation and adaptability into their populations.

Initially, it was suggested water bore the primary burden of transporting pollen grains from male to female seagrass plants. However, in 2009, a team of researchers from National Autonomous University of Mexico led by  Brigitta van Tussenbroek observed small invertebrate crustaceans visiting turtlegrass (Thalassia testudinum) flowers in a manner that reminded them of terrestrial bees.

To explore whether or not these small creatures had the capacity to truly serve as pollinators, they moved their exploration in the controlled setting of a laboratory. They put turtlegrass and pollinators in tanks sans current, and monitored the movement of pollen grains as well as successful instances of pollination. Both successfully occurred in tanks where crustaceans had been added, but not in tanks where the animals were absent. The research team coined a new term, zoobenthophilous pollination, to describe the marine process they observed.

Seagrasses are vital to human wellbeing in ways similar to oyster reefs, coral reefs, and mangroves, and provide a wealth of services to the environments they thrive in. They are an important food source for manatees, dugongs, turtles, and other creatures. Their root systems stabilizes sea floors. They may serve as nursery grounds for minuscule juvenile fish needing protection from predators. But seagrasses have seen vast decline worldwide, in what could be called a global crisis. Now that we are learning seagrass survival may also have dependence on pollinators, we can only hope we do a better job of conserving these little sea bees than we have their terrestrial counterparts.

Speck of Science 12/1/16 – How Elephants Are Losing Their Tusks

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Small-tusked elephant, source: African Wildlife Foundation

Nature has a fickle way of removing the wheat from the chaff. When organisms are less suited to survival, their chances of lasting long enough to reproduce may be in serious jeopardy. If the deleterious traits are genetic in nature, then there is limited chance they will be handed off to future generations. We call this process natural selection.

One example proving that humans can act as a shaping force similar to mother nature by chiseling the genetic outlook  of a creature is presented in this recent Independent article.The piece describes how African elephants in some regions are being born with smaller tusks or entirely without them, presumably in response to the selective pressure of poaching. While there always have been an elephant here or there born without tusks, the preferential culling of ivory has increased the prevalence of tuskless elephants.

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Photo credit: National Geographic

However, as Snopes suggests (not a source I was expecting to comment on the issue), this particular phenomenon has been noted and written about for years prior. A 1995 paper published in the African Journal of Ecology noted in Queen Elizabeth National Park had jumped from 3-4% up to 9-25%. Collectively in South Luangwa National Park and nearby Lupande Game Management Area, the change was from 10% up to 38% in a 20 year period.

While elephants may be the charismatic mascot for poaching issues, undoubtedly it is an issue that for a multitude of animal species reverberates well beyond just their population size and deeply into the very tapestry of their DNA.

The freeloading lifestyle of fresh water mussels

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Conglutinates of the Ouachita kidneyshell – Chris Barnhart

I study oystery things. In my little myopic scientific snowglobe, I know a few things about shellfish, and I know a few more things about oysters. Then I know the most things about oyster filtration. So there’s still plenty of room for surprise.

This very thing happened this year during a local American Fisheries Society (AFS) meeting where I heard a talk about freshwater mussels. Probably because I always seem to be mucking about in briny water rather than its fresher counterpart, I was rather taken aback learning that many of these species have parasitic larval stages.

After females collect sperm that males eject externally, they fertilize their eggs and stow them in their gills where they develop into a minuscule larval stage called glochidia. These juvenile mussels cannot fully develop however until they somehow reach a host fish. They will encyst themselves into the host’s tissue where they will stay until more fully formed, at which point they will drop off and settle on the river floor. The host fish has graciously and perhaps unknowingly provided the small creature with protection and dispersal.

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The strangest detail of this whole process seems to be the intricate tactics mussels have developed to get their little parasitic spawn into hosts. Some species concentrate their glochidia into structures called conglutinates that they then release into the water. Many resemble prey items attractive to fish like in the video  and picture below:

Others, like mamas in the Lampsilis family keep their little ones closer to them while dangling parts of their mantle tissue to the same affect at the conglutinates described above.

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Lampsilis’ display attracts host fish – Paul L. Freeman, Nature Conservancy

For most species of freshwater mussel, the choice of host fish seems to be relatively specific. In some cases, the species of host has yet to be discovered, which provides fertile ground for research into the topic such as the work that Florida Wildlife Commission’s Blackwater Research and Development Center in Holt, Florida has done.

As with other symbiotic relationships within nature, freshwater mussels are incredibly dependent on the health of their host and the system around them. This has further increased the need for continued research and conservation, and in some instances agencies and institutions have fostered cultivation and propagation efforts.

Speck of Science 11/29/16 – The Bathing of the Tortoise

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A photo of Jonathan dated at around 1886 – Wikimedia Commons

Jonathan, a 184 year old tortoise touted as perhaps the oldest living land animal, seemed a little surprised at times in this video released by the St. Helena government.

The solid scrubbing appeared to be an attempt to renew the vim and vigour of his shell, as Joe Hollins, the vet who did the deed stated: “It is purely for aesthetic reasons.  We want visitors and tourists on the Island to witness the tortoises in their true form, without the obstruction of moss and lichen on their shells.  There is so much interest in Jonathan, St Helena’s most famous animal resident, and we want all who visit him to see him at his best.”

In recent years, Hollins also oversaw an overhaul of Jonathan’s diet, which seems to have increased his overall well being. Sounds like Jonathan has a pretty savvy ally and friend.