- Terrestrial hermit crabs
- Focus on the Lesser Siren
- The Malagasy Giant Chameleon
- New on the Market!
- The Redbellied Shortneck turtle
- Wild Killies from Peru
Aug 022013
Aug 022013
Original story by AAP at The Australian
TRIPLING the nation’s short-term target for cutting CO2 emissions is a good start but environmentalists warn it won’t do enough to avoid the worst impacts of climate change.
The federal government’s climate advisory group is reportedly recommending Australia reduce its emissions by 15 per cent of 2000 levels by 2020 – three times the current bipartisan target.
Kellie Caught, WWF National Manager – Climate Change. Photo © Fiora Sacco
The report from the Climate Change Authority, leaked to some news organisations on Friday, also reportedly recommends slashing emissions by 90 per cent by 2050.
The independent authority is undertaking its first review of Australia’s emissions reduction targets, and is due to present its draft recommendations to the government in October.
The World Wide Fund for Nature said the current five per cent goal was “way out of sync” with the world’s major economies, and lifting the target would show Australia was willing to do its fair share.
“Anything less than that would imply that Australia expects other countries to do more, which is unlikely to be well received within the UN climate negotiations,” the WWF’s Kellie Caught said in a statement.
Other groups were pushing even harder.
“We’re still advocating that Australia should step up to a 40 per cent cut by 2020,” the Australian Conservation Foundation’s Tony Mohr told AAP on Friday.
Australian Greens leader Christine Milne said developed nations had a responsibility to cut emissions by between 25 and 40 per cent by 2020 and she was alarmed the authority was considering a lower target.
She urged the authority to be guided by science, not politics, when it makes its final recommendations.
Aug 022013
Original story by Mark Hamann, James Cook University and Kimberly Riskas, James Cook University at The Conversation
The Hawksbill Turtle (Eretmochelys imbricata) is one of the seven species of marine turtles and one of six in the family Cheloniidae. It is easily distinguished from other turtle species by its beak-like mouth and overlapping scales, or scutes. Harvested for centuries for their exquisitely patterned shell, some hawksbill populations now face an uncertain future.
Hawksbills, while widely distributed throughout the world’s tropical oceans, prefer warm, shallow waters and lagoons. Although hawksbills are most commonly associated with coral reef systems, they sometimes nest in mangrove-fringed islands or beaches. Like other marine turtles species, hawksbills are migratory and can swim long distances between breeding and feeding grounds.
A female Hawksbill turtle nesting in northern Australia. Photo: Scott Whiting
Hawksbills spend most of their lives at sea, only coming ashore to lay eggs. Little is known about turtles’ habitat use or behaviour during the “lost years” between hatching and their initial appearance at foraging grounds.
Much of what we know about the species comes from studies on nesting turtles and a few long-term foraging area studies. Sponges and algae make up the bulk of the hawksbill’s prey, though their omnivorous diet also includes sea anemones and the highly venomous Portuguese Man o’ War (Physalia physalis).
Hawksbills nest on the beaches of dozens of different nations, and the species is further divided into smaller genetically distinct management units or populations. Separating the species in such a way allows scientists to determine which populations are healthy and which are at risk. Thus, the species as a whole is made up of several management units, each with its own potential for recovery or decline.
Status
Amid much debate the hawksbill turtle was listed globally by the IUCN as Critically Endangered in 2008. The debate largely centred around two areas.
First, some scientists argued that the IUCN Red List criteria are not suitable for listing marine turtles and that the species could not be critically endangered according to IUCN definitions.
Second, hawksbill turtles were traditionally used to supply Japan bekko (Hawksbill turtle shell) markets. Experts debated whether this use was sustainable.
One issue with using the IUCN Red List Criteria for hawksbill and other marine turtle species is that the status of the species varies throughout the world – certainly there are populations in trouble and those doing well. But for many there are few data to indicate status. Monitoring multiple populations can be challenging, especially when nesting occurs on far-flung islands and remote beaches.
In Australia, the hawksbill is listed as Vulnerable under the EPBC Act of 1999. The species is separated into three populations, but the status is only known for the population in far north Queensland, which is declining at 3% each year.
Hawksbills nest at low densities in the Great Barrier Reef and Torres Strait, although this population is not well studied. Together, the Dampier Archipelago and Montebello Islands off the northwest coast of Australia are thought to host one of the largest hawksbill populations in the world.
Threats
Across the globe hawksbill turtles have suffered from large-scale commercial use for the turtle shell trade. Trade ceased in 1994 when Japan withdrew objections to the turtle’s listing on the Convention on International Trade in Endangered Species (CITES). Although the selling of hawksbill products is now illegal, many populations have not yet recovered.
Existing threats include consumption (mainly of eggs), predation of eggs by animals such as varanid (or monitor) lizards, incidental capture by fishers and coastal development.
In North Queensland, hunting pressure overseas and predation of eggs by goannas are suspected to be responsible for the observed 3% decline. Elsewhere in Australia, the main threats include habitat loss or change caused by the oil and gas industry; and light pollution, which disrupts hatchlings when hatching and adult orientation during nesting.
Strategy
There are several international agreements that act to manage hawksbill turtles. At a global level, the species are listed as Appendix 1 in CITES, which prevents international trade of the turtles or any of their products. At regional levels, instruments such as the Indian Ocean-South-East Asia Marine Turtle Memorandum of Understanding and the Inter-American Convention for the Protection and Conservation of Marine Turtles act to coordinate research, monitoring and management action.
In Australia, monitoring and management actions are guided by the Australian Government’s marine turtle recovery plan. There are also regional frameworks such as the Great Barrier Reef World Heritage Area, the Barrow Island Long Term Marine Turtle Management Plan, and the actions of traditional land title holders (Groote Eylandt and Torres Strait).
Hawksbills in Northern Queensland in particular are in need of urgent management intervention. Managing Australian populations will require a concerted effort to reduce the predation of eggs by goannas and mitigate the impacts of lights and coastal developments on key rookeries. We will also need a multi-national approach to curb overseas hunting.
Conclusion
Hawksbill turtles are a key part of coral reef ecosystems around the tropical world. They have survived what many consider to be some of the longest, and most pervasive, turtle harvests across the globe. This species currently faces a panoply of additional threats, from capture in fisheries to coastal development. Strengthening political co-operation and international conservation efforts is an essential first step. Furthermore, addressing knowledge gaps for each population is critical in protecting the hawksbill from further decline.
The Conversation is running a series on Australian endangered species. See it here
Mark Hamann receives funding from the National Environmental Research Program and has previously received funding from the ARC, industry, and government. He is Co-vice Chair of the IUCN Marine Turtles Specialist Group (Australasia).
Kimberly Riskas does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.
This article was originally published at The Conversation.
Read the original article.
Aug 022013
Original story by Susan Lawler, La Trobe University at The Conversation
The pandora virus is a brand new form of life, and it’s a bit like a knitted potato. No one can imagine a knitted potato. Photo: Klara Kim
A recent paper in Science has announced the discovery of an organism that is going to require a reappraisal of our assumptions about viruses, evolution and the history of life. The authors named the organism Pandoravirus, in memory of the Greek myth about Pandora, who also unleashed something surprising with far-reaching consequences.
The publication by a group of French scientists describes a new kind of virus, which sounds like a little thing, but isn’t in this case for many reasons. The first reason is that these viruses are enormous. Not only are they bigger than Megavirus, the largest virus known, they contain more DNA and the genes they carry are sufficiently different from anything previously sequenced to qualify as a fundamentally new type of life.
We are literally going to have to rewrite the textbooks.
One aspect of this story that personally excites me is that of the two species described, one was found in a pond at my University. I am familiar with the ponds of La Trobe University in Melbourne, because I spent a year wading in them with a dip net collecting chironomids (a type of aquatic midge). This means that I have personally met the species Pandoravirus dulcis, at least biochemically. We just hadn’t been introduced until now.
Should I be worried about having contact with a really big virus? Does this mean I might get a big disease? No, because these viruses infect aquatic amoebas that live in muddy sediments. There is no evidence that they attack humans. Although, given how little we know about Pandoraviruses, we cannot rule out anything with confidence.
In an article about the discovery, a virologist is quoted as saying, “It’s like finding a sasquatch!” Except that it isn’t, because people have been actually looking for sasquatch, while until recently, nobody was looking for giant viruses.
These organisms were large enough to be seen using a light microscope, but unrecognised because everybody “knew” that you can’t see viruses with a microscope. They were hiding in plain sight.
Of course, it is impossible to tell if a cell is a virus just by looking at it. French scientists Jean-Michel Claverie, Chantal Abergel and their colleagues deserve credit for not only deciding to look for something that was considered more unlikely than a sasquatch, but for developing methods that allowed them to recognise what they had found.
In 2003, these scientists found a virus large enough to be seen by microscope. They named it Mimivirus, for “microbe mimicking virus”. It was so big it even had its own parasites, called virophages. Mimivirus also had far more genes than expected for a virus. As a comparison, the Aids virus has 10 genes and the influenza virus has 13; Mimivirus had up to 900 genes! For the first time it made sense to search for large viruses.
The French scientists began by inoculating Acanthamoeba with water samples collected from around the world and then watching for patterns of cell death that indicated a viral infection. In other words, when the amoebas began to explode, the scientists took a closer look. In 2011 they found a virus larger than any seen before and named it Megavirus.
Pandoravirus are massive at one micrometre: almost twice as big as Megavirus. The larger species, Pandoravirus salinus, was found at the mouth of a river in Chile, and the smaller species, P. dulcis, was found in Melbourne. This does not mean that these organisms are rare. Indeed, the discovery of two closely related organisms in distant locations suggests that they are probably quite common and have a worldwide distribution.
When the researchers examined the Pandoravirus DNA they found multiple surprises. Pandoravirus have far more genes than any other virus: up to 2556 protein coding sequences in P. salinas and 1502 genes in P. dulcis. Although they share 14 of the 31 genes usually found in large viruses, 93% of their genes resemble nothing known. (They even have introns!) And yet Pandoravirus still meet the criteria for being a virus: they do not have any genes for protein translation and they do not reproduce by binary fission.
In fact, the description of their reproductive cycle is fascinating. The particles disappear when they first enter the amoeba’s cell, but then thousands of viruses inside an envelope are assembled in a “a manner similar to knitting”. This is hard to explain, but imagine a bag full of potatoes where the potatoes are assembled along with the bag. I think this is extraordinary. Who knits potatoes?
These organisms will surely live up to their name, which the authors chose for “the surprises expected from their future study”. One of those surprises will be the ability to look at the evolution of viruses. Looking for large viruses is a way of looking back in time.
A virus is a cell without enough components to even be considered alive, technically. In some circles, at least, they are considered inert particles, more chemistry than biology. The typical virus contains only few genes and cannot reproduce without using the machinery of a host cell. There must have been a time when their ancestors had a full set of genes and lived independently. Pandoravirus is a window into that world.
It is also likely to lead to a reappraisal of the main branches of the tree of life. The three Domains (bacteria, archaea and eukaryotes) may soon become four. There are few discoveries that can claim to require such a substantial rethink about the nature of life.
And to think it came from some mud that I have literally washed from between my toes!
Susan Lawler does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.
This article was originally published at The Conversation.
Read the original article.
Aug 022013
Original story by Craig Moritz and Rosa Agudo at The Conversation
In work we published in Science today we look at two conflicting ideas on whether species can adapt to climate change. Are our ideas about extinction too catastrophic, or do we actually need to do more to protect biodiversity?
Climate change means some mountain species are just clinging on, but can they adapt? Australian Alps/Flickr
Picture a polar bear, perched precariously on a small iceberg somewhere in the diminishing Arctic icecap. This iconic image is often used to portray the fate species will suffer as human-driven climate change accelerates. Yes, the forecasts are dire. Using various modelling approaches, researchers predict major reductions in species distributions and increased rates of extinction, especially in the tropics and globally across mountains.
But the past tells a different story. There seems little evidence in the fossil record for elevated species extinction during periods of rapid warming, such as the transition from the last ice age into the current Holocene period. Rather, species such as north American trees and mammals shifted geographically, albeit idiosyncratically, or in some cases appear to have adapted without moving.
One obvious result is that, as individual species respond more or less to climate change, local communities change in composition. These results are borne out by comparative genetic studies. They show that the population size of many species fluctuated, but that fluctuation occurred differently across the same landscape.
So which of these two perspectives is closer to the truth? Either the record of past responses is somehow an unreliable guide to the future, or the dire predictions for the future overstate vulnerability. In our invited Science review, we highlight this problem and, as a bridge, consider evidence on species’ responses to the 20th century climate change.
For those species to persist, they have just two options – adapt or move. But theory tells us that only species with short generation times and high rates of potential population growth will be able to adapt, without moving, in the face of rapid climate change. Species may also be less vulnerable than coarse-scale models predict if they are able to adjust how they use local habitats (for example, by being active at different times or concentrating in cooler places).
The 20th century record reveals a middle ground. Yes, species ranges are shifting – often towards higher latitude and upwards. In some mountain species, this is resulting in severe loss of geographic range and measureable decline in genetic diversity. There are also documented changes in the timing of migration or reproduction and shifts in body size or leaf width, though whether these changes are heritable remains an open question. But, consistent with the fossil record, even closely related species vary in their response – some stay put, while others shift, resulting in changes in the make-up of local groups of species. But why do species vary so much in response? The simple answer is that we don’t yet know, making it all the more difficult to predict vulnerability species by species.
Returning to the disparity between (observed) past and (predicted) future response, it may be that the fossil record underestimates future species vulnerability because of limited resolution – often fossils can only be classified to genus rather than species. Or it may be because species in the distant past had more options to respond as they didn’t have to cope with human-altered ecological systems. In particular, reduction and fragmentation of natural habitats, compounded by introduced predators and herbivores, add additional, potentially fatal constraints to the ability of species to respond to future climate change.
Whatever the true magnitude of impact on species under future climate change, there is no room for complacency. Reducing emission increases as soon as possible will help conservation policy-makers and practitioners increase the resilience of natural systems. We need to take actions now to give species as many opportunities as possible to remain viable – even if not within their current geographic range.
Despite the above “known unknowns”, we do know enough to inform conservation policy. Reducing other ecological stressors – such as invasive species and inappropriate fire regimes – is the right thing to do. Managing already threatened species to maintain large population sizes and ecological breadth remains important. Identifying landscapes that can function as places of refuge from climate change and managing large landscapes to enable dispersal to these refuges is crucial. Inevitably this needs a multi-sectoral approach. National parks are the keystone, but will not be enough.
So how, in Australia are we doing? Community-driven efforts to rehabilitate habitats, such as through Landcare and catchment management plans, are laudatory and a vital element of our response. Ongoing expansion of areas managed explicitly for conservation, including Indigenous Protected Areas as part of the National Reserve System and increasing private investments through non-government organisations, is key. And connecting these efforts through regional, state and national corridor initiatives will increase resilience to ongoing climate change.
Yet recent moves to diminish the conservation value of our reserve system – allowing grazing or hunting in national parks – take us in exactly the wrong direction. We need to keep pressure on governments to take the long view if we are to sustain Australia’s amazing and unique evolutionary heritage.
Craig Moritz receives funding from The Australian Research Council, the National Science Foundation (USA) and the Australian Biological Resources Study
Rosa Agudo is funded by the Spanish private foundation Ramon Areces that covers her salary as a postdoc at the Australian National University.
This article was originally published at The Conversation.
Read the original article.
Aug 022013
By Tony Tucceri
Every ANGFA member knows the biggest show in town will be held right here in Melbourne on Saturday and Sunday 12-13 October 2013, at Ciloms Airport Lodge, 398 Melrose Drive, Tullamarine, Victoria There is even an AGM on Friday night for those members who wish to have their say in the national organisation.
All are welcome to the ANGFA Convention. It’s not too late, but please don’t leave it any longer. Price is a very reasonable $150 for members or $195 non-members. Even though your partner may not wish to participate, there will be a program available for them including guided tours of places of interest around Melbourne.
As for the venue, by popular demand, we have retained the same venue that was used at the last Melbourne convention (back in 2005), namely Ciloms Airport Lodge. It is located a short two minute drive from Melbourne Airport and offers all the comforts you would expect. An excellent standard and variety of accommodation is available at the venue, which can be viewed at www.ciloms.com.au Ciloms Airport Lodge is located at: 398 Melrose Drive, Tullamarine, Victoria, Australia, 3043. Contact them on Free Call: 1800 819 443 or telephone: +61 3 9335 2788 or facsimile: +61 3 9335 4388 or email ciloms@ciloms.com.au. Make sure you mention the ANGFA Convention when booking your accommodation as this will entitle you to a substantial discount on room bookings.
The convention itself is the highlight of the calendar for every ANGFA member. It features information-packed presentations from well-known speakers from across Australia and from overseas including Heiko Bleher, Peter Unmack, Nick Romanowski, Mark Bachman, Mike Hammer, Brian Andrews, Ian Morris, Franz-Peter Muellenholz, Adam Kerezsy, John Sinclair, Phil Littlejohn and Glenn Briggs.
ANGFA members will recognise the names and be aware our speakers are experts who will talk about some very topical subjects. Come and hear the experts give their informative presentations; you’ll find them fascinating as well as entertaining.
There is so much to do and see. The ANGFA auction of rare and very beautiful fishes will be conducted Saturday afternoon, conference attendance entitles you to join in the bidding. There will be a Trade Table operating the whole weekend where members can view and buy all manner of fish-related equipment, aquatic plants and other goods at a more leisurely pace. There is a convention dinner Saturday night which will be a buffet and cost is only $18 per person (partners are most welcome). There is a photographic competition too, with huge cash prizes and amateur photographers are encouraged to submit their favourite photo. It’s also a great chance for you to meet ANGFA identities in person. To encourage networking, you will have plenty of time across the weekend to talk, discuss, renew old acquaintances and make new friends.
With prizes, Special Efforts, the Trade Table, books, polos, shirts, vests, and other gifts, it all adds to the attraction of being at the ANGFA 2013 Convention – the biggest show ever in Melbourne.
See you there.
For information on the convention please go to the web site www.angfa.org.au
More details about the convention, including on-line registration can be found at the convention link http://convention.angfa.org.au
Regards,
Tony Tucceri – Hon Treasurer & Membership Officer
Aug 022013
Original story by Olivia Solon, WIRED.co.uk
A two-metre high, six-legged crab-shaped robot called Crabster CR200, has been put to the test under water near Geoje City in South Korea.
Crabster CR200 (Crabster is half-crab, half-lobster) has been developed by the Korean Institute of Ocean Science and Technology (KIOST) as an alternative to propeller-driven remotely-operated vehicles, which don’t cope well with strong tidal currents.
The Crabster is designed to be lowered to 200 metres below the surface by a crane. Once on the sea floor, our six-legged friend can move across the floor by bending its 30 joints. The legs serve to provide stability and don’t kick up so much sea floor goo as propellers. The dexterous robot’s two front legs have manipulators (read: claws) that can grab objects and store them away in compartments in its body.
Crabster is loaded with a load of optical cameras, sonar and an acoustic Doppler current profiler to allow it to explore shipwrecks in strong currents (as fast as 1.5 metres per second). To steady itself, Crabster can manoeuvre its limbs to reduce drag depending on the direction and intensity of the current.
Before you start campaigning against the Inevitable Crab Robot Uprising, it’s worth noting that four people are needed to operate Crabster — one controls walking and posture, another the claws, cameras and lights, then there’s a navigator and a sonar engineer.
Either way, all we can think about is this:
Aug 022013
Original story by Gregor Heard, Stock Journal
YABBY farming is just like any other farming sector, according to yabby producer Trevor Domaschenz.
You have good years, you have bad years and you’re always at the mercy of the elements.
Yabby producer Trevor Domaschenz
Prior to the breakdown of the Victorian yabby industry in 2004, Mr Domaschenz said he could grow up to four tonnes of yabbies a year, sold for a live weight of $10 a kilogram on farm or up to $15/kg in Melbourne during times of peak demand.
In the past most of his yabbies went overseas, some ended up in markets in Melbourne, with some going direct to restaurants.
“It’s different to other commodities, you’ve got to have the yabbies for the markets and consistently supply a good live product. You can never fill the market,” he said.
This year, in his first year back in the human consumption market for some years with a more viable licence, Mr Domaschenz has much humbler ambitions.
“We just want to try to re-establish the yabby industry – ruined by regulations that make no sense – and hopefully sell a few this Christmas.”
Central to a good season is getting sufficient rainfall to fill the turkey nest yabby ponds that cover around 25 hectares across his Patyah property.
“We are mainly sheep and grain farmers but yabbies can be very important to us in the wetter years that ruin our crops,” he said.
“This one is shaping that way, we are the wettest we have been in the middle of July since 1996.”
If the ponds have water, the yabbies will come up and breed. Once they have had time to grow out, Mr Domaschenz then catches them from boats in opera house nets.
“It’s the same as filling your household dam, we’re looking for good rain over the winter and spring to get enough water to fill the ponds.”
Once the yabbies are caught, they are taken into a storage shed for a period of purging – a requirement not necessary in other states.
“If we had our way, we’d store the yabbies in a holding dam in a large sock net, which is what they do elsewhere and is by far the best option for the yabbies themselves.
“Storing in a shed in summer is a backward step.”
Mr Domaschenz said getting involved in aquaculture had meant a steep learning curve .
“We initially got into it as a means of diversification and making use of our water in the late 80s.”
He said there had been a lot of work going into the location of the yabby ponds.
“We were always mystified as to why one swamp would be chock full of yabbies and one just down the road would have hardly any, and we think its because of soil type.
“They need free calcium for their shells they are very fussy about the conditions.”
Generally, there will be enough natural food for the yabbies, especially when the ponds are rotated over the seasons to allow the natural food sources to re-establish, but if feeding is required, Mr Domaschenz said lupins would be the preferred feed stock.
“If they didn’t eat them all, after a few days they float to the edge and don’t contaminate the water.”
There is still a lot to be learnt in terms of the humble yabby, Mr Domaschenz said.
“The trick is to get them to moult. Unlike fish, yabbies have to moult into a new shell.
“They absorb the calcium from their shell into little buttons in their head. Then they then grow a new shell, pump it full of water to the size they want and gradually replace the water with meat – during this stage they can nearly double in size.
“They then harden the shell from the button.”
Mr Domaschenz said a lot of research has been done into yabbies, but not many dams are suitable commercially – although the conditions found in his local West Wimmera shire were near ideal for yabbies.
“We reckon it’s the home of the yabby.”
Aug 022013
Media release from ACS
“Sediment Trapping by Dams Creates Methane Emission Hot Spots”
Environmental Science & Technology
With the “green” reputation of large hydroelectric dams already in question, scientists are reporting that millions of smaller dams on rivers around the world make an important contribution to the greenhouse gases linked to global climate change. Their study, showing that more methane than previously believed bubbles out of the water behind small dams, appears in ACS’ journal Environmental Science & Technology.
Photo: iStockphoto/Thinkstock
Andreas Maeck and colleagues point out that the large reservoirs of water behind the world’s 50,000 large dams are a known source of methane. Like carbon dioxide, methane is one of the greenhouse gases, which trap heat near Earth’s surface and contribute to global warming. Methane, however, has a warming effect 25 times more powerful than carbon dioxide. The methane comes from organic matter in the sediments that accumulate behind dams. That knowledge led to questions about hydroelectric power’s image as a green and nonpolluting energy source. Maeck’s team decided to take a look at methane releases from the water impoundments behind smaller dams that store water less than 50 feet deep.
They describe analysis of methane release from water impounded behind six small dams on a European river. “Our results suggest that sedimentation-driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7 percent,” said the report. It noted that such emissions are likely to increase due to a boom in dam construction fostered by the quest for new energy sources and water shortages.
The authors acknowledge funding from the German Research Foundation.
Aug 022013
Media release from UNSW
Slight changes in the timing of the annual loss of sea-ice in polar regions could have dire consequences for polar ecosystems, by allowing a lot more sunlight to reach the sea floor.
Fan worms (turquoise) and sponges (orange) under the sea ice in Antarctica near Casey Station. Photo: Graeme Clark
The research by scientists at UNSW and the Australian Antarctic Division predicts that biodiversity on some areas of the polar seabed could be reduced by as much as one third within decades, as the poles warm.
The study, Light-driven tipping points in polar ecosystems, will be published in the journal Global Change Biology.
Dr Graeme Clark, of the UNSW School of Biological, Earth and Environmental Sciences, says the team’s research shows that polar ecosystems may be even more sensitive to climate change than previously thought.
“Even a slight shift in the date of the annual sea-ice departure could cause a tipping point, leading to widespread ecosystem shifts. On the Antarctic coast this may cause unique, invertebrate-dominated communities that are adapted to the dark conditions to be replaced by algal beds, which thrive on light, significantly reducing biodiversity,” Dr Clark says.
The invertebrates lost could include sponges, moss animals, sea squirts and worms. These animals perform important functions such as filtering of water and recycling of nutrients and provide a food source for fish and other creatures.
“This is a prime example of the large-scale ecological impacts that humans can impose through global warming – even in places as remote as Antarctica,” says UNSW team member, Associate Professor Emma Johnston.
“Our modelling shows that recent changes in ice and snow cover at the poles have already transformed the amount of light reaching large areas of the Arctic and Antarctic annually.”
For the study, the team deployed light meters on the sea floor at seven sites near Casey Station in Antarctica, at depths of up to 10 metres. They used cameras to photograph the coast at midday every day for two and a half years, to determine sea-ice cover.
They determined the growth rates of Antarctic algae in the lab in different light conditions, and conducted experiments in Antarctic waters to test the sensitivity of algae to available light. They also surveyed species living on sub-tidal boulders, to see how communities varied with ice cover.
Tipping points are events where small changes in environmental conditions cause rapid and extensive ecological change.
The amount of sunlight reaching the poles is highly dependent on the seasons because the Earth’s tilt causes the sun to be above the horizon for considerably longer during summer than winter, and the lower solar angle during winter increases reflectance from the water surface.
“Early melt that brings the date of sea-ice loss closer to midsummer will cause an exponential increase in the amount of sunlight reaching some areas per year,” says Dr Clark.
Media contacts:
Dr Graeme Clark: 9385 1711, g.clark@unsw.edu.au
Associate Professor Emma Johnston: 9385 1825, e.johnston@unsw.edu.au
UNSW Science media: Deborah Smith: 9385 7307, 0478 492 060, deborah.smith@unsw.edu.au