Life Under Lake Ice: A Mysterious (and Threatened) World

Ice has become (pardon the pun) something of a hot topic lately.

Professional and amateur scientists alike have studied the timing of seasonal ice formation on lakes and rivers for hundreds of years, and the patterns that have emerged from these studies provide a window into the progression of climate change. Overwhelmingly, the data show that lakes and rivers are freezing up later in the winter and their ice cover is melting earlier in the spring than in the past.

Take Lake Suwa, in Japan. Observations of the lake’s winter freeze-up date back to 1443, when Shinto priests began to record the timing of the freeze-up as part of their religious observation. From 1443 through 1683, the date when the lake first froze over shifted later in the year by an average of 0.19 days per decade. More recently, between 1923 and 2014, the freeze-up date has been delayed by an additional 4.6 days each decade. The once-rare occasions when Lake Suwa remained ice free all winter have also increased in frequency: there were only three ice free years between 1443 and 1700, but this has happened twelve times between 1950 and 2004 (and five times between 2005 and 2014!).

Or consider Finland’s Torne River, whose ice breakup dates have moved an average of 0.66 earlier each decade since 1867. Or Lake Mendota in Wisconsin, USA, which has lost around 29-35 days of average ice cover since 1855.

Lake Mendota, 1984

Lake Mendota, 1984 (Image Credit: University of Wisconsin Digital Collections, CC BY 2.0)

Worryingly, scientists don’t yet fully understand just what we’re losing when lakes and rivers become increasingly ice free: a 2016 synthesis study of under-ice ecology warned that “we are losing ice without a deep understanding of what ecological processes are at stake”. Increasingly, scientists are working to describe and measure the impact that winter ice cover has on the year-round ecology of freshwater systems.

To be sure, we do already know quite a bit about life under the ice. Looking at a frozen lake in the wintertime, with no outward signs of life, you’d be forgiven for thinking that winter represents something of a “pause button” for aquatic ecosystems—but nothing could be further from the truth. You can think of the world underneath lake and river ice as a unique, ephemeral ecosystem that appears each winter and disappears each year as the ice melts. Many aspects of this ephemeral winter ecosystem are well understood, but others aren’t; the connections between winter ecology and the rest of the year are particularly under-studied.

Let’s start with some of the most well known aspects of under-ice ecology: animal species, and the adaptations that let them survive a harsh winter under ice. As anyone who has gone ice fishing knows, fish are active under the ice in winter. They still swim around, catching and eating prey—just, for most species, at a slower pace. To save energy, many fish species slow their growth rate and avoid unnecessary movements during winter. Some other fish species prefer colder water, and they tend to be pretty active in the winter, as long as the lake has enough oxygen under the ice to support their activity (lakes with a lot of organic matter can be low on oxygen; that’s why clearer cold lakes are sometimes more associated with coldwater fish species).

Other animal species have their own unique adaptations. Some amphibians and reptiles slow their metabolism and partially bury themselves in mud at the bottom of the lake. Many of these animals are aided by their ability to absorb oxygen through their skin. And some alter their body chemistry to essentially flood their veins with antifreeze, keeping their tissues and organs safe until spring arrives to thaw them out—some species can even let their heart stop beating in the winter, only to thaw out and awaken in the spring!

Some mammals have to deal with lake ice, too. Beavers might be one of the most fascinating examples—they spend the entire winter in lakeside shelters that they’ve constructed out of sticks and mud. The interior of these lodges are mostly above the surface of the lake, but the entrances are underwater. Once the lake ices over, beavers spend most of their time eating branches that they stockpiled in the lodge during the fall, though they also swim out under the ice occasionally in search of other food.

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Sampling fish under ice at the Mississippi National River and Recreation Area

As fascinating as animal adaptations are, the under-ice lives of smaller life forms—plants, plankton, and algaes—may be even more interesting, because they are far less well understood. A major conclusion of the Hampton et al. 2016 study is that photosynthetic algae remain highly active under ice, especially in lakes without much snow cover to block sunlight through the ice. Many of these photosynthesizers actually hang onto the underside of the ice, maximizing their access to sunlight. These algae are foundational to lake food webs, and might play a key role in feeding new zooplankton, insects, and fish that hatch before many new spring plants and algae have had a chance to grow.

On the other hand, other studies point out that longer ice-free periods can result in a longer growing season, leading to overall greater productivity in lakes (O’Beirne et al. 2017, Creed et al. 2018). Of course, this longer ice-free growing period may come with unforeseen consequences, such as greater input of terrestrial plant matter, greater year-round input of water from precipitation and runoff, and changes in lake chemistry.

The number of unknowns in under-ice ecology, combined with the urgency of studying a system that is quickly shrinking, mean that we can probably look forward to many more studies of life under lake ice in the years to come.

A ‘Stepping-Stone’ Approach to Endangered Species Release

Image Credit: Guy Monty, Image Cropped, CC BY-NC-SA 2.0

Optimizing release strategies: a stepping-stone approach to reintroduction (2019) Lloyd et al., Animal Conservation, 22.

The Crux

Restoring endangered species through breeding the species in captivity has become common practice over the last century, and has led to the successful recovery of many species. But the process is complicated, as there are always dangers inherent in releasing species that have become used to captivity back into the wild.

This week’s researchers wanted to test a new approach: rather than releasing species directly back into an area where they have disappeared from, they wanted to first release individuals into an already-occupied habitat patch, where predators and prey were present but the species had a high survival probability. This would be a stepping stone before a second release, intended to restore a population in a new area.

What They Did

The species here is the Vancouver Island marmot (Marmota vancouverensis), found only in the mountains of Vancouver Island, Canada. Conservation breeding started in 1997, with the wild population dropping below 30 in 2003. Marmots from four different Canadian institutions were transferred to one of the institutions, the Mt. Washington Marmot Recovery Centre, to undergo a period of quarantine before release.

Some of these marmots were then released for a year into a safe area on Mount Washington, Vancouver Island – the ‘stepping stone’. They were then released into a more challenging area on Vancouver Island, along with captive marmots who had not been exposed to the stepping stone, and wild marmots translocated from Mount Washington. These groups enabled the researchers to compare survival.

The researchers then modelled the survival of each marmot group against the release type, as well as the year and location of release.

Did You Know: Species Tracking

GPS technology has come a long way in recent years, and it has benefited ecologists enormously. This study utilised radio tracking on the miniscule marmot. But the size of radio trackers in the past often made them unethical. Australian Rakalis were notorious for being able to remove almost any radio tracker. However with advances in technology have come significant advances in our understanding of animal movement. Sirtrack in New Zealand are now able to place a radio tracker on a dragonfly.

What They Found

Marmots released into the stepping stone environment had high survival rates initially. These dropped when they were translocated to the wild, but rebounded after a year, coming close to the other wild marmots. Captive marmots released directly into the wild, however, had low survival rates for the first two years before rebounding, suggesting that there is potentially a two year acclimation period for the species.

Problems?

The experiment required a very specific type of habitat. It needed to have predators and prey, but not so many that the marmots are likely to be hunted at natural levels. In this experiment, human activities on Mount Washington kept predator levels low. This sort of habitat is not always possible to locate, especially for larger species.

So What?

Being able to increase the survival rates of captive-bred species is obviously a huge boost. As highlighted above though, this method is not simply possible for all species. However it does give conservationists a clear avenue forward for further research.

And lastly, studies like this really highlight the role human land use clearance plays in lowering species survival rates. The larger the suitable habitat area for a species, the more likely we are to be able to find suitable stepping stone environments for them.

Shelley Adamo: Consider the Invertebrate

Shelley Adamo was recently asked to testify before the Canadian senate as to whether or not lobsters felt pain (Image Credit: Marco Verch, CC BY 2.0)

Dr. Shelley Adamo is a full professor at Dalhousie University in Halifax, Nova Scotia, Canada. An internationally recognized expert in the field of ecoimmunology and comparative psychoneuroimmunology, Dr. Adamo has an enormous amount of scientific experience in both the lab and field. In addition to her stellar career in academia, she has also brought her expertise and knowledge to the public, as she was recently asked to testify before a Canadian senate committee to discuss whether or not insects feel pain.

During Shelley’s recent visit to my university, I took the opportunity to sit down and talk to her about appearing before the senate, the concept of pain in invertebrates, and the plight of the insect world in general.

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Why Australia is Approaching a ‘Climate Change’ Election

Image Credit: Tim J Keegan, CC BY-SA 2.0

This weekend, Australia will have a federal election. My country will vote, not on an individual leader, but on the party that will form government for the next 3-4 years. We’ve been led by the conservative Liberals (yes, the right-wing party are called the Liberals, it’s stupid) since 2013, and that time in Australia has not been kind to the environment. A tax on carbon was repealed almost as soon as it was implemented, prioritising large businesses has caused potentially irreversible damage to iconic ecosystems around the country, and a disregard for the potential impacts of climate change have been a trademark of the present government.

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How Different is Too Different?

This Peruvian warbling-antbird must walk a fine line between being different enough from its competitors to reproduce successfully, while staying similar enough to be able to recognize and outcompete the same competitors (Image Credit: Hector Bottai, Image Cropped, CC BY-SA 4.0).

Range-wide spatial mapping reveals convergent character displacement
of bird song (2019)
Kirschel et al., Proc B, https://dx.doi.org/10.1098/rspb.2019.0443

The Crux

In nature, many different organisms can be found in a single location, and sometimes those organisms are closely related to one another. When this happens, classical evolutionary theory predicts that these closely related species should differ in some ways, so as to differentiate members of their own species from others and avoid the costs associated with breeding with a mate that will not produce any viable offspring. This is called character displacement, and there are many examples of this in nature where two different species may be very similar when they live in different places (allopatry), but when they live in the same place (sympatry) they will differ in appearance, behavior, or the exact part of the local habitat that they live in (see Niche Partioning below).

A specific form of character displacement, called agonistic character displacement, occurs when traits or behaviors associated with competition differ between closely related species living in the same area. This is thought to reduce the costs of wasting energy on competing with an organism that you don’t really “compete” with. Agonistic character displacement can, however, result in greater similarity of traits when similar species live together, but previous studies in this area have not accounted for other causes of this similarity. Today’s authors wanted to do just that. Read more

Hvorfor er dyr hvor de er?

Image Credit: Endre Gruner Ofstad, CC BY-SA 2.0

Guest post by Endre Grüner Ofstad. English version here.

Use, selection, and home range properties: complex patterns of individual habitat utilization (2019) Endre Ofstad et al., Ecosphere, 10(4), https://doi.org/10.1002/ecs2.2695

Det essensielle

Stedene man finner dyr omtales gjerne som dyrets habitat. Habitat er et relativt vagt begrep. Hvor individ oppholder er som regel et utfall av en rekke vurderinger: hvor finner en mat, hvor unngår man rovdyr og hvor finner man noen å parre seg. Individ avveier blant disse for å maksimere hvor mange avkom de kan tilføre fremtidige generasjoner (også kalt for ‘fitness’).

Når vi skal vurdere hvilke habitat dyr befinner seg i så jobber vi som regel med habitatseleksjon. Habitatseleksjon er hvor mye et habitat blir brukt i forhold til hvor tilgjengelig det er, dvs. hva er den relative sannsynligheten for at et dyr vil bruke et habitat hvis det får muligheten. Hvor mye tid et individ velger å bruke (eller tettheten av individ) i et habitat er som regel en god indikator på hvor viktig et gitt habitat er. Habitatseleksjon blir derfor ofte brukt til å identifisere hvilke habitat forvaltningen bør iverksette tiltak.

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Idealism and Environmentalism: The Green New Deal

American politicians Alexandra Ocasio-Cortez and Ed Markey, champions of the controversial environmentalist bill, the Green New Deal (Image Credit: Senate Democrats, CC BY 2.0)

If you’ve lost track of what’s going on in US politics (very excusable), you might have missed out on yet another issue that is dividing people. I’m not talking about the Mueller report, or gun legislation, or health care. I’m talking about the Green New Deal, named after the New Deal, a compilation of programs and projects that gave Americans jobs after the Great Depression and built quite a lot of infrastructure. The newest “Green” version is meant to do the same following the Great Recession that America has been suffering the aftershocks of since late last decade. An initiative sponsored by Democrats, the Green New Deal has come under fire from both sides for a wide range of reasons. While the movement for action against climate change is a global phenomenon, I am going to give a brief synopsis of what the Green New Deal represents in the US, and why it has been the subject of so much controversy.

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