Tag Archives: fish

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.

Does Invading Change You?

The red lionfish, an aggressive, fecund, and competitive species invasive to the Atlantic Ocean (Image Credit: Alexander Vasenin, CC BY-SA 3.0).

The genomics of invasion: characterization of red lionfish (Pterois volitans) populations from the native and introduced ranges (2019) Burford Reiskind et al., Biological Invasions, https://doi.org/10.1007/s10530-019-01992-0(0123456789

The Crux

Invasive species are one of the most destructive forces and largest threats to native ecosystems, second only to habitat loss. The “how” and “when” of a species invading new habitats is obviously important, and as such many studies focus on if invasive species are present and if they are spreading. Yet these studies often disregard the mechanisms behind why a species is spreading or succeeding in these new environments. The mechanisms are important here, because by and large most invasive organisms will have very small populations sizes, leaving them vulnerable to stochastic events like environmental flux, disease, and inbreeding depression.

Two key paradoxes of invasive species are that these small groups of invasive organisms tend to not only have more genetic diversity than the native species (making them more adaptable to environmental change), but they are also able to outcompete the native organisms, despite having evolved in and adapted to what may be a completely different environment. The authors of this study used genomic approaches to address and try to understand these paradoxes.  Read more

The Ecology of a Mermaid

Adam regales us with one of the weirdest stories I’ve ever heard, and in case you were wondering, yes we do talk about how mermaids have sex. Jesus. Also there’s some cool ecology. Like how did mermaids evolve? Was it from a mutated baby tossed overboard? Probably not.

05:19 – Mermaids in Cinema
16:35 – Ecology of the Mermaids
33:25 – Mermaid Copulation (you were warned)
38:07 – The Mermaids vs. Jaws

You can also find us on iTunes and Google Play.

Finished Before You Even Started

Predators are known to affect prey while they are adults and juveniles, but what about when they haven’t even hatched yet?  (Image Credit: Bernt Rostad, CC BY 2.0)

Predation risk affects egg mortality and carry over effects in the larval stages in damselflies (2018) Sniegula et al., Freshwater Biology, p. 1-9

The Crux

In the natural world, one of the most dangerous things that a prey animal has to worry about is a predator. These organisms depend on the prey for their sustenance, and as such have become very good at finding ways to eat them. These are known as direct effects, as a predator eating prey is a direct interaction.

Another aspect of the predator-prey relationship is that of indirect effects, or effects that a predator has on prey that don’t involve it eating the prey animal. These can include predator-induced changes in the prey’s behavior, immune function, or even survival. These indirect effects are usually studied in prey species that are adults or juveniles, but the authors of today’s paper were interested in what indirect effects predators had on the eggs of prey species.

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How to Ecology Your Dragon

In our second week on the dragons of Dreamworks’ How to Train Your Dragon trilogy, we have a flamin’ good time discovering why those dragons are WAY too wacky, exactly how much intraspecies predation goes on in Berk and why you should really make up your mind about domestication.

03:49 – Vikings in Cinema
10:57 – Ecology of the Dragons
29:17 – Toothless vs. the Furious Five

You can also find us on iTunes and Google Play.

Fishers and Fish Science: The Australian Fish Scientist Perspective

Fishing is an important part of Australian society. So is communication between fish scientists and fishers strong enough?

Fishing is an important part of Australian society. So is communication between fish scientists and fishers strong enough? (Image Credit: State Library of Queensland, CC0)

Last Thursday, I posted an article on the need for more contact communication the fish scientist community and the fishing community, which you can find here. It gives a breakdown of why better communication between the two groups is mutually beneficial, and how it could be improved. The piece was written after talks with a number of prominent Australian fish biologists, whose thoughts I’ve shared in more detail below.

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Peter Unmack & Karl Moy: Saving an Endangered Fish from Extinction

A release of the formerly endangered Running River Rainbowfish. So how were they brought back from near-extinction?

A release of the formerly endangered Running River Rainbowfish. So how were they brought back from near-extinction? (Image Credit: Karl Moy, University of Canberra, CC BY-SA 4.0)

We talk a lot about getting the public interested in conservation and ecosystems on Ecology for the Masses, but we’ve rarely talked about how conserving a species is actually accomplished. Where does funding come from? How do you decide which individuals to save? And how do you allow a population room to grow?

In 2015, Peter Unmack was sampling in the Burdekin river system in northern Queensland, Australia, when he noticed an alien population of Eastern Rainbowfish had established in Running River. Specifically a 13km stretch bounded by two gorges, which housed the Running River Rainbowfish, a species distinct to this one stretch. Knowing that the presence of the Eastern Rainbowfish could spell the extinction of the local species, he started a crowdfunding initiative, and essentially saved the Running River Rainbowfish. I spoke to Peter and postgraduate student Karl Moy about the conservation effort.

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