At Rensselaer Polytechnic Institute, my colleague Rick Relyea and his lab are working to quantify how increases in salinity affect ecosystems. Not surprisingly, they have found that high salinity has negative impacts on many species. They have also discovered that some species have the ability to cope with these increases in salinity.
But this ability comes at a price. In a recent study, Rick and I analyzed how a common species of zooplankton, Daphnia pulex, adapts to increasing levels of road salt. We found that this exposure affected an important biological rhythm: The circadian clock, which may govern Daphnia‘s feeding and predation avoidance behaviors. Since many fish prey on Daphnia, this effect could have ripples throughout entire ecosystems. Our work also raises questions about whether salt, or other environmental pollutants, could have similar impacts on the human circadian clock.
In studying how road salt affects aquatic ecosystems, the Relyea lab showed that Daphnia pulex can adapt to handle moderate exposures in as little as two and a half months. These levels ranged from 15 milligrams of chloride (a building block of salt) per liter of water to a high of 1,000 milligrams per liter – a level found in highly contaminated lakes in North America.
However, an organism’s ability to adapt to something in its environment can also be accompanied by negative trade-offs. My lab’s collaboration with Rick’s began in an effort to identify these trade-offs in salt-adapted Daphnia.
In my lab, we study how our circadian rhythms allow us to keep track of time. We investigate how the molecules in our cells work together to tick like a clock. These circadian rhythms allow an organism to anticipate 24-hour oscillations in its environment, such as changes from light (daytime) to dark (nighttime), and are essential to an organism’s fitness.
Rick and I hypothesized that adaptation to high salinity could disrupt Daphnia’s circadian rhythms based on recent evidence showing that other environmental contaminants can disrupt circadian behavior. One important behavior in Daphnia that may be controlled by the circadian clock is the diel vertical migration – the largest daily biomass migration on Earth, which occurs in oceans, bays and lakes. Plankton and fish migrate down to deeper water during the day to avoid predators and sun damage, and back up toward the surface at night to feed.
Given what we know about circadian function, it would be logical to assume that exposure to pollution would not affect an organism’s circadian rhythms. While circadian clocks can incorporate environmental information to tell the time of day, they are heavily buffered against most environmental effects.
To understand the importance of this buffering, imagine that the timing of an organism’s day length responded to environmental temperature. Heat speeds up molecular reactions, so on hot days the organism’s 24-hour rhythm could become 20 hours, and on cold days it might become 28 hours. In essence, the organism would have a thermometer, not a clock.
To determine whether clock disruption is a trade-off to pollutant adaptation, we first had to establish that Daphnia is governed by a circadian clock. To do this, we identified genes in Daphnia that are similar to two genes, known as period and clock, in an organism that serves as a circadian model system: Drosophila melanogaster, the common fruit fly.
We tracked the levels of period and clock in Daphnia, keeping the organisms in constant darkness to ensure that a light stimulus did not affect these levels. Our data showed that the levels of period and clock varied over time with a 24-hour rhythm – a clear indication that Daphnia have a functional circadian clock.
We also tracked the same genes in populations of Daphnia that had adapted to increased salinity. Much to my surprise, we discovered that the daily variation of period and clock levels deteriorated directly with the level of salinity the Daphnia were adapted to. In other words, as Daphnia adapted to higher salinity levels, they showed less variation in the levels of period and clock over the day. This demonstrated that Daphnia’s clock is indeed affected by pollutant exposure.
We currently don’t understand what causes this effect, but the relationship between salinity levels and decreased variation in the levels of period and clock offers a clue. We know that exposure to pollutants causes Daphnia to undergo epigenetic regulation – chemical changes that affect the function of their genes, without altering their DNA. And epigenetic changes often show a gradual response, becoming more pronounced as the causal factor increases. Therefore, it is likely that high salinity is inducing chemical changes through these epigenetic mechanisms in Daphnia to suppress the function of its circadian clock.
We know that environmental conditions can affect what the clock regulates in many species. For example, changing the sugar that the fungus Neurospora crassa grows on changes which behaviors the clock regulates. But to our knowledge, this study is the first to show that genes of an organism’s core clock can be directly impacted by adapting to an environmental contaminant. Our finding suggests that just as the gears of a mechanical clock can rust over time, the circadian clock can be permanently impacted by environmental exposure.
This research has important implications. First, if Daphnia’s circadian clock regulates its participation in the diel vertical migration, then disrupting the clock could mean that Daphnia do not migrate in the water column. Daphnia are key consumers of algae and a food source for many fish, so disrupting their circadian rhythms could affect entire ecosystems.
Second, our findings indicate that environmental pollution may have broader effects on humans than previously understood. The genes and processes in Daphnia’s clock are very similar to those that regulate the clock in humans. Our circadian rhythms control genes that create cellular oscillations affecting cell function, division and growth, along with physiological parameters such as body temperature and immune responses.
When these rhythms are disrupted in humans, we see increased rates of cancer, diabetes, obesity, heart disease, depression and many other diseases. Our work suggests that exposure to environmental pollutants may be depressing the function of human clocks, which could lead to increased rates of disease.
We are continuing our work by studying how the disruption of Daphnia’s clock affects its participation in the diel vertical migration. We are also working to determine the underlying causes of these changes, to establish whether and how this could happen in the human brain. The impacts we have found in Daphnia show that even a simple substance such as salt can have extremely complex effects on living organisms.
By Jennifer Marie Hurley, Assistant Professor of Biological Sciences, Rensselaer Polytechnic Institute
This article was originally published on The Conversation. Read the original article.
As of Tuesday evening, the Weather Channel put the deaths at 12, but overnight that number increased. One elderly woman from Detroit was found by the custodian shoveling snow at a school, WXYZ reported.
Police say that the 96-year-old woman lived alone and seemed to have wandered away from her house. She was dressed only in a nightgown, robe and slippers. The family told police she had just been diagnosed with dementia. Temperatures in Detroit overnight were in the single digits with wind chills below zero.
Each year, the cold claims more deaths than heat waves, the CDC reported in 2016. According to the study, older people are more susceptible to succumb to extreme temperature variations than younger people. Income is also a factor in weather deaths. The Washington Post cited the analysis, finding “weather-related death rates were two to seven times as high in low-income counties as in high-income counties.”
Homeless people living on the streets might be bundled up, but hypothermia can set in after prolonged exposure. Poorer families also face dangers if they live without temperature-regulating luxurious like insulation or heat.
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Weather related deaths (Data via CDC - chart via Washington Post)[/caption]
The CDC found that cold kills 20 times more people than heat does. On average 144,000 die from cold weather, compared to 9,000 from hot weather.
The problem isn't unique to the United States. From 2012 to 2016 more than 120,000 people in England and Wales died from the cold weather or cold-related causes.
Here are seven terrifying things about this storm, including maps and projections that should warn you to bundle up over the next several days:
1. What is a bomb cyclone?
The term “bomb cyclone” is new to meteorological terminology, though phrases like "polar vortex" have been used in previous years. If the storm continues to develop as scientists expect it will, it's worth the impending doom weather experts are warning of. After a series of snow storms, temperatures are expected to plummet Thursday in record-setting freezes. The atmospheric pressure is also expected to drop Thursday in a way that has scientists glued to satellite data.
"It will be massive," National Weather Service meteorologist Ryan Maue warned on Twitter Tuesday.
2. It's colder in the lower U.S. than in Alaska
Tuesday night, meteorologists reported temperatures in Alaska were higher than Jacksonville, Florida.
“This is not record-breaking for Canada or Alaska or northern Siberia, it’s just misplaced,” said Judah Cohen, a winter storm expert for Atmospheric Environmental Research. He's forecasting a colder than normal winter for much of the U.S.
3. The pressure is expected to fall incredibly fast.
In the popular natural disaster film "The Day After Tomorrow," the eye of a freezing hurricane-like storm causes the temperatures to fall so quickly an American flag froze blowing in the wind. The atmospheric pressure isn’t expected to drop quite that quickly, but the Washington Post’s “Capital Weather Gang” believes the storm will undergo “explosive strengthening.”
4. It looks like a frozen hurricane:
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Pressure and wind visualization of storm off the coast of New England on Thursday. (WindyTV.com)[/caption]
The National Weather Service has already posted a winter storm up the coast of Florida. It'll continue it's path up the east coast like a kind of frozen hurricane
Also like something out of "The Day After Tomorrow," this polar vortex looks remarkably similar to the fictional one that ushered in a new Ice Age.
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Fake weather map from the film "The Day After Tomorrow" (Photo: Screen capture)[/caption]
5. This is the first winter storm warning issued by the National Weather Service office in Tallahassee in four years.
According to the Weather Channel, the NWS in Tallahasse had to issue a winter storm warning for the first time in four years. The last time was Winter Storm Leon, which produced ice and snow all over the southeastern United States. It caused a travel nightmare in Atlanta and across Florida and Alabama.
6. An ice storm is expected into northern Florida.
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Polar vortex predictions for 2018 (Photo: AccuWeather map screen capture)[/caption]
CNN meteorologist Chad Myers warned that every time "you see pink in Florida" you know things are going to be bad.
7. Snow is going to be bad
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(Photo: Weather channel screen capture)[/caption]
In an area of the country that doesn't see severe winter weather, things like snow plows or snow blowers aren't a staple for municipalities. So, when they get dumped on with snow, it will cause massive infrastructure problems. Roads won't be plowed with the speed seen in places like Ohio or Michigan.
