Environment

Shaken, not stirred: How climate change can upset the chemistry of freshwater lakes

Shaken, not stirred: How clima...
Climate change could shake up the ecology of freshwater lakes, such as Lake Tahoe
Climate change could shake up the ecology of freshwater lakes, such as Lake Tahoe
View 1 Image
Climate change could shake up the ecology of freshwater lakes, such as Lake Tahoe
1/1
Climate change could shake up the ecology of freshwater lakes, such as Lake Tahoe

Much like James Bond's favorite cocktails, freshwater lakes need to be shaken up in order to make sure vital ingredients are evenly distributed within. Without a giant cocktail shaker at its disposal, nature carries out this task by way of big storms in the colder months that turn over the bodies of water and preserve the health of the ecosystem. But scientists are now warning that rising surface temperatures may bring an end to this, which would give algae new rein over these lakes and seriously threaten fish populations and vital freshwater resources.

Recent data has shown that the average temperature of the Earth's lakes is rising by 0.61° F (0.34° C) each decade. This warming is expected to bring about an increase in algal blooms by as much as 20 percent, which would spell big trouble for fisheries, tourism, water supplies and the environment as a whole.

The buildup of algae is problematic and not just because it can poison water supplies. When it dies, its decomposition soaks up dissolved oxygen in the water, leaving low-oxygen dead zones for suffocating animal life to endure.

One way we are already contributing to the growth of algae in lakes and streams is through something known as nutrient pollution, or eutrophication. Fertilizer runoff, improperly monitored sewage systems and other human activity is loading up lakes and reservoirs with more nutrients than they can handle. This is in turn fertilizing the algae in the water and resulting in more frequent and severe algal blooms.

Scientists at the University of California, Davis (UC Davis) have now uncovered yet another source of nutrient pollution, which they have dubbed climate eutrophication. For almost 50 years, UC Davis researchers have tracked surface temperatures at Lake Tahoe, finding that they have risen by almost 0.9° F (0.5° C) since 1968.

This has had the effect of stabilizing the lake's thermal layers and lengthening of the so-called stratification season, in which water rests in separate layers as a result of varying temperature, by 24 days. This makes it more difficult for the storms that sweep through in fall and late winter to have their usual effect of shaking up the lake water, leaving dissolved oxygen in the surface layers and the starved lower layers left wanting.

Over time, if these stratification seasons continue to grow longer and the levels of dissolved oxygen in the lower levels keep diminishing, the livelihood of marine life operating at these depths won't be the only concern. The researchers say this will trigger a chemical reaction particular to low-oxygen environments that draws nutrients out of the lakebed and into the water, offering another avenue for nutrient pollution to impact the planet's freshwater reserves.

To get an idea of how this may affect Lake Tahoe in the future, the scientists came up with projections of future conditions based on a couple of carbon emission scenarios published by the Intergovernmental Panel on Climate Change, paired with a model of how water moves around the lake. One scenario had carbon emissions slow down and halted by the year 2100, while the other had them increasing rapidly. This saw the stratification season grow by 12 and 38 days, respectively.

This would be brought about by increases in air temperature between 4.5 and 7° F (2.5 and 4° C) and a drop in wind speeds by seven to 10 percent. While the study and these projections pertain only to Lake Tahoe, the researchers note that the process could also play out in other deep lakes around the world.

The research was published in the journal Limnology and Oceanography.

Source: The Conversation

7 comments
Kaiser Derden
what rising temperatures ? it hasn't gone up in 20 years ...
Lbrewer42
How much of the "greenhouse gas" CO2 has to be added to a greenhouse in order to make it warmer inside? Answer from High school level science: None. It is CO2 is incapable of holding in heat... fact. No extra CO2 is added b/c plants only need the amount of CO2 present in the air to make water vapor (just one of the products of photosynthesis) - which the greenhouse is designed to trap - b/c water vapor is what holds in the heat. Look it up in ANY high school (and lower level) science book. This is why the weather forecasters give a heat index related to water vapor or ... humidity. The political, powermonging (more regulation, more bureaucracy), money making scam of global warming suckered the uneducated masses by saying CO2 would raise the temperature globally. The perpetrators knew they would not be able to force people to pay for water vapor emissions since they could not sell water was damaging to the environment, so they turned to CO2 since people associate CO2 with plants, plants woth greenhouses, and greenhouses with heat. Re-read the science part. The media goes by the old saying that if you say something long enough, people will believe it. Have you been suckered? And, BTW, if some naysayer says increasing CO2 will only make more water vapor in the atmosphere - hence more heat - just like in a greenhouse... In nature, water vapor becomes precipitation. It is part of the natural hydrologic cycle. Precipitation does not raise temperatures either. In fact, even if man COULD produce enough CO2 to make a difference in the atmosphere overall, the plants would simply flourish with having more to respirate, and we would have more O2 and water vapor released by them. Dead issue. It was a long time ago, but the masses love being reprogrammed by the media. Welcome to the modern dark ages where the word "science" instead of "religion" is used to control.
Rann Xeroxx
Even if you buy into AGW, the over overall trend will be significant cooling in the next thousands of years as that is the geological patterns show peaks and valleys. We have already peaked.
christopher
Yesterdays headlines: a scientist disciplined for impugning the reputation of a fellow after pointing out his climate-doom report was using fake photos. It is now officially impossible to believe anything whatsoever that "climate scientists" report, because if it's pro-doom, it's OK, but if it's truthful, that's a punishable sin. Not to mention the minor fact - there's 7.5bn humans on our planet, and that quadruples in each of our lifetimes. No matter how much doom-crying goes on, there's not a licking bit of noticeable difference the few who care can ever make to our climate's direction.
Aloysius
And what if you all are wrong. Sure, sure, you're right, global warming is a hoax, climate change is just so those poor scientists can drive BMWs and those regulators can have the power to ban Muslims or whatever. But what if you're wrong? What if climate change is real? Well, you probably won't reap what you are sowing, but your children and grandchildren definitely will. So, I guess it's a win-win for you, you get to expound and beat your chest and feel intelligent, while leaving your kids to suffer for your foolishness. If, that is, you are wrong. But of course, you're never wrong, right?
CharlesTerry
More Propaganda wrapped up in faux science. Peer Review is not the College of Cardinals they are only the Spell, Grammar, Math and Plagiarism Check. The Peer Reviewers have refused to review any counter theories on AGW. That is why Debate is needed to put this all to rest. The problem is the Globul Warmies refuse to debate. They refuse so strenuously that debate on AGW is forbidden in Colleges and University. You can visit a debate class and see the topics available for debate including if the Earth is Round or Flat but no debate on AGW. Propagandist make excuses why not to debate. That is what a Brown Shirt does refuse to debate and cast insults not Science.
Nik
The current climate changes have nothing whatsoever to do with CO2, and are typical of the precursors to a return to an Ice Age, from our temporary inter-ice age. The inter ice age period lasts about 10k years, this one has already lasted that long. More heat = more evaporation, = more precipitation. The USA, and other countries, worldwide, have been experiencing their highest rain, and snowfalls on record. Each year, the heavier snow falls lies a little longer, they reflect sunlight, as does the increasing cloud cover. The effect is asymptotic. The smoke from increasing forest fires, caused by 10k years of rain washing the nutrients through the soil, out of reach of the trees, weakening them, and making them more vulnerable to disease, and fire, diminishes the sunlight reaching the ground, and also causing cooling. From deep sea and lake core drillings, which have shown climate changes over the last 1 million years, the change from inter ice age back to ice age can occur in as little as 20 - 50 years. Humans have more to fear from global cooling, not warming, although they are linked, one precipitates the other. As the seas warm they release dissolved CO2, the same way that beer loses its fizz when it warms. Atmospheric CO2 follows warming, it has never led warming, therefore cannot be the cause. A NASA scientist has predicted a return to an ice age within 40 years, not based on 'climate' but in predictable solar emissions, which NASA monitors assiduously.