Research looks at warming, browning effects on freshwater systems
DARTMOUTH COLLEGE
HANOVER, N.H. – October 25, 2021 – Climate change impacts on freshwater systems can lower nutrition and increase toxicity at the base of the food web, according to research from Dartmouth College and the Swedish University of Agricultural Sciences.
The research, published in Scientific Reports, focused on the effects of warming water temperatures and browning—a discoloration of water caused by increased dissolved organic matter—using controlled outdoor environments known as mesocosms.
“Climate change scenarios predict increases in temperature and organic matter supply from land to water,” said Pianpian Wu, a postdoctoral fellow at Dartmouth and lead author of the study. “For the first time, we used manipulated mesocosm systems to test the effects of warming and browning.”
Under the expected climate scenario of more warming, changing precipitation patterns, and higher levels of dissolved organic matter, the study looked at the fate of nutritious polyunsaturated fatty acids and toxic methylmercury in the food chain.
The research found that a combination of warmer, browner water resulted in the higher transfer of methylmercury from water to phytoplankton at the base of food web. Lower concentrations of essential polyunsaturated fatty acids in phytoplankton were also observed.
Long-chain polyunsaturated fatty acids—such as omega-3 and omega-6—support the growth and survival of animal and plant life by providing energy and by regulating immune systems. Methylmercury is a form of mercury that is easily absorbed by living organisms and acts a potent neurotoxin.
“The reduction of polyunsaturated acids at the end of the mesocosm experiment with both warming and browning effects was concerning,” said Wu, who began the research as a PhD candidate at the Swedish University of Agricultural Sciences.
Phytoplankton are the main suppliers of polyunsaturated fatty acids in aquatic ecosystems. According to the study, the less nutritious phytoplankton that result from browning and warmer water cause higher-level organisms—such as zooplankton, fish, other wildlife, and humans—to be exposed to more methylmercury as they consume more to achieve fatty acid quotas.
“This study shows that the food quality at the base of aquatic food webs deteriorates with climate change,” said Kevin Bishop, professor at the Swedish University of Agricultural Sciences and the senior researcher of the study. “The research is important because it places food web investigations within the context of active global change processes.”
While previous research on browning and warming has been conducted in natural environments, this is the only study to rely entirely on controlled mesocosm environments.
The researchers used 24 thermally insulated plastic cylinders to test the effects of various levels of warming and browning under four different scenarios, including a reference scenario without any weathering effect. The mesocosms were controlled at subalpine conditions that are highly prone to climate change effects and relatively poor in dissolved organic matter.
“The use of mesocosms to investigate questions related to ecosystem effects of climate change is particularly important,” said Celia Chen, research professor at Dartmouth and a co-author of the study. “The effects of factors such as temperature and browning can be tested individually and in combination while controlling other environmental conditions. Mesocosms also eliminate the need to travel long distances for field investigations.”
The study was conducted at the WasserCluster Lunz research facility outside of Vienna using lake water from Lunzer See in Lower Austria.
According to the research team, the findings point to the importance of factoring consumption levels in addition to concentration levels when looking at the quality of the food web in freshwater systems.
Martin Kainz and Katharina Winter, from WasserCluster Lunz- Biologische Station; Fernando Valdés, Uppsala University; Siwen Zheng and Rui Wang, Tongji University; and Brian Branfireun, Western University all served as co-authors of the study.
JOURNAL
Scientific Reports
DOI
ARTICLE TITLE
Elevated temperature and browning increase dietary methylmercury, but decrease essential fatty acids at the base of lake food webs
ARTICLE PUBLICATION DATE
19-Aug-2021
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”Phytoplankton are the main suppliers of polyunsaturated fatty acids in aquatic ecosystems. According to the study, the less nutritious phytoplankton that result from browning and warmer water ”
Does that mean that in areas that around say 2 degrees C warmer and with higher rainfall (closer to the equator) are less nutritious than in cooler zones?
I just can’t understand how nature can cope.
This study is a joke, established by a simple truth. The hot parts of the planet, that have been far hotter than the rest of the planet, did not experience this doom BS.
If it were true, they would only need visit and observer in those places and make empirically supported assertions.
Instead they made their own system and no doubt made changes that don’t happen in nature and in an extremely short time period compared to 100 years of alleged slow change over time because of future “predicted” warming.
This is a study method akin to putting corals in acidic water, it kills them, yet if you slowly change the pH to the same reasonably expected pH level over a 100 period, those corals would adapt (exactly how much I don’t know), but the outcome would be drastically different.
It’s the same with this study, not nature, a controlled system where it seems to me the scientists set out wanting to come to this conclusion, and building a study around that. (How can we make this system do what we want it to do?) and they did just that.
This is not science, it’s advocacy
I wonder how they explain how life functioned when the earth was several degrees warmer than now and it been that way for most of the history of the earth. Are they that ill informed?
“We changed the water contents of some barrels and tried to conclude what would happen to entire river systems. We try to do science at Dartmouth but we’re not as good at it as we are at keg parties.”
Simulations? So, no facts just a bunch of made up crap and leftarded lies.
Everything I’ve read about warmings all flora and fauna increased and then decreased as cooling came. With warming there is more tropical rain that floods into water bodies and includes snow/ice melts from the colder parts that brings nutrients to the flora and fauna. These people are nut cases.
Blah blah blah… the earth has been much warmer and had much more CO2 in the past. Life will adapt, even if there is one shred of truth in this paper, which itself is highly questionable.
Chinese scientist pushing global warming. Unsurprised.