FRONT PAGES: Climate Change Reduces Nutrition And Increases Toxicity At Food Web Base

dWeb.News Article from Daniel Webster dWeb.News

dWeb.News Article from Daniel Webster dWeb.News

dWeb.News Article from Daniel Webster dWeb.News

Newswise HANOVER, N.H. – October 25, – According to research by Dartmouth College, and the Swedish University of Agricultural Sciences, climate change impacts on freshwater systems may lower nutrition and increase toxicity.

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, organic matter supply from water to land,” said Pianpian W ,, a Dartmouth postdoctoral fellow and the lead author of this 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 showed that warmer and browner water results in a higher transfer of methylmercury to the food web’s base. It was also found that phytoplankton had lower levels of essential polyunsaturated fat acids.

Long chain polyunsaturated fat acids (such as omega-3 or omega-6) support the growth and survival both of plant and animal life. They provide energy and regulate immune systems. Methylmercury, a form mercury that can be easily absorbed by living organisms, is a neurotoxin.

” The decrease in polyunsaturated acid levels at the end of the mesocosm experiment that had both warming and browning effects was alarming,” Wu said. Wu started the research as a PhD student at the Swedish University of Agricultural Sciences.

Phytoplankton are the main suppliers of polyunsaturated fatty acids in aquatic ecosystems. The study found that phytoplankton with lower nutritional value due to browning and warmer waters causes higher-level organisms (such as fish, zooplankton and humans) to be exposed to more of the methylmercury to meet their fatty acid quotas.

“This research shows that aquatic food webs’ food quality is declining with climate change,” stated Kevin Bishop , senior researcher at the Swedish University of Agricultural Sciences. “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 thermo-insulated plastic cylinders to examine the effects of different levels of browning and warming under four scenarios. Subalpine climates are extremely prone to climate changes and have low levels of dissolved organic matter. The mesocosms were tested in subalpine environments.

” It is important to use mesocosms for investigating questions related to ecosystem changes caused by climate change,” stated Celia Chen , research assistant at Dartmouth, and co-author of this study. Mesocosms can test the effects of temperature and browning individually or in combination with 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 highlight the importance of considering both consumption and concentration levels when assessing the quality of freshwater systems’ food web.

Martin Kainz, Katharina Winter, WasserCluster Lunz – Biologische Station; Fernando Valdes (Uppsala University); Siwen Zheng, Rui Wang, Tongji University, and Brian Branfireun (Western University) were all co-authors.

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