Foraminifera are mostly marine organisms that have been around for about 550 million years and when they die, their shells accumulate on the ocean floor and become part of the ocean sediment.

While they are microscopic organisms (between 63 and 500 micrometers in diameter) they are still ‘big’ compared to other single-cell organisms, with each species having a unique shape. They live and are abundant in all marine sediments, from estuaries to the deep sea.

Geologists have studied them for a long time because their shells can fossilize, but we do not know much about their biology. Dr. Langlet is trying to understand how they move in the sediment and how this affects the entire sea bottom ecosystem.

Bioturbation occurs when organisms disturb the sediment by moving in it and creating burrows, which affects the mixing of the sediment particles. This affects the size of the particles, regulates water through the sediment, and changes the chemical composition of the sediment.

Bioturbators, often referred to as ’tillers of the soil’, play an important role in determining nutrient availability and providing food and shelter for many species. They also significantly contribute to many natural processes and outputs, collectively known as ‘ecosystem services’, that we humans greatly benefit from.

“Typically, at the surface of marine sediments oxygen is consumed by the organisms living in the sediment, and gradually the oxygen decreases as you go deeper. We asked the question, ‘Does foraminifera affect the oxygen distribution in the sediment when they move or when they create burrows?'” said Dr. Langlet.

“It was hypothesized for a long time that they affect the oxygenation and chemistry of the sediment, but it was never proven because they are so small that their impact is very difficult to detect.” Previous studies have shown that larger multicellular organisms, such as worms, increase the oxygen penetration in the sediment by creating burrows, but this has never been shown for single-cell organisms such as foraminifera.

By creating burrows, foraminifera are engineering their entire ecosystem at a small-scale, allowing them to live deeper in the sediment where there is usually no oxygen. The scientists show that through their burrowing, they affect not just oxygenation but organic matter, bacterial diversity and ultimately how much food there is available in the sediment.

Finding enough foraminifera for the experiment was a challenge. “For a big aquarium, we need to study many foraminifera and it is very time consuming to isolate them to know how many there are, so we must work with small amounts of sediment. It’s all about miniaturization, working with small systems,” Dr. Langlet explained.

The effect that these organisms have on their environment is relatively small because of their very small size, so the scientists needed very precise instruments, called microsensors, to accurately measure the distribution of oxygen in the sediment.

In his lab at OIST, Dr. Langlet worked with tiny sediment samples, each about 1 cm wide, placed in a tank filled with water. He added foraminifera to these samples and every few days measured how the oxygen levels changed at different depths. He found that with their burrows, foraminifera allow oxygen to go deeper into the sediment, increasing the amount of oxygen by 15 to 20 per cent. This causes a decrease in organic matter which leads to reduced bacterial abundance, which ultimately decreases the movement of oxygen from the water into the sediment.

Dr. Langlet’s future research will explore the interactions between foraminifera and other organisms of similar size, as well as larger animals such as worms. “Are foraminifera interacting with these worm-created burrows? Could their presence potentially amplify the effects of these burrows?” he asks. These questions will guide his future investigations.

“We look at more than a decade of precipitation events in the state of Wisconsin and quantify the increase in nutrient runoff right around the event and at the end of the growing season. Climate models predict that we’ll continue to see an increase in extreme events, and our works speaks to the challenging relationship between nutrient use and water quality,” said Marin Skidmore, assistant professor in the Department of Agricultural and Consumer Economics, part of the College of Agricultural, Consumer and Environmental Sciences (ACES) at U. of I. Skidmore is lead author of the study with coauthors Jeremy Foltz from University of Wisconsin-Madison and Tihitina Andarge from the University of Massachusetts-Amherst.

“Our focus on a single state allows us to accurately measure farm locations and practices, while keeping statewide regulation constant, in a way that would be difficult in a national study,” Skidmore added.

Livestock manure and crop fertilizer are major causes of nonpoint source pollution from agriculture. Wisconsin has a large dairy industry, where most farms are below the federal definition of concentrated animal feeding operations (CAFOs) and therefore not regulated under the Clean Water Act. Instead, they are subject to a patchwork of local regulations.

The researchers studied water quality across nearly 50 watersheds in Wisconsin from 2008 to 2020. They correlated ammonia and phosphorus concentration data from the Water Quality Portal with the location of livestock farms and crop acreages, and they determined nutrient levels after ½ inch, 1 inch, and 2 inches of rainfall.

They found spikes in nutrient concentrations immediately after extreme precipitation events, and the effect increased with the amount of precipitation. For example, within five days of an inch of precipitation, ammonia was 49% higher and phosphorus was 24% higher. If there was at least one day in a month with over an inch of precipitation, monthly ammonia was 28% higher and monthly phosphorus was 15% higher.

“We observe a significant interaction between rainfall, agricultural production, and runoff. It is not just a short-term spike in nutrient levels; at the end of the season, we still see persistent increases in phosphorus and ammonia attributed to those extreme precipitation events months earlier,” Skidmore stated.

However, the researchers found that agricultural management practices can help mitigate the effects.

“Our results show that cover crops planted in the winter can lower the amount of nutrients in the water. Areas with cover crops have significantly lower spikes in ammonia and phosphorus, and the effect persists until the end of the growing season. We already know cover crops are great for soils and nutrient management, but this is additional empirical evidence showing that cover crops are climate-smart practices that can help agriculture be resilient into the future,” Skidmore said.

The researchers also observed the presence of legacy nutrients, which are left behind from agricultural practices decades or even centuries ago.

“There is a direct impact of extreme precipitation on runoff that is unexplained by current activities. We attribute this to sedimented nutrients that remain in the soil from previous activities,” Skidmore noted. “One of the best ways to deal with legacy nutrients is to ensure soils are healthy. By preventing soil erosion, you keep the legacy nutrients in the soil and out of surface water. These findings further support the use of management practices such as conservation tillage, vegetative buffer strips, and cover crops.”

Wisconsin watersheds feed into North America’s two largest river systems, the Mississippi and Great Lakes/St. Lawrence. Nutrient pollution can have acute local impacts, such as green algal blooms, which can be toxic to humans and animals. If people can’t enjoy recreational activities like swimming or fishing, it leads to losses for local economies. Furthermore, downstream impacts continue along the Mississippi River into the Gulf of Mexico where nutrients contribute to a growing dead zone.

Finding solutions to dealing with nutrient pollution benefits the environment and society in general, Skidmore noted.

“Conservation strategies are not necessarily cost-effective for producers, so we must ensure there are policies in place to support their implementation. As we’re approaching the next Farm Bill, there are discussions around how to allocate funds from the Inflation Reduction Act for climate-smart and conservation ag practices. It’s important that such practices continue to receive funding so farmers can facilitate those benefits for all of us,” she concluded.

This phenomenon is known as a compound energy drought. In a new paper, researchers at Pacific Northwest National Laboratory (PNNL) found that in some parts of the country, these energy droughts can last nearly a week.

“When we have a completely decarbonized grid and depend heavily on solar and wind, energy droughts could have huge amounts of impact on the grid,” said Cameron Bracken, an Earth scientist at PNNL and lead author on the paper. Grid operators need to know when energy droughts will occur so they can prepare to pull energy from different sources. On top of that, understanding where, when, and for how long energy droughts occur will help experts manage grid-level battery systems that can store enough electricity to deploy during times when energy is needed most.

The team published the findings October 31 in the journal Renewable Energy and will be presenting at this week’s annual meeting of the American Geophysical Union.

Hunting for cloudy, windless days

In the past, researchers studied compound energy droughts on a state or regional scale. But not much has been studied on a nationwide scale. To find out more about the risk of energy droughts over the entire continental U.S., the researchers dug into weather data and then used historical energy demand data to understand how often an energy drought occurs when that energy is needed the most.

The team examined 4 decades of hourly weather data for the continental U.S. and homed in on geographical areas where actual solar and wind energy plants operate today. Weather data included wind speeds at the height of wind turbines as well as the intensity of solar energy falling on solar panels. Times when the weather data showed stagnant air and cloudy skies translated into lower energy generation from the wind and solar plants — a compound energy drought.

“We essentially took a snapshot of the infrastructure as of 2020 and ran it through the 40 years of weather data, starting in 1980,” Bracken said. “We are basically saying ‘here is how the current infrastructure would have performed under historical weather conditions.'”

The researchers found that energy droughts can occur in any season across the continental U.S., though they vary widely in frequency and duration. In California, for instance, cloudy and windless conditions might last several days, whereas the same conditions might last for only a few hours in Texas. Utah, Colorado, and Kansas experience frequent energy droughts both over several-hour timescales as well as several-day timescales. The Pacific Northwest and Northeast, meanwhile, seem to experience energy droughts that last several hours more frequently than several days. The different timescales (hourly versus daily) will help inform the energy drought’s impact on the grid — will it last just a few hours, or several days?

Overall, researchers found that the longest potential compound energy drought on an hourly timescale was 37 hours (in Texas), while the longest energy drought on a daily timescale was six days (in California).

Energy drought at peak demand

Simply knowing the where and how of energy droughts is just one piece of the puzzle, Bracken said. He also stressed that a drought of solar and wind power won’t necessarily cause an energy shortage. Grid operators can turn to other sources of energy like hydropower, fossil fuels, or energy transmitted from other regions in the U.S.

But as the nation aims to move away from fossil fuels and rely more on solar and wind power, grid operators must understand whether energy droughts will occur during times when the demand for electricity might exceed supply. Climate change brings hotter summers and more intense winter storms, and these are times when not only people use more energy to stay safe (for cooling or heating), but access to electricity might mean life or death.

To understand the possible connection between energy droughts and energy demand, the team mapped their historical, hypothetical generation data onto 40 years of historical energy demand data that also covered real power plants across the continent.

The data showed that “wind and solar droughts happen during peak demand events more than you would expect due to chance,” Bracken said, meaning that more often than not, windless and cloudless periods occurred during times when demand for power was high. For now, Bracken isn’t certain that the correlation means causation.

“This could be due to well-understood meteorological phenomenon such as inversions suppressing wind and increasing temperatures, but further study is needed,” Bracken said.

Energy storage for energy droughts

Studying patterns in the frequency and duration of energy droughts will also help inform the deployment of long-duration energy storage projects, said Nathalie Voisin, an Earth scientist at PNNL and coauthor on the paper. The paper is the first to provide a uniform standard of what a compound energy drought is and how long it can last in different parts of the country.

“We’re providing insight on how to adequately design and manage multi-day storage. So when you know an energy drought is going to last for five hours or five days, you can incentivize storage to be managed accordingly,” Voisin said.

Next, Bracken and the team will extrapolate weather and demand data into the future to see how climate change will affect the frequency and duration of energy droughts. The team plans to model energy droughts all the way to the end of the century combined with evolving infrastructure.

This research was funded by PNNL through its internal GODEEEP initiative.