climate change ‣ Data Nuggets

3.25.14

Coral bleaching and climate change

A Pacific coral reef with many corals

The activities are as follows:

Éste Data Nugget también está disponible en Español:

Corals are animals that build coral reefs. Coral reefs are home to many species of animals – fish, sharks, sea turtles, and anemones all use corals for habitat! Corals are white, but they look brown and green because certain types of algae live inside them. Algae, like plants, use the sun’s energy to make food. The algae that live inside the corals’ cells are tiny and produce more sugars than they themselves need. The extra sugars become food for the corals. At the same time, the corals provide the algae a safe home. The algae and corals coexist in a relationship where each partner benefits the other, called a mutualism: these species do better together than they would alone.

When the water gets too warm, the algae can no longer live inside corals, so they leave. The corals then turn from green to white, called coral bleaching. Climate change has been causing the Earth’s air and oceans to get warmer. With warmer oceans, coral bleaching is becoming more widespread. If the water stays too warm, bleached corals will die without their algae mutualists.

Scientist Carly working on a coral reef

Carly is a scientist who wanted to study coral bleaching so she could help protect corals and coral reefs. One day, Carly observed an interesting pattern. Corals on one part of a reef were bleaching while corals on another part of the reef stayed healthy. She wondered, why some corals and their algae can still work together when the water is warm, while others cannot?

Ocean water that is closer to the shore (inshore) gets warmer than water that is further away (offshore). Perhaps corals and algae from inshore reefs have adapted to warm water. Carly wondered whether inshore corals are better able to work with their algae in warm water because they have adapted to these temperatures. If so, inshore corals and algae should bleach less often than offshore corals and algae. Carly designed an experiment to test this. She collected 15 corals from inshore and 15 from offshore reefs in the Florida Keys. She brought them into an aquarium lab for research. She cut each coral in half and put half of each coral into tanks with normal water and the other half into tanks with heaters. The normal water temperature was 27°C, which is a temperature that both inshore and offshore corals experience during the year. The warm water tanks were at 31°C, which is a temperature that inshore corals experience, but offshore corals have never previously experienced. Because of climate change, offshore corals may experience this warmer temperature in the future. After six weeks, she recorded the number of corals that bleached in each tank.

Featured scientist: Carly Kenkel from The University of Texas at Austin

Flesch–Kincaid Reading Grade Level = 8.0

There are two scientific papers associated with the data in this Data Nugget. The citations and PDFs of the papers are below.

Kenkel CD, E Meyer, MV Matz (2013) Gene expression under chronic heat stress in populations of the mustard hill coral (Porites astreoides) from different thermal environments. Molecular Ecology 22:4322-433
Kenkel CD, G Goodbody-Gringley, D Caillaud, SW Davies, E Bartels, MV Matz (2013) Evidence for a host role in thermotolerance divergence between populations of the mustard hill coral (Porites astreoides) from different reef environments. Molecular Ecology 22:4335-4348

If your students are looking for more data on coral bleaching, check out HHMI BioInteractive’s classroom activity in which students use authentic data to assess the threat of coral bleaching around the world. Also, check out the two videos below!

A video in BioInteractive’s “Scientists at Work” series showing researchers working on the same hypothesis in another part of the world: Steve Palumbi & Megan Morikawa Study Coral Reef Damage in American Samoa

Another BioInteractive video, appropriate for upper level high school classrooms. Visualizes the process of coral bleaching at different scales. Video includes lots of complex vocabulary about cells and the process of photosynthesis.

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1.10.14

The ground has gas!

Measuring nitrogen (N2O) gas escaping from the soil in summer. Photo credit: Julie Doll, Michigan State University

The activities are as follows:

If you dig through soil, you’ll notice that soil is not hard like a rock, but contains many air pockets between soil grains. These spaces in the soil contain gases, which together are called the soil atmosphere. The soil atmosphere contains the same gases as the atmosphere that surrounds us above ground, but in different concentrations. It has the same amount of nitrogen, slightly less oxygen (O₂), 3-100 times more carbon dioxide (CO₂), and 5-30 times more nitrous oxide (N₂O, which is laughing gas!).

Measuring nitrogen (N2O) gas escaping from the soil in winter. Photo credit: Julie Doll Michigan State University.

Nitrous oxide and carbon dioxide are two greenhouse gasses responsible for much of the warming of global average temperatures. Sometimes soils give off, or emit, these greenhouse gases into the earth’s atmosphere, adding to climate change. Currently scientists are working to figure out why soils emit different amounts of these greenhouse gasses.

During the summer of 2010, Iurii and his fellow researchers at Michigan State University studied nitrous oxide (N₂O) emissions from farm soils. They measured three things: (1) the concentration of nitrous oxide 25 centimeters below the soil’s surface (2) the amount of nitrous oxide leaving the soil (3) and the average temperature on the days that nitrous oxide was measured. The scientists reasoned that the amount of nitrous oxide entering the atmosphere is positively associated with how much nitrous oxide is in the soil and on the soil temperature.

Featured scientist: Iurii Shcherbak from Michigan State University

Flesch–Kincaid Reading Grade Level = 9.2

More information on the research associated with this Data Nugget can be found here.

Data associated with this Data Nugget can be found on the MSU LTER website data tables under GLBRC Biofuel Cropping System Experiment. Bioenergy research classroom materials can be found here. More images can be found on the LTER website.

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1.9.14

Fertilizing biofuels may cause release of greenhouse gasses

An aerial view of the experiment at MSU where biofuels are grown. Photo credit: K. Stepnitz, MSU

The activities are as follows:

Greenhouse gases in our atmosphere, like carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O), trap heat from the sun and warm the earth. We need some greenhouse gases to keep the planet warm enough for life. But today, the majority (97%) of scientists agree that the levels of greenhouse gases are getting dangerously high and are causing changes in our climate that may be hard for us to adjust to.

Scientist Leilei collecting samples of gasses released by the growing of biofuels. Photo credit: K. Stepnitz, MSU

When we burn fuels to heat and cool our homes or power our cars we release greenhouse gasses. Most of the energy used today comes from fossil fuels. These energy sources are called “fossil” fuels because they come from plants, algae, and animals that lived hundreds of millions of years ago! After they died, their tissues were buried and slowly turned into coal, oil, and natural gas. An important fact about fossil fuels is that when we use them, they release CO₂ into our atmosphere that was stored millions of years ago. The release of this stored carbon is adding more and more greenhouse gases to our atmosphere, and much faster than today’s plants and algae can remove during photosynthesis. In order to reduce the effects of climate change, we need to change the way we use energy and think of new ways to power our world.

One potential solution could be to grow our fuel instead of drilling for it. Biofuels are a potential substitute for fossil fuels. Biofuels, like fossil fuels, are made from the tissues of plants. The big difference is that they are made from plants that are alive and growing today. Unlike fossil fuels that emit CO₂, biofuel crops first remove CO₂ from the atmosphere as the plants grow and photosynthesize. When biofuels are burned for fuel, the CO₂ is emitted back into the atmosphere, balancing the total amount that was removed and released.

Scientists are interested in figuring out if biofuels make a good replacement for fossil fuels. It is still not clear if the plants that are used to produce biofuels are able to absorb enough CO₂ to offset all of the greenhouse gases that are emitted when biofuels are produced. Additional greenhouse gases are emitted when producing biofuels because it takes energy to plant, water, and harvest the crops, as well as to convert them into fuel. In order to maximize plant growth, many biofuel crops are fertilized by adding nitrogen (N) fertilizer to the soil. However, if there is too much nitrogen in the soil for the crops to take up, it may instead be released into the atmosphere as the gas nitrous oxide (N₂O). N₂O is a greenhouse gas with a global warming potential nearly 300 times higher than CO₂! Global warming potential is a relative measure of how much heat a greenhouse gas traps in the atmosphere.

Leilei is a scientist who researches whether biofuels make a good alternative to fossil fuels. He wondered what steps farmers could take to reduce the amount of N₂O released when growing biofuel crops. Leilei designed an experiment to determine how much N₂O is emitted when different amounts of nitrogen fertilizer are added to the soil. In other words, he wanted to know whether the amount of N₂O that is emitted into the atmosphere is associated with how much fertilizer is added to the field. To test this idea, he looked at fields of switchgrass, a perennial grass native to North America. Switchgrass is one of the most promising biofuel crops. The fields of switchgrass were first planted in 2008 as a part of a very large long-term study at the Kellogg Biological Station in southwest Michigan. The researchers set up eight fertilization treatments (0, 28, 56, 84, 112, 140, 168, and 196 kg N ha⁻¹) in four replicate fields of switchgrass, for a total of 32 research plots. Leilei measured how much N₂O was released by the soil in the 32 research plots for many years. Here we have two years of Leilei’s data.

Featured scientist: Leilei Ruan from Michigan State University

Flesch–Kincaid Reading Grade Level = 10.1

Additional teacher resources related to this Data Nugget:

Data related to this Data Nugget can be found on the MSU LTER website data tables under GLBRC Biofuel Cropping System Experiment. The data in this activity is the Trace Gas Fluxes from Static Chambers dataset which has N₂O, CO₂, and CH₄ data.
More information on LTER climate change research can be found here.
Bioenergy research classroom materials can be found here.
More images can be found on the LTER website.

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