Chesapeake seagrasses help fight ocean acidification

By Alejandra Borunda 12-15 minutes

PUBLISHED June 2, 2020

A crab swims above a waving seagrass bed in the Chesapeake Bay.Photograph by Jay Fleming

When scientist Wen Jun Cai and his colleagues boated across the pea-soup-like waters of the upper Chesapeake Bay in the summer of 2016, water sampling kits and pH sensors in hand, they didn’t expect to find chemical magic at play.

The scientists were taking stock of a looming problem facing the 200-mile-long bay: the acidification of its waters, a human-caused phenomenon that threatens the health of the crabs, oysters, and fish iconic to the large estuary.

They started collecting their samples in the recently restored, vibrant underwater grass beds of the Susquehanna Flats near the top of the bay, and motored their way some 60 miles downstream to the deep central channel.

When they rounded up their hundreds of data points and analyzed them, they found evidence of something surprising and encouraging: Gently waving seagrasses in the bay are performing a magnificent chemical trick. As they photosynthesize in the beating sunshine, they produce tiny granules of a carbon-based mineral that acts like a miniature antacid tablet.

And those acid-neutralizing “micro-Tums” don’t stay put. They’re swept miles down the length of the bay, eventually dissolving into the deepest waters, which have long been soured by acidification caused by human sources like agricultural runoff and untreated waste.

“It’s like the seagrasses are producing antacids that counter the indigestion of the bay,” says Jeremy Testa, a marine ecologist at the University of Maryland and an author of the paper in Nature Geoscience describing the newly discovered phenomenon.

Without this acid-neutralizing trick, the bay’s waters and shelled creatures would be even more vulnerable to the human-caused threats, he says.

Acid waters run deep

The Chesapeake gets its name from the Algonquin word for “great shellfish bay.” For thousands of years, its rich ecology depended on the ways its shellfish, grasses, fish, and other species interacted; each influenced the chemistry and biology of the others, in a delicate biological dance.

Seagrasses and other underwater plants packed the bay’s shallows, stilling and smoothing the surrounding water, leaving it clear and clean for baby fish, crabs, and shellfish to populate. Vegetation stabilized the muddy bottom during storms. And it absorbed the brunt of wind and waves, protecting shorelines against erosion.

But as more and more people populated the land around the bay, the grasses took hit after hit. A steady flow of nitrogen-rich pollutants overloaded the waters; the grasses and other underwater plants died off en masse. Between the 1950s and 1980s, vegetation coverage across the bay plummeted. Only 10 percent of sites in the upper bay had vegetation when they were surveyed in 1980.

The nutrient overload also spurred enormous, suffocating algal blooms at the water’s surface. When such blooms happen, the algae die off and sink to deeper water, where they’re eaten by bacteria that use up any oxygen in the water and breathe out carbon-rich acid waste, creating “dead zones.” Almost nothing can survive in such corrosive waters. Worse, during strong winds or at certain times of the year, currents can sweep that deep, super-acidic water into places populated by creatures like oysters and crabs, potentially eroding their ability to maintain their calcium-carbonate based shells.

“Acidified waters can be really challenging for oysters, especially in their larval stage,” says Allison Colden, a biologist with the Chesapeake Bay Foundation.

In other coastal regions, particularly along the U.S. West Coast, acidification has already damaged shellfish populations, thinning their shells and messing with their offspring’s ability to mature. But scientists aren’t totally sure if those same effects have hit the East Coast. In estuaries like the Chesapeake, natural acid levels vary a lot, so shell-forming creatures have a built-in ability to deal with some amount of ups and downs. The worry, for some scientists, is that there might be a tipping point beyond which the iconic species of the bay might not be able to adjust.

“We don’t have enough data anywhere in the world to tell us exactly how those creatures are going to meet the thresholds of acidification,” says Doug Myers, a scientist also with the Chesapeake Bay Foundation.

They’re particularly concerned because there’s another force, besides nutrient overloading, that’s making the bay’s water more acidic: human-caused burning of fossil fuels. That leads to the buildup of carbon dioxide in the air, which gets pulled into the surface waters as ocean and air make their way toward equilibrium, where it dissolves and makes the water more acidic.

During the early 2000s, states bordering the bay collaborated to rein in polluting runoff, putting the bay a “nutrient diet—” and in response, it began to heal. Old seagrass seeds, long buried in the gooey sediments, started to sprout as the water above them cleared. By the mid-2010s, underwater vegetation covered expanded over an extra 65 square miles of the Bay, more than 300 percent more area than was covered in the 1980s.

Those grasses, like the ones in the Susquehanna Flats, can offset some of the acidity. But they’ll have to work harder and harder as carbon dioxide concentrations in the atmosphere grow.

“This is one of the big questions for us all,” says Emily Rivest, a biologist at the Virginia Institute of Marine Science. “What’s going to happen to our oysters, our blue crabs, all the things that live in our waters, as the waters get more acidic?”

Grasses to the rescue

It’s obvious just from looking at the Susquehanna Flats that they’re doing something special, Testa says. Outside the beds, the water often looks pea-green. But inside, it’s crystal clear and much warmer than the water outside the Flats. When they looked closely, they found that even the chemistry was different.

As they photosynthesize, seagrasses and other vegetation pull particular forms of carbon out of the surrounding water, making that water less acidic. They use some of that carbon to build their plant bodies, but turn some of it into tiny crystals of calcium carbonate, a chemical variant on the material that shells are made of. The plants hoard these crystals—which are essentially tiny antacids—both inside and on the surface of their leaves.

The crystals are big enough to feel with your fingers, like a fine grit coating the leaves, says Myers. When a grass dies, it disintegrates, releasing the built-up crystals from its inside as well as out.

The crystals make a big difference for the water chemistry and biology up near the Susquehanna Flats. But they also make a big difference far downstream, demonstrating with unusual clarity how interconnected the ecology of the bay can be. In total, the team calculated, the seagrass-sourced crystals reduced the acidity of the down-bay waters, some 60 miles away, by about 0.6 pH units. They reduced the acidity of the water by four times than it otherwise might have been (because the pH scale is logarithmic, small changes in the numbers on the pH scale mean big changes in terms of acidity).

“If not for the dissolution [of the tiny crystals], the pH downstream would be even lower,” says Cai (a lower value of pH signifies a more acidic environment). “So the vegetation upstream provides a more stable environment for what’s living down the bay.”

Seagrasses and other vegetation do this chemical trick elsewhere, as well, and scientists have seen similar local chemistry shifts in places where grasses have been restored, like the estuaries fringing the Loire River and Tampa Bay. But they haven’t seen this long-range effect before.

It’s not yet clear exactly what impact the seagrass-driven help has on the blue crabs or the oysters. But it does seem clear to many scientists that the whole bay can benefit from the effect as the grasses spread their little acid-neutralizing crystals far and wide—also serving as building material for the shell-growers downstream.

“The dissolving of last year’s grass beds is helping to feed this year’s oysters [to help them build their shells],” says Myers.

The new discovery makes a strong case for restoring even more of the seagrasses in the bay, says Jonathan Lefcheck, an ecologist at the Smithsonian Environmental Research Center in Edgewater, Maryland. “You just see so clearly that there are these knock-on effects [from the seagrass restoration],” he says.

“Everything is connected. Something that was happening under our noses—this big unintended benefit, this added value—it turns out we’re solving two problems by attacking just one.”

Bumblebees bite plants to make them flower early, surprising scientists

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Bumblebees bite plants to make them flower early, surprising scientists

How it actually works remains a mystery, but if replicated by humans, it could be a boon for agriculture.

By Virginia Morell PUBLISHED May 21, 2020

A buff-tailed bumblebee flies among flowers in England. Many bumblebee species are declining due to climate change.Photograph by Stephen Dalton, Minden Pictures

Bumblebees aren’t merely bumbling around our gardens. They’re actively assessing the plants, determining which flowers have the most nectar and pollen, and leaving behind scent marks that tell them which blooms they’ve already visited. null

Now, a new study reveals that bumblebees force plants to flower by making tiny incisions in their leaves—a discovery that has stunned bee scientists.

“Wow! was my first reaction,” says Neal Williams, a bee biologist at the University of California, Davis. “Then I wondered, how did we miss this? How could no one have seen it before?”

Consuelo De Moraes, a chemical ecologist at the Swiss Federal Institute of Technology in Zurich, had the same reaction when one of her students, Foteini Pashalidou,noticed buff-tailed bumblebees making tiny incisions in the leaves of their greenhouse plants. The insects didn’t seem to be carrying off the bits of leaves to their nests or ingesting them. null Watch pollen-deprived bumblebees damage plant leaves

Suspecting the bees were inducing the plants to flower, the team set up a series of experiments. The results show that when pollen sources are scarce, such as in a greenhouse or during early spring,bumblebees can force plants to bloom up to a month earlier than usual.

The research is promising for two reasons. For one, it strongly suggests bumblebees manipulate flowers, a particularly useful skill as warming temperatures worldwide are causing the pollinators to emerge before plants have bloomed. The insects depend nearly exclusively on pollen for food for themselves and their larvae in the early spring. (Read how bumblebees are going extinct in a time of climate chaos.)

It’s also a potential boost for the human food supply: If agriculturalists can coax their crops to flower early, it could increase food production of some plants.

Master gardeners

For the study, De Moraes, Pashalidou—the study’s lead author—and colleagues placed flowerless tomato and black mustard plants in mesh cages with pollen-deprived buff-tailed bumblebee colonies. They then removed the plants after worker bees made five to 10 holes in their leaves.

The small punctures caused the black mustard plants to flower two weeks earlier than usual, and the tomato plants a month sooner than normal, according to the study, which was published May 21 in Science.

The scientists also placed pollen-fed and pollen-deprived bumblebee colonies in mesh cages with the flowerless plants to compare their behaviors. Worker bees from the pollen-fed colonies rarely damaged the plants, while those from the pollen-deprived colonies busily did so.

To ensure that their results weren’t due to the lab’s artificial conditions, the scientists placed bumblebee colonies and a variety of flowerless plant species on their Zurich rooftop in late March 2018.

The bees—a very common European species—were free to forage as far afield as they liked. Yet they set to work damaging the leaves on all the nonflowering plants nearest to their hives. The bees’ interest in this activity tapered off toward the end of April as more local flowers came into bloom—again, establishing that the bees’ leaf-biting behavior is driven by the availability of pollen, the scientists say. (See seven intimate pictures that reveal the beauty of bees.)

They continued their rooftop experiment through July and found that wild workers from two other bumblebee species (B. lapidgrius and B. lucorum) came to their nonflowering patch of plants to puncture the leaves.

It remains to be seen how widespread the behavior is in other bumblebees, over 250species of which are found around the world, the authors say.

Cracking the code

The mutually beneficial relationship between insect pollinators and flowers extends back some 130 million years. Plants provide the pollinators with food; in exchange, the pollinators fertilize their flowers. (Read more about nature’s “gold dusters.”)

But neither benefits if they’re out of synch with each other, so they’ve found ways to communicate. Saving Bumblebees Became This Photographer’s Mission

“That’s what this study shows,” says Lars Chittka, a behavioral ecologist at Queen Mary University of London, who wrote an essay accompanying the Science paper. “In a sense, the bees are signaling, Hey, we need food. Please speed up your flowering, and we’ll pollinate you.”

“It’s a very sophisticated type of communication,” adds Santiago Ramirez, a chemical ecologist at the University of California, Davis, who wasn’t involved in the study. “It seems bees have cracked the code that causes plants to flower.”

But many questions remain. Why do the incisions cause the plants to flower?

And, asks Chittka, “Does flowering early lead to higher fitness for the plants—meaning, do they have a larger number of offspring?”

Boost for agriculture?

When the study authors used metal forceps and a razor to mimic the holes the bees made, the plants bloomed earlier than normal, but not as soon as they did in response to the bees’ bites.

“They do something we haven’t quite captured,” says study co-author Mark Mescher, an evolutionary ecologist also at the Swiss institute. “It could be they introduce a biochemical or odor cue” from a saliva gland. “We hope to figure this out.”

Doing so could create a whole new way for humans to cultivate plants, a potentially major boon for agriculture. (Here are nine ways to support bees and other pollinators at home.)

For bee experts, one of the greatest marvels of the study is that it started with simple, old-fashioned observation.

“Charles Darwin followed bumblebees around,” says Williams. “Anyone interested in bumblebees has likely spent hours watching them on flowers. But probably not on plants that aren’t in bloom.”

Then Pashalidou did just that—and opened an entirely new phenomenon to our eyes.

Toilet Paper Substitutes: Plants You Can Use As Toilet Paper Toilet Paper Substitutes: Plants You Can Use As Toilet Paper 3-4 minutes Toilet paper is something most of us take for granted, but what if there was a shortage?

Ever considered what you would do in the absence of this most standard of daily needs? Well, perhaps you could grow your own toilet paper. That’s right! Many plants are useful as a substitute for this hygiene product. Leaves for toilet paper are often more soothing, softer, and as an added bonus, compostable and sustainable. Can You Grow Your Own Toilet Paper? Certain situations can cause toilet paper woes, so it’s best to be prepared. Few things are worse than being shy on some comforting tissue after you do your duty. Good news! You can use plants as toilet paper should the situation call for it. Learn which plants you can use as toilet paper and get growing so you’re never caught short. Toilet paper has only been standard for about a century, but humans had to use something to wipe up. The wealthy used fabric and washed themselves, but everyone else used what was at hand, which in most cases turned out to be plants. Toilet paper substitutes are something you should think about. Why? Imagine a world without toilet paper. It’s not a pretty thought but you can be prepared by growing your own. These plants aren’t flushable but can be buried to compost naturally. In some cases, using leaves for toilet paper is better for the environment and your bum. What Plants Can You Use as Toilet Paper? Following in our ancestor’s footsteps, plant leaves are useful, easy to grow, readily available, and practically free. Plant leaves with a fuzzy texture are particularly delightful. The towering mullein plant (Verbascum thapsis) is a biennial that produces popcorn-like yellow flowers in its second year, but has furry leaves in spring through fall. Similarly, lamb’s ear (Stachys byzantina) has large leaves soft as a rabbit (or lamb’s ear), and the plant comes back every year. Thimbleberry isn’t quite as fuzzy, but the overall texture is soft and the leaves are as large as an adult’s hand, so you only need one or two to get the job done. Some other options for toilet paper from the garden are: Common Mallow Indian Coleus Pink Wild Pear (tropical hydrangea) Large Leaf Aster Blue Spur Flower Tips on Using Plants as Toilet Paper While the listed plants are generally non-toxic, some people may be sensitive. Before you try the leaves on your bottom, swipe the leaf across your hand or wrist and wait 24 hours. If no reaction occurs, the leaf will be safe to use on more sensitive areas. Because many of these plants lose their leaves in winter, you will have to harvest and stockpile for the cold season. The leaves can be dried flat and stored for future use. The amount of absorbency may be affected a bit, but once the leaf touches its target, the moisture there will reconstitute the foliage.

Toilet Paper Substitutes: Plants You Can Use As Toilet Paper