Discovery News: Environmental

Nemo's Nose

Today Discovery News published an article about research showing how orange clownfish follow the smell of leaves and anemones, presumably to find their way back to the reef anemones they live within.

The researchers recorded how much time each fish spent on either side of a chamber where each side contained water from different sources. This allowed them to measure the fishes' preference for different-smelling water. (Read the details here.)

Above is a video from Jelle Atema of Boston University, who developed the chamber, showing how the experiment works.

He tested a juvenile blue damsel fish with water from its home reef and from a reef 15 miles away. Watch how the fish switches sides when Atema swaps which side carries the familiar water. The fish quickly swims back into its homey water.

The researchers in the study described today observed similar behavior with the clownfish they studied.

I particularly enjoyed reporting on this research because it was such a great example of the scientific method.

The experiments were as simple as a school science fair project in their straightforward comparisons: No particle accelerators or DNA extractions required. But the tests were clever and the results were clean.

What was incredibly striking is just how strong the fishes' preferences were. When presented with beach water, anemone-scented water, or rainforest-leaf-scented water, the fish spent anywhere from 89 to 98 percent of their time in those waters compared with what you might call "unscented" water. When offered water laced with the scent of an unfamiliar tree leaf, all of the fish scooted out of it immediately, spending 100 percent of the time in the neutral water.

This struck me because when I was in college, I took a class in behavioral ecology where we had to try to measure some aspect of guppy behavior for a class project. We were each given a dozen guppies and a wading pool and sent back to our dorm rooms to run an experiment.

Our groups' experiment was to see whether the size of a guppy school affected how fast the guppies found food. We put six little feeding stations (fish flakes floating inside loops made of drinking straws) around the perimeter of the pool and released schools of 1, 2, 4, 6 and 12 fish, and timed how long it took them to find food in the station that was stocked with food (randomly selected by rolling a die).

The problem was, first of all, that we didn't get the experiment done before winter break. So, we decided that I would carry the guppies home on the airplane and do the experiment in my parents' basement. We figured I could just buy a kiddie pool when I got home.

Somehow, it didn't occur to us that NOBODY sold wading pools in December in Colorado.

Then, one of the guppies gave birth and died, so I went to the pet store to replace the guppy with another grownup. Pregnancy might have been a confounding factor anyway.

After borrowing a wading pool from some neighbors, I retreated to the basement for the guppy time trials ... which failed miserably. The fish just swam around. There was no real trend, and I didn't really have time to make sure the guppies got hungry again in between searches, so who knows what they were looking for.

The whole experience (which, I should add, followed a project earlier in the semester for which I chased squirrels around a campus lawn trying to monitor their nut-caching behavior) convinced me that trying to make quantitative measurements of animal behavior was impossible, or at the very least would lead to several decades in graduate school waiting for animals to get hungry again.

So that's why I took note that the Jones' groups fish time trials come out so cleanly... I guess I should have realized that all those animal research journals weren't just reporting on aimless guppy wandering, so there must be better observations to be made. Still, it's great that this group for found such opinionated fishes.

(Video: Jelle Atema, Boston University)

Sex in Acid Has Low Returns

You've probably heard that ocean acidification is predicted to cause problems for calcifying sea critters, like certain plankton, which are anticipated to have trouble building their calcium carbonate skeletons in lower pH seas.

Research published today in Current Biology uncovers another possible problem with a more acidic future ocean: sperm-meets-egg may not work as well. At pH levels predicted for the end of this century, Jon Havenhand of Sweden's University of Gothenburg and colleagues found sea urchin sperm swam more sluggishly (that is, both speed and motility were significantly reduced.) They also found a 26 percent reduction in the number of eggs that developed into swimming larvae under such conditions.

Havanhand expects his results will apply to fertilization in other ocean species. "Of course, this is a fairly sweeping extrapolation, and many more data are required before we can say anything definitive on the topic," Havenhand told Discovery News. "However as a first look at the effects of acidification on fertilization in marine invertebrates, this doesn't paint an encouraging picture!"

Antarctic Wildlife Feels the Heat

Today at Discovery News we reported on work by three researchers who study different aspects of the Antarctic ecosystem, and who decided to get together and tell the combined story of the changes they've seen over the last two or three decades as a result of climate change.

We thought we'd post it here so you could have your say. Do you care about what's happening in Antarctica? Are you ready to start marching for the penguins? What strikes you about the researchers' findings?

Also, stay tuned at the end of the post for some extra tidbits that didn't fit in the original story.

(Photo: Juvenile krill, Jim McClintock)

At Antarctic Peninsula, Fast Change
Jessica Marshall, Discovery News

 

July 10, 2008 -- From the tiny phytoplankton living under the ice to the penguins at the top of the food chain, the ecosystem of the Antarctic Peninsula is changing fast, driven by warming waters and a loss of sea ice.

Three researchers who have spent decades studying Antarctica's denizens paint a picture of interconnected changes at the bottom of the Earth that are changing the ecology over just decades after some 30 million years of relative isolation.

"The changes are profound," said Hugh Ducklow of the Marine Biological Research Laboratory in Woods Hole, Mass.

He and colleagues James McClintock of the University of Alabama at Birmingham and William Fraser of Polar Oceans Research Group in Sheridan, Mont. compiled their findings from studying different aspects of the Antarctic ecosystem in an article in the current issue of American Scientist.

Nowhere on Earth is climate change happening faster than on the neck of land stretching north from the Antarctic continent more than 900 miles toward South America. The average midwinter temperature on the Antarctic peninsula has increased more than 10 degrees Fahrenheit since 1950, five times the global average.

The changes the researchers see begin at the base of the food web, with phytoplankton -- tiny photosynthetic organisms that, in Antarctica, are evolved to live in the sea ice. As the extent of sea ice has decreased, so has the amount of phytoplankton.

"Sea ice is not just ice," Ducklow said. "It's a habitat for organisms."

Indeed, juvenile krill, tiny shrimplike organisms that serve as the main food source for Adélie penguins and baleen whales, graze on the phytoplankton under the sea ice.

"Juvenile forms of krill are not as strong swimmers as adults," Ducknow said "By congregating on the underside of the ice, they get a shelter from predators, and it's where the food is."

Krill have been declining for decades, the authors note, although sea ice decline may not be the only reason.

With less krill to feed on, organisms at the top of the food chain like Adélie penguins suffer. Their populations have been decreasing in the central and northern Antarctic peninsula.

The Adelie penguins also rely on the sea ice directly. In winter, they use the sea ice to get out to hotspots of food. As this shrinks, their food will be too far away to swim to.

In contrast, two related species, the gentoo and chinstrap penguins, do not rely on sea ice for winter feeding. Their populations are rising on the Peninsula.

Meanwhile, another Antarctic community is poised to change because of rising sea temperatures.

Since the Antarctic Peninsula separated from South America 25 to 35 million years ago, Antarctica has been encircled by the Antarctic Circumpolar Current, a clockwise roundabout current that holds cold water near the continent and isolates it from the rest of the ocean.

Crabs and other predators that get prey by cracking shells with strong forces were excluded from the region once the current was established, because they cannot survive at such cold temperatures.

Without such predators to guard against, animals like snails and clams in Antarctica evolved delicate, thin shells. But as the ocean warms, crab predators may move in and have defenseless prey to capitalize on. A colony of king crabs was recently found in deeper waters off the peninsula.

"It's only a matter of time before they can move up into even shallower water," said lead author McClintock, who studies Antarctica's invertebrates. "When crabs get into those communities of clams and snails and brachiopods, they are going to be history."

McClintock notes that the reproductive cycle of invertebrates is also closely tied to temperature, and warming may lead to larvae hatching out of sync with the availability of their plankton food supply.

But, he adds, kelp-like macroalgae are likely to thrive with the greater availability of sunlight thanks to reduced sea ice. And jellyfish will probably also increase in number.

What is clear is that these populations are shifting fast in relation to one another, and the ecosystem that emerges will be different from the one that has existed in isolation for millions of years.

"People say, why Antarctica? Who cares about that?" Ducklow said. "It's a canary in the coal mine. We're seeing things happen rapidly there. It's a good wakeup call for us that there is climate change, and ecosystems really are responding to it."

******************************************

Now, here's the extra bit that I'll call

Amazing Antarctic Facts

• The reason that crabs have heretofore been unable to survive in Antarctic waters is that they cannot expel magnesium from their bloodstream. Magnesium acts as a narcotic whose effect is enhanced at low temperatures. So, until now, any crabs that decided to go strolling in too-chilly waters became immobilized and died.
• Another species that is threatened by changing sea ice is the Waddell seal. Female adult seals get a private, predator-protected birthing room by using their ice-chipping teeth to scratch open a hole in the sea ice from underneath. They pop through the hole onto the surface when they're ready to pop out their young. According to McClintock, "The price they pay for these teeth is that over the years they wear down the teeth and they starve." They live about half as long as other seals, he said, but more of their young survive.
• About 70 percent of Antarctic species are found nowhere else.
• The sea ice in midwinter is about as big as the lower 48 U.S. states, but with a lot fewer Starbucks.
• Antarctic ice holds almost 2/3 of Earth's freshwater.
• Climate change has brought more snowstorms to the Peninsula. These have also harmed Adélie penguins. When it snows in spring, the nests can flood, killing eggs and hatchlings.
• If warming trends continue, the average midwinter temperature will be above freezing (for seawater) by mid-century. Sea ice will no longer form.

Volcanic Death Plume

I hope you checked out the amazing videos of undersea volcanic explosions in the Pacific posted today at Discovery News.

In addition to offering glowing lava, exploding rock, and billowing, sulfurous clouds, this environment supports some interesting biology.

The main macrofauna consists of a pair of shrimp species living within a few hundred feet of the vent. One type of shrimp grazes on bacterial mats growing on chemicals spat out by the volcano. The other type feeds on the smaller shrimp.

While the volcano supports life below, it kills life above. The team found that if fish or other marine life in the upper ocean swim into the plume of water rising from the volcano, the unusual chemical composition of the water stuns or kills them. They drop to the sea floor, and the shrimp get some tasty snacks. Who says there’s no such thing as free lunch?

Check out some pictures of plume-kill and videos of the shrimp here.

For more information and videos from the expedition, charismatically called the "Submarine Ring of Fire 2006 Exploration", check here.

(Image: Image Submarine Ring of Fire 2006 Exploration, NOAA Vents Program)

Welcome to EnvironMental Case!

Today’s is the first installment of the Discovery News environmental blog. I’ll be bringing you updates on all things environmental from my home in Saint Paul, Minnesota.

Who am I, the EnvironmMental Case? I started out as a chemical engineer before becoming a science journalist. One thing I realized after I made the switch is that scientists (and engineers) and journalists are not all that different. Both are looking for the truth. Both aim for objective analysis of the facts. Both are investigators, looking to uncover something new.

That's all great, but since this is the first installment of this blog, I'm taking a much baser approach to attracting readership, using a proven blockbuster formula: penguins on film.

I wrote a story yesterday about how DDT levels in Adélie penguins in Antarctica have stayed relatively constant since DDT was banned in the 1970s, in contrast to the Arctic where levels have dropped. The researcher, Heidi Geisz of the Virginia Institute of Marine Science, kindly shared some of her videos of the penguins, which don’t really have anything to do with DDT, but are nonetheless fun to watch. Here they are.

The last shows a "feeding chase". Here’s what Geisz says about these:
“The parent birds return to a creche or group of chicks huddled together for predatory protection and then call - the mechanism for recognition in these birds. Once the chick or chicks (they lay up to two eggs and have two chicks) recognizes the parent's call, the babies run out of the 'crowd' in pursuit of the parent for nourishment - regurgitation.
The reason for these chases is not entirely clear. Fitness: if one chick is stronger than the other in a poor foraging year, resources are allocated to only one offspring? Strength training? “

I hope you’ll add EnvironMental Case to your daily reads, and leave lots of comments here. I want to know what you think!