Just a Small Piece of the Larger Puzzle–Silica

Joanna Carey is conducting her silica research at Babson Creek. Don't let the marsh's seemingly lack of fine sand particles fool you! The marsh is full of silica (L.Weisenfluh/ July 2010).

Its that time of the year again–summer time, or as I like to call it–vacation time (booyah!). After weeks of careful planning, you manage to take a few weeks off from work and head to your favorite lake house for some well needed vacation time. However, upon arrival to your lake house, you gape in horror as you see that your beloved vacationing spot has turned a murky green. That’s right–no swimming for you. In an outrage, you demand to know why your beloved vacation spot has turned a ghastly green. The answer lies in a phenomena that is known as eutrophication.

Eutrophication is the result of nutrient run-off from human industries, including fertilizer from farming activities. After fertilizing the plants, the fertilizer will find itself in some nearby lake or pond. And because these nutrients function as a food source for phytoplankton, phytoplankton will dramatically increase in numbers,  thus turning the body of water into an unhealthy green color. While the phytoplankton is flourishing, other organisms will perish due to the lack of oxygen and sunlight.

When I personally think of nutrient run-off, I have been automatically trained to relate it to nitrogen and phosphorus (the most widely studied nutrients when it comes to eutrophication). But thinking about eutrophication just in terms of nitrogen and phosphorus completely ignores the fundamentals of ecology–that is, that everything is connected. In fact, nitrogen and phosphorus are just tiny parts of the ecological equation, yet receive most of the scientific attention. Nitrogen and phosphorus must be interacting with other chemicals that receive far less scientific attention. How about… silica, or instance?

Now that's a sandy beach! A shot from back home, Point Reyes, California (L. Weisenfluh/ August 2009)

Most people know silica for its presence on beaches in the form of small quartz pieces–sand. But silica isn’t just found on beaches, but other bodies of water, such as marshes. In fact, the presence or absence of silica  is very influential in an ecosystem. Silica provides organisms with protection from desiccation and predation through its hardening capabilities. Diatoms (phytoplankton algae) use silica to maintain their cell walls; diatoms will actually bloom according to the availability of silica. Under normal circumstances, silica will be found in a 1:1 ratio with nitrogen in an ecosystem, meaning that, under this ratio both diatoms and nitrogen-feeding phytoplankton will live harmoniously in balance (relatively speaking, of course). However, when the silica to nitrogen ratio is less than one, silica concentrations will be low and not able to sustain a high diatom population, thus allowing non-silica limited algae (i.e. nitrogen-limited algae) to bloom and out compete diatoms. This results in rather nasty business for the environment, including eutrophication and red tides.

Because silica has this important regulatory role in an ecosystem, scientists are very interested in learning more about silica, hoping that it might give them some insight pertaining to eutrophication. However, we must address another concern before we can even venture to explore these implications: we have very little idea as to how silica travels through an ecosystem. Therefore, before we can even start to hash out implications of these correlations, we must determine something called a silica budget.

No, I am not talking about money. Rather, I am using the term “budget” in a purely ecological sense. When an ecological talks about a “budget”, he/she is referring to an attempt to quantify the distribution of particular elements (silica, in this case) and how it is transported throughout an ecosystem. Ecologists make budgets for all types of nutrients—nitrogen, phosphorus—and yes, even silica. Thing is, there haven’t been any attempts to make a silica budget in Northern America. That is…until now. Joanna Carey, a PhD. Candidate at Boston University is attempting to create a silica budget for a coastal wetland within Acadia National Park (Babson Creek, anyone?), with the hopes that this information can ultimately be used to infer how silica affects the biogeochemistry of an ecosystem. And just how is this accomplished? Very carefully…

Researchers take silica measurements out of the PVC contained marsh samples. Before using these PVC pipes, researchers were measuring silica over a large marsh flume. However, water was moving too fast over the flume for an accurate measurement, therefore requiring researchers to use PVC pipes as a smaller flume enclosure (L.Weisenfluh/July 2010).

In her project, she is measuring two different types of silica: dissolved silica and particulate silica. Now, before the technicality of these terms chases you away, let me explain their significances: dissolved silica is silica that has yet to be used by organisms, and therefore indicates the amount of silica that is available for biological processes. Particulate silica (i.e. biogenic silica) is silica that has been hydrated (contains water), as a result of plankton biological processes. It can be found and measured in sediment and vegetation.

One can use these particulate and dissolved silica measurements to determine a silica budget. Both of these measurements are taken as water flows into large PVC tubes (a small replica of the larger marsh) under dark conditions (as to measure silica fluxes under non-photosynthetic processes, such as respiration). Researchers sample the water within these tubes for silica, phosphorus and nitrogen concentrations every 75 minutes for 5 hours.

Joanna Carey collects vegetation samples from the marsh by giving it a "haircut". By analyzing this vegetation sample back at the lab, she will be able to determine the amount of particulate silica found inside the vegetation.

The particulate silica can also be measured by examining silica concentrations in sediment and vegetation. This is done by taking sediment cores (you essentially core the marsh’s sediment, and then analyze this sediment for silica). Once the sediment is cored and extracted for measurement, researchers insert another tube into the marsh–a tube with dialysis membranes lining the outside edges of the tube. Dialysis membranes allow the salt water of the marsh to equilibrate with the water inside the dialysis tubes. Once the two environments have equilibrated their ion concentrations, researchers collect the dialysis tubes and analyze the samples to determine silica, nitrogen and phosphorus values. Researchers also take vegetation samples (of two widespread vegetation types—Spartina patens and Spartina alterniflora) and analyze their silica content back at the lab.

We shall see what the results of her research dictate… Ms. Carey is still in the process of carrying out her field work. But until then, don’t take that sand beneath your toes for granted–its small and unseemly presence is a part of something much greater and more important… rather an entire ecosystem.

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Picture of the Day

Perched on South Bubble Mountain, Bubble Rock is one of Acadia National Park's most popular destinations (SERC Institute/P. Morgan). This large, granite boulder is what geologists call an "erratic," and has been deposited by glaciers thousands of years ago. The word "erratic" derives from the Latin word meaning "to wander," which sums up the history of these glacial deposits.

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Relatively Speaking

When I first heard about ecological change from a nature documentary, I immediately jumped from my living room couch and ran outside. I was ten years old and I wanted to personally witness how we, humans, were affecting our environment.

Yup... still blue. (L.Weisenfluh, July 2010)

The sky was still blue. Birds were still cheerfully chirping. Rollie pollies were still… rolling? Ants were still… being ants? And better yet, I was still comfortably warm in my apple tree sweater outfit (complete with leggings and all) on a crisp fall day.  The house had always been here. And the car? Definitely nothing new. My young and naive mind translated these brief observations into a rather unscientific hypothesis: ecological changes…hmmph…where?

Ten years later, and I have finally figured out that one’s perception of the environment is all relative–that is, based on one’s very own baseline observations of the environment. In other words, if you don’t know know about something’s past, then how can you know if it’s changing?

Take, the passenger pigeon, for example. Right–I know, passenger pigeon? What? But that’s exactly point. During the 19th century, passenger pigeons would literally flood the skies. Accounts tell of migratory flocks of up to two billion passenger pigeons passing overhead, occasionally taking hours to pass.  And so, people started to hunt them. What’s one less passenger pigeon from a billion? Well, folks, passenger pigeons are no longer with us, having been hunted to extinction. If I have never seen one, then how am I to know that it ever existed? This very predicament brings me to my main point: it’s all relative.

How can ecologists scientifically prove that ecological change is occurring without baseline data? As a result, some of the most compelling studies that convincingly imply climate change result from comparisons between data collected years ago and present day data.

Dr. Bryan Windmiller and Glen Mittelhauser of Hyla Ecological Services, Inc., and Maine Natural History Observatory (respectively) are doing  this same kind of work, aiming to compare their own data on freshwater invertebrate communities to baseline data gathered by  William H. Procter more than sixty years ago.

Dragonfly larvae are one type of freshwater invertebrate (USGS photo).

In a recent study, the researchers surveyed twelve freshwater wetlands in Acadia National Park to determine freshwater invertebrate species composition and abundances. By comparing this newly compiled data set to the data collected by William H. Procter, scientists will be able to glean how the ecology of freshwater wetlands has changed over the past sixty years. This also means that we might be able to see how past events, like the Great Fire of 1947, changed the ecology of aquatic insect community compositions.

But is 60 years a good enough baseline to signify ecological change? It’s a start. For now, we have to take what we can get–we are lucky to have such a thorough collection as Procter’s–and look at ecological change of freshwater invertebrate communities over the past 60 years.

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Searching for Quills

Branches snap. We push apart webs with the force of our faces, hands and shoulders; the spiders scramble. A few birds sing from the tops of red cedars and pines, as we crush fallen, dead trees with the weight of our shoes.

It’s a few hours into the afternoon and deep in the forest we cut our own paths through thicket, bog, and high grass. We listen for crunching–the promise of footsteps in a wilderness less frequented by humans. We pause at every rocky area or uprooted tree to search for dens; we scan the ground for scat; and look for bare patches on bark with rolled out sides…all signs of the creature we just can’t seem to find. The forest is so vast, our eyes get lost searching the canopy.

Porcupines are generally not elusive, but today they remain undercover.  Dr. Linda Ilse, a part time professor at the University of Maine in Orono, doesn’t seem discouraged; for more than twelve years she’s studied the North American Porcupine, Erethizon dorsatum, and is comfortable with the unpredictability of fieldwork. And anyway, variation holds its own significance. It helps Dr. Ilse answer her central question: what habitat do porcupines prefer? Since the 1930s and 1940s, the porcupine’s range has shifted. So far, data from recent studies shows that wet, marshy areas are uninhabited by porcupines. A number of reasons are possible–perhaps the creatures don’t like walking on the springy moss.

Dr. Ilse carries a GPS which she refers to as a virtual Hansel and Gretel bread crumb track. Every move we make is recorded and by the end of the day, she hopes to cover an area of ground graphically similar to a soft-cornered “M”. She’s already covered other land around Schoodic and marked points for return trips, when she’ll come back to gather more precise data (like tree measurements) on the areas with evidence of porcupine activity.

“It’s tough. It’s a thankless job–but somebody’s gotta do it,” she says, crawling under a fallen tree branch.

She pauses to analyze the pile of animal droppings on the ground–scat. But whose? Deer, rabbits, moose, bobcats, and porcupines coexist in these forests. Dr. Ilse informs us that porcupine scat is similar to deer’s, but slightly more curved on the end and lighter in color. Furthermore, porcupine scat is usually spread out over an area, instead of piled up. She picks a piece up, and crumbles it between her fingers–if it’s very fibrous, it could be porcupine.

Porcupines are strictly herbivores, and a large portion of their diet consists of tree bark. They may remain in one tree for a couple days at a time, stripping away the inner bark with their teeth. Where patches of bark have been stripped away, new growth curls inwards around the perimeter of the damaged spot.

We stand looking at some tree damage when we hear loud rustling behind us…could it be? Lauren looks in the distance and YES! Porcupine of the day spotted high in a tree. We walk over and Dr. Isle marks a point on the GPS. This is a place to return to.

Generally, porcupines do not kill trees, although bark stripping does weaken the trees vascular system (which is in charge of transporting nutrients and water from the roots to the leaves). Girdling–the process of completely removing a strip of bark around a tree’s circumference–can kill the tree, but porcupines often move up and down branches, not around them. In response to porcupine gnawing, a damaged tree will seep a protective layer of sap (sort of like the human bodies response to send blood platelets to plug a cut in the skin), which remains on the tree for years and looks like as a frozen, translucent stream.

Under a damaged tree you’ll usually find a scattering of droppings, similar to the ground layer of a porcupine den. Porcupines don’t build their own dens, but seek out sheltered places like uprooted trees or rocky areas. A female porcupine remains pregnant for seven months until giving birth to a single baby, and outside of its den will often stash the baby under fallen trees or in thicket to protect it while she feeds. Although a baby’s quills are soft and wet at birth, they harden within only a couple hours!

After hours of walking through thick brush, my legs lose coordination. I begin making less precise movements, practically flailing my body in the forward direction. I try to save energy by using roots as steps and branches as hand holds. Porcupines also consider energy conservation when seeking out a tree to climb. No sense in trying to climb a tree without a built-in ladder… Many of the trees in the forest begin their leafy layers way at the top, but they at least have branch stubs that wind around the lower trunk like a spiral staircase. Porcupines prefer to scale these than trees with bare trunks.

After seven hours, we break through the boundary leading to the road. We smell of dirt and cedar. Dr. Ilse checks the GPS and tells us we walked only under 3 miles….We all agree to tell the other stat: we covered an area of 77 acres.

I think back to something Dr. Ilse said earlier when I asked her why she got involved in studying porcupines. Out in the field doing other research, she said she felt some sort of presence, that there was something in the forest watching her, and she wanted to study whatever it was. The forest does have eyes–hundreds of thousands of them; total, we only had eight. As we squinted and scanned, searching for the brown, needled bodies, perhaps the porcupines were there, looking down on us…sitting quietly, munching on tree bark, watching the evening sun illuminate the forest floor.

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Photo of the Day

Long to be King of the World? Or say, Queen of the World? Well, I can't promise you a kingdom, but I can promise you breathtaking Acadian views that will make you feel like royalty! Views from the summit of Penobscot Mountain stretch as far as the eye can see. From Eagle Lake to the surrounding islands, the scenery does not disappoint... you'll feel all powerful--guaranteed. (L. Weisenfluh, July 2010)

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The Way of the Earthworm

This past year at the University of Tennessee I took a class entitled Writing for Science and Medicine. One of our reading assignments in the Best of Science Writing booklet was a piece by David Quammen on earthworms…It was, appropriately, called “Thinking About Earthworms”. Quammen confronts society’s tendency to be mentally absorbed in our current ways-of-the-world and suggests we all take more Darwinian approach to life. In a sense, he dares we step outside the music-blasting party and venture off into the backyard woods. His point: break free from a designated place, physically or mentally. Be like Darwin, the famous man with controversial ideas, who spent hours of his life thinking about something so forgotten and understudied as earthworms. Venturing into the unknown opens us up to new discoveries and fascinations. Certainly with Darwin this was the case. He wrote a book which nowadays stands in the shadows of On the Origin of Species but was, according to Quammen, a great success initially. It’s called The Formation of Vegetable Mould, Through the Action of Worms. Now doesn’t that sound exciting?   Actually, it turns out that earthworms (Oligochaeta) do play a critical (and almost shocking) role in shaping the lands we live on, and are quite interesting little guys themselves…

#1: There are more than 7,000 species of earthworms. The Oregon giant earthworm (Driloleirus macelfreshi) can grow 3 feet long…and what’s crazier, is that it apparently gives off the smell of lily flowers when handled! Whaaaat?!

#2: Earthworms are hermaphrodites: organisms possessing both female and male sexual organs. An earthworm, unlike a chicken, relies on intercourse to reproduce (did I shock anybody there? Because I certainly didn’t know chickens laid eggs on a cyclic basis, no fertilization required). So as earthworms are doin’ the dirty, sperm from one earthworm is deposited into the other worm, and vice versa; but the fertilization happens later…The worm excretes a mucous ring from its clitellum (ever noticed that funky thicker ring around one end of a worm?) that travels to the other end. Along the way the ring passes first the eggs, and then the sperm. When the ring passes over the egg receptacles, eggs stick to it, and slide along until they reach the sperm receptacles, where they are deposited. Egg + sperm = fertilization. The fertilized ring slips off the worm’s head, self-seals into a cocoon, and waits on the ground for baby worms to develop and break free. Voila! Weird.

Copulation is the first step in fertilization. During mating, the earthworms mutually exchange sperm. The eggs are fertilized later, after the worm forms a ring from its clitellum that slips down the worm's body and deposits the eggs into the sperm receptacles (Wiki Commons).

Environmental conditions greatly impact the ability of new eggs to hatch; most will hatch between 3 weeks and 5 months. Each cocoon can contain many eggs, depending on the species. Young worms sexually mature in 10-55 weeks (USDA photo).

#3: A long, long time ago my sister, two friends and I were down the hill playing in the sandbox. And our playmate found a worm; and he tore it in half. My sister and I were horrified. I’m pretty sure that the worm did NOT evolve into two separate worms, like Ryan suggested. But he was on to something. Earthworms DO have the power of regeneration, but this power is not all-encompassing. Worms cannot grow new heads, but they can grow new tails. A torn/cut/broken worm may only survive if the area of severance is located roughly 10 segments behind the clitellum (that thick ring). An earthworm generally has about 100-150 segments. Along these segments are bristles, which the worm uses to maneuver through the ground and hold on tight to the walls of its burrows if a bird tries pulling it out.

#4: Earthworms are decomposers; they can digest around 36 tons of soil each year! Their excrement is deposited in the form of castings, which are rich in nutrients and help create the soil that grows our crops and trees (microbial activity in the castings ensures the nutrients are readily available for plants.) Worms constantly borrow through the layers of the soil and castings are partially deposited on the soil’s surface, specifically at night and during rain when the worm’s skin can remain moist. In this way, earthworms can turn over the top six inches of soil in 10-20 years. The fact that worms turn the world “inside out” was the central theme of Quammen’s article.

#5: Earthworms enhance soil porosity, which refers to how much water the soil can hold. When the soil is already packed full of moisture, rainwater has nowhere to go, thus leading to the washing-away of soil layers.  The burrows of earthworms serve as passages for water drainage, helping curb erosion (the passages also provide space for root growth, allowing plant and trees to grow tall and strong.) Surface runoff decreases with increased soil porosity. Agricultural runoff, high in nitrate and phosphate from fertilizer residue, stimulates the growth of algal blooms, which deprive bodies of water of oxygen and lead to aquatic ecosystem deterioration.

It may be helpful to know that there are 3 major ecological groups of earthworms: epigeic species (found in compost piles), endogeic species (live in the upper soil strata) and anecic species (deep-burrowing).  The latter make burrows that can extend several meters into the soil; therefore, they are important for increasing soil porosity!

#6: An acre of land can contain millions of worms (each square yard may have 50-500 worms depending on soil type: cropland is typically less nutrient-rich than, say, grassland or woodlands, so you’d expect to find more worms in the latter. There are 4840 square yards in one acre…So, upwards of 2.4 million worms per acre!)

~*~

But there’s a catch to all this. Everything exists in balance. And various ecosystems exhibit differentiating physical and chemical characteristics; species adapt to these specific ecosystem requirements and play specific roles in particular environments. Earthworms illustrate the concept of order perfectly: an earthworm in your garden is a friend, but an earthworm in the forest is a pest.

Earthworms are non-native in areas stretching from central-Illinois to Canada; those that exist in the temperate forests are considered invaders. They have opposite, negative impacts on the ecosystem: they increase soil erosion and decrease soil porosity. The forest is covered by a rich layer of leafy, organic debris; earthworms gobble up this layer, thereby exposing the ground and making it susceptible to erosion and soil compaction.

Many years after Darwin, the earthworm remains an understudied topic of interest; and concern. In 2007, researchers Nick Mikash, Kaloyan Ivanov, and Shimshon Balanson submitted a proposal to survey the earthworms and terrestrial isopods present around Acadia National Park. Surveys not only give us a picture of what communities of these creatures look like right now, but also provide “baseline data” that can be used as the foundation for future research projects. Future data (collected, say, in a few decades or even a century from now) can be measured against this baseline data  to assess ecological changes over time. Are earthworms more abundant now than they were then? Has the distribution of different types of earthworms shifted over time? How have these earthworms altered the forest ecosystem? Some scientists suggest that the worm is altering the ability of the forest to act as a natural carbon sink because of its impacts on nutrient cycling.  Continued research on the earthworm is needed to evaluate the risks it poses to forest ecosystems and global cycles. That’s a lot of impact from such a little guy!

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Photo of the Day

Going...going...gone? Not quite. Actually, not even close. Bubble Rock may look like it is about to tumble from South Bubble Mountain at any moment, but it actually rests in a small granite depression that keeps it quite stable. Bubble Rock is a glacial erratic, a boulder picked up and transported by glacial ice; the boulder was left perched on the cliffside as the glacial ice receded at the end of the last ice age (L. Weisenfluh, June 2010)

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Photo of the Day

Visitors to Acadia National Park can enjoy tranquil views of beautiful Somes Pond. (L. Weisenfluh, July 2010)

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How do you roll?

When I imagine myself visiting Acadia National Park fifty years from now, I arrive in a public space shuttle, having just come from my lovely vacation home on the Moon. I step outside of my vehicle, and hop onto a hoverbus headed to Jordan Pond, where I will enjoy my tea outside while thinking to myself, “By golly, has transportation changed around here!”.

Okay, okay. So, maybe that’s a bit far-fetched. Let’s rewind: fifty years from now, I arrive at Acadia National Park from my vacation home in Canada by bullet-train, and jump on the bus to Jordan Pond House for scones and tea.

Sound far-fetched? Perhaps not…

For those of you who aren’t familiar with Acadia National Park, Acadia National Park provides free public transportation for visitors–a little something we like to call the Island Explorer Shuttle Bus. Personally, I was shocked to see such a progressive system in place.

If you are like me, you have grown up in a society where cars are not simply a luxury, rather a necessity if you would like to have any independence whatsoever. Sure, I ride my bike during the school semester, walk when I can, and love taking the train…but other than that, I drive. Psst, and I consider myself “green”.

It appears that members of the Federal Government have begun to understand this very conundrum. They also understand that road congestion is no fun for the average national park visitor. As a result, the Code of Federal Regulation states that parks and other public lands should make an effort to reduce private travel and encourage people to travel using public transportation. National parks are told that they need to use funds to establish public and sustainable means of transportation.

And the results of this are…? Well, the Island Explorer Bus, for one. But I’m hoping that’s just the beginning of it.

It sounds like I will not be disappointed. In fact, researchers from the University of Vermont are in the field this summer trying to understand what motivates people to travel like they do… is it related to money? Convenience? Enjoyment? And what motivations correlate with using the shuttle bus verses a car verses a bicycle?

How do you roll and what motivates you to do so? Or, even better: how can someone get you to do the green thing? Its a difficult question. Why would someone choose to give up their sense of independence to catch the 1:30 bus to Sand Beach? “Being green” and avoiding traffic congestion don’t seem to be motivation enough to encourage major reductions in the number of car users in the park. But, researchers are trying to pinpoint other motivations that will.

Me–I’m hoping that the hoverbus is not so far off in the future…but I’ll gladly take the shuttle bus in the meantime.

Planning a trip to Acadia NP? Use the Route Finder to find the right bus to get you where you want to go! For more on the Island Explorer Shuttle Bus, contact info@exploreacadia.com or visit http://www.exploreacadia.com or http://www.nps.gov/acad/planyourvisit/bus.htm.

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Photo of the Day

Sheep Porcupine Island, as seen while sailing just off the coast of Bar Harbor. There are a total of four Porcupine Islands, including Burnt Porcupine Island, Long Porcupine Island, Bald Porcupine Island, and, of course, Sheep Porcupine Island. (L. Weisenfluh, July 2010)

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