Aaron Stoler
My research
Scroll down to read the research projects I have been involved in
Maple syrup in southern New Jersey and Philadelphia?
Research project in a nutshell:
1. Investigate the feasibility of producing maple syrup from red maple trees in southern New Jersey and the Philadelphia region
2. Understand environmental factors associated with sap flow, such as tree diversity, soil chemistry, litter mass, and weather.
3. Develop a community-centered model of syrup production that has the potential for profitability while maintaining sustainability.
4. Engage the community through social mediate, citizen science, program planning, and other targeted outreach efforts
I'm going to be honest. I never tapped a tree before 2019. That makes 34 years of my life where I was completely clueless about how to make maple syrup. But a friend of mine peaked my interest. My initial thoughts were..."wait, isn't that something they do in Vermont? Don't we live in the Pine Barrens?" Southern NJ doesn't have sugar maples, and these are the trees that most people use to make maple syrup. Also, southern NJ doesn't really have a strong winter season, which is usually needed for high sap production.
But we do have red maples. Like...everywhere. Actually, red maples can be found from Canada to Florida. And they produce sap. Lots of sap. And they produce sap even when the winter isn't that strong. So what's a pancake-loving ecologist supposed to do? Research!
Three years and two sizeable USDA grants later, maple syrup production in southern NJ and Philly is in full swing. We are exploring how to use modern technology - including vacuum assist sap flow, reverse osmosis, and seriously efficient evaporators - to make high quality maple syrup and maple syrup products in an area that was previously off the maple map. We are exploring questions related to forest biodiversity and sap production, faunal characteristics of maple forests, sugar sap content and population genetics of low- and high-productive trees, and other science-y sounding things. We are making lasting change in southern NJ and Philly through community-building activities and by funding the establishment of community-operated sugarshacks (i.e. the place where you boil sap into syrup). You can visit one of them here: www.oaklanemaple.com.
And to those of you who know my academic background in aquatic ecology: why is a freshwater ecologist dabbling in maple syrup-ology? First and foremost, I consider myself a scientist. Second, I'm an ecologist. Third, I'm a freshwater and forest ecologist. I'm a glutton for a good scientific question, wherever it can be found. This was a good scientific question. And I have loved every minute of it.
Tapping trees is easy. Drill a hole. Stick a tap in. That size hammer was probably overkill.
In our sugarbush, we are installing a tube and vacuum system to draw higher sap yields. Masks, courtesy of COVID 19
Proof that we can produce maple syrup from red maple trees in southern NJ.
Extent and ecotoxicology of microplastics in freshwaters
Research project in a nutshell:
1. Explore the extent of microplastic pollution in freshwater ecosystems.
2. Understand how microplastic pollution affects freshwater communities.
Plastic is all around us. We make our clothes out of it. We eat off of it. We give our children toys made out of it. We use it in our pharmaceuticals. Not surprisingly, plastic is one of the most common physical pollutants. Most of us can easily bring to mind images of plastic littering the beach, and shorebirds with guts full of plastic. However, this is not the bulk of plastic waste. In fact, the bulk of plastic waste is the stuff you can't see: the microplastics that so tiny that they can drift in the wind and float in our drinking water. Microplastics are defined as any plastic item smaller than 5 mm. Where does this plastic come from? Consider your clothes; most are polyester (i.e. plastic) blends made of recycled plastic. When you wash your clothes, polyester threads come off in the water and flow down the drain. When you walk down the street, polyester threads come off our clothes. When you accidentally step on a brittle plastic bottle, it breaks into smaller plastic items. Resin beads used in personal care and pharmaceutical compounds also make their way into the water. This stuff is everywhere.
For the past few decades, researchers have noticed an increasing amount of plastic waste in our environment. In fact, there is now a Texas-sized island in the Pacific Ocean composed entirely of plastic waste, known as the Great Pacific Garbage Patch. Most research into plastic waste has focused on marine ecosystems, since that is where the problem was first identified. But researchers are increasingly turning their attention to freshwater systems, like streams and rivers. If you've been kayaking in any lake, you've probably seen plastic waste along the shoreline. Again...that's only the stuff that you can see. What about all the microscopic stuff?
From an ecological perspective, the micro stuff is really important. Most organisms are really small (think bugs and plankton) and this plastic looks an awful lot like food. A polyester thread is REALLY difficult to distinguish from a strand of algae (trust me, I've tried). Bad, right? Actually, we don't know. Animals ingest lots of things that they can't actually digest. Bottom-feeding fish accidentally eat sand all the time. Predators eat bones that they don't digest. Even herbivores that eat algae tend to pass a lot of that algae through their gut because they can't digest the cell walls. Is plastic similar? Once again: we don't know. We don't even know the extent of the problem (i.e. how much plastic is actually in our ecosystems).
My research is aimed at understanding the extent of the problem and how it affects freshwater communities. I am currently conducting a state-wide survey of microplastics in freshwater lakes through New Jersey. I am also conducting several mesocosm and laboratory studies in which I expose animals to plastic pollution.
Microplastic are plastic items smaller than 5 mm in size
The Great Pacific Garbage Patch is a Texas-sized island of trash in the middle of the Pacific Ocean
I conduct mesocosm studies in which I create minature wetlands - fully stocked with the major components of any common wetland food web. I add contaminants like microplastic to these systems to see how they affect freshwater systems.
The Jefferson Project at Lake George
Research project in a nutshell:
1. Developing a lake food web model that incorporates real-time data from new-age sensing technology, and also predicts the contribution of individual species to the overall economic value of the food web
2. Understanding the effects of road salt, pesticides, and other contaminants in freshwater ponds and wetlands.
3. Understanding the interaction between natural subsidies (e.g., leaf litter, fertilizer) and anthropogenic contaminants on freshwater wetland functioning.
4. Linking forest diversity with stream ecosystem functioning at the watershed scale.
In 2015, I joined The Jefferson Project at Rensselaer Polytechnic Institute as a postdoctoral researcher. This project is collaboration between IBM, Rensselaer, and the FUND for Lake George. Which means that I get to work with some awesome people. Seriously...the people at IBM are like magicians. I never know what kind of technology they will pull out of their sleeve.
The goal of the Jefferson Project is to revolutionize the way we research, monitor, conserve, and interact with aquatic ecosystems. We are combining cutting-edge sensing technology (e.g., underwater sensors, weather stations) with state-of-the-art computing and visualization power (e.g., the Blue Gene supercomputer) to fast-forward our understanding of lake ecosystems. We are integrating computer scientists, chemists, engineers, biologists, geologists, and artists. The stuff coming out of this project is amazing (and also proprietary...so wait for the publications).
Underneath all of this, we are simply trying to conserve land protect lake ecosystems and fresh water resources. We need water; we need it to support our bodies, but we also need it for recreation, wildlife, and electricity. We need it to support a healthy atmosphere and to cool our planet. We need it to water our lawns and provide the green spaces that let people chill out. Most importantly, we need it for beer, wine, and whiskey. Can you imagine a world without those things? I thought not. The Jefferson Project has a singular goal: monitor and protect water resources by using modern technology and integrative scientific approaches.
We are using Lake George (NY) as a case study for this goal. I was brought into the project to help develop the food web of Lake George and to understand how disturbances alter that food web. We are working in a variety of experimental venues, such as still-water mesocosms, flow-through channels, and laboratory microcosms. We will be conducting stream and lake surveys, involving countless hours of dipnetting, seining, gill-netting, snorkeling, and SCUBA diving. In other words, why am I getting paid again?
You can read more about the Jefferson Project here.
This just doesn't happen.
If you've never been to a temperate deciduous forest, you're missing out. When autumn happens, it looks like fireworks
Obviously. If you want to know why there is a picture of a beaver here, I suggest you read the text. You know you want to.
Competition between two species for a limiting nutrient can often result in the elimination of weaker competitors.
After absorbing most of the nutrient from leaves, they then fall to the ground and decompose.
Frequently, leaves make their way to bodies of water, which leaches stuff out of the leaves and accelerates decomposition
As leaves decompose, the fleshy material often decomposes first, leaving behind the tougher veins
Pine needles, as from this scotch pine tree, often decompose much slower than other types of leaf litter
Those little white dots on the branches are actually a bunch of scale insects that are decimating Eastern Hemlock trees
Browsing from mammals like deer are often responsible for the lack of a tree species regeneration
Aquatic-terrestrial linkages
Research in a nutshell:
1. How does the variable chemistry of leaf litter subsidies to wetlands alter the structure and function of aquatic food webs?
2. How does the diversity (i.e. species richness, trait richness) of terrestrial subisides alter the structure and function of aquatic food webs?
3. How do natural terrestrial subsidies interact with anthropogenic contaminants (e.g., road salt, pesticides)
I am interested in the connections between ecosystem processes, environmental conditions, community complexity, and diversity. Environmental conditions determine what species are where. In turn, species alter environmental conditions. Let's face it: you can't put a tropical plant in the middle of the arctic and you can't put a penguin in the middle of the Sahara desert. Well, you could try. Good luck. I'll alert PETA.
One of the most important things that determines what happens inside of an ecosystem is the stuff that goes in and out of the ecosystem. Think about a bird that flies from the south, lands in a pond, and poops (egests, for all you biology nerds). That poop then provides nutrients and energy for lots of other animals, likes snails and tadpoles. Then a tadpole emerges as a frog and hops somewhere in the forest, gets eaten by a bird, and then gets pooped back out. The ecosystem would be much different without that bird flying into the pond.
At the same time, environmental conditions play a large role in determining when and where stuff goes in and out of the ecosystem. For example, a bird doesn't fly north until the temperature heats up. A bird might also choose to land in a pond that is clean and has relatively little pollution. Or maybe the bird will only fly into a pond that has fish. Or maybe birds are dumb. I don't know. I'm not a bird-ologist (ornothologist for you people that know better).
And then when bird poop falls into a pond, who gets to eat it? That really depends on what is in the pond. What type of bacteria and fungi are in the pond? Are there animals that eat the poop? Is there enough light for plants to grow and suck up the poop through roots? Is there a lot of diversity in the pond that can make use of all different types of poop? Are you getting tired of reading the word poop? Tough. Everybody poops. It's a book. Read it.
And then what happens with something invades the ecosystem and completely changes who is there and what happens to the poop? Maybe the bird won't even come to the pond any more! Or maybe the invasive critter will just replace some other species and nothing will happen. Or maybe the invasive species will actually benefit the other animals in the pond (then we probably shouldn't call it invasive...).
Anyway, I study all of that in ponds and lakes. Things are complicated. If things were easy, I would be on a yacht in the Caribbean. And I’m not. Unfortunately.
To better understand some of the specifics about my research, read further. Or don't. I don't blame you.
Leaf litter as a major input to aquatic ecosystems
When you go into a forest during fall, what do you see on the ground? Leaves! When you walk back to the forest in the springtime, what do you see on the ground? No leaves! Congratulations, you just passed kindergarten. Now for the more difficult questions. What happens to the leaves, how does it happen, and why does it happen?
Obviously, the leaves disappear. Actually, they decompose. In autumn, the tree absorbs much of the nutrients from the leaves (you notice this when the leaves start turning different colors), and then they fall. Why would a tree do this? Interesting you should ask. I wrote a blog post on it. Read it here.
Next question. How do the leaves disappear? Well, if the leaves fall onto land, the leaves will gradually turn to mush as rain and snow fall on them. Water is actually a very corrosive and sticky substance (just because you drink it all the time does not make it unreactive - water has oxygen, and oxygen is one of the most reactive elements common to our world!). Earthworms and spiders move the leaves around and fungi use the chemicals. When the leaf falls into water, the same thing happens, but faster. Water is constantly hitting the leaf, so it breaks down even faster. Also, you get detritivores (mostly insects) which eat the leaves!
And the final question. Why do the leaves disappear? If you are looking for a philosophical answer, consult your local deity. But physically, organisms in the forest rely on either the nutrients in the soil or in the water to form the base food supply which they rely upon. You can't grow without food - neither can bacteria, bugs, frogs, spiders, fish, and everything else in the forest. The only way that nutrients can get into the soil or water is from stuff dying or from input outside forests. Conveniently, every autumn, leaves die. Ecologically speaking, leaves form the base of the nutrient cycle in forests.
In addition to putting a whole bunch of good nutrients in the water, leaves and needles also put a bunch of bad chemicals in the water, such as tannins and alkaloids (tannins are the same stuff found in tea and coffee which most people find bitter). These chemicals are difficult for organisms to digest because they bind to proteins (which is also why people put milk in their coffee - the tannins bind to the milk and make the drink more digestible and less bitter). Tannins are known anti-microbial agents, they can kill tadpoles, and they can even mummify a live human (No kidding...click here!)
To add to the story, we must recognize that there are MANY types of trees in forests. Each type of tree has different associated chemical compositions. Every forest has a unique composition of plant-life; therefore every forest has a unique input of chemical components. These chemical components generate unique environments. For example, the input of red maple litter into an aquatic systems pumps a lot of nutritional nitrogen and dissolved carbon into the environment. The addition of chestnut litter puts a bunch of toxic tannins into the environment. Something like oak litter decays so slowly that it puts hardly anything at all into the environment. Where would you rather live?
This research question is becoming increasingly important as our forests change. Fire suppression, clear-cutting, over-grazing by mammals, invasive introductions, disease, and other disturbances (both anthropogenic and natural) are dramatically changing the landscape of eastern American forests. For example, red maple (Acer rubrum) is taking over most oak forests and eastern hemlock (Tsuga canandensis) is disappearing because deer are eating all the saplings. How will the loss and gain of such species affect the nutrient and chemical stock available to forested food webs, and how will the food webs change in response?
Putting it in context - Communities!
Ok. Let's sum all that up and just say that leaves are important.
Now, think of a pond in a forest. Pretty nasty place...lots of dirt, lots of leaves, lots of muck, and LOTS of life. For such dirty places, they are a growth medium for an incredible diversity of life! Tadpoles, amphipods, crayfish, snails, midges, zooplankton, phytoplankton, periphyton, water bugs, dragonflies, and salamanders (among a bunch of other organisms) need these ponds. They can't live in streams because they can't deal with constantly flowing water, so they live in ponds.
The chemistry of the litter changes the conditions of the pond. The conditions of the pond must meet the tolerance level of the organisms living in that pond. You wouldn't live in a place that you can't tolerate, would you? Neither would an insect, frog, or anything else that lives in a pond. That'.s the basics of what I'm studying
Dabbling in temperature change
Research in a nutshell:
1. What is the effect of temperature variability on wetland ecosystem functioning?
It is generally found that leaf litter decomposition happens faster when temperatures warm up. Bacteria, fungi, and all the cute critters (I think they're cute) that decompose the litter are exothermic - that is, they regulate their metabolism according to environmental temperatures.
So what? Well, temperatures are rising due to climate change. In addition, logging, fragmentation, and many other human - and natural - processes are transforming the landscape in ways that alter local temperatures. To manage our ecosystems and the processes we rely upon for our existence, we must understand how changes in temperature will influence the community.
There are an infinite number of questions to ask. But I'll give you a taste what I'm tackling. First, does temperature differentially influence the decomposition rate of different plant species? If this occurs, then there is a severely overlooked interaction between shifts in plant diversity and global climate change.
Second, how does increased decomposition rate translate to the community? Does faster nutrient release translate into more trophic levels, increased consumer biomass, or shifts in species composition?
We are tackling these questions in a state-of-the-art, heated mesocosm array that I just finished construction on. It's pretty amazing people. You can all worship me. Actually, don't do that. We might piss off a diety. I already drink and curse too much.
Leaf litter and pathogens
Research in a nutshell:
1. Does the chemistry of natural subsidies interact with the growth and proliferation of amphibian pathogens?
Admit it, parasites and pathogens are awesome. Yeah, sure...they cause death and gross stuff, but they are so incredibly important for ecosystem functioning! For example, did you know that the majority of nutrient cycling in the open ocean is likely to arise from pathogens infecting cells, causing those cells to burst open and release nutrients that other cells can use? Cool! You don't think so? Well, you should.
In all seriousness, parasites form a crucial yet unappreciated role in nearly every ecosystem. Some parasites cause animals to slow down so they are more vulnerable to predators. Other parasites cause widespread death, providing a severe selection event that drives rapid evolution. Other parasites cause mild effects that alter population trajectories, such as reduced productivity. Still other parasites cause zombie outbreaks that lead to the end of time as we know it.
The rate of transmission between parasites and their hosts is dependent on numerous factors, such as temperature, nutrient availability, and host density. As environmental factors change, both parasite and host must acclimate to novel conditions. For example, if temperature rises by a degree, both the parasite and the host must cope with this change or go extinct.
What happens if one is better at coping with the change than the other? Let's say that the parasite is better at dealing with changes in temperature than the host. Theoretically, the parasite is going to win; more hosts will be infected and parasite populations will increase in abundance. Sucks to be a host.
Through collaboration with Dr. Tom Raffel, I am exploring various aspects of this question with a tadpole-parasite system in our nifty new heated mesocosm setup.
And just because I love leaf litter, I'm throwing some litter-related questions into the mix. After all, the input of litter is just another environmental factor that can influence both the host and the parasite. How does the chemical traits, diversity, and abundance influence host-parasite interactions?
Tadpole stoichiometry
Research in a nutshell:
1. Do tadpoles, with their complex life history, challenge the assumption of consumer stoichiometric homeostasis?
2. How does the stoichiometry of tadpoles change through ontogeny?
Stoy-kee-om-it-tree: the study of products and reactants in a chemical equation. Except, I'm not a chemist. Ecological stoichiometry refers to the mass balance of inputs and outputs within some ecological systems. For example, if you eat a hamburger with a certain concentration of protein, I would like to know how much of that protein you incorporate into your body and how much you get rid of through urination and defecation.
I am NOT going to go around collecting human poop.
Instead, I'm examing the stoichiometry of tadpoles (their poop is much smaller and easier to deal with). Specifically, I'm examining the interaction betwen resource nutrient concentration, tadpole development rate, and excretion rates. This is a collaborative project between Tom Raffel, Keith Berven, Scott Tiegs, Jeff Stephens and yours truly.
