Invasive species transport demo

I recently completed a second AmeriCorps term with the National Park Service, working in the Ocean and Coastal Resources branch. My task was to research ballast water transport of invasive species and report on ways the parks might respond to the issue.

Humans transport organisms all over the world in a variety of ways, from muddy boots to bugs tucked in produce shipments. One prolific vector is ballast water: water that vessels – often very large cargo ships – use to maintain buoyancy in different voyage and cargo conditions. Vessels typically uptake ballast water straight from the ocean and all the little aquatic organisms in it come along for the ride. This includes critters ranging from human pathogens like E. coli to microscopic crab larvae. Ballast water has introduced some very high-profile invasive species to new locales, such as the zebra mussel to the Great Lakes.

Luckily, we’ve developed multiple treatment strategies for reducing the organism load in ballast water, and increasing levels of regulation mean that invasive species transport will continue to decrease over time. (Of course, it’s another one of those environmental issues where you think “if only we started this fifty years ago instead of twenty…”, but I try not to dwell on that too much.)

For the outreach component of my internship, I developed a hands-on activity demonstrating how human activity moves organisms around the world. The activity is simple: a guest pushes a magnetic model boat across the ocean, and it picks up magnetic organisms. When the boat reaches the opposite shore, stronger magnets pull the “organisms” off the boat, representing the introduction of a species to a new location.

Finally, in order to demonstrate that it is possible to prevent species introduction, I included a purple magnetic wand to represent the use of ultraviolet light to disinfect ballast water.

Activity participants can remove organisms with a “UV wand”.

I made three of these activities (in-progress shots below) and they’ve been shipped out for use at Isle Royale National Park and Indiana Dunes National Park. Maybe someday you’ll encounter them out there!

Soil science demo: Hands-on molecules

Back in 2018, I had the opportunity to participate in the Pacific Science Center’s Science Communication Fellowship Program. Not only did I take classes on science communication, I made my very own, hands-on demo of my research topic.

My graduate research focused on how water interacts with soil, addressing the question of why soil sometimes does not absorb water from a molecular standpoint. Most rocks and minerals are readily wettable, so any water resistance must come from the other major component of soil: the organic material from soil microorganisms and decaying plants. I focused on one particular class of molecule, the phospholipid, which forms cell membranes. One end of a phospholipid readily interacts with water; the other does not. The hydrophobic ends of molecules like these were hypothesized to cause soils to repel water. I wanted to find out if and how that might occur.

Demonstrating the whole scale of my project was a big hurdle for designing my demo. I opted to start at the macroscopic and work my way down to the molecular.

The very first time I ran my demo! I would start at the left with a jar of dirt and work across the table to the molecular scale.

Starting off with a jar of dirt, I asked participants to tell me what they saw inside the soil. Typically, participants were quick to find small rocks. I would then ask them if they saw the twigs and pine needles as well. This way, I introduced the concept of soil’s two major components: inorganic (rock and mineral) and organic (plant and animal matter).

Next, I had a box full of plush mineral grains, single-cell organisms, and plant detritus. I asked participants if they could find all the soil components they saw in the real dirt in the box. I included a big drop of water to spark conversation about how water might move through soil. Most participants guessed quickly that the purple blobs were bacteria and other microorganisms, which let me segue into talking about cell membranes and the molecules that make them up.

Magnified “dirt”. Green = plant detritus, purple = microorganisms, brown = sand and clay, blue = water.

Lipids can self-aggregate in a number of ways depending on their surroundings; they have polar ends that interact with water, and long carbon tails that do not interact with water. To demonstrate the behavior of lipids, I made model lipids with magnetic “heads” and velcro “tails.” I also made magnetic water droplets to demonstrate how the different ends of lipids behave. Once visitors had played with the molecules and figured out how they interacted with each other and water, I would ask them to form their own hypothesis for how lipids could make soil hydrophobic. (See photo gallery below. Purple = lipid head groups, yellow = lipid tails.)

Having now done this demo several times, I’ve seen that the magnetic/velcro molecules get the best reception from visitors. Once in-person interaction resumes, I plan to revamp the activity to mostly focus on the molecular scale. I will make magnetic “mineral grains” so that participants can build the lipid structures that have been hypothesized to form on mineral surfaces. As a bonus, since I’ve now finished my Ph.D. project, I can tell them if their results match mine!