Copper sediment toxicity and partitioning during oxidation in a flow-through flume
A new paper is out from the Costello Lab. This paper summarizes a large experiment studying how the geochemistry and toxicity of Cu contaminated sediments changes as sediment oxidize. The paper is online now in Environmental Science & Technology. Click the link below or email Dave for a reprint.
Copper sediment toxicity and partitioning during oxidation in a flow-through flume
In an effort to boost updates about what is happening with the Costello Lab we have moved most of our activities to Twitter. Stay tuned below or follow us @CostelloLab
Congrats to PhD student Andi Fitzgibbon for receiving a research grant from the Huron Mountain Wildlife Foundation. She will be spending a few weeks in June at the Stone House. He study will look at algal metabolism in the Salmon-Trout River using our new field microprofiling system. Great job Andi!
The newest paper from the Costello lab is out in the new journal Elementa: Science of the Anthropocene. The paper summarized an experiment that was completed in the summer of 2010 while Dave was a post doc at the University of Michigan. The journal is open access so anyone can get a copy of the paper.
Read the paper here: Response of stream ecosystem function and structure to sediment metal: Context-dependency and variation among endpoints
Last week myself and my new PhD student (more about her later) traveled to Aarhus, Denmark for a training workshop. The training was held by Unisense, which is a company that makes microsensors for measuring chemistry at really small scales. Some of their sensors are 10 µm wide, which is thinner than human hair! We saw sensors being made, received a lot of information about potential applications, and got to play with all the new equipment.
Much of our recent research has focused on the sediment surface in stream ecosystems. The stream bottom (or benthos) is where most stream organisms live (e.g., invertebrates, algae) and where those organisms interact with toxic chemicals that might be in the sediments. There are dramatic changes in chemical and biological conditions as you go vertically from the water in a stream into the sediment. For example, stream water is often fully saturated with dissolved oxygen but within a few millimeters into the sediment all of that oxygen is gone. Small changes in the depth to which oxygen penetrates into the sediment can make a big difference in how many elements cycle in the stream. Standard sensors cannot measure at this small scale, but Unisense makes the very tiny sensors that can measure at a µm scale.
While at the University of Michigan I had access to Unisense microsensors and used them on quite a few projects (typically measuring oxygen). I even took the sensors outside to work stream-side, which wasn't exactly easy. This equipment is made for indoors with access to power outlets. We had to make due with a car battery, power inverter, and lots of AA batteries. Luckily Unisense is making a new battery powered field system that has simpler power requirements and is also waterproof. While in Denmark we were able to test out this new equipment before it is for sale. We are looking forward to purchasing the field system and are excited about the research possibilities!
Slowly but surely our new lab at Kent State is starting to round into form. A large effort has gone into selecting and ordering equipment and consumables to outfit our lab; most of this equipment is standard for a biogeochemistry lab, but it's all necessary to start answering the research questions that we're interested in. The main piece of equipment for our lab is a brand-new Optima 8000, which will be used for doing inductively coupled plasma optical emission spectrometry (ICP-OES).
This unassuming box contains a very sophisticated piece of equipment that can detect and measure 70% of the naturally occurring elements on the periodic table (from Ag-Zr). Behind the black window (center of image) is a torch where radio waves, and magnets work together to produce a plasma of argon that is very, very hot (~12,000° F). When a pump introduces a sample into that super high-energy plasma all the molecules in that sample break down into their respective atoms. As the atoms move through the plasma they emit light, and each element gives off a very specific light signature. The spectrometer (R side of image) measures this emitted light as intensities at specific wavelengths. By looking at individual wavelengths of light that are "fingerprints" of individual elements, we can extract the signal of that element and determine how much was in the sample (concentration). The ICP-OES can measure multiple elements within the same sample, which can give us a picture of the unique elemental chemistry of an individual water or soil sample.
In our lab, we'll be using the ICP-OES to measure metals (Fe, Mn, Cu, Ni, Zn, Pb) in stream waters and sediment. However, this machine is a shared resource and will be used by many researchers across different departments at Kent State. The flexibility of the ICP-OES and relatively simple operation makes it a useful tool for many researchers studying elemental cycles. Right now, our machine is going through initial tests and we plan on generating our first data in the next few weeks.
In one week we are starting a new experiment. The setup for this experiment presents some challenges that require me to add some new skills to my resume. We are testing how the toxic metal nickel, when found in sediments (read: mud), affects the growth of a common freshwater amphipod. We'll be conducting this test in 160 small beakers in the lab. The trick to these tests is to make sure the water in the beakers stays clean throughout the test. Usually, we can accomplish this by exchanging the water daily, but that won't work for these tests. Nickel is very mobile and can "leak" out of the sediment and build up in the water, which potentially might cause problems for the amphipods. A previous study by some colleagues showed that if you change the water every three hours you can keep the water clean. We have very dedicated undergraduates that work in our lab but even I wouldn't expect them to come to the lab at 3 am to change water in 160 beakers!
The best option for frequent water changes is to use an electronically-controlled water dispensing system. I am sure we could have contacted an engineer to design such a system but our budget for this project is already stretched thin and paying for a professional system was not in the original budget. Thus, the task becomes do-it-yourself, which is not an uncommon phenomenon in our field. Thankfully, I have a brother who is an electrical engineer, and he gave me some free advice for designing and programming the system. We decided on a system that uses solenoid valves, which are normally closed but can be opened by passing an electric current through them. By connecting these valves to timers we can automatically program the valves to open at specific times and stay open for a sufficient amount of time to exchange the water.
Inevitably, what I naively assumed would be a relatively simple task turned out to be pretty complex. Choosing the right size solenoid valve required some hydrologic calculations and a bit of shopping around. We didn't want to have to buy a solenoid valve for each of the 160 beakers so we had to build splitters to evenly divide water from one solenoid valve to multiple beakers. I installed switches for manual control of the solenoids and a serious controller for the automatic program. Luckily, I completely relied on my brother for writing the automated program from the controller. All told, the system required 500 PVC fittings, 300 ft of wire, 50 ft of tubing, and quite a few hours of my time. Initial tests of the system show that it is working as intended and hopefully our water changes will run smoothly for our experiment.
In the end, setting up this single experiment required a basic understanding of plumbing, electrical, hydrology, and programming. As I said above, this is not an unusual situation for experimental ecologists. Much of the equipment we need cannot be purchased off the shelf or even out of specialty catalogs. Some of the equipment is passed down through the ages or can be built from designs by others, but most of the time a particular experiment requires a significant time investment in tinkering, building, and adapting. The difficulty in designing and building equipment is a relatively invisible facet of an experiment that is often downplayed in presentations and publications. Anyone who has tried to replicate an experimental apparatus is likely well aware of the missing details about equipment; however, most of the time the people that initially designed an experiment and the necessary equipment are more than willing to help. In the end I think all the effort is worth it because well-designed equipment leads to better experiments, which generates better data and advances our science.
The Costello Lab website is up and running! Although the lab itself won't open until 2014 this website should give a good introduction of what to expect the lab at Kent State to be like. Dave will continue research at Michigan until December 2014 but many of the ongoing projects will continue at KSU.
I envision this blog as a good space to highlight current research, introduce future lab members, and promote examples of how our research has been applied to real-world problems. I hope you return to this space to check out the current Costello Lab news!