I am now finishing up my research projects in Australia, and since I have collected so much video while I’ve been working on my projects, I made a short video to explain some of what I have been doing at Macquarie University in Sydney, Australia.
My goal is to use oysters that have grown up in areas acidified by acid sulphate soils (a natural process that occurs in some parts of Australia) to understand how ocean acidification may impact an oyster’s ability to protect itself from crabs. Ocean acidification is expected to dissolve shell material, in much the same way chalk dissolves in vinegar, or teeth dissolve in soda. However it will be a slow process of acidification, so animals such as oysters may have time to get used to the extra acid in the system. In Australia, the oysters that grow up in areas with acid sulphate soils have had generations to adapt or acclimate to changes, so this is a great place to start. Will oysters that grew up in acidic conditions be eaten faster by predatory mud crabs? Or have they figured out some way to compensate? How might oysters respond to gradual changes in acidity, as is expected to happen world wide with climate change and ocean acidification? Hopefully after I analyze all of my data, I will have some answers.
This morning I am making my last few travel plans for my next big adventure. In less than three weeks I will be boarding a plane for Sydney, to spend 10 weeks exploring and studying one of the most unique places on earth. Since I will be posting a lot about my research in Australia, this week’s topic will be an introduction of one of my main research interests, which also happens to be a very complex and serious issue facing the world’s oceans: ocean acidification. Get ready, I’m about to bust out some chemistry.
Ocean acidification is the process of the oceans becoming gradually more acidic, due to increasing levels of carbon dioxide in the atmosphere. This is how it works. As we hear almost every day, atmospheric concentrations of CO2 are increasing at an alarming rate. This is the driver of climate change. More CO2 in the atmosphere means that more CO2 will come in contact with ocean surface waters, where gas exchange occurs. After CO2 is dissolved in water, it takes part in a number of reactions. The products of these reactions are carbonic acid, bicarbonate, and the carbonate ion. There is, however, one other important byproduct of these reactions. At each step, hydrogen ions are lost into the water. More hydrogen ions in a liquid means the liquid become more acidic. The result is a decrease in seawater pH, because a lower pH means a solution is more acidic. Under some scenarios, if the current rate of CO2 emissions continues, we can expect a decrease in pH of 0.4 units by the end of the century. While this may not seem like a significant decrease in pH, it actually represents a three-fold increase in hydrogen ions.
Acid can harm many organisms in the ocean. Fish gills are very sensitive to acidity, and more acid in the blood stream is, as you can imagine, very stressful. The main concern is usually for young life stages of many ocean species, because young animals are usually more sensitive to changes in the environment. In addition to the direct effect of acid, there are other, potentially more harmful consequences of ocean acidification. For example, carbonate ions are a natural buffer for seawater. They are the Tums of the ocean- just as Tums help relieve extra acid in your stomach, carbonate ions help eliminate extra acid in the ocean. As ocean acidification continues, the result is a loss of carbonate ions from the ocean. By the end of the century, there may be 60% fewer carbonate ions in the ocean. This means there will be less “Tums” to rid the ocean of extra acidity.
I addition to acting as Tums, carbonate ions are one of the building blocks for shell material. As carbonate ions get used up to buffer acid in the ocean, there are less carbonate ions available for the animals that need them to build hard shells, such as crabs, clams, oysters, corals, and some plankton which form the base of the ocean food web. Not only will there be less material for them to use to build shells, but if the oceans get acidic enough shell material may even begin to dissolve away, just as Tums dissolve in your stomach. Hard shells protect and provide structure for these animals. If the shells weaken or dissolve, these animals cannot grow and are less likely to survive an attack by a predator.
Despite the importance and complexity of this issue, relatively little research has been done on ocean acidification. Besides coral, which has been studied extensively, few species have been included in ocean acidification experiments. Many studies experiment with extremely low pH values which have dramatic effects on animals, but are unlikely to be seen in the oceans in the next century. Perhaps the greatest problem is the lack of long-term ocean acidification studies. Most of the research that has been done covers a period of less than 7 days. Such a short-term study is not adequate to understand the effects that ocean acidification may have over an organism’s lifetime, let alone the effect it might have on generations of animals that have a chance to adapt to change.
There are some places in the world that are already experiencing acidification on a small scale, due to a variety of natural (and sometimes unnatural) phenomena. This acidification occurs in polluted bays, at carbon dioxide seeps, around deep-sea volcanoes, and on the East coast of Australia, where acidic soil rinses acid into coastal waters. In Australia, acidification from acid soil is a natural process that has been going on for the last 10,000 years. The acidic soils form when iron-rich sediment is exposed to seawater, which then evaporates or recedes and leaves behind sulfide, a substance that is naturally found in seawater. The sulphide combines with iron to form iron-sulphide sediments. When this sediment is dried out and exposed to oxygen, the iron sulphides undergo a chemical reaction to form sulphuric acid. Then every time it rains or the tide comes in, all of that sulphuric acid is washed into the coastal water. The animals that live there must find a way to adapt to the acid in the water, or they will die.
While I am in Australia I will be taking a look at the communities of oysters living in the acidic bays and estuaries near Sydney, to see if they have been able to adapt to the long-term acidification of Australian coastal waters. Since my interests lie in predator-prey interactions, I will be looking at how oysters and crabs interact, and whether oyster shells are weaker and result in more acidified oysters being eaten by crabs. This study in Australia will serve as a natural experiment to help scientists understand the effect of the slow process of ocean acidification on animals as they adapt to their environment from generation to generation. It is important to understand the effects of ocean acidification because if some shellfish species are going to have a hard time, commercial shellfish farmers and harvesters may find their livelihoods threatened. Fisheries aside, plenty of animals have shells. These animals are an important component of the food web, and figuring out which ones are likely to disappear from the ocean will help us to predict if there will be large changes to the flow of energy in the ocean.
In the meantime, I will share some stories about my research and my travels in Australia this summer. Australia is full of unique landscapes and creatures, so I will undoubtedly have some cool facts that I pick up along the way, and share with all of you on my blog. Stay tuned for some adventures on the reef and in the mangrove.
At the beginning of my graduate school career I remember sitting in on a seminar about a recent program implemented by several students called “draw a scientist”. Students involved in a GK-12 program, where graduate students bring science to middle school and high school classrooms, were asked to draw their version of a scientist. In the drawings, crazy hair, flasks, and lab coats were a common element. Students described their scientists using adjectives like smart, crazy, chemicals, mixing, nerd, weird, lab coat, old, lab work, hard-working, and cool. At that age, I probably would have drawn the same thing, except my scientist would have been female, and I would have most definitely included the word “cool” in my description. However, my experience as a scientist has not led me to don a lab coat very often. I have held a few jobs that included pristine labs with white, crisp coats and flasks, but more often than not, I am wearing muddy waders, hiking boots, or dive suits.
I am a marine scientist, and I study the interactions between animals that live in the ocean. Right now I am studying predator-prey interactions in the Chesapeake Bay, which is not exactly the ocean but it is pretty salty. It is an estuary, where the rivers from the land meet the ocean and a mix of fresh and salt water occurs. The Chesapeake Bay is home to many species found in the Atlantic, as well as some that are only found in estuaries. I am focusing my research on two predators, the blue crab and the cownose ray, and a few of their prey species, including the soft-shell clam (steamers in New England), hard clams (or quahogs), razor clams (often used as bait), mussels, and Eastern oysters. My research is attempting to answer the question, how will these predator-prey interactions change in the future as climate change impacts the Chesapeake Bay in various ways?
Scientists never really prove anything; they can only provide supporting evidence for a phenomenon, and as the amount of evidence grows, so does the scientist’s confidence that their answer is correct. Thus my research project that I am completing for my PhD will collect a variety of evidence to answer my research question. I have to look at the problem in a number of different ways, using not only experiments in the laboratory, but also observations and experiments from the Chesapeake Bay itself, and predictions from mathematical models. That is why getting an advanced degree in science takes so long and involves so much work. Scientists-in-training are learning how to build a body of evidence to try and answer a research question. When completed, my dissertation will consist of four different chapters which summarize eight (or more) research projects, all designed to provide some evidence pointing towards the answer of my research question. In the end I still won’t have an answer; just a starting point and a hundred more questions. Remember, science is a journey.
So what do I actually do? In the summer I go out on some rivers that feed into the Chesapeake Bay, like the York River, in a small boat and collect samples in shallow water. Most of my samples are suction samples. To take these samples I use a large pump that works as an underwater vacuum, allowing me to vacuum up the mud and sand on the bottom of the river. I use these samples to understand how many clams are in an area. I also tow nets behind the boat to collect fish and crabs (the predators in the area), and snorkel along a 50 m rope laid out on the bottom of the shallow parts of the river to count the pits that rays make when they feed. This is a much easier way to figure out how many rays are in an area than actually catching the rays.
The water is mostly muddy but every so often, when the conditions are right, I feel like I am snorkeling in the tropics. Those are the best days, when I get to see vast expanses of seagrass, the terrapins (a type of swimming turtle that gets about the size of a dinner plate) swim next to me, and I can see all of the little clams and worms on the river bottom going about their business, excavating burrows and spewing out streams of mud that look like something that comes out of a Play-Doh pasta factory. But most days I can only see about a foot in front of my face, and the view is frequently obstructed by translucent jellyfish tentacles that appear too late for any sort of evasive maneuver, and the resultant burning pain is just treated as part of the overall experience. Hey, it could be worse. We could be in our office.
For the rest of the year I devote my time to a number of activities. These include sorting through the suction samples to pick out the clams, holding an active leadership role in graduate student government, keeping up to date on the latest science discoveries in my field, fulfilling my current funding requirements (this year, I was a guest scientist in a 7th grade classroom for a couple of days every week), writing grant proposals to fund my education next year, writing reports (and soon my own scientific articles to be published in a journal), and working on a project in the seawater laboratory (see video).
I visit the seawater laboratory every day of the week, devotedly, except for Sunday. All of my critters (blue crabs, clams, mussels, and oysters) seem to behave on Sunday. However, if I fail to visit any other day of the week, disaster abounds. I return to rampant cannibalism (in the blue crab tank, of course), escapees, clogged plumbing, leaky ceilings, broken water heaters, overflowing tanks, you name it. For a while I was convinced that the brand-new seawater laboratory was haunted. Now I know that this is just one of the things that makes ecology so interesting and exciting. Since I am always working with live critters, things never really go as planned. I have spent most of my time in graduate school anticipating the evil intentions of invertebrates, some of which don’t even have brains. As a result I have had many chances to exercise creative, out-of-the-box thinking, and when I fail, the consequences are usually pretty hilarious.
For instance, last summer I was running an experiment in several tanks where crabs were offered clams for food. There were various scenarios that made it harder to get at the food (i.e. clams were hidden underneath a layer of shell), and crabs are lazy, so it shouldn’t surprise me that the crab starring in this story had had enough, and was ready to strike out on his own to find a more promising food source. Despite precautions to prevent this type of thing from happening, the crab climbed out of the tank and into an adjacent tank. This rarely happens; the tanks are round and only overlap for a small portion, but in this case the crab was on a mission and the result certainly paid off. The day before I spent 8 hours with a volunteer painstakingly marking clams and placing them in containers to be deployed in the York River the next week. The crab had discovered a buffet of epic proportions, and the next day I arrived in the lab to find shell splinters and an extremely well-fed blue crab.
My experiences may not be typical of the average scientist, but I would argue that white lab coats are not typical of the average scientist, either. Scientists are just as likely to be “outdoorsy” as they are likely to be holding chemicals over a Bunsen burner. Programs like GK-12, sponsored by the National Science Foundation, help to inspire the next generation of scientists and to change the way people think of scientists. As a result these programs produce a more diversified next generation of scientists, and hopefully increase public trust in science programs. This is especially important because public trust in scientists is very low. This should be very concerning for scientists, a group of people who base their lives and careers on a quest for truth.