Journey to the Center of the Pluff

Lauren Rodgers, Rutgers University

Version 2The Approach: In my previous blog post I discussed the importance of iron in ocean ecosystems. Because so many living things rely on iron to live and grow, it is important for us to understand how iron cycles, as it enters the ocean, exits the ocean, and changes from one form to another. Zetaproteobacteria are marine bacteria that rely on iron to create energy for themselves, but in this process, they also turn dissolved iron into solid iron. So these bacteria make rust as they grow. Unfortunately, rust isn’t very good for other organisms, and the Zetaproteobacteria effectually remove iron from the ocean. But still, these organisms are one half of the iron cycle and therefore play an prominent role. With our research, we aim to determine whether these bacteria are present in Charleston’s estuaries, and extrapolate how they might be impacting the local iron cycle.

Now, you most likely have one thing on your mind: How are they going to study all of this!? From our lofty research aims, we must simplify those down to into bite sized goals so we can have a successful summer of sampling.

Our Goals:

  1. Identify whether Zetaproteobacteria can be found in the sediments around Charleston.
  2. Measure the amount of Fe(II) and Fe(III) in the sediments

The first thing that we did in order to accomplish these goals is pick sampling sites. We wanted to sample the sediments for these Zetaproteobacteria, so we chose muddy regions close to tidal rivers that empty into the ocean. We wanted tidal rivers because Zetaproteobacteria live in salty waters, and these rivers mix with salt water from the ocean. We decided to look for these muddy regions along the Ashley River, Wando River, Stono River, and Cooper River, picking easily accessible sites far up the river where the water is fresher, midway down the river where the salt content is at a mid-range, and low down on the rivers, near the ocean, where the water is salty.

 

After identifying the sites that we wanted to sample at, we needed to figure out how to sample. We wanted to sample the mud at different depths, so we decided to use syringes to suck up the mud.

 

Once all of the samples were collected it was time to get back into the lab to analyze the data. In order to confirm the presence of Zetaproteobacteria we conducted PCR, which is a process that tells us if there was any DNA belonging to the Zetaproteobacteria in the samples.

 

 

 

To analyze the iron a ferrozine assay was conducted. In a ferrozine assay, different chemicals are added to the samples, which then turn different shades of purple depending on how much iron is present in them.

 

While we have already completed a lot of the data collection, we still have more to do. In the next few weeks we will focus on collecting the last few samples and analyzing them in the lab. Soon all of the results will be ready for interpretation!


I would like to thank my mentor, Dr. Heather Fullerton, for guiding me through this research. I would also like to thank the National Science Foundation for funding this research as well as the College of Charleston and Grice Marine Lab for their support.

Advertisements

Bacteria in the Ocean? That Eat Iron??

Lauren Rodgers, Rutgers University

Version 2The problem: Have you ever asked yourself, what is iron? It is an element? A rock? Some weird orange-ish substance? Is it the tool that you use to get the wrinkles out of clothes? And what does iron even do? Does it just sit there? Does anything eat it? Can we make things out of it? Iron is one of the most abundant elements on earth, yet not many people know much about the important role it plays in our lives.

Iron is more than just an element, or something found within a rock. It’s a nutrient, something necessary for the growth and metabolism of almost every living organism on Earth (Hedrich & Johnson, 2011). In the ocean, iron is found in two different forms, ferrous iron or Fe(II), which is soluble in water, and ferric iron or Fe(III), which is insoluble in water (Hedrich & Johnson, 2011). Because ferrous iron is soluble it is the form of iron that can be used by most organisms in the water (Hedrich & Johnson, 2011). This ferrous iron, however, is limited in the ocean despite its abundance in the Earth’s crust. In fact, Fe(II) is present only in incredibly small concentrations, making it a major limiting factor of growth for all of the plants and algae in the ocean. This is important because these plants and algae serve as the base of many food chains, so if there is a limitation on the growth of these organisms, it affects every other organism throughout the food chain. Though iron is an extremely important nutrient for many living organisms, it is still not well understood. One of the least understood aspects is how iron specifically cycles through different marine environments. Does it ever change form? Does anything add iron to the ocean? Does anything take iron out of the ocean? These questions bring us to Zetaproteobacteria.

Zetaproteobacteria is a recently discovered class of iron-oxidizing microbes. This just means that the bacteria eat iron in the form of Fe(II) and produce Fe(III) as a waste product (Emerson et al., 2007; Chiu et al., 2017). In fact, these waste products can take on the form of hollow tubes, also called tubular sheaths, or twisted stalks that you can see under the microscope!

 

Zetaproteobacteria were initially described in 2007 near hydrothermal vents, utilizing the large concentrations of Fe(II) that were present in the fluid that spewed from the vents (Emerson et al., 2007).

Iron Mat

Iron mat composed of Zetaproteobacteria on a lava rock near the submarine Loihi volcano. (A. Malahoff, Hawaii, Loihi Volcano, July 1988)

How do Zetaproteobacteria relate to the cycling of iron? 

Zetaproteobacteria, with their role in eating iron and transforming it from its soluble Fe(II) state into its insoluble Fe(III) form may have an important role in the cycling of iron through the environment, functioning as an important source of iron removal.

Since their discovery, Zetaproteobacteria have also been observed in many other habitats, including coastal estuarine habitats with lower levels of iron, similar to that of Charleston, SC. (Laufer et al., 2017; Chiu et al., 2017). Our study will try to identify if these Zetaproteobacteria are present in the muddy soils around Charleston, as well as measure the levels of Fe(II) and Fe(III) in the rivers where these bacteria may be found.

 

This slideshow requires JavaScript.

Hopefully, through the study of the distribution of Zetaproteobacteria across the globe, including the chemical characteristics of the different environments that they inhabit, we may get a clearer picture of how iron cycles in aquatic environments and the role that these Zetaproteobacteria play.


I would like to thank my mentor, Dr. Heather Fullerton, for guiding me through this research. I would also like to thank the National Science Foundation for funding this research as well as the College of Charleston and Grice Marine Lab for their support.


References 

Chiu, B. K., Kato, S., McAllister, S. M., Field, E. K., & Chan, C. S. (2017). Novel pelagic iron-oxidizing Zetaproteobacteria from the Chesapeake Bay oxic-anoxic transition zone. Frontiers in Microbiology, 8(JUL), 1–16. https://doi.org/10.3389/fmicb.2017.01280

Emerson, D., Rentz, J. A., Lilburn, T. G., Davis, R. E., Aldrich, H., Chan, C. S., & Moyer, C. L. (2007). A novel lineage of proteobacteria involved in formation of marine Fe-oxidizing microbial mat communities. PLoS ONE, 2(8), e667. https://doi.org/10.1371/journal.pone.0000667

Hedrich, S., Schlömann, M., & Johnson, D. B. (2011). The iron-oxidizing proteobacteria. Microbiology,157(6), 1551–1564.

Laufer, K., Nordhoff, M., Halama, M., Martinez, R. ., Obst, M., Nowak, M., … Kappler, A. (2017). Microaerophilic Fe(II)-oxidizing Zetaproteobacteriaisolated from low-Fe marine coastal sediments – physiology and characterization of their twisted stalks. Applied and Environmental Microbiology, 83(February), AEM.03118-16. https://doi.org/10.1128/AEM.03118-16

Mori, J. F., Scott, J. J., Hager, K. W., Moyer, C. L., Küsel, K., & Emerson, D. (2017). Physiological and ecological implications of an iron- or hydrogen-oxidizing member of the Zetaproteobacteria, Ghiorsea bivora, gen. nov., sp. Nov. ISME Journal, 11(11), 2624–2636. https://doi.org/10.1038/ismej.2017.132

Invasive Species: Friend or Foe

Melanie Herrera,  University of Maryland – College Park

Invasive species…. Haunting, domineering, and downright evil. Or are they? Unlike the infamous Zebra Mussels, dominating the Great Lakes, or Fire Ants, constantly wreaking havoc, Gracilaria Vermiculophylla, are giving invasive species a good name. Don’t get me wrong, invasive species infuriate me just as much as the next guy; but Dr. Tony Harold and I are here to draw out the benefits of this invasive sea grass to baby fish.

Unlike the native, simpler sea grass previously occupying Charleston Harbor, Gracilaria is characterized by coarse branching structures that appeal to many species of fish as protective homes. We are particularly interested in fishes in the larval and juvenile stages (the young ones) that associate with these complex habitats. Having access to more protective sea grass, such as this invasive, in these vulnerable life stages can help determine how many of these little guys make it into adulthood. Similar macro-algae to Gracilaria, such as seaweeds, have been known to be preferable hideouts for larvae and juveniles, reducing the pressures of predation. Since Gracilaria is on the rise in our local estuary, the Charleston Harbor, it’s important to find out the role they play in keeping our fish alive and well.

Our project is designed to better understand the level of association of local fish such as Gobies, Atlantic Menhaden, Atlantic Silversides, and other estuary-occupying fishes, with Gracilaria. We will compare abundance and distribution of young fish in dense patches of Gracilaria to sparse patches. Maybe these young fishes prefer the familiarity that native sea grass and open water brings. Or maybe Gracilaria’s “new and improved” design is too advantageous to resist. After we figure this out, we can go on sustainably managing local fish critical to commercial and recreational use and condemning the rest of the invasive species.

Screen Shot 2017-06-19 at 4.48.43 PM.png

An example of a collection site characterized as a “dense” habitat of Graclaria vermiculophylla.  Photo Credit: Melanie Herrera

Screen Shot 2017-06-19 at 4.48.34 PM.png

An example of a collection site characterized as a “sparse” habitat of Gracilaria vermiculophylla. Photo Credit: Melanie Herrera

 

Thank you so much to my mentor Dr. Tony Harold and his lab for his advice and guidance. Thank you to Mary Ann McBrayer for helping me facilitate this project. This research is funded through the National Science Foundation and College of Charleston’s Grice Marine Lab.

 

Works Cited

Munari, N. Bocchi & M. Mistri (2015) Epifauna associated to the introduced Gracilaria vermiculophylla (Rhodophyta; Florideophyceae: Gracilariales) and comparison with the native Ulva rigida (Chlorophyta; Ulvophyceae: Ulvales) in an Adriatic lagoon, Italian Journal of Zoology, 82:3, 436-445, DOI: 10.1080/11250003.2015.1020349

 

Our complicated relationship with chemicals

Nina Sarmiento, Binghamton University

Chemicals found all around us that have been altered, mimicked, and synthesized to be added to our products, are behind the success of our modern society. They have made our plastics strong, our crops prosperous, and our medicines effective. But I have always wondered about the toxicity of these chemicals.  When you look at their biological activity, a chemical might possess the potential to do harm, like interfere with biological processes. The safety of a potentially harmful chemical is based on exposure and dose. It is important to know if we are touching it, eating it, or breathing it in, and for what period of time. The study of evaluating the harmful effects of substances on exposed organisms is what toxicology is all about. They have such an important job because their findings influence what we know is safe and unsafe, for us and organisms all around us.

I learned early on from pursuing biology that we are exposed to many things we are unaware of. Not only are we exposed to potentially harmful chemicals, but we facilitate exposure to other living organisms that may more sensitive. Take dogs for simple example. The toxic dose of something like chocolate for humans is very high, whereas leaving a small amount of chocolate out for a dog to eat could easily kill it.  Rachel Carson is someone I greatly admire, whose work on the pesticide DDT also exemplifies this reality. Food crops were the target for DDT, but birds were indirectly ingesting it, explaining the decline in the Bald Eagle population.  She is one of the people that sparked my interest in ecotoxicology, looking at the effects of harmful substances on ecology, not just humans.

unnamedThis is an example of some of the questions ecotoxicologists ask when there is a potentially harmful substance found in the environment. Photo credit: globe.setac.org.

Here is a chemical product you may not suspect as a threat, sunscreen. In sunscreens, UV filters protect you from getting burned, but also can act as endocrine disruptors, altering hormones and growth (1). Sunscreens are only meant for human skin, however they end up in our lakes, rivers and oceans through swimming or through waste water treatment effluent (2). Unintentionally, many more organisms become exposed.

Toxic-Sunscreen

Photo credit: thesleuthjournal.com

In my project I will be using sea urchins as a model organism to study the effects sunscreens might be having on coral reefs.  I am learning how to preform toxicity tests on sea urchin sperm and embryos which involve an exposure period with sunscreen formulations and then evaluation of effects. I hope to investigate if the chemicals from sunscreens in the water can have negative impacts on coral reproduction.  My work can potentially help create understanding of how humans are contributing to coral reef decline, and influence others to take action to protect them.

image

This is a picture of sunscreen water accomodated fractions (WAFs) I am making. They are a mix of sunscreen and seawater and I will be exposing the sea urchin embryos to each solution!

IMG_5703

This is me in the lab with a microscope I use to look at sea urchin sperm and embryos! Photo by Bob Podolsky

My research is funded by the National Science Foundation and College of Charleston partnered with National Oceanic and Atmospheric Administration

noaaCofClogoUnknown-4

Works cited:

1 Krause M.,, Klit A., Jensen M., Soeborg T., Fredrickson H., Schlumpf M., Litchensteiger W., Skakkebaek N E., Drzewieck K T. 2012. Sunscreens: are they beneficial for health? An overview of endocrine disrupting properties of UV-filters. International journal of andrology. 35 424-436.

2Kyungho C., Kim  S. 2014. Occurances, toxicities, and ecological risks of benzophenone-3, a common component of organic sunscreen products: a mini review. Environment International. 70 143-157.

Benthic Microalgae Research – A day at the beach

Jessica Lowry, Coker College

Featured image

I’m Jessie Lowry, a rising senior Biology major at Coker College, which is located in the tiny, homy town of Hartsville, SC. I am really excited to be here in my hometown this summer with opportunity to do research through the College of Charleston REU at Ft. Johnson. My research project this summer that I am working with Dr. Craig Plante on is investigating what factors influence the communities of benthic microalgae, or photosynthetic microorganisms in sediment.

Before we begin researching what species of diatoms make up the benthic microalgal communities, we need to do some preliminary sampling to measure things like pH, salinity, temperature, grain size, and moisture, at the three local beaches where I will be sampling at.

I’m not sure what I had envisioned for doing research this summer, but what I did not expect was for it to be like a day at the beach! Yesterday, Dr. Craig Plante and I went to Isle of Palms and Folly Beach, and today we are going to Kiawah.

My mentor, Dr. Craig Plante carrying research supplies out to the water at Folly Beach, SC.

We took several samples of seawater and sediment at each beach and we will do tests back at the lab. Unfortunately, I will not be spending every day researching at the beach. It was really great to get some sand, salt, and sun during a day of research.

Samples of seawater and sediment from Isle of Palms and Folly Beach that we collected to measure pH, salinity, grain size, and moisture.

Samples of seawater and sediment from Isle of Palms and Folly Beach that we collected to measure pH, salinity, grain size, and moisture.

Also, the temperature was in the 90s, the water was slightly warmer than the air, and the sand at one point at Folly Beach was a scorching 120° F! Dipping our feet in the water definitely felt great.

Funding

This research is funded by the National Science Foundation Reseach Experience for Undergraduates program at College of Charleston’s Grice Marine Lab.

Unknown-4Unknown-3

Shrimp kabob, shrimp gumbo…shrimp sickness?

 

Alessandra Jimenez, Whitworth University

DSCN0046

Are you a fan of shrimp? You’re not the only one – billions of people around the world depend on shrimp fisheries and aquaculture for this wonderful source of food. Other predators in the sea rely on shrimp for their daily meals. Here’s the catch: shrimp may not last long enough to make it to your plate. Like us and other animals, crustaceans in general have to deal with so many obstacles that threaten their survival. One obstacle that is not often thought about is bacterial infection. Did you know that seawater is literally teeming with hundreds of millions of bacteria? The only way a shrimp can make it is by using its immune response – the “quick, potent, and effective” way of defending against a huge, microscopic army! Sounds like the perfect shield, right?

shrimp food

Shrimp is a common food source for many people. @Leslie Fink

Turns out that, like everything else in the science world, immunity comes at a big cost. It has been recently discovered that the immune response in crabs and shrimp against bacteria actually has a bad side effect: metabolic depression. In fact, the way the shrimp gets rid of bacteria in its bloodstream is by moving the bacteria to the gills, where it gets lodged and stays there for quite some time. The consequence? The lodged bacteria block blood flow through the gills, and the shrimp can’t get enough oxygen from the water. (Want to learn more? Click here)

Ouch, talk about a double whammy – fighting sickness plus oxygen blockage. One basic question comes to mind: can the shrimp still do what it needs to do while under such metabolic stress? This is where I come in. This summer, I am working under Dr. Karen Burnett in Hollings Marine Laboratory as an intern through the Research Experience for Undergraduates (REU) program in marine biology. We will be testing whether or not a shrimp’s immune response to a common bacteria affects its ability to perform daily activities. The activity of interest is called ‘tail-flipping’ (fancy name: caridoid escape reaction. Want to learn more? Click here)This really fast, reflex-like action needs to be in top shape for the shrimp to survive from predator attacks and to help it during feeding time.

Caridoid_escape_reaction

Also known as the ‘tail-flip’ reaction, this response is a shrimp’s primary means of escape. @Uwe Kils

The shrimp species of interest is Farfantepenaeus aztecus, or ‘Atlantic brown shrimp’. This fella is a familiar catch for fishermen throughout the Southeastern US and the Gulf of Mexico. This is the first time that a study like this is going to be done on a wild shrimp species in general, let alone this specific type!

Penaeus aztecus

Farfantepenaeus aztecus, aka ‘Atlantic brown shrimp’. @Virginia Living Museum

So, can an immune response impact tail-flipping in wild shrimp? If ‘yes’, would the potentially handicapped shrimp be able to survive in its natural environment? We will soon find out!

Happy shrimping!

Alessandra Jimenez

REFERENCES:

Burnett, L. E., Holman, J. D., Jorgensen, D. D., Ikerd, J. L., & Burnett, K. G. (2006). Immune defense reduces respiratory fitness in Callinectes sapidus, the Atlantic blue crab. Biological Bulletin, 211(1), 50-57.

Fuhrman, J. A. (1999). Marine viruses and their biogeochemical and ecological effects. Nature, 399(6736), 541-548.

Latournerie, J.R., Gonzalez-Mora, I.D., Gomez-Aguirre, S.G., Estrada-Ortega, A.R., & Soto, L.A. (2011).                   Salinity, temperature, and seasonality effects on the metabolic rate of the brown shrimp Farfantepenaeus Aztecus (Ives, 1891) (Decapoda, Penaeidae) from the coastal Gulf of Mexico.Crustaceana 84(12-13), 1547-1560. doi: 10.1163/156854011X605738

Scholnick, D. A., Burnett, K. G., & Burnett, L. E. (2006). Impact of exposure to bacteria on metabolism in the penaeid shrimp Litopenaeus vannamei. Biological Bulletin, 211(1), 44-49.

Many thanks to College of Charleston for hosting my project, Dr. Karen Burnett and Hollings Marine Laboratory for guidance and work space, and NSF for funding the REU program.

HMLnsf-logoCofClogo