Exploring the “Secret Garden”

Christine Hart, Clemson University

Interim report picture

On a walk along the beach, have you ever noticed the garden growing at the water’s edge? During low tide patches of green and gold speckle the sand, growing what researchers have called a “Secret Garden.”

The “Secret Garden” is made up of a variety of microorganisms like cyanobacteria, flagellates, and diatoms. These small, sand-dwelling organisms are collectively known as benthic microalgae (BMA). BMA are responsible for 50% of primary production in estuary systems through photosynthesis and an extracellular polymeric secretion. Though small, these photosynthetic powerhouses form the basis of ocean food webs. BMA are also important indicators of ecosystem health. Scientists have documented the response of BMA to a variety of environmental conditions. As humans change natural estuary conditions, BMA will serve as a bioindicator for changes in ecosystem health.

The visible patches of green and gold at low tide indicate an increasing density—or biomass—of BMA. Currently, researchers do not know the mechanism for the visible change in BMA biomass. Our study will focus on two possible mechanisms of biomass change. One mechanism may be the vertical migration of BMA to the top of the sand.  The increase in biomass could also result from growth among BMA species due to sunlight exposure.

In addition to the unknown mechanism, the particular BMA species associated with the green and gold sheen have not been well studied. Like plants in a garden, BMA species are diverse and serve their own roles in maintaining a healthy environment. To better use BMA as a bioindicator, we will characterize the type of BMA contributing to the visible biomass changes.

Our study will focus on the mechanism of changes in biomass during low tide, while also identifying changes in the presence of BMA species. The results from the study will give us a greater understanding of the BMA that are essential to estuary systems. This information will establish a basis of BMA dynamics that can be used as an indicator of the health of estuaries.

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Thank you to my mentor, Dr. Craig Plante, and my co-advisor, Kristina Hill-Spanik, for their support and guidance.  This project is funded through the National Science Foundation, and supported by The College of Charleston’s Grice Marine Laboratory.


Literature Cited

Lobo, E. A., Heinrich, C. G., Schuch, M., Wetzel, C. E., & Ector, L. (n.d.). Diatoms as Bioindicators in Rivers. In River Algae (pp. 245-271). Springer International Publishing. doi:10.1007/978-3-319-31984-.

MacIntyre, H.L., R.J. Geider, and D.C. Miller. 1996. Microphytobenthos: the ecological role of
 the “Secret Garden” of unvegetated, shallow-water marine habitats. I. Distribution, abundance and primary production. Estuaries 19: 186-201.

Plante, C.J., E. Frank, and P. Roth. 2011. Interacting effects of deposit feeding and tidal resuspension on benthic microalgal community structure and spatial patterns. Marine Ecology Progress Series 440: 53-65.

Rivera-Garcia, L.G., Hill-Spanik, K.M., Berthrong, S.T., and Plante, C. J. Tidal Stage Changes in Structure and Diversity of Intertidal Benthic Diatom Assemblages: A Case Study from Two Contrasting Charleston Harbor Flats. Estuaries and Coasts. In Review.

Underwood, G.J.C., and J. Kromkamp. 1999. Primary production by phytoplankton and 
microphytobenthos in estuaries. Advances in Ecological Research 29: 93-153.


What’s living in the sand?

Jessie Lowry, Coker College


Visible microalgae seen on the surface of wet sand at Folly Beach.

Next time you go to the beach this summer, I want you to think about the sand that you are walking on. Did you know that there are tons of microscopic photosynthetic organisms, aka microalgae, that live on the surface of sand? Before this summer, I didn’t know about these organisms either. Here is a picture of visible microalgae on the surface of the sand. Look for this next time you’re at the beach!

Microalgae communities in sand are made up of single-celled eukaryotic algae and cyanobacteria living in the top several millimeters of the sand (Miller et al., 1996). These organisms play important roles in ecosystem productivity and food chain dynamics, as well as in sediment properties, such as erodibility (Miller et al., 1996).


Dr. Craig Plante and Jessie Lowry collect samples of sediment from Folly Beach. Photo credit: Kristy Hill-Spanik.

I am studying these microalgal communities and what factors influence community structure. For example, does pH, salinity, nutrients, or grain size shape microalgal community structure? Or does geographic distance shape communities? To answer these questions, I am collecting samples from Kiawah Island, Folly Beach, Isle of Palms, and Pawley’s Island, SC. We are measuring environmental variables at each location, and using molecular tools to study microalgal community structure.

I am extracting the DNA from samples collected, amplifying specific regions from these samples using polymerase chain reaction (PCR), and then we will be getting these regions sequenced using Ion Torrent technology. We will then use QIIME to determine how similar these benthic microalgal communities are.


Jessie Lowry preparing samples for PCR, or polymerase chain reaction, which is used to make millions of copies of a piece of DNA.

Diatoms, a group of microalgae, have been proposed as bioindicators of environmental health (Desrosiers et al., 2013). Bioindicators are really cool because instead of telling a snapshot of an environmental condition, such as pH, temperature, or amount of oxygen in an environment, biological indicators reflect those changes and can give an idea of how the ecosystem is being affected. This research will further our knowledge of what factors shape benthic microalgal communities, and give a better understanding of these organisms as a potential bioindicator. In addition, this research will add to knowledge about the distribution of microorganisms, which is also not fully understood.

Learn more:




Desrosiers, C., Leflaive, J., Eulin, A., Ten-Hage, L. (2013). Bioindicators in marine waters: benthic diatoms as a tool to assess water quality from eutrophic to oligotrophic coastal ecosystems. Ecological Indicators, 32, 25-34.

Miller, D.C., Geider, R.J., MacIntyre, H.L. Microphytobethos: The ecological role of the “Secret Garden” of unvegetated, shallow-water marine habitats. Estuaries, 19(2A): 186-212.


Thank you so much to my mentors Dr. Craig Plante, and Kristy Hill-Spanik. This research is funded through the National Science Foundation and College of Charleston’s Grice Marine Lab.


Making Renewable Energy An Even Cheaper Alternative!

Yoel Cortes-Pena, Georgia Institute of Technology


Fig 1. Picture of me

I’m Yoel Cortes-Pena, a chemical engineering senior student at Georgia Tech and future scientist and entrepreneur.  My research interests lie in renewable energy and environmental sustainability. Additionally, although I am an engineering student during the day, I am also part of Hip-Hop culture at night. My hobbies include dancing, beatboxing and rapping. Here is a link to my channel. 

Through this blog, I want to share with you my research experience as part of the Fort Johnson Undergraduate Summer Research Program. When I received the acceptance letter, I was surprised and happy that I would be working with Dr. Harold May in Microbial Electrosynthesis. This new technology uses microbes to fix carbon dioxide and electrons from an electrode to produce fuels and highly valued chemicals such as hydrogen, methane and acetate.


Fig 2.Picture of Microbial Electrosynthesis Reactor. The graphite rod on the left is the cathode (electron donor) and the rod on the right is the anode (electron acceptor). The left side of the reactor is being sparged with CO2. The microbes, located on the left side of the reactor, are fixing the CO2 and producing hydrogen (visible bubbles) and acetate (dissolved in solution).

One of the many applications of microbial electrosynthesis includes the storage of energy without contributing to carbon emissions. Solar, wind and other renewable energy forms output a variable amount of energy that tends to exceed public demand, especially during off-peak hours. Consequently, this surplus electricity becomes stranded energy that cannot be used. Microbial Electrosynthesis can utilize this excess or stranded energy and store it in fuel, valorizing the use of renewable energy technology.


Dr. Harold May’s Enviromental Microbiology lab is affiliated to the Medical University of South Carolina (MUSC).This project is possible thanks to funding from the NSF College of Charleston Summer REU program and the Grice Marine Laboratory. Lab space and facilities are provided by the Hollings Marine Laboratory.