Exploring the “Secret Garden”

Christine Hart, Clemson University

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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

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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).

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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.

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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:

http://web.vims.edu/bio/shallowwater/benthic_community/benthic_microalgae.html

http://www.aims.gov.au/docs/research/water-quality/runoff/bioindicators.html

References

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.

Acknowledgements

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.

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Benthic Microalgae Research – A day at the beach

Jessica Lowry, Coker College

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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.

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