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.

 

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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.

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

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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

 

Stressing Out My Algae

Emily Spiegel, Bryn Mawr College

Emily Carboy 170612

One intern’s perspective on lab work, South Carolina, and the coolest organisms in and out of water: phytoplankton.

 

The lab itself is large, packed to bursting with equipment, boxes, cabinets, monitors, and glassware. An antechamber acts as a sterile room for the most delicate of procedures, demanding precision and care. Many things reside in this room, but never quiet. The constant whirling of a machine’s fan, the hum of a freezer housing samples from a time beyond easy recollection, the typing of a research assistant hunched over innumerable data sheets…all these and more cut through the quiet throughout all hours of the day and night.

 

And at the heart of it all is the algae.

 

Small, marine microorganisms constituting a larger class known as phytoplankton, algae are the unsung heros of the environmental world. Energy, or the basic ability to do work, is the key to survival, growth, and reproduction. Without it you (and your genes) aren’t going anywhere. Algae harness the energy readily available from sunlight and convert it into a useable currency in a process known as primary production. This energy is then distributed to the many higher animals that eat them. They are the foundation of the marine food web and of the world’s energy supply, contributing to 45% of the planet’s primary production (Brierley 2017). In short, algae are cool.

So cool in fact, I’ve decided to spend my entire summer studying them. More specifically, I’ll be studying patterns of their reproduction and growth. A grad student running an experiment in this lab last year got unexpected results when she raised algae in 24 hours of continuous light instead of the normal 12 hours of light:12 hours of darkness she had followed previously.  Despite a limitation in the nitrogen added to these samples, which typically inhibits growth, the populations grown in 24 hours of light were able to grow successfully. So researchers went looking for answers.

One potential explanation is that the continuous light conditions caused the induction of sexual reproduction in the algae samples. Algae, like the rest of us, don’t like to be stressed. And being constantly exposed to light, which they automatically begin to utilize for primary production, is very stressful. It’s kind of like giving a kid a bunch of candy bars. A little is nice, a lot induces a sugar high and headaches for anyone within a 20m radius. The algae have too much energy and so they start to adjust their behavior to accommodate for the stressful conditions. One accommodation is sex. That’s right, stress out your algae and they might just turn on the Marvin Gaye and set the mood. Normally the species I’m studying (Fragilariopsis cylindrus, or just Frag for anyone without a PhD) reproduces asexually allowing high growth rates within the population. My lab is also curious as to whether low light conditions (a cycle of 6 hours of light and 18 hours of darkness) might be equally stressful to the algae and cause a similar response.

This is where I come in. This summer I’ll be exposing algae to conditions of varying light and nutrient stress in order to determine if stress actually does cause them to start reproducing sexually. Along the way, we’ll keep track of growth rates by measuring biomass, or the amount of live material within a sample. This can be measured by a variety of cool devices which tell me the number of cells in a particular volume of sample and the amount of chlorophyll being utilized in that sample. Chlorophyll is a component of the cycle of photosynthesis and is therefore a measure of the primary producers (i.e. the algae) in the sample. Eventually I’ll also run genetic analyses, tracking the utilization of genes involved in sexual reproduction as a way to determine if the algae are reproducing sexually instead of asexually.

All in all, it’s bound to be an interesting summer. Full of days at the beach, early mornings with a culture counter, and lots and lots of algae.

 

I’d like to acknowledge the entire DiTullio/Lee lab at the National Oceanographic and Atmospheric Administration as well as the National Science Foundation’s Research Experiences for Undergraduates program organized by the College of Charleston Grice Marine Laboratory. This project would not be possible without the support and guidance from these institutions and individuals. 

 

Works Cited

Brierley, Andrew. “Plankton.” Current Biology Magazine 27 (2017): 478-83.