The BMA of Today

Christine Hart, Clemson University

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In previous blog posts I described the sand-dwelling microalgae, also known as benthic microalgae (BMA), which are essential to estuary ecosystems. Not only do they produce the air we breathe and food we eat, they also inform us about the subtle changes that are occurring in our environment. Changes that otherwise may go unnoticed.

How do BMA show these environmental changes? By forming the foundation of estuarine energy, they provide a snapshot of how the estuary is functioning as a whole. If changes occur in BMA patterns, this may indicate changes in the overall ecosystem. BMA are also easily characterized and compared using modern molecular approaches. These qualities make BMA living indicators, or bioindicators, that are important in monitoring future ecosystem health.

BMA become visible in the upper layers of sediment at low tide. Later, they decrease in density—or biomass—as the tide rises. Our project studied the mechanism for the increase of biomass during low tide. Previous studies suggested that the mechanism for biomass increase is vertical migration of BMA from lower layers to upper layers of sediment. We also tested whether BMA growth due to high light exposure contributes to the biomass increase.

Our results indicated that both vertical migration and growth due to sunlight exposure were important to the increase in biomass. This is the first contribution to literature that recognizes a multifaceted approach to BMA biomass changes.

Additionally, we studied in how the biomass increase was connected to patterns in the type of BMA in Charleston Harbor. Previous studies suggested that increasing biomass was connected to changes in the abundance of BMA species; therefore, we expected to see the amount of certain BMA species change based on their exposure to migration and sunlight.

We were surprised by our findings. In this study, we found that BMA did not vary over short time periods (by tidal stage or by exposure to migration and sunlight). Instead, we found that BMA varied spatially and over a period of 6 years. In fact, only one of the dominant species of BMA remained the same from 2011 to 2017 (Figure 1).  The long-term change in community coincides with geological changes in the sampling site (Figure 2).

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Figure 1. The relative abundance of each dominant BMA species from 2011 to 2017 is shown immediately after sediment exposure (T0) and 3 hours later (TF). Only one species—Halamphora coffeaeformis—remains dominant in 2017. This is evidence of a dramatic change in the dominant type of BMA in Grice Cove.

These are positive results for the use of BMA as bioindicators. If types of BMA are invariable over short periods of time, measurements of BMA will be more precise. Bioindicators must be capable of showing changes that are occurring on a larger environmental scale; therefore, it would be a good sign if the change in BMA community reflects the changing geological environment (Figure 2). Still, more studies on the temporal and spatial patterns of BMA communities should be conducted before BMA can be used as bioindicators.

Changes in Grice Cove

Figure 2. Aerial view of Grice Cove sampling site over time. The approximate location of the sampling site is shown by the white line. Sampling sandbar has changed over time, possibly contributing to community changes. Source: “Grice Cove” 32 degrees 44’58”N 79 degrees 53’45”W. Google Earth. January 2012 to March 2014. June 20, 2017.

This study contributed new information to the studies of BMA biomass during low tide, and showed that the BMA of today in Grice Cove are significantly different than in previous years.

 

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 College of Charleston’s Grice Marine Laboratory.

 

Literature Cited:

Holt, E. A. & Miller, S. W. (2010) Bioindicators: Using Organisms to Measure Environmental Impacts. Nature Education Knowledge 3(10):8.

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.

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.

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Living Life as a Sea Urchin Momma

Hailey Conrad, Rutgers University

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Me working hard to make my sea urchin babies

For my project I am using the same technique that the father of genetics, Gregor Mendel, used to establish his Laws of Heredity: cross breeding. So, I have to breed and raise a whole lot of sea urchins. For a refresher, I’m trying to determine if there is heritable genetic variation in how sea urchin (specifically an Arbacia punctulata population from Woods Hole, Massachusetts) larvae respond to ocean acidification. To do this, I’m rearing sea urchin larvae in low and high carbon dioxide conditions and measuring their skeletal growth. I’m breeding 3 sea urchin males with 3 sea urchin females at a time, for a total of 9 crosses. To tease apart the impact of genetic variation on just the larvae themselves, I will be fertilizing the sea urchin eggs in water aerated with either current atmospheric levels of carbon dioxide, about 410 parts per million, or 2.5 times current atmospheric carbon dioxide levels, about 1,023 parts per million. Then, I will be rearing the larvae in water aerated with either 409 ppm CO2 or 1,023 ppm CO2. This will give me four different treatments for each cross, giving me 36 samples in total. By fertilizing and rearing them in the same and different levels of carbon dioxide I will be able to see how much of an impact being fertilized in water with a higher carbon dioxide concentration has on larval growth versus just the larval growth itself. It’s important for me to make that distinction because I just want to identify genetic variation in larval skeletal growth, and separate out any extraneous “noise” clouding out the data. I’m rearing the larvae in a larval rearing apparatus. Each of the 36 samples will be placed in jar with water aerated with the correct CO2 treatment. Each jar will constantly have atmosphere with the correct CO2 concentration bubbled in. Each has a paddle in it that is hooked to a suspended frame that is swayed by a motor. This keeps the larvae suspended in the water column. The jars are chilled to 14 C by a water bath.

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My larval rearing apparatus

After a 6-day period the larvae are removed from the jars and their skeletal growth is measured. They are preserved with 23% methanol and seawater and frozen.

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An Arbacia punctulata pluteus

You’re probably curious how the heck I am able to measure the larva’s skeletons. They’re microscopic! Well, I use a microscope coupled to a rotary encoder with a digitizing pad and a camera lucida. Which, looks like this:

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A microscope coupled to a rotary encoder with a digitizing pad and a camera lucid hooked up to a computer

This complicated-sounding hodge-podge of different devices enables me to do something incredible. I can look through the microscope at the larva, and also see the digitizing pad next to the microscope, where I hold a stylus in my hand. When I tap the pad with the stylus and the coordinates of various points on the anatomy of the plutei that I am tapping at get instantly recorded on my computer! The rotary encoder is the piece attached to the left side of the microscope and it enables me to record coordinates in three dimensions. Then, I can use those coordinates to calculate the overall size of the skeleton. My favorite part of doing science is learning how scientists are able to do the seemingly impossible- like measuring something microscopic.

After I gather all of my data, I will do some statistical analysis to see the affect that the male parents have on the skeletal growth of their offspring. I will not be focusing on the impact that females have on the skeletal growth of their offspring. The quality of the egg itself could be an influencing factor on the size of the offspring, whereas sperm is purely genetic material. Like how I’m trying to isolate the influence of ocean acidification during larval rearing from during the act of fertilization, I am trying to isolate just genetic influences on larval skeletal growth from egg quality. Check back to see how it goes!

Special thanks to the National Science Foundation for funding this REU program, the College of Charleston and Grice Marine Laboratory for hosting me, and Dr. Bob Podolsky for mentoring me!

 

 

 

Searching in the Sand

Christine Hart, Clemson University

Interim report picture

In “Exploring the Secret Garden” I discussed our studies of the benthic microalgae (BMA) that inhabit the intertidal regions of beaches. The goal of our study is to identify the mechanisms involved in the visually noticeable increase of BMA during low tide. This mechanism will be linked to changes in the type of BMA dominating the sand flat. To accomplish these goals our study will incorporate field work, molecular techniques, and DNA analysis.

During field work we will collect and manipulate sediment to distinguish between an increase in BMA by either vertical migration or growth mechanisms. The sediment will be collected on a sand flat in Grice Cove (Figure 1). Sand will be sampled using corers, which pick up a layer of sand without disturbing the vertical organization. The collected sand will be split between measurements of biomass, or BMA density, and DNA analysis. Biomass is measured by finding the concentration of chlorophyll a in the sediment. BMA synthesize chlorophyll a; therefore, the concentration of chlorophyll a is proportional to the density of BMA.

Sampling Site.png

Figure 1. Aerial view of Grice Cove sampling site with the approximate location of the 50 m sand flat transect site. Sampling sand flat is open to the Charleston Harbor. Source: “Grice Cove” 3244’58”N 7953’45”W. Google Earth. March 20, 2017. June 20, 2017.

The methods for field work are represented in Figure 2. There are two vertical migration treatments: filter and mesh. Filter treatments prevent vertical migration between cored and surrounding sediment. Mesh treatments permit vertical migration. If migration is important to the biomass increase, biomass measurements in mesh will be greater than in filter treatments. Filter and mesh treatments will also be exposed to shade and light conditions to interpret the impact of growth on biomass. Sunlight provides the energy necessary for BMA growth. Without sunlight growth will be limited. If growth is the mechanism of biomass increase, the shaded samples will have a lower biomass than the light exposed samples.

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Figure 2. Field work methods visualization. Locations of replicates along the 50 m transect are chosen using a random number generator and marked with flags. Random coordinates and a quadrat of 50 cm by 50 cm are used to determine where sediment will be sampled and treatments will be placed. Three controls (T0, TM, and TF) are taken at time intervals 1.5 hours apart after sand exposure. During TM and TF time points, samples are taken from the 4 treatments shown above: filter, mesh, filter + shade, and mesh + shade. Filter treatments prevent vertical migration, while mesh treatments permit vertical migration. Shaded and non-shaded filter and mesh treatments will be important in determining the role of sun exposure in biomass increase.

To link the mechanism of biomass increase to the BMA composition, we will use molecular techniques and analyze the DNA found in the sediment. DNA will be extracted from the sediment and amplified using a polymerase chain reaction (PCR). The DNA will be sequenced using High Throughput Ion Torrent technology. The results from sequencing will identify the BMA present at each time point and within each treatment. This information will link the mechanism of biomass increase to the changes in BMA composition. Our understanding of BMA dynamics will establish a basis for the BMA ecology in the Charleston Harbor. In the future, BMA dynamics could be compared to our study to assess changes caused by human influences in Charleston estuaries.

 

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 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.

Playing with Plutei

Hailey Conrad, Rutgers University

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Me! Photo Credit: Kady Palmer

Ocean acidification is known as climate change’s evil twin. When the pH of ocean water drops, carbonate ions in the water form carbonic acid instead of calcium carbonate. Calcium carbonate is the form of calcium that marine animals that have calcium-based skeletons (like us!) and shells use to build their bones and shells. Having smaller and weaker skeletons or shells impacts their ability to survive. However, some individuals within certain species or populations of species have genes that make them more resistant to ocean acidification. If these individuals are able to pass on these genes to their offspring, then the species has the ability to evolve in response to ocean acidification instead of going extinct. This summer I’m working with Dr. Bob Podolsky in College of Charleston’s Grice Marine Field Station to study the extent to which ocean acidification affects Atlantic purple sea urchins, Arbacia punctulata. We are specifically trying to see if any individuals within a population from Woods Hole, Massachusetts, have any heritable genetic resistance to the negative impacts of ocean acidification. We hypothesize that there will be genetic resistance given that the northern Atlantic coast naturally has lower levels of saturated calcium carbonate, so a population that has evolved to live in that type of environment should have some resistance to lower calcium carbonate levels already (Wang et al 2013). We’re using a basic cross breeding technique to rear Arbacia punctulata larvae to their plutei stage, when they have four main body rods. At this stage they look less like sea urchins than they do like Sputnik!

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A sea urchin pluteus larvae with four body rods

Then, we will look to see if any of the male parents consistently produce male offspring that are more resistant to ocean acidification.  If males like these exist within this population, then the species has the capacity to evolve in response to ocean acidification, instead of going extinct! This is a very big deal, and could potentially be very hopeful. Even if we don’t get the results that we are hoping for, the results of this research could inform policy and management decisions.

Literature Cited:

Wang, Z. A., Wanninkhof, R., Cai, W., Byrne, R. H., Hu, X., Peng, T., & Huang, W. (2013). The marine inorganic carbon system along the Gulf of Mexico and Atlantic coasts of the United States: Insights from a transregional coastal carbon study. Limnology and Oceanography, 58(1), 325-342. doi:10.4319/lo.2013.58.1.0325

Thank you to the National Science Foundation and College of Charleston’s Grice Marine Laboratory for funding my project. And, special thanks to Dr. Bob Podolsky for being a wonderful and supportive mentor!

 

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.