One Fish, Two Fish…

Ana Silverio, The University of Texas at Austin

The Approach: In my previous post, I explained how important small fishes are to the food web and how their new found interaction with Gracilaria vermiculophylla came about. Now, measuring something such as diversity and abundance may sound confusing but it’s as simple as one, two, three!

Abundance is the number of individuals per species in an ecosystem and relative abundance is the overall evenness of those individuals. Diversity is more of a measurement of variation or how many different species are counted in a designated area/habitat.

Fine mesh seine net being dragged over the 15-meter transect to capture our fish.
Photo Credit: Norma Salcedo

Now that we understand what we are measuring… what’s next? As mentioned before, the Charleston harbor has been introduced with an invasive species of seaweed, but it has served as a home for the juvenile fish. To measure diversity and abundance we have to take samples from two different sites affected by this invasive species. Luckily, it’s a short stroll over to Grice Beach behind our marine lab to find a section of Gracilaria with 20% coverage for our sparse site and one with 80% coverage for our dense site. After establishing our sample sites, we take a 15-meter transect which we will pull our fine-mesh seine net through at about knee-deep water. We quickly but gently pull the net up to the beach and start sorting through our samples placing the fish in a half-gallon jar while discarding any invertebrates. We repeat this at our second site and voilà we have our samples!

Initial sorting process for our samples
Photo Credit: Norma Salcedo

Are we done yet? Of course not! Once we collect both of our samples from the different patches of Gracilaria, we take them back to the lab to set in preservatives for about a week and begin the sorting process. While we sort each jar, we try to identify each fish down to the lowest classification if possible (in a perfect world we would have all of our critters down to species). After identification is complete, we start our measurements of diversity and abundance by counting our fish. When we are finished counting, we organize our data and use statistical analyses to see if there is a significant difference in diversity and abundance in our two sample sites. We have followed procedures from the past two summers and each time we have sampled this summer to make sure we can compare our data at the end.

And now for the big reveal… Drumroll please! Will we find a difference in diversity? In abundance? In neither or both? Will we finally win a battle against the dreadful pluff mud? Although the last part seems unfortunately unlikely, join me next time to finally find out what secrets Gracilaria has tangled up in the Charleston Harbor!


Special thanks to my mentor, Dr. Harold for his support and guidance throughout this project. Also, to Dr. Podolsky and Grice Marine Lab for giving me the opportunity to conduct this research. This project is supported by the Fort Johnson REU program, NSF DBI-1757899.

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Gracilaria: New Intruder Weeding Through Charleston

Ana Silverio, The University of Texas at Austin

The Problem: Invasive species are animals that enter a new habitat away from their own home and are known for usually bringing about negative effects on natives in the area. Invasive species thrive in new environments when they can adapt to local conditions, and cause troubles in the way it works. With their usual predators not around, chaos can erupt, as they take away from some resources from the animals who call this habitat home (Albins et al 2015). Gracilaria vermiculophylla is a type of seaweed but also an invasive species from Asia and first seen on the Virginia coast. Although it is an invasive species, this seaweed seems to be singing a different song than usual (Nyberg et al 2009). Since it was first seen on the beaches of North America, it has taken a different role by providing a new habitat to local fishes. Gracilaria vermiculophylla is a dark brownish red seaweed with tangled strands that brush up against anything wading through the shallow water. Perfect for smaller fish to hide in. Although this seaweed seems to be bringing good things to the fishes not much is understood about what life was like for them under the waters of Charleston before our new stranger came about so we can’t comment on that part of the story. On the other hand, an interaction is indeed unfolding before our eyes and the story behind our new visitor is a bit fishier than one may think.

Example of a sample site: sparse patch of Gracilaria vermiculophylla on Grice Beach.
Photo taken by: Norma Salcedo

Gracilaria vermiculophylla is hard to miss on the shorelines of Charleston, it can be found in patches when the tide dwindles or on the seafloor. Its branches provide an ideal habitat along with a hiding space for juvenile fish during their vital first years of life and increases their numbers (Munari et al 2015). The preservation of these fishes during their early life stages is important to maintaining a healthy food web that keeps marine life afloat. Food is energy and energy is moved up to some of the biggest fisheries in this country from the very bottom of the smallest animals. It is important to know how the bigger fish’s food source is interacting with its habitat to make sure it’s healthy. Understanding how the interaction is working is a key factor in creating conservation plans and maintaining the ecosystem in good health.

Dense patch of Gracilaria vermiculophylla.
Photo taken by: Norma Salcedo

This summer, my research focus is on untangling Gracilaria vermiculophylla’s ecological relationships with these small fishes for a better understanding how diverse life is underwater. Replicating a design from the past two summers, I am curious to see the differences in diversity and abundances based on different patches of seaweed and if body size plays a significant role. Will more seaweed correlate with more diversity? The past two summers revealed some common patterns between fish diversity and patterns of seaweed patches but also some surprising differences between the two field seasons. Will we have a tie breaker this summer? Stay tuned to find out!


Special thanks to my mentor, Dr. Harold for his support and guidance throughout this project. Also, to Dr. Podolsky and Grice Marine Lab for giving me the opportunity to conduct this research. This project is supported by the Fort Johnson REU program, NSF DBI-1757899.


References

 Albins MA (2015) Invasive Pacific lionfish Pterois volitans reduce abundance and species richness of native Bahamian coral-reef fishes. Mar Ecol Prog Ser 522:231-243. 

Munari, C., N. Bocchi, and M. Mistri. “Epifauna associated to the introducedGracilaria vermiculophylla (Rhodophyta; Florideophyceae: Gracilariales) and comparison with the nativeUlva rigida(Chlorophyta; Ulvophyceae: Ulvales) in an Adriatic lagoon.” Italian Journal of Zoology 82.3 (2015): 436-445.

Nyberg, C. D., M. S. Thomsen, and I. Wallentinus. “Flora and fauna associated with the introduced red algaGracilaria vermiculophylla.” European Journal of Phycology 44.3 (2009): 395-403.

The BMA of Today

Christine Hart, Clemson University

2017-06-22 10.29.36

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).

QualitativeLvM-MS

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.

One Fish, Two Fish, Red Fish, Killifish

Melanie Herrera, U. of Maryland, College Park

After 9 sampling days, 18 collections, and over 3000 fish, we’ve discovered fishes’ habitat preferences are much more complex than we thought. To recap, our hypothesis predicted fish would prefer dense sites of the invasive seaweed, Gracilaria vermiculophylla, over sites with more open water (thus, less Gracilaria).  We also predicted that dense site would have greater diversity by attracting various types of fish due to its branches that conceal fish from predators.

Our belief that Gracilaria would fulfill the refuge effect, attracting more fish and more diverse species, was supported through the copious amounts of fish found in Gracilaria. Despite more abundance in the dense sites of Gracilaria, more diversity was shown in sparse sites (Figure 1). Among both the dense and sparse sites Atlantic Silversides and Bay Anchovies, Pipefish, and Striped Killifish were the most abundant and common species. While similar species occurred in both habitats, the sparse site had more occurrences of species that were considered rare in dense sites. For example, sparse sites had more occurrences of Spade fish and Florida Pompanos than dense sites. Additionally, sparse sites had species of fish such as leatherjackets and lizardfish that never occurred in dense sites.

Screen Shot 2017-08-07 at 6.29.24 PM

Figure 1: Rank abundance patterns of fish in dense sites (represented by triangles) and sparse sites (represented by circles) of G. vermiculophylla at Grice Cove. The number of fishes were calculated as a logarithm as a measure of relative abundance of fish at each site. Species are ranked from most abundant (1) to least abundant (8-10). Slopes show differences in species evenness amongst sites. Steeper slopes exhibit less species evenness.

 

Supporting our hypothesis, dense sites did demonstrate more abundance. In total, 2944 fish were collected from the dense sites while 361 fish were caught in the sparse sites. It is predicted that smaller-bodied fish used Gracilaria more as a refuge because of their increased vulnerability to threats as small animals. Lack of abundance in sparse sites could be explained by increased exposure to predators and environmental threats.

Increased use of the dense sites shows Gracilaria does contribute towards housing all types of fish, most importantly economically important fishes. According to the National Marine Fisheries Service’s report on fisheries economic in 2011, the seafood industry alone brings in a minimum of $88 million dollars annually. In order to support this important industry, commercial fisheries can use our research to establish sustainable fisheries by understanding the various habitats that help rear economically important fishes. Our identification of the invasive seaweed’s role on housing fish can be used as a protective measure for these fish in future sustainable management.

 

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Figure 2: Two of the top three most abundant species collected from dense sites of Gracilaria. (Left: Striped Kilifish; Right: Atlantic Silversides).

 

Thank you so much to my mentors Dr. Tony Harold and Mary Ann McBrayer for their advice and guidance. This research is funded through the National Science Foundation and College of Charleston’s Grice Marine Lab.

 

Catch of the Day(s)

Melanie Herrera, University of Maryland College Park

South Carolina is known for its iconic southern cuisine, including a staple of fresh seafood which fuels the buckets of shrimp & grits and “catch of the day”. In order to support this huge industry (and fill the bellies of every South Carolinian), I am conducting an experiment to figure out where this seafood is holing up prior to its demise. Dr. Harold, his graduate student, Mary Ann McBrayer, and I are out on Grice Beach collecting fishes, crabs, shrimps, and much more in order to figure what exactly is there… And what they are using to survive.

Using a seine net, we encircle marine animals in dense and sparse patches of an invasive sea grass, Gracilaria, for collection. We hypothesize that Gracilaria is helping the local economy (a surprising contribution from an invasive species) by creating refuge for young animals. On the beach, we submerge separate samples of animals (from dense versus sparse areas of Gracilaria) into a euthanizing solution to bring them up to the lab for preservation and analysis (Figure 1).

Dense v Sparse.png

Figure 1: An example of animals caught in separate habitats at Grice Cove. The left exhibits animals caught in a dense area of Gracilaria and the right exhibits animals caught from a sparse area of Gracialaria. Credit: Melanie Herrera

In the lab, separate samples (dense versus sparse) undergo a few transfers into different fixatives (10% seawater formalin, 25% isopropyl, and 50% isopropyl consecutively) to keep the fish from decaying. After this preserving process, fish and other animals are separated and categorized by family, genus, and species. This categorization enables us to identify and analyze what types of animals and how many of each are using different habitat. Our analysis will give us insight on what type of habitat, either patches dominated by Gracilaria or areas with more open water, benefits fish. Specifically, we will be able to identify if Gracilaria is more advantageous to young fish or if their survivorship is independent from their habitat.

So far, we have collected lots of pipefish, narrow skinny fish that resemble a hair strand-size snake, Atlantic Silversides, a fish that looks exactly like it sounds, and more shrimp than anyone needs (Figure 2). Although some of these animals do not directly contribute to the seafood industry, its presence in the Charleston Harbor can tell us a lot of things. For example, we have seen some fishes that usually stay in warmer waters in the Southern U.S. Their expanding habitat can lead us to some more hypotheses on climate change and warm weather moving northward. In addition, we can find out if Gracilaria has a stake in rearing economically important fish in the future.

Pipefish, Silversides, Grass Shrimp.png

Figure 2: (From left to right) Pipefish, Atlantic Silversides, and Grass Shrimp caught for analysis.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.

 

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.

 

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.