Invisible Neighbors: How Gracilaria Changes Bacterial Communities

Lilia Garcia, Illinois Wesleyan University

The Problem: It only takes a walk along the mudflats to notice large patches of wiry, red seaweed. The seaweed is called Gracilaria vermiculophylla, an invasive organisms that is native to East Asia (SERC, 2019)  The seaweed is hard to miss, but its effects on the ecosystem are not easily seen. This summer I will be studying how Gracilaria affects a bacterial community invisible to the naked eye.

Mudflat with Gracilaria, taken by L. Garcia

According to previous studies, Gracilaria is found to increase the amount of a bacteria called Vibrio (Gonzalez, et al., 2014). This may not mean much at first, since most of us don’t think about microscopic interactions. Bacteria, however, are important in maintaining the health of complex environments like estuaries. They cycle and break down nutrients and organic matter, influencing oxygen, carbon, and nitrogen levels. An increase in one group of bacteria, such as Vibrio, can change these patterns. And like most of us know, bacteria tends to spread easily. There are a few strains, or types, of Vibrio, such as V. vulnificus, V. parahaemolyticus, and V. cholera, that are dangerous to human health. An increase in these strains may cause an increase in disease from swimming or eating infected food.†

Vibrio growing on petri dish, taken by L. Garcia

We known Vibrio levels increase with Gracilaria, but we do not know how this happens. We also don’t know if all Vibrio strains increase together, or if only a few strains grow. To understanding the relationship between Gracilaria and Vibrio, I will record how much total Vibrio and how many strains of Vibrio grow in and away from patches of Gracilaria. In order to preserve its own health, Gracilaria produces compounds that promote or stop organisms from growing around it (Assaw et al., 2018). These are compounds I will test against different strains to study the mechanism Gracilaria uses affect specific Vibrio levels. I want to see how the growth of each strain is affected by different extracts. Will the strains further away from the Gracilaria be unable to grow when exposed to a certain type of extract? Will other strains grow better with the extract?

We tend to think about invasive species on a large scale, assessing the damage it causes to other familiar animals and plants. The ecosystem relies on tiny, cellular organism and studying how bacteria changes leads to a deeper understanding of environmental health. An invisible community is changing as Gracilaria flourishes, and there is a lot left to learn about it. 

Acknowledgements

Thank you to my mentor Dr. Erik Sotka, and our collaborator Dr. Erin Lipp. I would also like to thank Dr. Alan Strand and Kristy Hill-Spanik for their supporting guidance. Lastly, thank you to Dr. Loralyn Cozy (IWU) for preparing me to succeed in the lab. All research is funded by Grice Marine Lab and College of Charleston through the Fort Johnson REU Program, NSF DBI-1757899

References

Assaw S, Rosli N, Adilah N, Azmi M, Mazlan N, Ismail N. 2018. Antioxidant and Antibacterial Activities of Polysaccharides and Methanolic Crude Extracts of Local Edible Red Seaweed Gracilaria sp. Malays Appl Biol. 47(4): 135-144. 

Fofonoff PW, Ruiz GM, Steves B, Simkanin C, & Carlton JT. 2019. National Exotic Marine and Estuarine Species Information System. 

Gonzalez D, Gonzalez R, Froelich B, Oliver J, Noble R, McGlathery K. 2014. Non-native macroalga may increase concentrations of Vibrio bacteria on intertidal mudflats. Mar Ecol Prog Ser. 505: 29-36.

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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.

Gracilaria: A dynamic habitat

Nick Partington, St. Olaf College

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Findings: In my previous post, I described the methods we would be taking this summer to explore how the biodiversity of fishes differ among dense and sparse patches of the invasive alga Gracilaria vermiculophylla. We followed these methods, and we produced some interesting results!

We finally sorted and identified all of the fishes we collected from our samples this summer, and were able to measure the biodiversity between dense and sparse habitats. In particular, we were interested in four measurements of biodiversity. The first, abundance, is simply the overall number of fishes collected from each habitat type. The second, species evenness, measures how evenly individual fishes

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Some of the fishes we collected this summer, separated by species and sample.

are distributed among the different species collected in each habitat type. Finally, diversity took into account species richness, which counts the total number of species collected, and the Simpson’s Diversity Index, which quantifies diversity based on the number of species and the relative abundance of each of those species.

These measurements provided us with some interesting results. In the end, we collected a greater abundance of individuals in sparse sites than in dense sites. We also saw both greater species evenness and greater species richness in dense sites. Additionally, the Simpson’s Diversity Index showed a greater diversity of fishes in dense sites.

As I mentioned, abundance of individuals and species richness were both calculated by simply counting the overall number of individuals and species, respectively, collected in each site. Species evenness, on the other hand, required a bit more analysis. Figure 1 shows rank abundance curves for both sparse and dense patches of G. vermiculophylla. These curves tell us how evenly individuals are distributed among the species collected from each site. For each habitat type, species are ranked from 1 to 10 in decreasing order of abundance. That rank is then compared with the abundance of each species. The slope of the resulting line is what we are interested in. Basically, the flatter the line, the greater the species evenness. In our analysis, the line representing dense sites had a flatter slope, signaling greater species evenness in dense sites than in sparse sites.

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Figure 1. Rank abundance curves for both dense and sparse habitats. The slope of the curve representing dense habitats is closer to 0, indicating greater species evenness in those sites.

As I mentioned, overall we found a greater abundance of individual fishes in sparse sites, while we had greater species evenness, species richness, and diversity in dense sites. These differences between sites are very interesting in themselves. But what is even more interesting is that these results are the complete opposite of what was concluded after this same study was conducted last summer. Therefore, there must be some factor(s) that changed between these two studies. We’re not exactly sure what these factors are, but nonetheless, this highlights the importance of long term studies, as well as the importance of continuing this study to see how these trends in biodiversity change and pan out in the long run. I think a very interesting takeaway from this project is that invasive species, like G. vermiculohylla, can potentially provide benefits and sustain biodiversity in ecosystems here in Charleston and throughout the world.


Special thanks to Tony Harold and Mary Ann Taylor for their guidance in this research project. This project is funded by the National Science Foundation and is supported by the Fort Johnson REU Program, NSF DBI-1757899.

Gracilaria: What are you hiding?

Nick Partington, St. Olaf College

Screen Shot 2018-07-03 at 10.37.44 AMThe approach: In my previous post, I discussed how we will primarily be researching differences in abundance and diversity of fish and fish species that utilize Gracilaria vermiculophylla as habitat in the Charleston harbor. In order to do so, we have been collecting several samples of fish from the two habitat types this summer. We then sort and identify fish from each sample to determine the number of individuals per species found in each habitat type, and will later carry out statistical analyses to determine if any significant differences exist between the two habitat types. Each of these steps, from collecting to identifying to analyzing, consists of techniques that must be replicated for each sample in order to ensure consistency.

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Sampling in a “sparse” patch of G. vermiculophylla

The first step is to collect the samples. We do this at Grice Cove, just a few minutes’ walk from Grice Marine Lab. On site, we have identified a section where about 20% or less of the beach is covered by G. vermiculophylla. These are the “sparse” patches. The “dense” patches are further down the beach, where about 80% or more of the beach is covered by the algae. At each site, we pull a fifteen foot seine net through about 1-2 feet of water for a distance of 15 meters. We then sort through the net, saving all of the fish and discarding plant matter and invertebrates such as crabs and shrimp. The next step is to sort and identify the specimens that we collected.

IMG_5628

An early stage of sample sorting. This sample includes a flounder (upper right), pipefish (upper left), and several anchovies (middle).

 

 

After being fixed in preservatives for about a week, we sort through our samples, grouping identical fish and identifying specimens to the lowest classification possible (hopefully to the species level). After the sorting and identifications are complete, the numbers of fish of each species for each sample are recorded. Later, after we have collected all of our data, we will perform statistical analyses on the data to discern any significant differences in diversity and abundance of fish that might exist between dense and sparse patches of G. vermiculophylla. Stay tuned to hear about our findings!


Special thanks to Dr. Tony Harold for his guidance in this research project. This project is funded by the National Science Foundation and is supported by the Fort Johnson REU Program, NSF DBI-1757899.

Gracilaria: A Weedy Invader

Nick Partington, St. Olaf College

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The problem: Invasive species come in many different shapes and sizes, with a great variety of effects on the environment. For example, some invasive species infiltrate and destroy native trees, while some are introduced into lakes where they may displace native species and absorb nutrients. Whether aquatic or terrestrial (or perhaps even extraterrestrial), invasive species have been shown to have considerable effects on the environments they invade, and have been proven to play a major role in affecting global change (Vitousek, 1996). Gracilaria vermiculophylla is an invasive seaweed that has been introduced to many regions throughout the world, including the east coast of the United States (Thomsen, 2006, 2007, 2009). It takes the form of a thin, brownish red algae and originated off the coasts of Japan, from which it has dispersed throughout the world by hitching a ride in the ballasts of commercial ships (Krueger-Hadfield, 2017). In South Carolina, it can be observed in dark patches on beaches when the tide recedes.

IMG_5618

A patch of Gracilaria vermiculophylla on Grice Beach, where we will be collecting samples this summer.

Many small fishes use G. vermiculophylla as habitat; it provides them with food, as well as shelter from predators (Byers, 2012). Many of these fishes serve as prey to larger fishes, and eventually the energy they contain travels up the food web to commercially and recreationally important fishes across the world, including within the Charleston harbor area. That is, G. vermiculophylla provides habitat to fishes, which in turn serve as food for larger fishes that are consumed by humans. Having a good understanding of how these fishes use G. vermiculophylla as habitat can aid the conservation and fishing industries in understanding this low-level component of the food web.

My research project this summer is aimed at improving this understanding. We will be replicating the design of a study implemented in the summer of 2017 by studying fish communities occurring in patches of Gracilaria vermiculophylla. Particularly, we will be exploring differences in the abundance and diversity of fishes utilizing dense patches of G. vermiculophylla as compared to sparse patches. We are also interested in any differences that might exist between dense and sparse patches concerning habitation patterns among different developmental stages of these fish species. Our findings may support that which was discovered last summer, or they might reveal a completely new piece of information. I am excited to see what we will find!


Special thanks to Dr. Tony Harold for his guidance in this research project. This project is funded by the National Science Foundation and is supported by the Fort Johnson REU Program, NSF DBI-1757899.


References:

Byers, J. E., P. E. Gribben, C. Yeager, and E. E. Sotka. 2012. Impacts of an abundant introduced ecosystem engineer within mudflats of the southeastern US coast. Biological Invasions 14:2587-2600.

Krueger-Hadfield, S. A., N. M. Kollars, A. E. Strand, J. E. Byers, S. J. Shainker, R. Terada, T. W. Greig, M. Hammann, D. C. Murray, F. Weinberger, and E. E. Sotka. 2017. Genetic identification of source and likely vector of a widespread marine invader. Ecology and Evolution 7:4432-4447.

Thomsen, M. S., K. J. McGlathery, and A. C. Tyler. 2006. Macroalgal distribution patterns in a shallow, soft-bottom lagoon, with emphasis on the nonnative Gracilaria vermiculophylla and Coldium fragile. Estuaries and Coasts 29:465-473.

Thomsen, M. S., K. J. McGlathery, A. Schwarzschild, and B. R. Silliman. 2009. Distribution and ecological role of the non-native macroalga Gracilaria vermiculophylla in Virginia salt marshes. Biological Invasions 11:2303-2316.

Thomsen, M. S., T. Wernberg, P. Staehr, D. Krause-Jensen, N. Risgaard-Petersen, and B. R. Silliman. 2007. Alien macroalgae in Denmark – a broad-scale national perspective. Marine Biology Research 3:61-72.

Vitousek, P. M., C. M. D Antonio, L. L. Loope, and R. Westbrooks. 1996. Biological invasions as global environmental change. American Scientist 84:218-228.