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.

Screen Shot 2017-06-19 at 4.48.43 PM.png

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

Screen Shot 2017-06-19 at 4.48.34 PM.png

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


Grac Attack!

Aaron Baumgardner, The University of Akron

The only thing more pervasive than the constant thoughts of, conversations about, and stress from Gracilaria vermiculophylla in Dr. Erik Sotka’s lab is the invasion of this red alga that is occurring along the coasts of North America and Europe (Sotka, et al. 2013). After only a few short weeks in Charleston, I have seen how prevalent and successful this seaweed is. The success of G. vermiculophylla along the southeastern coasts of the United States is due in part to the established mutualism between it and the decorator worm Diapatra cuprea. This mutualism provides a secure site for the seaweed to grow (Kollars, Byers, and Sotka unpublished manuscript), but it does not explain the success of G. vermiculophylla to thrive in environmental conditions that differ from its native Japanese range.

G. vermiculophylla colonizes a mudflat in Charleston Harbor by clinging to tube-building decorator worms. Credit, Erik Sotka

G. vermiculophylla colonizes a mudflat in Charleston Harbor by clinging to tube-building decorator worms. Credit, Erik Sotka.

Researching G. vermiculophylla can help us understand how aquatic invasions occur. Do introduced populations evolve novel characteristics or do they simply benefit from the phenotypic plasticity of their source populations? To answer this question, it is necessary to test plasticity in response to varying environmental conditions on native and non-native populations (Huang, et al. 2015). Since G. vermiculophylla has spread outside its latitudinal range and into high salinity environments (Kollars, et al. 2015), I will be testing the plasticity of native and non-native G. vermiculophylla populations to a range of temperatures and salinities. Photosynthetic efficiency will be measured using a PAM fluorometer to provide a more objective way to quantify stress (Rasher and Hay 2010).

I would like to thank the College of Charleston for this internship opportunity, Dr. Erik Sotka for mentoring me on my project, and the National Science Foundation for funding REU programs.

CofClogo    nsf-logo


Huang, Q. Q., et al. (2015). Stress relief may promote the evolution of greater phenotypic plasticity in exotic invasive species: a hypothesis. Ecology and Evolution 5(6), 1169-1177.

Kollars, N. M., Byers, J. E.,  & Sotka, E. E. (unpublished manuscript). Invasive décor: a native decorator worms forms a novel mutualism with a non-native seaweed.

Kollars, N. M., et al. (2015, in review). Development and characterization of microsatellite loci for the haploid-diploid red seaweed Gracilaria vermiculophylla. PeerJ.

Rasher, D. B., & Hay, M. E. (2010). Chemically rich seaweeds poison corals when not controlled by herbivores. PNAS 107(21), 9683-9688.

Sotka, E. E., et al. (2013). Detecting genetic adaptation during marine invasions. Grant proposal to the National Science Foundation.