Meagan Currie, Swarthmore College
The ocean is approximately 1.3 billion cubic kilometers (Eakins, 2010). A single cubic kilometer can hold 400,000 Olympic-sized pools. So much does it really matter if human-made chemicals end up in our oceans? What could such small concentrations of chemicals really do to marine organisms?
These are the questions that are fueling my research project this summer at the Hollings Marine Laboratory. I have the privilege of working in the lab of Dr. Cheryl Woodley, who specializes in marine toxicology and coral health. Here I will be using two environmentally and biologically important marine organisms – sea urchins and coral – to understand more about the effects of manmade chemicals on the health and development of marine life.
Of course, given our limited time I am not going to investigate all of the over 70,000 different chemicals produced by the US. I will focus on the compound nonylphenol, which has been recognized by the US Environmental Protection Agency (EPA) as a chemical of emerging concern (US EPA, 2012). This forbidding title is given to chemicals that have been recently detected in the natural environment that are believed to have harmful effects on humans and natural wildlife.
Nonylphenol is added to products as a detergent, as it helps dissolve oils and other compounds more easily in water, and is produced and distributed in very large quantities. Approximately 500 million pounds of nonylphenol is produced every year, although in the last ten years the EPA has developed new rules to attempt to limit its application in products (Helmut, 2002; US EPA, 2016). It is used in most commercial laundry detergents, soaps and cleaners, meaning that it often funnels down the drain and into wastewater treatment plants, or even directly into seawater . Unfortunately, nonylphenol isn’t broken down easily and is moderately bioaccumulative, meaning that it collects and remains in the systems of organisms that come into contact with the chemical.
Another element of nonylphenol’s chemical story is that it is an endocrine disruptor. This means that nonylphenol behaves like a common biological hormone, estrogen, and can negatively impact the hormonal systems of organisms. Marine invertebrates are particularly vulnerable to endocrine disruptors because many, including sea urchins and coral, exist as tiny, free-swimming organisms at early stages of development. Early embryos and larvae are known to be more susceptible to the effects of toxins, particularly hormonal disruptors, than adult organisms (Shirdel, 2016).
This summer I will work with the gametes (egg and sperm) and juveniles of the lovely sea urchin Lytechinus variegatus. This species of urchin is native to much of coastal South America as well as Florida and South Carolina.
I will see how sea urchin sperm responds to nonylphenol at different concentrations, and whether or not exposure affects the ability of sperm to fertilize eggs. I will also watch the development of sea urchin larvae exposed to the chemical to see if nonylphenol changes the pace or physiology of developing urchins. Finally, I will investigate the effects of nonylphenol on regrowth and regeneration of one of the most important organisms in our oceans: coral. Coral reefs host nearly a quarter of all marine species and are critical to maintaining the biodiversity and resources that we derive from the oceans (Coral Reef Alliance, 2017). If you want to know more about coral reefs and maintaining reef health, you can follow the Coral Reef Alliance blog, which releases recent information about efforts to protect coral.
I will be examining how a threatened species of coral, Acropora cervicornis, responds to nonylphenol. To do this I will see how nonylphenol influences the speed and effectiveness of recovery if the coral tissue is injured and then exposed to the chemical. I will also gauge how healthy the coral is by measuring how much the coral is photosynthesizing, which will tell us about how much energy it is producing.
I am very excited to be working with two incredible marine model organisms, and investigate such a prevalent and interesting compound! Our results will hopefully better inform the US EPA and other organizations about the threats of nonylphenol to marine aquatic environments and the many organisms that may be exposed at different stages of their lifecycle. Many thanks to Dr. Cheryl Woodley for welcoming me into her lab, and to the Fort Johnson Summer REU program for giving us this incredible experience.
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