V. L. Shinde, V. Suneel, and B. D. Shenoy, 2017, Diversity of bacteria and fungi associated with tarballs: Recent developments and future prospects. Marine Pollution Bulletin 117:28-33. DOI: http://dx.doi.org/10.1016/j.marpolbul.2017.01.067
We live in an oil-filled world…
Have you ever wandered along the shores of your favorite beach, and come across discarded fishing lines or fragments of plastic bits (“microplastics”) that seem to be a somber reminder of our impact on our only Earth? An emerging threat to our marine ecosystems resembles the far-reaching impacts of microplastics, and is a by-product of crude oil: the tarball.
We live in a world dominated by the use of fossil fuels, from coal and oil, to petroleum-based plastics that exist in our daily lives. Unfortunately, human dependence on fossil fuels and activities that extract these energy-rich reserves has resulted in over a century of greenhouse gas pollution and oil spills. With these concerns about marine pollution and adverse effects on marine life in mind, Shinde et al. reviewed and synthesized current research on the importance of tarballs, by-products of crude oil, as conduits of pollutants to marine life and beaches around the world.
What is a tarball?
When crude oil is released into marine environments, different physical, chemical, and biological processes interact to form solid to semi-solid tarballs. Some physical processes such as weathering, and chemical and biological processes such as UV light degradation and biodegradation by microbes contribute to the formation of tarballs. Because of these processes, tarballs differ chemically from their parent crude oil, and they can contain a surprising array of potentially toxic compounds and microbes.
Tarballs can attract various heavy metals, including nickel, copper, and cobalt, to their surfaces. Due to different weathering processes, tarballs can accumulate high concentrations of heavy hydrocarbons, organic compounds that only contain carbon and hydrogen, such as polycyclic aromatic hydrocarbons (PAH). PAH’s are common in coal and tar deposits, and many are suspected to cause cancer in humans.
It’s scary enough that heavy metals and PAH’s can accumulate on the surfaces of these tarballs, but recent research has suggested that the presence of metals can increase the toxicity of the PAH’s. Given the unfortunate facts that oil spills and leakages are all too common, we should be concerned about the long-term effects of these oil spill artifacts on our marine systems.
What are the effects of tarballs in the marine environment?
Although recent efforts have uncovered the potential toxicity of tarballs, the adverse effects of these pollutants on coastal economies and the environment are poorly understood. One of the major concerns regarding these particles is the potential for economic losses. Researchers speculate that tarballs washed ashore on beaches will negatively affect local economies because tourists will be offended by the petroleum-like odor. Sticky tarballs can get caught in fishing nets, making them difficult to clean and a nuisance for local fisheries.
Since tarballs can attract heavy metals and PAH’s, they could contribute to causes of cancer if ingested by marine animals. Because these oil by-products come in a variety of shapes and sizes, sea turtles may mistake them for food particles, eat them, and die from the toxic compounds attached to the tarballs.
Other organisms, including fish, may consume smaller bits of tarballs, and if a hungry shark chomps down on some fish that just finished its tarball dinner, the risk of biomagnification, the process in which a compound increases its concentration as it moves up the food chain, becomes a real risk.
Threats to human health?
While the potential impacts on coastal economies remain uncertain, the effects on human health are nothing short of frightening. A 2010 study found 10 times higher densities of flesh-eating bacteria on tarballs in the Gulf of Mexico compared to surrounding water.
A silver lining?
You might be surprised, given all the negative aspects of crude oil and tarballs on marine ecosystems, that these particles contain a high diversity of microbes on their surfaces. From diatoms, to yeast, and a whole bunch of different bacteria, tarballs seem an unlikely home for living things. The microbes associated with tarballs may help degrade these oil by-products, potentially rendering them less harmful to marine life and humans.
Many microbes play important roles in biodegradation, the breaking down of organic matter by bacteria and fungi, in the marine environment. We now know that tarballs harbor high concentrations of PAHs and heavy metals, which we want to steer clear of, but some species of bacteria use these compounds as energy and nutrient sources. However, not many people have undertaken research on microbial biodegradation of tarballs, partly due to the difficulty of keeping some of these microbes alive in a lab setting.
What will the future hold?
Beaches all over the world are exposed to tarball pollution. The authors in this review urged more research on the potential adverse effects of tarballs and their associated heavy metals and PAHs on human health and marine food webs. There is cautious optimism about the potential for microbes to degrade tarballs, but more research is needed to understand how microbes consume and accumulate tarball pollutants. This is clearly an issue that will not go away, and the need to understand further persistent pollutants in our oceans and beaches will help guide clean-up and restoration efforts.
Kate received her Ph.D. in Aquatic Ecology from the University of Notre Dame and she holds a Masters in Environmental Science & Biology from SUNY Brockport. She currently teaches at a small college in Indiana and is starting out her neophyte research career in aquatic community monitoring. Outside of lab and fieldwork, she enjoys running and kickboxing.