ABSTRACT

Plastic marine debris is a recent introduction to marine ecosystems resulting from the widespread use of polymers in consumer goods after World War II. The current global annual production of plastic is 245 million tonnes or 35 kg of plastic for each of the 7 billion humans on the planet, rivaling the combined biomass of all humans. Drifter buoys and physical oceanographic models demonstrate that surface particles passively migrate from the coastline to the central gyres in less than 60 days, illustrating how quickly human-generated debris can impact the pristine gyre interiors, more than 1000 km from land. Plastic debris has been implicated as a vector for transportation of harmful algal species and persistent organic pollutants, and provides a substrate for microbes that moves between environments and lasts much longer than most natural floating substrates. Despite increases in plastic production no significant trend in plastic accumulation has been observed since 1985. Physical shearing and photodegradation are known mechanisms of plastic degradation, but microbial degradation has also been implicated. Unpublished data employing pyrotag amplicon sequencing targeting bacterial and eukaryotic small subunit ribosomal RNA gene sequences, together with Scanning Electron Microscopy (SEM) data are consistent with the notion that plastic debris harbors a unique association of microbes including members capable of degrading plastic. The term "Plastisphere" describes this unique microbial community attached to and surrounding marine plastic debris and distinct from microbes in the surrounding seawater and on natural substrates such as macroalgae.

This project will: (1) characterize diversity through amplicon sequencing and comparative -omics combined with SEM and confocal microscopy to investigate the microbial composition of the Plastisphere; (2) describe function of the Plastisphere taking a cultivation-independent environmental DNA gene expression approach, as well as a cultivation-based approach to interrogate environmental clones and microbial isolates for the ability to degrade hydrocarbons; and (3) determine key biological factors that control the fate of plastic debris in the upper water column.

Intellectual Merit. Plastic is now the most abundant form of marine debris. Gaining an understanding of how plastic is affecting the very foundation of the food web in delicate open ocean environments is a first order question that will be addressed in this proposal and provides a base for an emerging research topic that has been identified as a high-priority research area. Understanding how microbes interact with plastic debris that accumulates in the North Atlantic Subtropical Gyre and North Pacific Subtropical Gyre (two of the largest biomes on Earth) will provide a foundation for follow-up research questions such as: Do microbial biofilms provide sustenance for filter feeding zooplankton?; how is the abundance of plastic debris affecting the health of these delicate biomes?; and can a truly biodegradable plastic be formulated that will have minimal impact on the oligotrophic environment? With a growing human population and second and third world economic growth, it is inevitable that more plastic debris will find its way into the ocean and collect in convergence zones such as the gyres.

Broader Impacts. The field component of this project is built around independent research projects by undergraduate students participating in Sea Education Association?s SEA Semester research cruises in the Atlantic and Pacific oceans. In addition to mentoring SEA Semester students who will be collecting samples and helping with this project throughout the year, the project will engage faculty and students from the Caribbean region who are studying at St. Georges University in Grenada. Underrepresented minorities in the US will be mentored through the Partnership Education Program (PEP) program, the WHOI minority fellowship program, and the MBL REU Site program in Biological Discovery in Woods Hole. Outreach to the general public and K-12 teachers and students will be delivered through a dedicated website for the "Plastics at SEA expedition" in 2010 by adding a section that specifically addresses microbial ecology and the role of plastic marine debris in open ocean marine ecosystems. All members of the research team will contribute to a newly developed undergraduate curriculum in "Marine Biodiversity and Conservation" via lectures and participation aboard ship.