Anthropogenic impacts on community structure and function within intertidal ecosystems

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The relationship between ecosystem function and community structure is complex and dynamic. Understanding the mechanisms underlying this complex interplay and how this relationship changes as we modify our environment is a challenging problem. This challenge is especially relevant now as anthropogenic activities such as climate change and pollution are rapidly altering aquatic and terrestrial communities and hence how nutrients and elements cycle through these systems. The maintenance of ecosystems is a requirement because as a society we are dependent on these systems for healthy soils, clean air and water. In 2004, the term “microplastics” was introduced to describe a newly recognized pollutant; microplastics less than 5 mm (e.g., microbeads in cosmetic scrubs) and microplastics whose origin is the degradation of larger plastic items (e.g., bottles). An exponentially growing body of literature has demonstrated the threat these pollutants pose to marine ecosystems and those species, including humans that rely on these ecosystems for their services and goods. There are still more questions than answers as to the impact microplastics may have on aquatic ecosystems. Data gaps include the “geochemical” behavior of microplastics within sediments with respect to their ability to sorb metals, the bioavailability of metals associated with microplastics within sediments, and the potential for these metals to move through marine foodwebs to higher trophic levels including humans. Traditionally, sediments have been described as percent organic matter and oxides of manganese and iron. These three components are key factors influencing sediment processes such as metal bioavailability to sediment-ingesting organisms. With the high concentrations of microplastics that occur within sediments (up to 8000 microplastics kg-1 sediment) and the potential for these particulates to influence geochemical processes, sediments must be viewed as being comprised not only of the classic geochemical parameters, but now, also microplastics. Microplastics have the potential to act as a 4th sorption site for toxic metals such as cadmium by outcompeting the other three sediment components providing an as yet quantified entry of metals into foodwebs. Metal sorption by microplastics could also be dependent on the sediment matrix (e.g., sediments high in organic matter would result in less sorption of metals by microplastics versus sediments low in organic matter) and the type of microplastic (e.g., microbead versus fiber). The objective of my 5 year research plan is to address these key data gaps and determine the role of microplastics in the transfer of toxic metals through intertidal foodwebs. This new information can then be applied to evaluate coastal ecosystems at greatest risk to the presence of microplastics within sediments with respect to their role in the transfer of pollutants within marine food webs.