Submitted by Matthew Potts on
The Amazonian region of Madre de Dios, Peru is undergoing rapid
environmental and social change as a result of the expansion of informal gold mining. Along
with deforestation, informal gold mining in Madre de Dios utilizes toxic mercury. Mercury is
used in mining to separate and bind diffuse gold particles found in alluvial soils. Mercury and
gold bind together to form a complex or amalgam that is later roasted to purify the gold. The
burning of this amalgam releases mercury vapor into the atmosphere, while the addition of
mercury to sediments also leads to its accidental release into waterways. As a result, there has
been an increase in efforts to understand the ecological and human health implications of
mercury contamination in the region.
This project seeks to understand how mercury spreads beyond the boundaries of a gold mine and
into aquatic and terrestrial ecosystems via food web interactions. Informal gold mining creates
landscapes of abandoned mining pits. These mining pits cover greater than 20% of the total area
deforested as a result of gold mining. The mining pits are colonized by fish, insects, birds, and
reptiles when nearby rivers flood and fill the abandoned pits. These man-made systems become
potential sources of mercury for the rest of the ecosystem as mercury enters the food web and
increases in concentration or biomagnifies up the food chain. As one part of this project, we have
collected emerging aquatic insects to study how mercury moves laterally from mining pits into
surrounding forested ecosystems. These emerging insects become prey for spiders (Family:
Tetragnathidae) found in mining pits. Bats, birds and other small mobile predators in turn predate
upon these spiders and increasingly magnify the effects of mercury contamination in these
tropical food webs. To understand the potential effects of this lateral transfer we will identify and
analyze the mercury content of aquatic insects and spiders in these mining pits.
The undergraduate with the support of the graduate student mentor will help design, analyze, and write-up a research project related to the movement of mercury between aquatic and terrestrial ecosystems.
The undergraduate should be willing to work on taxonomic identification of insects involving many hours at a microscope. The undergraduate should be self-motivated and able to work with limited guidance. Knowledge of aquatic insect identification is a plus. The graduate student mentor is also committed to working closely with the undergraduate to develop and make progress towards his or her own personal career goals.