Environmental risk from contaminated aquatic sediments requires an understanding of its spatial distribution, bioavailability and rate of transfer to resident aquatic and terrestrial biota. We hypothesized that macroinvertebrates play a role in the sequestration, distribution, and dispersal of lead from lead shot contaminated sediments. To assess this, we sampled the predominant aquatic macroinvertebrate, Leptocerus americanus, from sites within the La Crosse River Marsh (La Crosse, Wi) identified to contain high levels of lead contamination. We measured lead content in larval cases, larval tissues and emergent adult tissues. Lead concentrations within whole larvae correlated with levels of lead within sediments, and lead was differentially partitioned between larval tissue and their silk cases. Over 90% of the lead was retained in larval cases, while the rest was distributed to the body tissue, which was largely conserved during the process of metamorphosis. Our models support that L. americanus emerging from the marsh in the contaminated area transfer as much as 160 mgPb out of the aquatic habitat each year. Our work demonstrates that macroinvertebrates affect the mobilization and dispersal of contaminants within aquatic sediments, and this role should be evaluated when making management decisions regarding contaminated ecosystems.
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Acknowledgements We acknowledge Alicia Rivera-Perez for her work and assistance on implementing and sampling emergence traps. Additional field and lab assistance was provided by Ryan Moncada, Trevor Cyphers, Kaali Fedor, Andrew Revak, Courtney Schneiders, Amanda Smith, Alex Olson, Kevin Lee, Pat Deflorin, and John Frawley. This work was supported by Environmental Protection Agency Urban Water’s Grant #UW00E01025, the University of Wisconsin La Crosse, and the University of La Crosse River Studies Center.
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- Lead bioavailability
- Lead shot
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