Biomonitoring Heavy Metal Pollution Using an Aquatic Apex Predator, the American Alligator, and Its Parasites

PLoS One. 2015 Nov 10;10(11):e0142522. doi: 10.1371/journal.pone.0142522. eCollection 2015.

Abstract

Monitoring the bioaccumulation of chemical elements within various organismal tissues has become a useful tool to survey current or chronic levels of heavy metal exposure within an environment. In this study, we compared the bioaccumulations of As, Cd, Cu, Fe, Pb, Se, and Zn between the American alligator, Alligator mississippiensis, and its parasites in order to establish their use as bioindicators of heavy metal pollution. Concomitant with these results, we were interested to determine if parasites were more sensitive bioindicators of heavy metals relative to alligators. We found parasites collectively accumulated higher levels of As, Cu, Se, and Zn in comparison to their alligator hosts, whereas Fe, Cd, and Pb concentrations were higher in alligators. Interestingly, Fe levels were significantly greater in intestinal trematodes than their alligator hosts when analyzed independently from other parasitic taxa. Further analyses showed alligator intestinal trematodes concentrated As, Cu, Fe, Se, and Zn at significantly higher levels than intestinal nematodes and parasites from other organs. However, pentastomids also employed the role as a good biomagnifier of As. Interestingly, parasitic abundance decreased as levels of As increased. Stomach and intestinal nematodes were the poorest bioaccumulators of metals, yet stomach nematodes showed their ability to concentrate Pb at orders of magnitude higher in comparison to other parasites. Conclusively, we suggest that parasites, particularly intestinal trematodes, are superior biomagnifiers of As, Cu, Se, and Zn, whereas alligators are likely good biological indicators of Fe, Cd, and Pb levels within the environment.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alligators and Crocodiles / parasitology*
  • Animals
  • Environmental Monitoring*
  • Metals, Heavy / pharmacokinetics
  • Metals, Heavy / toxicity*
  • Predatory Behavior*
  • Tissue Distribution
  • Water Pollutants, Chemical / pharmacokinetics
  • Water Pollutants, Chemical / toxicity*

Substances

  • Metals, Heavy
  • Water Pollutants, Chemical

Grants and funding

This study was funded by NSF-Graduate Research Fellowship Program Award No. DGE-0946816, https://www.nsfgrfp.org/, Funding assisted in data collecting and heavy metal analysis; IUCN/Species Survival Committee-Crocodile Specialist Group’s Student Research Assistant Scheme, http://www.iucncsg.org/pages/General-Information.html, funding assisted in data collection and heavy metal analysis; Chicago Herpetological Society Graduate Student Research in Herpetology Award, http://www.chicagoherp.org/index.php?link=grants, funding assisted in data collection; Sigma Xi Student Research-in-Aid Award, https://www.sigmaxi.org/programs/grants-in-aid, funding assisted in data collection.