Isotopic evidence for anthropogenic impacts on aquatic food web dynamics and mercury cycling in a subtropical wetland ecosystem in the US Yang Wang a, ⁎, Binhe Gu b , Ming-Kuo Lee c , Shijun Jiang d, ⁎, Yingfeng Xu a a Department of Earth, Ocean & Atmospheric Science, Florida State University and National High Magnetic Field Laboratory, Tallahassee, FL 32306–4100, USA b South Florida Water Management District, West Palm Beach, FL 33406, USA c Department of Geology and Geography, Auburn University, Auburn, AL 36839, USA d Institute of Hydrobiology/Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institutes, Jinan University, Guangzhou, Guangdong 510632, China HIGHLIGHTS • δ 13 C, Δ 14 C, and δ 15 N of fishes from a subtropical wetland ecosystem were analyzed. • Data revealed impacts of land-use change on food chains and Hg bioaccu- mulation. • In reference wetlands, fishes relied on modern primary production. • In impacted wetlands, old peat was a significant C source for fishes. • Data suggest a shorten food chain and less Hg bioaccumulation in impacted areas. GRAPHICAL ABSTRACT abstract article info Article history: Received 20 December 2013 Received in revised form 12 April 2014 Accepted 16 April 2014 Available online xxxx Editor: Mae Mae Sexauer Gustin Keywords: Stable isotopes Radiocarbon Fish Mercury Food web Bioaccumulation Everglades Quantifying and predicting the food web consequences of anthropogenic changes is difficult using traditional methods (based on gut content analysis) because natural food webs are variable and complex. Here, stable and radioactive carbon isotopes are used, in conjunction with nitrogen isotopes and mercury (Hg) concentration data, to document the effects of land-use change on food webs and Hg bioaccumulation in the Everglades – a subtropical wetland ecosystem in the US. Isotopic signatures of largemouth bass and sunfish in reference (relatively pristine) wetlands indicate reliance on the food supply of modern primary production within the wet- land. In contrast, both fish in areas impacted by agricultural runoff had radiocarbon ages as old as 540 years B.P., and larger isotopic variability than counterparts in reference wetlands, reflecting differences in the food web between impacted and reference wetlands. Consistent with this difference, particulate and dissolved organic matter in impacted areas had old radiocarbon ages (N 600 years B.P.), indicating that old carbon derived from his- toric peat deposits in the Everglades Agricultural Area was passed along the food chain to consumers. Significant radiocarbon deficiencies in largemouth bass and sunfish, relative to mosquitofish, in impacted areas most likely indicate a reduced dependence on small fish. Furthermore, largemouth bass and sunfish from impacted areas had much lower Hg contents than those from reference wetlands. Taken together, these data suggest a shift toward lower trophic levels and a possible reduction in mercury methylation in impacted wetlands. Our study provides Science of the Total Environment 487 (2014) 557–564 ⁎ Corresponding authors. Tel.: +1 850 644 1121; fax: +1 850 644 0827. E-mail addresses: ywang@magnet.fsu.edu (Y. Wang), sjiang@jnu.edu.cn (S. Jiang). http://dx.doi.org/10.1016/j.scitotenv.2014.04.060 0048-9697/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv