Biomagnification of mercury through a subtropical coastal food web off Southwest Florida

Abstract

Total mercury and stable isotopes of nitrogen (δ15N) were measured in samples from 57 species of invertebrates (17 species) and finfish (40 species) from the coastal waters off southwest Florida, USA, to evaluate the biomagnification of mercury through the food web. Mercury concentrations (wet wt) and δ15N values were highly variable among species, ranging from 0.004mg/kg in an unidentified species of brittlestar (class Ophiuroidea) to 2.839±1.39mg/kg in king mackerel (Scomberomorus cavalla) and from 4.67‰ in a Florida fighting conch (Strombus alatus) to 13.68‰ in crevalle jack (Caranx hippos). In general, observed Hg levels were in the upper range of levels previously reported for other Gulf populations. Species means of log-transformed Hg concentrations were positively correlated with δ15N (p<0.001, r2=0.66) and had a slope of 0.21. A trophic magnification factor of 5.05 was calculated from the relationship between log-transformed mean Hg concentrations and trophic level (calculated from δ15N), indicating that Hg increased by a factor of 5 with each increase in trophic level. The log10[Hg]-δ15N slope and trophic magnification factor were also in the upper range of values reported from other regions and ecosystems. © 2013 SETAC.