Half a century of changing mercury levels in Swedish freshwater fish.

Staffan Åkerblom,Anders Bignert,Marcus Sundbom,Lars Sonesten,Markus Meili

doi:10.1007/s13280-014-0564-1

Staffan Åkerblom, Anders Bignert + Show 3 more

Open Access

https://doi.org/10.1007/s13280-014-0564-1

Copy DOI

Abstract

The variability of mercury (Hg) levels in Swedish freshwater fish during almost 50 years was assessed based on a compilation of 44 927 observations from 2881 waters. To obtain comparable values, individual Hg concentrations of fish from any species and of any size were normalized to correspond to a standard 1-kg pike [median: 0.69 mg kg−1 wet weight (ww), mean ± SD: 0.84 ± 0.67 mg kg−1 ww]. The EU Environmental Quality Standard of 0.02 mg kg−1 was exceeded in all waters, while the guideline set by FAO/WHO for Hg levels in fish used for human consumption (0.5–1.0 mg kg−1) was exceeded in 52.5 % of Swedish waters after 2000. Different trend analysis approaches indicated an overall long-term decline of at least 20 % during 1965–2012 but trends did not follow any consistent regional pattern. During the latest decade (2003–2012), however, a spatial gradient has emerged with decreasing trends predominating in southwestern Sweden.

Highlights

High mercury (Hg) levels in the environment have been of concern in Sweden since they were recognized during the late 1950s in dead birds contaminated by fungicide-treated seed (Borg 1959; Borg et al 1965), and during the 1960s in freshwater fish in remote areas (Johnels et al 1967; Ackefors 1971)
In order to test the performance of the transfer function, we identified 200 instances where Hg had been determined in both perch and pike from the same lake within a month’s time
Using the 514 resampled waters for spatiotemporal analysis, the current study showed that the change in fish Hg concentration was not evenly distributed

Summary

Introduction

High mercury (Hg) levels in the environment have been of concern in Sweden since they were recognized during the late 1950s in dead birds contaminated by fungicide-treated seed (Borg 1959; Borg et al 1965), and during the 1960s in freshwater fish in remote areas (Johnels et al 1967; Ackefors 1971). Human hair Hg levels, a good indicator of Hg exposure to humans, are positively correlated to the consumption frequency of freshwater fish in Swedish angling societies (Johnsson et al 2004). The exposure of Hg from small fish species to piscivorous birds during egg laying and hatching was significant compared to other periods (Eagles-Smith and Ackerman 2009). This imposes that selection of size and species for monitoring purposes, and timing for field collection, needs to be considered in the strategic design of monitoring programs

Objectives

Methods

Results

Conclusion