Millennial scale impact on the marine biogeochemical cycle of mercury from early mining on the Iberian Peninsula

Abstract

[1] The high-resolution mercury record of a Posidonia oceanica mat in the northwest Mediterranean provides an unprecedented testimony of changes in environmental mercury (Hg) loading to the coastal marine environment over the past 4315 yr BP. The period reconstructed made it possible to establish tentative preanthropogenic background Hg levels for the area (6.8 AE 1.5 ng g -1 in bulk sediments). A small, but significant, anthropogenic Hg increase was identifiable by~2500 yr BP, in agreement with the beginning of intense mining in Spain. Changes in the record suggest four major periods of anthropogenic Hg pollution inputs to the Mediterranean: first, during the Roman Empire (2100-1800 yr BP); second, in the Late Middle Ages (970-650 yr BP); third, in the modern historical era (530-380 yr BP); and fourth, in the industrial period (last 250 years), with Hg concentrations two-, four-, five-, and tenfold higher than background concentrations, respectively. Hg from anthropogenic sources has dominated during the last millennium (increase from~12 to~100 ng g -1 ), which can be related to the widespread historical exploitation of ore resources on the Iberian Peninsula. The chronology of Hg concentrations in the mat archive, together with other Hg pollution records from the Iberian Peninsula, suggests regional-scale Hg transport and deposition and shows earlier marine Hg pollution than elsewhere in Europe. Moreover, the mat also records a higher number of historic contamination phases, in comparison with other natural archives, probably due to the fact that the bioaccumulating capacity of P. oceanica magnify environmental changes in Hg concentrations. In this study, we demonstrate the uniqueness of P. oceanica meadows as a long-term archive recording trends in Hg abundance in the marine coastal environment, as well as its potential role in the Mediterranean as a long-term Hg sink.

Are red mullet efficient as bio-indicators of mercury contamination? A case study from the French Mediterranean

“…Corsica is commonly considered as a weakly impacted zone, subjected to limited anthropogenic pressures. Several early papers compared Hg concentration in sediment, mussels or the seagrass Posidonia oceanica and observed lower mercury concentrations in Corsica than in other parts of the Western Mediterranean (Andral et al, 2004;Galgani et al, 2006;Lafabrie et al, 2007;Pergent-Martini, 1998;Pergent et al, 2011;Serrano et al, 2013). The oligotrophy of Corsican waters (in comparison with the waters of the Gulf of Lions and Provence area, Bosc et al, 2004) may be a major factor causing the discrepancy between low environmental Hg concentrations and high concentrations in red mullet.…”

A multitracer approach to assess the spatial contamination pattern of hake (Merluccius merluccius) in the French Mediterranean

“…Le Grau du Roi is close to the Rhône River mouths and high levels of contamination would be expected (Bodiguel et al, 2009a;Dierking et al, 2009). The Bastia site in Corsica is located beyond the influence of the Gulf of Lions, with low urban and industrial development, and might consequently be expected to be a semi-pristine area (Porte et al, 2002;Galgani et al, 2006;Serrano et al, 2013). Samples were collected in the zone usually harvested by fishermen, on the continental shelf (between 50 and 80 m depth) of the Gulf of Lions and along the shelf break in Corsica (between 300 and 450 m depth), as the continental shelf is thinner.…”

Molecular composition of plant parts and sediment organic matter in a Mediterranean seagrass (Posidonia oceanica) mat

“…The role of P. oceanica in sequestering and storing CO 2 on centennial to millennial scales in the mats is being evaluated as a novel aspect of the global C cycle (Fourqurean et al 2012;Duarte et al 2013) and the recent focus on C trading has intensified the interest in quantifying the capacity of these ecosystems to store C (Lavery et al 2013). Secondly, these mats form a repository of palaeo-environmental information (Mateo et al 2002(Mateo et al , 2010López-Sáez et al 2009;Serrano et al 2011Serrano et al , 2012Serrano et al , 2013Lopez-Merino et al 2015), very much like terrestrial peat archives. Although a wealth of technical and scientific literature is available on the role of seagrass sediments as C sinks and palaeoarchives, these fields of research have critical knowledge gaps concerning some fundamental issues: (i) the origin of the accumulated C (i.e.…”