High Hg biomagnification in North Atlantic coast ecosystems and limits to the use of δ15N to estimate trophic magnification factors. (1st May 2023)

• Record Type: Journal Article
• Authors: Boquete, M. Teresa; Aboal, Jesús R.; Villares, Rubén; Dorado-García, Uxía; Fernández, J. Ángel
• Is Part Of: Water research. Volume 234(2023)
• Publication Date: 2023-05-01
• Subjects: Dogwhelk -- Food chains -- Mussel -- Nitrogen isotope ratio -- Marine pollution; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2023.119793
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Hg declined significantly in the North Atlantic coast of spain between 1990 and 2021. Despite its overall low concentrations, hg biomagnified in the studied food chain. Hg pollution can be hazardous even when found at low levels in lower trophic levels. Nitrogen pollution differentially affected the δ15N signatures of the species studied. The use of δ15N in biomagnification studies may be limited by nitrogen pollution. Abstract: Mercury contamination is a global environmental problem. This pollutant is highly toxic and persistent which makes it extremely susceptible to biomagnify, i.e. increase its concentrations as it moves up the food chain, reaching levels that threaten wildlife and, ultimately, ecosystems' function and structure. Mercury monitoring is thus crucial to determine its potential to damage the environment. In this study, we assessed the temporal trends of the concentrations of Hg in two coastal animal species closely connected by a predator-prey interaction, and evaluated its potential transfer between trophic levels using the δ 15 N signatures of the two species. For this, we performed a multi-year survey of the concentrations of total Hg and the values of δ 15 N in the mussel Mytilus galloprovincialis (prey) and the dogwhelk Nucella lapillus (predator) sampled along ∼1500 km of the North Atlantic coast of Spain over a 30-year period (five surveys between 1990 and 2021). Concentrations of Hg decreased significantly between the first and the last survey in the two species studied. Except for the 1990 survey, the concentrations of Hg in mussels were amongst the lowest registered in the literature for the North East Atlantic Ocean (NEAO) and the Mediterranean Sea (MS) between 1985 and 2020. Nonetheless, we detected Hg biomagnification in almost all surveys. Worryingly, trophic magnification factors obtained here for total Hg were high and comparable to the found in the literature for methylmercury, the most toxic and readily biomagnified form of this element. The δ 15 N values were useful to detect Hg biomagnification under normal circumstances. However, we found that nitrogen pollution of coastal waters differentially affected the δ 15 N signatures of mussels and dogwhelks limiting the use of this parameter for this purpose. We conclude that Hg biomagnification could constitute an important environmental hazard even when found at very low concentrations in the lower trophic levels. Also, we warn that use of δ 15 N in biomagnification studies when there is some underlying nitrogen pollution problem might lead to misleading conclusions. Graphical abstract: Image, graphical abstract