Mercury Bioaccumulation in Benthic Invertebrates: From Riverine Sediments to Higher Trophic Levels

Abstract

Riverine sediments are important sites of mercury methylation and benthic invertebrates may be indicators of Hg exposure to higher organisms. From 2014 to 2018, sediments and invertebrates were collected along a mercury gradient in the Toce River (Northern Italy) and analyzed for THg and MeHg. Concentrations in invertebrates, separated according to taxon and to Functional Feeding Group, ranged from 20 to 253 µg kg−1 dry weight (d.w.) for THg, increasing from grazers (Leuctra, Baetis, Serratella) to predators (Perla). MeHg ranged from 3 to 88 µg kg−1 d.w. in biota, representing 6–53% of THg, while in sediments it was mostly below LOD (0.7 µg kg−1), accounting for ≤3.8% of THg. The Biota-Sediment Accumulation Factor (BSAF, ranging 0.2–4.6) showed an inverse relation to exposure concentrations (THg in sediments, ranging 0.014–0.403 µg kg−1 d.w.) and to organic carbon. THg in invertebrates (up to 73 µg kg−1 wet weight), i.e., at the basal levels of the aquatic trophic chain, exceeded the European Environmental Quality Standard for biota (20 µg kg−1 w.w.), posing potential risks for top predators. Concentrations in adult insects were close to those in aquatic stages, proving active mercury transfer even to terrestrial food chains.

Response of Chironomidae (Diptera) to DDT, Mercury, and Arsenic Legacy Pollution in Sediments of the Toce River (Northern Italy)

“…The values of contaminants (DDT, Hg, and As) in sediments downstream of the industrial plant are typical of legacy contamination [ 19 , 20 , 49 , 50 ]. Despite covering a relatively narrow range, concentrations exceeded the consensus-based Threshold Effect Concentrations (cb-TECs), indicating thresholds below which toxic effects for benthic invertebrates are not expected (5.28 µg kg −1 1%OC for total DDT, 180 µg kg −1 d.w. for Hg, 9.79 mg kg −1 d.w. for As) [ 51 ], showing maxima up to 15.7 µg kg −1 1%OC for DDT, 197 µg kg −1 d.w. for Hg, and 55.7 mg kg −1 d.w. for As.…”

“…Data indicate that contamination is slowly decreasing due to the natural recovery determined by the transport of uncontaminated sediments from upstream [ 18 ]. At the river mouth, total DDT concentrations decreased from 142 µg kg −1 normalized to 1% organic carbon (1% OC) in 2001 to 3.2 µg kg −1 1% OC in 2018; Hg shifted from 949 µg kg −1 dry weight (d.w.) in 2008 to 68 µg kg −1 d.w. in 2018; As decreased from 48 mg kg −1 d.w. in 2008 to 17 mg kg −1 d.w. in 2018 [ 18 ], but concentrations in sediments and in the aquatic biota still remain above background levels [ 19 , 20 ].…”

Regional variation in diet may be an underappreciated modulator of mercury uptake in species of concern: A case study using Alligator Gar (Atractosteus spatula)

“…However, we maintain the idea that the coastal region could have less bioavailable Hg due to biodilution processes or from being immobilized in Hg sul des. Because of this, primary consumers and benthic foraging species from coastal regions may be less likely to encounter bioavailable Hg while feeding and thus less Hg would accumulate into the basal level of the food web and Alligator Gar prey (Benoit et al 1999;Marziali et al 2021).…”

Analisis Longitudinal Struktur Komunitas Makrozoobentos yang Tercemar Limbah Pertambangan Emas Skala Kecil di Sungai Cikondang, Jawa Barat

“…Penentuan konsentrasi Hg pada sedimen dan makrozoobentos mengacu pada metode US-EPA 7473 Mercury in Solids and Solutions by Thermal Decomposition, Amalgamation, and Atomic Absorption Spectrophotometry. Sebanyak 0,025 g berat kering makrozoobentos dan 0,1 berat kering sedimen dianalisis menggunakan automatic mercury analyzer (Marziali et al, 2021).…”