Metals and metalloids in freshwater fish from the floodplain of Tablas de Daimiel National Park, Spain

Rafael Mateo,Jhon J. López-Perea,Rosa C. Rodríguez Martín-Doimeadios,Sergio Fernández-Trujillo,María Jiménez-Moreno

doi:10.1016/j.ecoenv.2020.111602

Abstract

The Tablas de Daimiel National Park (TDNP) is a floodplain ecosystem in central Spain with a potential risk of heavy metal and metalloid pollution. The objective of this study was to know the accumulation of arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), and selenium (Se) in muscle of six species of freshwater fish from the floodplain of TDNP. We obtained muscle samples of Cyprinus carpio (n = 89); Squalius pyrenaicus (n = 16); Ameiurus melas (n = 9); Lepomis gibbosus (n = 8); Micropterus salmoides (n = 6) and Carassius auratus (n = 5). A. melas, which is a predatory species, had significantly higher Hg concentrations than omnivorous or herbivorous species (i.e. C. carpio). On the contrary, A. melas showed lower concentrations of As, Pb and Se than omnivorous species (i.e. S. pyrenaicus and L. gibbosus ). The concentration of Hg was positively associated with fish size in C. carpio and A. melas. Some individuals of C. carpio (5.7%) and S. pyrenaicus (12.5%) showed Pb muscle concentrations above the maximum residue levels established by the European legislation for human consumers. The observed muscle Se concentrations can be associated with adverse effects on fish such as blood changes, reduced growth, mortality of juveniles and reproductive failure. The accumulation of Se in this floodplain located in a seleniferous area and the contamination produced by spent Pb shot pellets used for hunting in the past are discussed as potential sources of the elevated levels of these two elements in fish from this floodplain wetland.

Highlights

Floodplains provide human society with many important ecosystem services but are one of the most threatened types of wetlands in semiarid regions (Postel and Carpenter, 1997; Laguna et al, 2016)
Tablas de Daimiel National Park (TDNP) is a Mediterranean floodplain in central Spain declared as Biosphere Reserve (MAB Programme UNESCO) and Ramsar site, which presents a unfavourable conservation status (Green et al, 2017) because of groundwater extraction for irri gation in the upper Guadiana river basin (Alvarez-Cobelas et al, 2001; Laguna et al, 2016) and the input of insufficiently treated effluents from wastewater treatment plants (WWTPs) through the Cigüela and Guadi ana rivers (Berzas Nevado et al, 2000; Navarro et al, 2011; SanchezRamos et al, 2016; Rivetti et al, 2017; Lopez-Perea et al, 2019)
The aim of this study is to determine the accumulation of several metals and metalloids (As, Cd, Hg, Pb, and Se) in muscle of six species of freshwater fish from TDNP subjected to selective fishing since 2015

Summary

Introduction

Floodplains provide human society with many important ecosystem services but are one of the most threatened types of wetlands in semiarid regions (Postel and Carpenter, 1997; Laguna et al, 2016). During the period 2012–2015, waterfowl populations in the TDNP showed a marked decrease linked to the deterioration of submerged macrophyte stands by invasive freshwater fish, such as the common carp (Cyprinus carpio) This species affects aquatic vegetation directly by consuming macrophytes such as Chara spp. that are in the basis of the floodplain ecology (Laguna et al, 2016). Common carp can dislodge aquatic macrophyte roots from the sediment, suspending solids and increasing water turbidity (Parkos et al, 2003; Chumchal et al, 2005) This effect increases nutrient release, with the consequent growth of algal biomass, which attenuates the light necessary for the growth of aquatic macrophytes (Sidorkewicj et al, 1999; Laguna et al, 2016).

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