Origin, transfer and effects of heavy metals in a soil-plant-snail food chain in polluted ecosystems of Biesbosch National Park

Emissions of heavy metals result in pollution of the soil, the atmosphere and the hydrosphere, and this pollution is a potential threat to the health of humans and ecosystems. Biesbosch National Park (the Netherlands) is exposed to chronic and diffuse pollution of heavy metals. The park is the floodplain area in which the rivers Rhine and Meuse join. They contained high loads of heavy metals in the 1960s and 1970s, and polluted sediments were deposited in the floodplains. These polluted layers of sediment are still present. This study investigates heavy metal pollution in a terrestrial soil-plant-herbivore food chain in the Biesbosch. A characteristic food chain was selected, including the plant species Urtica dioica (stinging nettle) and the snail Cepaea nemoralis (grovesnail or brown-lipped snail). Both species are very common in the Biesbosch. They often occur together, because C. nemoralis includes stinging nettle leaves in its diet. Three main research questions were formulated: 1. What is the extent of metal transfer through the soil-plant-snail food chain? 2. What is the origin of Pb in the soil-plant-snail food chain? 3. What are the effects of metal pollution on the organisms in the food chain? The heavy metals studied were zinc (Zn), copper (Cu), lead (Pb) and cadmium (Cd). Four polluted research locations were selected in the Biesbosch, and two relatively 'clean' reference locations were selected outside this area. In addition, a highly polluted location was selected near a Zn factory in Belgium. The extent of metal transfer in the food chain was investigated by determining the concentrations of Zn, Cu, Cd and Pb in the compartments of the food chain. To investigate metal transfer from nettle leaves to snails more extensively, cadmium accumulation in C. nemoralis snails was studied at low, but field-relevant Cd concentrations in the diet (U. dioica leaves). The origin of Pb pollution in the food chain was studied by means of Pb isotope ratios. The effects of metal pollution on snails were studied in two experiments using natural food (U. dioica leaves), snails and soil in order to simulate the field situation. The research shows transfer of heavy metals to and within the terrestrial soil-plant-snail food chain in Biesbosch National Park. The 'old' pollution in the soil still contributes to food chain transfer of metals. This old pollution contains metals derived from industrial activities in the hinterland of the rivers Meuse and Rhine. Contemporary atmospheric Pb pollution also contributes to Pb pollution levels in plant leaves and snails, despite the low Pb concentrations in the atmosphere. The elevated concentrations in nettle leaves and C. nemoralis snails in the Biesbosch do not cause sub-lethal effects on consumption and reproduction of snails, and effects on growth are not likely either. The excretion of Cd, and perhaps other metals, via the mucus is possibly contributing to the absence of sub-lethal effects on snails at the low bioavailable metal concentrations in the soils and nettle leaves of the Biesbosch floodplains.Aerts, M.A.P.A. [Promotor]Rozema, J. [Promotor

Heavy metal pollution affects consumption and reproduction of the landsnail Cepaea Nemoralis fed on naturally polluted Urtica dioica leaves.

This study is one of the very first that investigates the effects of heavy metal pollution on food consumption and reproduction of terrestrial snails under semi-realistic field conditions. Two experiments were carried out using snails (Cepaea nemoralis) and food (Urtica dioica leaves) from different metal polluted locations and one reference location. The first experiment showed that both polluted and reference snails fed on high-metal leaves from a highly polluted location had significantly lower consumption rates than snails consuming leaves from the reference location. In the second experiment, snails from both locations used in the consumption experiment and from two low-polluted locations were kept on native soil and food in order to reproduce. No negative effect of heavy metal pollution on clutch size was found for the snails from the reference location and the low-polluted locations. Snails from the highly polluted location laid no eggs. This suggests that at high levels of metal pollution, reproduction is strongly negatively affected. We suggest that the absence of egg laying by snails from the highly polluted location results from a combination of decreased consumption and an increased demand of energy for the accumulation and detoxification of metals (decreased scope for growth). © Springer Science+Business Media, LLC 2006

Heavy metal concentrations in a soil-plant-snail food chain along a terrestrial soil pollution gradient.

We investigated concentrations of Zn, Cu, Cd and Pb in the compartments of a soil-plant (Urtica dioica)-snail (Cepaea nemoralis) food chain in four polluted locations in the Biesbosch floodplains, the Netherlands, and two reference locations. Total soil metal concentrations in the polluted locations were 4-20 times higher than those in the reference locations. Positive relationships between the generally low leaf concentrations and the soil concentrations were found for Zn only (

The landsnail Cepaea nemoralis regulates internal Cd levels when fed on Cd-enriched stinging nettle (Urtica dioica) leaves at low, field-relevant concentrations.

We studied Cd accumulation in Cepaea nemoralis snails at low, but field-relevant Cd concentrations in the diet (Urtica dioica leaves). Six treatments of U. dioica plants were grown, resulting in leaf Cd concentrations between 0 and 2.6 μg

Investigating the origin of Pb pollution in a terrestrial soil­-plant-­snail food chain by means of Pb isotope ratios

Lead isotope ratios were used to trace the origin of Pb in a soil-plant (Urtica dioica)-snail (Cepaea nemoralis) food chain in two polluted locations in the floodplains of the rivers Meuse and Rhine (Biesbosch National Park) and one reference location in the Netherlands. Lead isotope ratios and concentrations were determined in soil, litter, plant leaves, snails, rainwater and airborne particulate matter. Anthropogenic Pb in the soils of all locations was found to be derived from deposition of Pb polluted river sediments. Discharging rivers influenced the reference location before being reclaimed from the sea. The river sediment contains anthropogenic Pb from various sources related to industrial activities in the hinterland of the rivers Meuse and Rhine. Lead in the atmosphere contributed substantially to Pb pollution and Pb transfer in plant leaves and snails in all locations. Lead pollution in plant leaves and snails can be explained from a mixture of river sediment-Pb and atmospheric Pb from various transfer routes that involve low concentrations. © 2008 Elsevier Ltd. All rights reserved

Do high levels of diffuse and chronic metal pollution in sediments of Rhine and Meuse floodplains affect structure and functioning of terrestrial ecosystems?

This paper (re)considers the question if chronic and diffuse heavy metal pollution (cadmium, copper, lead and zinc) affects the structure and functioning of terrestrial ecosystems of Biesbosch National Park, the floodplain area of rivers Meuse and Rhine. To reach this aim, we integrated the results of three projects on: 1. the origin, transfer and effects of heavy metals in a soil-plant-snail food chain; 2. the impact of bioavailability on effects of heavy metals on the structure and functioning of detritivorous communities; 3. the risk assessment of heavy metals for an herbivorous and a carnivorous small mammal food chain. Metal pollution levels of the Biesbosch floodplain soils are high. The bioavailability of metals in the soils is low, causing low metal levels in plant leaves. Despite this, metal concentrations in soil dwelling detritivores and in land snails at polluted locations are elevated in comparison to animals from 'non-polluted' reference sites. However, no adverse effects on ecosystem structure (species richness, density, biomass) and functioning (litter decomposition, leaf consumption, reproduction) have been found. Sediment metal pollution may pose a risk to the carnivorous small mammal food chain, in which earthworms with elevated metal concentrations are eaten by the common shrew. Additional measurements near an active metal smelter, however, show reduced leaf consumption rates and reduced reproduction by terrestrial snails, reflecting elevated metal bioavailability at this site. Since future management may also comprise reintroduction of tidal action in the Biesbosch area, changes in metal bioavailability, and as a consequence future ecosystem effects, cannot be excluded. © 2008 Elsevier B.V. All rights reserved