Chronic toxicity of silver to the sea urchin (Arbacia punctulata)

Abstract

The chronic toxicity of silver to the sea urchin (Arbacia punctulata) was determined in 30 per thousand salinity seawater during a three-part study: A fertilization test (1-h sperm exposure), a 48-h embryo test, and a 30-d adult test. Combined data from the three tests resulted in a lowest-observed-effect concentration of 19 microg/L, a no-observed-effect concentration of 8.6 microg/L, and a maximum acceptable toxicant concentration of 13 microg/L, based on measured concentrations of dissolved silver. The 96-h median effective concentration was 40 microg/L, and the acute to chronic toxicity ratio was 3.1. During the tests, measured concentrations of free ionic silver (Ag+) were only 0.0027 to 0.0046% of dissolved silver concentrations, as predicted by ion-speciation theory. Some measured Ag+ concentrations were lower than predicted, indicating the presence of other ligands in the seawater test media. These strong sulfide ligands were exuded by the exposed sea urchins into the seawater (where Ag-sulfide complexes formed) in amounts that increased in direct proportion to the silver concentration during the toxicity test. This suggests a toxicity-defense mechanism that functioned by modifying the chemistry of the surrounding external medium.

Interactions of silver nanoparticles with the marine macroalga, Ulva lactuca

“…Presumably, our observations are related to differences in the physical and chemical properties of Ag in aqueous and nanoparticulate forms and kinetic constraints on the partial conversion of the latter to the former. The concentration at which aqueous Ag is measurably toxic in the marine environment, evaluated using a variety of organisms and end-points, appears to be in the range \1 to about 15 lg l -1 (Luoma et al 1995;Bianchini et al 2005;Ward et al 2006), quantitatively consistent with observations made in the present study. Since Ag does not appear to form particularly strong complexes with organic ligands in sea water (Miller and Bruland 1995), its aqueous speciation is dominated by various chloro-complexes (see Table 1).…”

The effect of food on the acute toxicity of silver nitrate to four freshwater test species and acute-to-chronic ratios

“…Previously, Dupont and Ahner (2005) have shown that phytoplankton exude strong metal ligands, which were small peptides containing thiols from cysteine residues when under metal challenge. Ward et al (2006) showed a similar pattern of decreasing Ag ? resulting from exudates for sea urchins when confronted with increasing silver challenges.…”

“…Ag-CRS complexation and the overall bioavailability of the Ag ? that contributes to toxicity may be affected by several factors in a defined test chamber including: the rate of dosing, the number (surface area and weight) of organisms, the particular organism (e.g., fish vs. invertebrates), the presence of food and food type (present study; Ward et al 2006), and the nutritional impact of the food to the organism. Use of an experimental design that addresses these factors in a consistent manner is necessary to achieve an improved characterization of the toxicity of silver, and possibly other metals, to different organisms over a range of exposure scenarios.…”

Environmental Risks of Inorganic Metals and Metalloids: A Continuing, Evolving Scientific Odyssey

“…When metals concentrations are sufficiently elevated, from either anthropogenic or natural sources, selection for metals-resistant populations can occur, resulting in inheritable genetic adaptations by animals (Vidal and Horne 2003a, b;Zaldibar et al 2006), plants (Deng et al 2007), and bacteria (Jin et al 2007). In some cases reduced metals uptake (Hansen et al 2006) or accumulation and detoxification mechanisms may be sufficient to deal with metal influxes without selection for a metal-tolerant population (Zhou et al 2003), for instance regulation of metals via mucus production by snails (Notten et al 2006), biofilm production by algae (García-Menza et al 2005), or exudation of strong thiol ligands into seawater (Ward et al 2006). In other cases detoxification may be insufficient to avoid toxicity (Giguère et al 2006).…”