Acute silver toxicity in the euryhaline copepod Acartia tonsa: Influence of salinity and food

Abstract

The euryhaline copepod Acartia tonsa was exposed to silver (AgNO(3)) in either the absence or the presence of food (diatom Thalassiosira weissflogii; 2 x 10(4) cells/ml). Standard static-renewal toxicity tests that included a fixed photoperiod of 16: 8 h light:dark and temperature (20 degrees C) were run in three different salinities (5, 15, and 30 ppt) together with measurements of pH, ions (Na(+), Cl(-), K(+), SO(4)(2-), Mg(2+), and Ca(2+)), alkalinity, dissolved organic carbon, and total and dissolved (0.45 microm) silver concentrations in the experimental media. In the absence of food, the 48-h EC50 (concentration causing effect to 50% of the individuals tested) values based on total and dissolved silver concentrations were 11.6, 87.2, and 163.2 microg Ag/L and 7.1, 79.2, and 154.6 microg Ag/L at salinities 5, 15, and 30 ppt, respectively. In the presence of food, they were 62.1, 98.5, and 238.4 microg Ag/L and 48.4, 52.3, and 190.9 microg Ag/L, respectively. In all experimental conditions, most of the toxic silver fraction was in the dissolved phase, regardless of salinity or the presence of food in the water. In either the absence or the presence of food, acute silver toxicity was salinity dependent, decreasing as salinity increased. Data indicate that changes in water chemistry can account for the differences in acute silver toxicity in the absence of food, but not in the presence of food, suggesting that A. tonsa requires extra energy to cope with the stressful conditions imposed by acute silver exposure and ionoregulatory requirements in low salinities. These findings indicate the need for incorporation of both salinity and food (organic carbon) in a future biotic ligand model (BLM) version for estuarine and marine conditions, which could be validated and calibrated using the euryhaline copepod A. tonsa.

Chronic copper toxicity in the estuarine copepod Acartia tonsa at different salinities

“…It was previously analyzed and considered free of major contaminants, such as metals and organics (pesticides and hydrocarbons). Physicochemical parameters of this seawater were previously reported [5,[15][16][17]. Algae were kept under constant white fluorescent lights at 208C with mild continuous aeration, for no more than 7 d. Algal density was measured using a 0.1-mm depth hemocytometer (Neubauer chamber; Laboroptik).…”

“…Adult copepods (A. tonsa) were obtained from cultures of the Laboratory of Zooplankton of the Universidade Federal do Rio Grande (Rio Grande, RS, Southern Brazil) and cultivated as previously described [5,[15][16][17]. Briefly, copepods were held in 20-L plastic buckets containing water at salinity of 15 or 30 ppt under mild continuous aeration.…”

“…In fact, studies performed to determine the influence of salinity on acute Cu toxicity showed higher Cu sensitivity in lower water salinities [4]. It was also reported that increasing water salinity is protective against the acute Ag toxicity in the euryhaline copepod Acartia tonsa [5]. It is important to note that waterborne Cu and Ag show a similar mechanism of toxicity in freshwater animals [6].…”

Protein‐based electrochemical biosensor for detection of silver(I) ions

“…The three-electrode system consisted of a hanging mercury drop electrode (HMDE) with a drop area of 0.4 mm 2 , an Ag/AgCl/3 mol/dm 3 KCl reference electrode, and a carbon counter electrode. The raw data were treated using the Savitzky and Golay filter (level 2) [31] and the moving average baseline correction (peak width 0.03), both implemented in General Purpose Electrochemical System (GPES) software 4.9 (EcoChemie).…”

“…In aquatic ecosystems, heavy metal ions accumulate, and their distribution and bioavailability are higher compared with terrestrial ecosystems. Silver(I) ions are extremely toxic to aquatic animals [2][3][4][5][6][7]. The organisms viewed as most sensitive to silver(I) ions are small aquatic invertebrates, particularly in the embryonic and larval stages [8][9][10][11][12].…”