Responses of Daphnia magna to pulsed exposures of arsenic

Abstract

Research on the toxicity of arsenic has focused on sublethal effects that do not provide sufficient information for risk estimation. While most studies have focused on organism response to constant arsenic exposures, organisms in nature are exposed to fluctuating As concentrations. Consequently, results obtained from standardized bioassays with constant exposures may not adequately characterize risk to indigenous biota. This research was designed to characterize the response of Daphnia magna to fluctuating arsenic exposures during 21-day experiments. At concentrations > or =3000 microg/L As, 21-day pulsed exposure mortality increased as a function of exposure concentration and duration. In addition, 21-day pulsed exposure mortality increased with increasing recovery time. Pulsed As exposure did not affect the growth of D. magna over 21 days. Twenty-one day accumulative reproduction of D. magna was only affected by pulsed exposures of high As concentration and long durations.

Morphology and Ecological Characteristics of Paracyclops Novenarius Reid, 1987: A Cyclopoid Copepod Inhabiting a Highly Contaminated Aquifer in Central-North of Mexico

“…A signi cant difference in body size by arsenic concentration was found. This differs from other zooplanktonic groups such as cladocerans, where body growth was not signi cantly altered by arsenic (Hoang et al 2007). However, differences in mean length between individuals by season are minimal, compared with other studies where copepods showed a more signi cant difference in body size but without any pollutant agent (Cervantes-Martínez et al According to Fisher's principle, sex ratio (F:M) is expected to be 1:1 in a natural environment or skewed to the sex in which the female invested least in the embryo phase (Hirst et al 2010).…”

Transcriptomic, biochemical and individual markers in transplanted Daphnia magna to characterize impacts in the field

“…Responses of the retinoic receptor RXR followed a distinct pattern being positively and negatively related with the above mentioned and other pollutants like caffeine and analgesic opiates. An excess of suspended solids, salt and of metals like Ni inhibits growth or/and reproduction in D. magna (Baillieul et al, 1996;Burton et al, 2005;Diamond et al, 1992;Hoang et al, 2007;Pane et al, 2004;Robinson et al, 2010). Psychiatric drugs such as selective serotonin re-uptake inhibitors are known to disrupt signaling gene pathways of molting, reproduction, sugar and amino acid metabolism at environmental relevant concentrations close to 1 μ/L (Campos et al, 2013).…”

Evidence of potential long term effects in (aquatic and terrestrial) invertebrates after short term pulsed exposure. Literature reviews on ecotoxicology of chemicals with special focus on plant protection products

“…Early life stage exposure to aqueous phase arsenic altered reproduction of D. magna exposed according to U.S. EPA methodology (U.S. EPA 2002, Hoang, et al 2007). Both 24-hour exposures of 4,000 and 5,000 µg/L and a 6-hour exposure to 6,000 µg/L arsenic to neonates…”

“…Additionally, the inclusion of recovery times of 24, 96, or 168 hours between a double-pulsed exposure of arsenic (6, 12, or 24 hour pulses of 3000ppm or 4000ppm, and 3, 6, or 9 hours of 5000ppm) had no ameliorating effect on the magnitude of response (Hoang, et al 2007). Hence, recovery from pulsed arsenic exposure is likely to require more time than recovery from other compounds.…”