Foraging, feeding and reproduction on silica substrate increases the toxicity of waterborne zinc to the estuarine epibenthic amphipod Melita plumulosa

Publisher:
John Wiley & Sons
Publication Type:
Journal Article
Citation:
Environmental Toxicology and Chemistry, 2011, 30 (7), pp. 1649 - 1658
Issue Date:
2011-01
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Artificial substrates consisting of fine milled silica with or without a-cellulose were evaluated for their capacity to support survival, growth, and fecundity in the amphipod Melita plumulosa. There were no significant differences in the survival and fecundity of adult amphipods maintained for up to 13 d on natural sediment, silica-only, or silica/a-cellulose substrate when fed two algal foods, Sera® micron and Rotiselco®-ALG. However, growth among juveniles maintained on the silica/a-cellulose mixture was significantly inhibited over 14 d compared with natural sediment. Addition of a microencapsulated shrimp feed, Frippak®, to the algal foods improved juvenile growth over 28 d but still did not match the nutritive value of natural sediment. Fine silica without cellulose was subsequently used in acute and reproductive toxicity tests with waterborne zinc. With food, a 10-d median lethal concentration (LC50) of 140?µg Zn/L and a 10-d no-effect concentration (NEC) of 80?µg Zn/L were obtained for juvenile survival on silica. In contrast, a 10-d LC50 of 200?µg Zn/L and a 10-d NEC of 180?µg Zn/L were obtained for juveniles in water-only exposures. Similarly, exposure of adult females to Zn without food on silica compared with water-only exposures gave 10-d LC50s of 380 and 490?µg Zn/L and 10-d NECs of 130 and 370?µg Zn/L, respectively. The reproduction toxicity test indicated significant adult mortality at 92?µg Zn/L and significantly reduced fecundity at 22?µg Zn/L. We surmised that the toxicity of waterborne zinc to M. plumulosa increased when maintained on nutrient-depleted silica compared with water-only exposure because of increased energy expended through foraging, in concert with the likely increased exposure to Zn via the digestive tract and the gills
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