Developing rainbow trout were chronically exposed to silver (as AgNO3) from fertilization to swim-up, in moderately hard water (120 mg CaCO3l-1) in the presence and absence of an additional 12 mg C/L of dissolved organic carbon (DOC, as humic acid, Aldrich). Nominal silver concentrations were 0, 0.1 and 10 μg l-1 total silver in a flow-through set-up maintained at 12°C. The objectives of the study were to investigate the possible protective effects of DOC on growth, mortality, time to hatch and swim-up, and sublethal ionoregulatory disturbances during chronic exposure to ionic silver. Throughout development, there was a large increase in % daily mortality at 10 μgl-1 total silver (in the absence of DOC), that was associated with an ionoregulatory disturbance, in particular a 35% reduction in whole body Na+ just prior to hatch. At nominal 10 μgl-1 total silver, the presence of additional DOC (reducing dissolved silver to 4.7±0.3 μg l-1) resulted in a significant reduction in % daily mortality up to hatch, demonstrating a protective effect of DOC. Interestingly, DOC did not appear to mitigate the ionoregulatory disturbance, with the exception of whole body [Cl-] on day 44 of exposure. Exposure to 0.1 μgl-1 total silver (in the absence of DOC) resulted in a statistically significant reduction in growth, and DOC did not prevent an ionoregulatory disturbance [based upon (Jin Na+), whole body Na+,K+ ATPase activity and whole body (Na+)] at this silver concentration relative to controls+DOC. DOC exerted a direct effect on growth and ionoregulatory development that complicates interpretation of the data, however, these data indicate that protective effects of DOC (in the form of Aldrich humic acid) during chronic silver exposure appear to be less than that observed during acute exposure. The ultimate goal of this and future studies is to develop a model that can predict chronic toxicity on a site-specific basis, taking into account protective effects of various ligands present in different waters, as is presently being employed for some metals during acute exposure.
|Number of pages||13|
|Journal||Comparative Biochemistry and Physiology - C Toxicology and Pharmacology|
|State||Published - Sep 1 2002|
- Dissolved organic matter (carbon)
- Oncorhynchus mykiss
ASJC Scopus subject areas
- Health, Toxicology and Mutagenesis