The effect of exposure route on the uptake and depuration of silver in the polychaete Capitella teleta

Magnus Elias Fundal

Studenteropgave: Speciale

Abstrakt

Deposit feeders are exposed to contaminants both via water and via sediment. This study examines the importance of uptake route to the ability of an organism to clear itself of a contaminant. Groups of Capitella teleta were exposed to silver via either water only (WO) or as sediment-bound only (SBO) for 6 days, then allowed up to 10 days to depurate in either seawater or sediment. To examine the effect of feeding on depuration rate, water-exposed worms would depurate in water (WW) or sediment (WS), and sediment-exposed worms would depurate in either sediment (SS) or water (SW). Nominal concentrations were 25 μg Ag L⁻¹ in water, 100 μg Ag (g DW)⁻¹ in sediment, while measured concentrations were (6.80 ± 0.36) μg Ag L⁻¹in water, (87.2 ± 1.9) μg Ag (g DW)⁻¹ in the sediment (mean ± standard error of mean). After 6 days of depuration, body burdens measured via atomic absorption spectroscopy were (4.19 ± 3.05) μg Ag (g DW)⁻¹ for WO, ( 0.5973) μg Ag (g DW) for SBO. In general, the body burdens in SBO worms were at noise level, and WO body burdens were orders of magnitude lower than those of Ramskov et al. (2015). To estimate uptake and depuration rates, silver loads were log-transformed, and a weighted linear regression was carried out on WW and WS in isolation or together. while the depuration constant of WS was higher (kd = 0.16 for WS versus kd = 0.11 for WW), they were not statistically different (ANCOVA p>0.7). A joint regression with WW and WS gave kd = −0.10432. (p=0.022). growth rates were estimated from the projected area and length of worms on a set of photos, but with a high imprecision. At a glance, WS seemed to depurate faster than WW, but this difference was not significant (ANCOVA p>0.6). Viewed together, a log-linear regression gave WW and WS a depuration rate of (10.4 ± 0.042) day⁻¹, and a mean growth rate of (−0.012 ± 0.055) day⁻¹ for There was a significant effect of spiking on ingestion rate measured via production of fecal pellets (p=0.58). In SBO, there was an effect of spiking on Specific growth rate (SGR) (p=0.0275), but the same was not true for WO (p=0.48). The negative growth rate of non-feeding worms was significantly higher during depuration than during exposure (p=0.02), while the positive growth rate of feeding worms was lower, but not significantly so (p=0.07). During depuration, all treatments except SS seemed to decrease in body volume, possibly due to mortality of worms, which showed no clear pattern. Sediment-exposed worms had very low body burdens compared to similar experi- ments. This suggests that the sediment-bound silver was not sufficiently bioavailable, possibly because of sulfide in the sediment. It is of note that some studies using sediment-bound silver had acidified the stock solution before mixing it with the sediment, which could improve bioavailability.

UddannelserMiljøbiologi, (Bachelor/kandidatuddannelse) Kandidat
SprogEngelsk
Udgivelsesdato28 sep. 2016
Antal sider42
VejledereHenriette Selck & Gary Thomas Banta