Comparing 10‐ and 28‐Day Sediment Toxicity and Bioaccumulation of Fluoranthene in Hyalella azteca Using Passive Sampling Techniques

Abstract

Understanding the changes in the temporal and spatial concentrations of chemical substances in sediment toxicity tests facilitates interpretation of their toxicity and accumulation in benthic organisms because benthic organisms are affected by chemicals via multiple exposure pathways. However, such investigations using chronic sediment toxicity tests have rarely been performed. To examine the concentration profiles of a hydrophobic organic chemical using chronic spiked-sediment toxicity tests, we performed 28-day sediment toxicity tests of fluoranthene with a freshwater amphipod, Hyalella azteca, using a semiflow-through system and compared the results with those of 10-day tests. In these experiments, we measured various types of fluoranthene concentrations over the test periods: total dissolved (C diss ) and freely dissolved (C free ) concentrations in overlying water and porewater as well as sediment concentrations. We also examined which concentration correlated with the amphipod bioconcentration factor (BCF). We found that both overlying water and porewater C free did not differ significantly on days 10 and 28. Sediment concentrations remained almost stable for 28 days, whereas C diss in overlying water varied temporally. These results suggest that the 28-day test provides almost constant concentrations of fluoranthene, particularly in porewater, even in a semi-flow-through system. In addition, the comparison of BCF of fluoranthene on day 10 in the present study with that obtained from water-only tests reported in the literature suggested that C free in pore water was the most representative indicator of bioaccumulation in H. azteca. Our findings support the possible use of a water-exchange system in chronic spiked-sediment toxicity tests of hydrophobic organic chemicals. However, further studies using sediments and chemicals with different properties are warranted to generalize the findings of the present study.

Influence of water exchange rates on toxicity and bioaccumulation of hydrophobic organic chemicals in sediment toxicity tests

“…These findings are consistent with our previous study on the semi flow-through spiked-sediment toxicity tests of BaP, fluoranthene, and chlorpyrifos with H. azteca . 6,38 Note that these results do not negate the role of sediment and DOC ingestion in the uptake of BaP by the amphipod, as C free,pore -based BCF did not exactly match that in water-only tests. As shown recently, DOC ingestion can lead to higher bioaccumulation of BaP in H. azteca .…”

“…To measure the actual bulk C free,over more accurately, it is recommended to place the fibers away from the sediment surface, as suggested in our recent study. 38…”

“…Since this 7 cm fiber for C free,over was partially exposed to the sediment–water interface where C free was higher than that in the bulk overlying water, the measured C free,over would be somewhat higher than the actual bulk C free,over . 38 On Day 10, the PDMS fibers were retrieved from the overlying water and sediment, wiped with moist lint-free tissues (Kimwipes, Kimberly-Clark), transferred to a 1.5 mL vial and extracted with 1 mL of acetonitrile. In our previous study, we confirmed that 10 days are enough to achieve equilibrium for the three PAHs between PDMS fibers and water.…”

Improving Sediment Toxicity Testing for Very Hydrophobic Chemicals: Part 2—Exposure Duration, Upper Limit Test Concentrations, and Distinguishing Actual Toxicity from Physical Effects

“…Considering their different physiologies and traits, this is not surprising; but the exact reason why VHOC concentrations in Hyalella lipid decrease to lower levels than in Lumbriculus is not clear. Recently, metabolism was suggested as an explanation for the observation that fluoranthene concentrations were lower in 28‐day‐ than in 10‐day‐exposed Hyalella (Nishimori et al, 2022). However, it should be noted that the present chemical set, for instance, also included HCB, which is not expected to be metabolized in Hyalella and Lumbriculus , but did yield the peak‐shaped uptake pattern.…”

A Review of Mechanistic Models for Predicting Adverse Effects in Sediment Toxicity Testing

“…In that study, the author's mechanistic analyses concluded exposures are dependent on contaminant hydrophobicity and bioavailability, the organism's life history and habitat, and sediment characteristics. Similarly, recent work by Hiki et al, (2021Hiki et al, ( , 2023 and Nishimori et al (2022) examined the toxicokinetics of contaminant exposures to organisms in standardized sediment toxicity tests with the freshwater epibenthic amphipod Hyalella azteca. These studies are examples of the high-quality investigations needed to better understand the temporal and spatial distribution of contaminants in sediment toxicity testing systems.…”