Effects of <Emphasis Type="Italic">Urechis unicinctus</Emphasis> juveniles on chemical characteristics of organically contaminated coastal sediment |
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| Authors: | Kyoung Ho Kang Zhifeng Zhang Jae Min Kim Seung Chun Seon Mingyu Shao |
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| Institution: | 1. Department of Aquaculture, Chonnam National University, Yeosu 550-749, R. O. Korea
2. Laboratory of Marine Genetics and Breeding of Ministry of Education, Ocean University of China, Qingdao 266003, P. R. China |
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| Abstract: | Biological activities of marine benthos such as burrowing and feeding may change sediment characteristics. We conducted three
experiments to examine the potential of using juveniles of a spoon worm Urechis unicinctus to improve the quality of organically contaminated coastal sediment. Sediment samples were collected from a site that was
heavily contaminated with organic matter (Seonso) and two sites that were clean (Myo-do, Dolsan-do). Urechis juveniles, obtained by artificial fertilization and cultured in the laboratory, were introduced to the sediment (weight 3
kg, depth 10 cm) at a density of 500 individuals per aquarium (length 50 cm, width 35 cm, height 30 cm) (Experiment 1), or
at densities ranging from 100 to 900 individuals per beaker (Experiment 2). To examine how sediment contamination can be modified
by the effects of Urechis, 500 individuals (per aquarium) were exposed to the Seonso contaminated sediment that had been mixed with 0–100% clean sand
(Experiment 3). Each experiment lasted two months and sediment samples were collected every 15 d to determine the several
indexes of sediment quality, which included acid volatile sulfide (AVS), chemical oxygen demand (COD) and total ignition loss
(TIL). In Experiment 1, the existence of Urechis did not result in significant changes in quality indexes in the sediments collected from Myo-do, Dolsan-do. However, AVS,
COD and TIL of the Seonso sediment all decreased significantly after co-incubation with Urechis juveniles for 30 to 45 d. Experiment 2 showed that a density of at least 300 juveniles per beaker was necessary to significantly
reduce all three quality indexes, and the magnitude of reduction was positively correlated with juvenile density. Experiment
3 revealed that Urechis juveniles were effective in reducing the AVS, COD and TIL of the Seonso sediment that had been mixed with 60%, 80%, and 80%
of clean sand, respectively. The results of the present study therefore indicated that juveniles of this spoon worm have the
potential to be used to improve the quality of organically contaminated sediment in coastal waters. |
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| Keywords: | Urechis unicinctus sediment improvement acid volatile sulfide (AVS) chemical oxygen demand (COD) total igni- tion loss (TIL) |
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