| Summary: | 碩士 === 國立成功大學 === 水利及海洋工程學系 === 105 === In this study, we try to understand the particle size distribution of eDNA and the movement of eDNA in static water environments for Channa micropeltes by using eDNA method. Our results showed that particle size of Channa micropeltes eDNA is most abundant from 1 to 10 μm. In sedimentation experiment, eDNA was detected in all water samples from six different water depths (0 to 1.5 m) after 2 hours from the time adding the water sample which contains eDNA into the surface water of the water column, so we infer that eDNA can be assumed as suspended particles. Besides, we detected higher eDNA concentration ratio in the deeper water samples when the fine sand (5 to 20 μm) was added into the water column. Therefore, we infer that eDNA can attach on the fine sand and settle down with the fine sand together. We also calculated the theoretical value of eDNA concentration when the sedimentation experiment was without adding sand. The results showed that the theoretical concentration is overestimated more obviously when the water depth is shallower. Therefore, we infer that there is a negative correlation between the degradation rate and the particle size of eDNA. We think the water depth is an important factor when using eDNA method to investigate biomass or degradation rate of eDNA. Besides, our results showed that eDNA can attach on the fine sand, so it is better to know the turbidity of water body before determining the water depth that we sample at in static water.
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