本研究利用環境DNA偵測技術，希望藉由實驗瞭解從小盾鱧(Channa micropeltes )身上脫落的eDNA粒徑分布與小盾鱧eDNA在靜止水體中的移動情形，小盾鱧喜好棲息於靜水域，對環境的適應能力強，現今已侵入台灣南部的許多水庫以及河川，造成水域生態系統的負面影響，也減少許多經濟魚種的數量，因此選擇小盾鱧作為本研究的目標魚種。
粒徑分析的結果顯示，大約有半數的小盾鱧eDNA存在於粒徑介於1.0 ~ 10 μm的顆粒之中。沉降實驗的結果指出經過2小時之後，六個不同的的採樣水深在不同的實驗設計之下都有檢測出小盾鱧eDNA濃度，所以推論小盾鱧eDNA具有懸浮顆粒的性質。其中，比較無加入砂粒與加入細砂粒的實驗組，前者在水深較深處的小盾鱧eDNA濃度明顯高出許多，推論小盾鱧eDNA可能會附著於細砂粒，與細砂粒共同沉降。此外推求無加入砂粒組別的小盾鱧eDNA濃度，結果指出越接近表層水，理論濃度被高估的情況越明顯，推斷是因為含有小盾鱧eDNA顆粒的粒徑越小，降解的速率越快，至於水深較深的點位之預測結果較為準確。
沉降實驗與擴散實驗的結果指出，小盾鱧eDNA在靜水環境中的垂直方向(向下)移動能力明顯優於水平方向的移動能力，因此將小盾鱧eDNA假設為懸浮顆粒。若要藉由水樣之中eDNA濃度隨著時間的改變以探討eDNA的降解作用，盡可能將eDNA在水中的深度也一併納入考量。另外，由於eDNA會附著於細砂粒，所以在靜水環境之中檢測目標魚種的eDNA濃度，可以先判斷水體的濁度，再選擇採樣的位置較合適。

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.

1. Ahrens, J. P. Simple equations to calculate fall velocity and sediment scale parameter. Journal of waterway, port, coastal, and ocean engineering, 129(3), 146-150. (2003)
2. Alldredge, A. L., & Gotschalk, C. C. Direct observations of the mass flocculation of diatom blooms: characteristics, settling velocities and formation of diatom aggregates. Deep Sea Research Part A. Oceanographic Research Papers, 36(2), 159-171. (1989)
3. Asper, V. L. Measuring the flux and sinking speed of marine snow aggregates. Deep Sea Research Part A. Oceanographic Research Papers, 34(1), 1-17. (1987)
4. Barnes, M. A., Turner, C. R., Jerde, C. L., Renshaw, M. A., Chadderton, W. L., & Lodge, D. M. Environmental conditions influence eDNA persistence in aquatic systems. Environmental science & technology, 48(3), 1819-1827. (2014)
5. Barnes, M. A., & Turner, C. R. The ecology of environmental DNA and implications for conservation genetics. Conservation Genetics, 17(1), 1-17. (2016)
6. Bogich, T. L., Liebhold, A. M., & Shea, K. To sample or eradicate? A cost minimization model for monitoring and managing an invasive species. Journal of Applied Ecology, 45(4), 1134-1142. (2008)
7. Bohmann, K., Evans, A., Gilbert, M. T. P., Carvalho, G. R., Creer, S., Knapp, M., ... & De Bruyn, M. Environmental DNA for wildlife biology and biodiversity monitoring. Trends in Ecology & Evolution, 29(6), 358-367. (2014)
8. Boothroyd, M., Mandrak, N. E., Fox, M., & Wilson, C. C. Environmental DNA (eDNA) detection and habitat occupancy of threatened spotted gar (Lepisosteus oculatus). Aquatic Conservation: Marine and Freshwater Ecosystems, 26(6), 1107-1119. (2016)
9. Calvignac‐Spencer, S., Merkel, K., Kutzner, N., Kühl, H., Boesch, C., Kappeler, P. M., ... & Leendertz, F. H. Carrion fly‐derived DNA as a tool for comprehensive and cost‐effective assessment of mammalian biodiversity. Molecular ecology, 22(4), 915-924. (2013)
10. Clusa, L., Ardura, A., Gower, F., Miralles, L., Tsartsianidou, V., Zaiko, A., & Garcia-Vazquez, E. An Easy Phylogenetically Informative Method to Trace the Globally Invasive Potamopyrgus Mud Snail from River’s eDNA. PloS one, 11(10), e0162899. (2016)
11. Craig, D. L., Fallowfield, H. J., & Cromar, N. J. Comparison of decay rates of faecal indicator organisms in recreational coastal water and sediment. Water Science and Technology: Water Supply, 2(3), 131-138. (2002)
12. Egan, S. P., Barnes, M. A., Hwang, C. T., Mahon, A. R., Feder, J. L., Ruggiero, S. T., ... & Lodge, D. M. Rapid invasive species detection by combining environmental DNA with light transmission spectroscopy. Conservation Letters, 6(6), 402-409. (2013)
13. Eichmiller, J. J., Miller, L. M., & Sorensen, P. W. Optimizing techniques to capture and extract environmental DNA for detection and quantification of fish. Molecular ecology resources, 16(1), 56-68. (2016a)
14. Eichmiller, J. J., Best, S. E., & Sorensen, P. W. Effects of temperature and trophic state on degradation of environmental DNA in lake water. Environmental science & technology, 50(4), 1859-1867. (2016b)
15. Ficetola, G. F., Miaud, C., Pompanon, F., & Taberlet, P. Species detection using environmental DNA from water samples. Biology letters, 4(4), 423-425. (2008)
16. Foote, A. D., Thomsen, P. F., Sveegaard, S., Wahlberg, M., Kielgast, J., Kyhn, L. A., ... & Gilbert, M. T. P. Investigating the potential use of environmental DNA (eDNA) for genetic monitoring of marine mammals. PloS one, 7(8), e41781. (2012)
17. Goldberg, C. S., Pilliod, D. S., Arkle, R. S., & Waits, L. P. Molecular detection of vertebrates in stream water: a demonstration using Rocky Mountain tailed frogs and Idaho giant salamanders. PloS one, 6(7), e22746. (2011)
18. Goldberg, C. S., Turner, C. R., Deiner, K., Klymus, K. E., Thomsen, P. F., Murphy, M. A., ... & Laramie, M. B. Critical considerations for the application of environmental DNA methods to detect aquatic species. Methods in Ecology and Evolution, 7(11), 1299-1307. (2016)
19. Jane, S. F., Wilcox, T. M., McKelvey, K. S., Young, M. K., Schwartz, M. K., Lowe, W. H., ... & Whiteley, A. R. Distance, flow and PCR inhibition: eDNA dynamics in two headwater streams. Molecular Ecology Resources, 15(1), 216-227. (2015)
20. Jeng, H. C., England , A. J., & Bradford , H. B. Indicator organisms associated with stormwater suspended particles and estuarine sediment. Journal of Environmental Science and Health, 40(4), 779-791. (2005)
21. Johnson, C. P., Li, X., & Logan, B. E. Settling velocities of fractal aggregates. Environmental science & technology, 30(6), 1911-1918. (1996)
22. Klymus, K. E., Richter, C. A., Chapman, D. C., & Paukert, C. Quantification of eDNA shedding rates from invasive bighead carp Hypophthalmichthys nobilis and silver carp Hypophthalmichthys molitrix. Biological Conservation, 183, 77-84. (2015)
23. Kraemer, F. B., Chagas, C. I., Cosentino, D. J., & Garibaldi, L. A. Adsorption and affinity of Escherichia coli to different aggregate sizes of a silty clay soil. International Journal of Sediment Research, 28(4), 535-543. (2013)
24. Lacoursière‐Roussel, A., Rosabal, M., & Bernatchez, L. Estimating fish abundance and biomass from eDNA concentrations: variability among capture methods and environmental conditions. Molecular ecology resources, 16(6), 1401-1414. (2016)
25. Lee, P. G., & Ng, P. K. L. The snakehead fishes of the Indo-Malayan Region. Nature Malaysiana, 16(4), 113-129. (1991)
26. Li, F., Mahon, A. R., Barnes, M. A., Feder, J., Lodge, D. M., Hwang, C. T., ... & Tanner, C. E. Quantitative and rapid DNA detection by laser transmission spectroscopy. PLoS One, 6(12), e29224. (2011)
27. Maggi, F. The settling velocity of mineral, biomineral, and biological particles and aggregates in water. Journal of Geophysical Research: Oceans, 118(4), 2118-2132. (2013)
28. Mahon, A. R., Barnes, M. A., Li, F., Egan, S. P., Tanner, C. E., Ruggiero, S. T., ... & Lodge, D. M. DNA-based species detection capabilities using laser transmission spectroscopy. Journal of the Royal Society Interface, 10(78), rsif20120637. (2012).
29. Maruyama, A., Nakamura, K., Yamanaka, H., Kondoh, M., & Minamoto, T. The release rate of environmental DNA from juvenile and adult fish. PLoS One, 9(12), e114639. (2014)
30. Matsui, K., Honjo, M., & Kawabata, Z. Estimation of the fate of dissolved DNA in thermally stratified lake water from the stability of exogenous plasmid DNA. Aquatic Microbial Ecology, 26(1), 95-102. (2001)
31. Medema, G. J., Schets, F. M., Teunis, P. F. M., & Havelaar, A. H. Sedimentation of Free and AttachedCryptosporidium Oocysts and Giardia Cysts in Water. Applied and Environmental Microbiology, 64(11), 4460-4466. (1998)
32. Merkes, C. M., McCalla, S. G., Jensen, N. R., Gaikowski, M. P., & Amberg, J. J. Persistence of DNA in carcasses, slime and avian feces may affect interpretation of environmental DNA data. PloS one, 9(11), e113346. (2014)
33. Nichols, R. V., KOeNIGSSON, H. E. L. E. N. A., Danell, K., & SPONG, G. Browsed twig environmental DNA: diagnostic PCR to identify ungulate species. Molecular ecology resources, 12(6), 983-989. (2012)
34. Ogram, A., Sayler, G. S., & Barkay, T. The extraction and purification of microbial DNA from sediments. Journal of microbiological methods, 7(2-3), 57-66. (1987)
35. Olson, Z. H., Briggler, J. T., & Williams, R. N. An eDNA approach to detect eastern hellbenders (Cryptobranchus a. alleganiensis) using samples of water. Wildlife Research, 39(7), 629-636. (2012)
36. Piaggio, A. J., Engeman, R. M., Hopken, M. W., Humphrey, J. S., Keacher, K. L., Bruce, W. E., & Avery, M. L. Detecting an elusive invasive species: a diagnostic PCR to detect Burmese python in Florida waters and an assessment of persistence of environmental DNA. Molecular Ecology Resources, 14(2), 374-380. (2014)
37. Pilliod, D. S., Goldberg, C. S., Arkle, R. S., & Waits, L. P. Estimating occupancy and abundance of stream amphibians using environmental DNA from filtered water samples. Canadian Journal of Fisheries and Aquatic Sciences, 70(8), 1123-1130. (2013)
38. Pilliod, D. S., Goldberg, C. S., Arkle, R. S., & Waits, L. P. Factors influencing detection of eDNA from a stream‐dwelling amphibian. Molecular Ecology Resources, 14(1), 109-116. (2014)
39. Rees, H. C., Bishop, K., Middleditch, D. J., Patmore, J. R., Maddison, B. C., & Gough, K. C. The application of eDNA for monitoring of the Great Crested Newt in the UK. Ecology and evolution, 4(21), 4023-4032. (2014)
40. Renshaw, M. A., Olds, B. P., Jerde, C. L., McVeigh, M. M., & Lodge, D. M. The room temperature preservation of filtered environmental DNA samples and assimilation into a phenol–chloroform–isoamyl alcohol DNA extraction. Molecular ecology resources, 15(1), 168-176. (2015)
41. Rosin, P., Rammler, E. The laws governing the fineness of powdered coal. J. Inst. Fuel., 7, 29-36. (1933)
42. Rubey, W. W. Settling velocity of gravel, sand, and silt particles. American Journal of Science, 25(148), 325-338. (1933)
43. Shanks, A. L., & Trent, J. D. Marine snow: sinking rates and potential role in vertical flux. Deep Sea Research Part A. Oceanographic Research Papers, 27(2), 137-143. (1980)
44. Simon, M., Grossart, H. P., Schweitzer, B., & Ploug, H. Microbial ecology of organic aggregates in aquatic ecosystems. Aquatic Microbial Ecology, 28(2), 175-211. (2002)
45. Strickler, K. M., Fremier, A. K., & Goldberg, C. S. Quantifying effects of UV-B, temperature, and pH on eDNA degradation in aquatic microcosms. Biological Conservation, 183, 85-92. (2015)
46. Taberlet, P., Coissac, E., Hajibabaei, M., & Rieseberg, L. H. Environmental DNA. Molecular ecology, 21(8), 1789-1793. (2012)
47. Takahara, T., Minamoto, T., Yamanaka, H., Doi, H., & Kawabata, Z. I. Estimation of fish biomass using environmental DNA. PloS one, 7(4), e35868. (2012)
48. Takahara, T., Minamoto, T., & Doi, H. Using environmental DNA to estimate the distribution of an invasive fish species in ponds. PloS one, 8(2), e56584. (2013)
49. Thomsen, P., Kielgast, J. O. S., Iversen, L. L., Wiuf, C., Rasmussen, M., Gilbert, M. T. P., ... & Willerslev, E. Monitoring endangered freshwater biodiversity using environmental DNA. Molecular ecology, 21(11), 2565-2573. (2012)
50. Turner, C. R., Barnes, M. A., Xu, C. C., Jones, S. E., Jerde, C. L., & Lodge, D. M. Particle size distribution and optimal capture of aqueous macrobial eDNA. Methods in Ecology and Evolution, 5(7), 676-684. (2014)
51. Turner, C. R., Uy, K. L., & Everhart, R. C. Fish environmental DNA is more concentrated in aquatic sediments than surface water. Biological Conservation, 183, 93-102. (2015)
52. Wang, A., Ye, X., & Chen, J. Observations and analyses of floc size and floc settling velocity in coastal salt marsh of Luoyuan Bay, Fujian Province, China. Acta Oceanologica Sinica, 29(3), 116-126. (2010)
53. Wilcox, T. M., McKelvey, K. S., Young, M. K., Lowe, W. H., & Schwartz, M. K. Environmental DNA particle size distribution from Brook Trout (Salvelinus fontinalis). Conservation genetics resources, 7(3), 639-641. (2015)
54. Wu, R. M., Lee, D. J., Waite, T. D., & Guan, J. Multilevel structure of sludge flocs. Journal of Colloid and Interface Science, 252(2), 383-392. (2002)
55. Xu, C. C., Yen, I. J., Bowman, D., & Turner, C. R. Spider web DNA: a new spin on noninvasive genetics of predator and prey. PloS one, 10(11), e0142503. (2015)
56. Zobeck, T. M., Gill, T. E., & Popham, T. W. A two-parameter Weibull function to describe airborne dust particle size distributions. Earth Surface Processes and Landforms, 24(10), 943-955. (1999)
57. 侯晨昕，「建立一環境DNA偵測技術用於調查小盾鱧與環境參數之關係─以曾文水庫為例」，國立成功大學碩士論文，(2015)
58. 陳柳豪，「水文現象與環境參數影響eDNA偵測技術之探討」，國立成功大學碩士論文，(2016)
59. 高瑜苹，「以光學式濁度計探討不同混凝劑對含藻人工原水處理效果之研究」，國立聯合大學碩士論文，(2007)
60. 許盈松、蔡俊鋒、魏綺瑪、黃宏莆，「水庫泥沙濁度與濃度率定關係研究-以石門水庫為例」，農業工程學報，53(1)，62-71，(2007)
61. 經濟部水利署南區水資源局，「維持曾文水庫有效庫容之整體規劃─規劃報告」，經濟部水利署南區水資源局，(2014)