Purpose: The present study evaluated whether the environmental trace element, cadmium, could have bioaccumulation effects on both phytoplankton C. vulgaris and zooplankton D. pulex.
Methods: We developed an in vitro assay system to detect toxic compounds in the aquatic environment using the 5(superscript th) generation water flea (cladoceran) eggs. The eggs were placed in a culture medium containing nature-imitating water (hard water). Then, cadmium chloride was added at various doses in a series of experiments in which we performed acute toxicity tests for EC50 values, LC50 values, growth inhibition, accumulation of CdCl2 in the C. vulgaris and D. pulex. We then estimate the relationship among the test results.
Results: We found 24h-EC50 and 48h-EC50 of Cadmium chloride on D. pulex neonate to be 0.060 mg/L and 0.023 mg/L, respectively. The normal growth curve of Chlorella vulgaris showed that the growth rate increased with the concentration of the culture medium, and the growth rate was significantly better than that of the control group (p<0.05). On the other hand, the effects of CdCl2 on C. vulgaris showed that the growth rate decreased with the concentration of CdCl2, and was significantly less than the control group (p<0.05). The result showed that the 24h-LD50 and 48h-LD50 of CdCl2 adsorbed with C. vulgaris and feed with D. pulex were 0.038 mg/L and 0.030 mg/L, respectively.
Conclusion: From the results, we conclude that CdCl2 could be adsorbed by C. vulgaris which was consumed by the primary consumer D. pulex. The accumulation of CdCl2 is related to aquatic food relation. It can be inferred that the accumulation of CdCl2 is in D. pulex leads to hurt or death, depending on CdCl2 concentration. 目的：探討環境中微量鎘對於小球藻生長速率是否有影響，在小球藻吸附重金屬鎘後被圓水蚤食入後，是否會產生生物毒性累積的現象。
方法：採用已建立之研究生態毒理學模式，研究室自行培養五代以上之圓水蚤(Daphnia pulex)為測試生物，試驗之測試藥劑皆以仿自然水體溶液為稀釋水配製系列濃度測試溶液，於每次實驗前進行配製使用。檢驗重金屬鎘對小球藻及圓水蚤的毒性影響；包括試驗藥劑對圓水蚤急毒性試驗、對小球藻生長抑制現象，將吸附有試驗藥劑的小球藻餵食圓水蚤，觀察其間之相關情形，並計算試驗藥劑之半數影響濃度值(EC50 value)及半數致死濃度值(LC50 value)。
結果：氯化鎘對圓水蚤的急毒性24h-EC50值為0.060mg/L，48h-EC50值為0.023mg/L。小球藻的正常生長曲線試驗顯示，實驗組隨著培養液的濃度增加，生長速度增加，其成長情形較控制組顯著(P<0.05)。生長在氯化鎘序列濃度之小球藻，隨著藥劑濃度的增加，小球藻的生長速度逐漸緩慢；相較於控制組其生長速度明顯減少(P<0.05)；且生長於氯化鎘溶液中之小球藻生長數量明顯少於正常生長試驗的數量(P<0.05)。吸附有氯化鎘之小球藻餵食圓水蚤的試驗結果在24h-LD50的值為0.038mg/L，在48h-LD50的值為0.030mg/L。
結論：本研究證實小球藻對於重金屬鎘具有吸附作用，可經由生物攝食的關係，使重金屬鎘進入生物體內，並進一步造成生物的損害受傷甚至死亡的現象。推論：小球藻吸附重金屬鎘後被圓水蚤食入會造成傷害或死亡的現象。
