耳石有機物穩定性碳氮同位素之生態意義

Ecological significance of carbon and nitrogen stable isotopes in otolith organic matter

彭裕揚(Yu-Yang Peng)

指導教授 ： 蕭仁傑

國立臺灣大學/理學院/海洋研究所/碩士(2021年)

https://doi.org/10.6342/NTU202104130

摘要

魚類代謝性組織的穩定性碳氮同位素已被廣泛運用於探討消費者在生態系中之食物來源與食階，但分析代謝性組織只適用於現生樣本，而生物體中非代謝性組織，例如魚類耳石則可以彌補此不足。有關魚類代謝性組職與耳石有機物穩定性碳氮同位素之關係之研究甚少，且此方面研究之結果存在許多分歧，因此擴展對於魚類代謝性組織與非代謝性組織穩定性碳氮同位素差異之理解實屬必要。本研究以桃園石門水庫 (鯁魚、唇䱻、鯽魚、筍殼魚)、新竹寶山第二水庫之魚種 (大頭鰱、鯽魚)以及養殖場之黃錫鯛、金目鱸、虹鱒以及大西洋鮭魚及野生之太平洋黑鮪作為實驗對象，取代謝性組織(肌肉)與胃內容物，經研磨後以元素分析儀連結穩定性同位素質譜儀(EA-IRMS)分析，而耳石取出後則先經鹽酸溶解後，再用Amicon Ultrafilter萃取其中有機物後再以EA-IRMS分析，並分別從各季節 ( 2、4、7、10月) 取各水庫之表層藻類及浮游動物量測其同位素變化。結果顯示絕大部分之魚種肌肉穩定氮同位素值均高於耳石有機物以及胃內容物的同位素值，且呈顯著性差異( one way ANOVA, p < 0.05 )；但是少部份資料包括鯁魚於4月份的數據在三者間無顯著差異、筍殼魚於10月份及小型黃錫鯛肌肉與胃內容物(或是餌料)無顯著差異、大西洋鮭魚及太平洋黑鮪耳石有機物及肌肉無顯著差異( one way ANOVA, p > 0.05 )。兩水庫之各魚種之碳同位素值大致上都呈現胃內容物的δ13C值顯著低於耳石有機物及肌肉，而耳石有機物與肌肉的δ13C值並無顯著性差異的情形，但黃錫鯛及金目鱸皆在肌肉有著最高的δ13C值，另一方面，虹鱒、大西洋鮭魚以及太平洋黑鮪卻顯示耳石有著最高的δ13C值。水庫中的浮游生物氮同位素在4月有較高值，推測與該時段浮游動物密度有關，而碳同位素則在7月有較高值，推測是因為光合作用旺盛的緣故，使得碳同位素的分化較小，而這也反映到了各水庫物種肌肉在7月時都有較高的碳同為素值。此研究對於代謝性組織與非代謝性組織穩定性碳氮同位素值之關係提供了更詳盡的資料，並希望能為日後的研究奠定一個更好的基礎。

關鍵字

穩定性碳氮同位素 ； 耳石有機物 ； 代謝性組織 ； 元素分析儀連結穩定性同位素質譜儀

並列摘要

Stable carbon (δ13C) and nitrogen (δ15N) isotopes of fish metabolic tissues have been widely used to explore the food sources of consumers in the ecosystem, but this method is mostly applied to living samples. There are very few studies to compare the δ13C and δ15N values between fish metabolic tissue and otoliths, and some of the results are controversial among the studies. Therefore, more studies to understand the relationship between fish metabolic tissues and non-metabolic tissues of δ13C and δ15N values is needed. In this study, fish species from Shimen Reservoir, Baoshan Second Reservoir, fish farms and wild fish were used as experimental samples. Metabolic tissues (muscles) and diet (stomach contents) were analyzed via Elemental Analyzer/Isotope Ratio Mass Spectrometry (EA-IRMS), and the proteins in the otoliths were extracted by the Amicon Ultrafilter and analyzed for the stable isotope compositions via EA-IRMS, The phytoplanktonand zooplankton were collected from the reservoir upper layers to measure their isotopic compositions. The results show that most of the fishes has a highest δ15N value in the muscle, and no significant difference between otolith and diet δ15N values. But the isotopic values of Cirrhinus molitorella collected in April show no significant difference among the three tissues, no significant difference of the δ15N values between muscle and stomach contents of Oxyeleotris marmorata collected in October, and the small sized Rhabdosargus sarba, while the otolith δ15N values were not significantly different from the values in the muscle of Atlantic salmon and Pacific Bluefin tuna. For most species, the δ13C values were not significantly different between the otolith and the muscle, which were both higher than the values in the diet. However, Rhabdosargus sarba and Lates calcarifer/Lates uwisara have the highest the δ13C values in muscle. On the other hand, rainbow trout, Atlantic salmon and Pacific Bluefin tuna have the highest δ13C value in the otoliths than the values in the muscle. The δ15N values of the plankton were highest in April, which is speculated to be related to the higher density of zooplankton during this period, while the carbon isotope has a higher value in July, which might be due to the and less isotopic fractionation during the strong photosynthesis. This study provides further insight into the relationship between the muscle and otoliths δ13C and δ15N values, and form a base for future researches.

並列關鍵字

Stable carbon and nitrogen isotopes ； otolith organic matter ； metabolic tissues ； Elemental analyzer-IRMS

參考文獻

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