植物性及動物性有機碎屑對於臺灣河口型及海岸型紅樹林的相對貢獻

Relative Contribution of Plant- and Animal-derived Detritus in Riverine and Fringe Mangroves in Taiwan

楊沛茌(Pei-Chih Yang)

指導教授 ： 任秀慧

國立臺灣大學/生物資源暨農學院/生物環境系統工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202100649

摘要

紅樹林生態系因位處河海接界處而受到上下游之影響，其健康狀況可作為評估整體生態系提供之經濟效益。紅樹林為異源生態系，其主要食物來源為植物性(落葉)及動物性有機碎屑(動物屍體)。生態系利用較多動物性碎屑時，其提供之經濟效益上升，然而前人研究鮮少著重於紅樹林食物來源貢獻度受氣候變遷及人類活動的影響。本研究於2019年夏季在臺灣選定四個紅樹林生態系橫跨亞熱帶及熱帶氣候，包含挖仔尾、客雅、芳苑、七股紅樹林生態系進行生物採集、環境調查、碳氮穩定同位素混合模型以瞭解食物網結構、自源性藻類及異源性植物性及動物性碎屑、細顆粒有機物質四項主要的食物來源對不同攝食功能群生物之貢獻度差異。藉由迴歸分析以找出影響生物間營養傳輸及食物來源貢獻程度差異的主要因子。本研究根據碳氮穩定同位素混合模型(MixSIAR)的分析結果顯示動物性有機碎屑(動物屍體)在紅樹林生態系中貢獻度極高、落葉及細顆粒有機物質之貢獻度小於動物性碎屑且其樣點間變動較小、藻類貢獻度於不同樣點間變動大。高級消費者於競爭壓力高之環境中由利用動物性碎屑為主轉而利用較多的植物性碎屑，且迴歸分析結果顯示水中營養鹽濃度(PO4-P, NO3-N)和植物性碎屑於高級消費者體內占比呈正相關(R2 = 0.43)；受潮汐影響程度不同造成食物來源貢獻程度於低潮差之紅樹林生態系有明顯差異，其迴歸分析結果顯示，動物性碎屑於高級消費者體內占比和海水低潮位呈正相關，和最高潮位及最大潮差呈負相關(R2 = 0.50)。由研究結果得知有機碎屑生產量及沉積量差異並非形塑臺灣紅樹林生態系食物來源貢獻程度之主要因子，而水體優養化及氣候變遷(海平面上升)造成紅樹林生態系提供之經濟效益降低因植物性碎屑貢獻度上升及動物性碎屑貢獻度下降。

關鍵字

紅樹林食物網 ； 植物性碎屑 ； 動物屍體 ； 氣候 ； 營養 ； 碳氮穩定同位素 ； 混合模型

並列摘要

Being as integration of marine and terrestrial conditions, the ecological conditions of mangroves have long been considered as an important indicator for economic support from upstream to downstream ecosystems. Major basal resources in mangrove ecosystems, as heterotrophic food webs, were plant- (leaf litter) and animal-derived (carrion) detritus. Mangrove ecosystems enhanced ecological conditions by utilizing more animal-derived detritus. Under effects of climate change and anthropogenic activities, there was lack of study on reaction of basal resources relative contribution in mangrove food webs. This study investigated the food web structure, and the contribution of four basal resources including autochthonous algae, and allochthonous plant- and animal-derived organic matters and fine particulate organic matter (FPOM) basal resources to trophic consumers and five major functional feeding groups in the four mangrove ecosystems including WZW, KY, FY and QG distributing from north to south Taiwan across subtropical and tropical climate during 2019. Carbon and nitrogen stable isotope analysis coupled with MixSIAR were used to study the trophic importance of the four study basal resources and PLS analysis was used to determine the influential factors controlling trophic interaction among consumers for different trophic level and factors shaping mangrove food web structure. Results showed that the relative contribution of animal-derived organic matters, i.e. carrion, was the highest, leaf litter and FPOM relative contribution was stable but less than carrion, algae relative contribution was highly site dependent according to carbon and nitrogen stable isotope analysis. Top predators under high competition stress in high-tide range mangroves shifted their basal resources utilization from animal-derived detritus to more plant-derived detritus, and the result of PLS regression showed that water nutrient quality (PO4-P, NO3-N) was positively related (R2 = 0.43) to relative contribution of plant-derived detritus to top predators. Different extent of tidal influences caused strong variation in the relative contribution of basal resources in low-tide range mangroves. Results of PLS regression showed the relative contribution of animal-derived detritus to top predators in low-tide range mangroves was positively related to min tide level and negatively related to max tide level and max tide range (R2 = 0.50). This study revealed that nutrient input and sedimentation effects were not major factors for characterizing the relative contribution of different basal resources in mangrove food webs in Taiwan. However, impacts of eutrophication and climate change (sea-level rise) reduced ecological services by increasing leaf litter relative contribution and decreasing carrion relative contribution in mangrove ecosystems.

並列關鍵字

Mangrove food web ； Plant detritus ； Carrion ； Climate ； Nutrients ； Carbon and nitrogen stable isotope ； MixSIAR

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