變換菜單: 浮游生物食物網內跨食階攝食行為強度對體型分布頻譜之影響

Changing the menu: Effect of omnivory on the structure of size spectrum in a plankton foodweb

何珮綺(Pei-Chi Ho)

指導教授 ： 謝志豪

共同指導教授 ： 三木健

國立臺灣大學/理學院/海洋研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.03057

摘要

生物的族群大小與其體型的關係可由體型大小頻譜來表示。過去採樣研究的結果揭露體型大小頻譜與群集內掠食行為及環境因子的相關性: 較平緩的頻譜斜率對應群集內較大的掠食者-獵物體型比與較佳的能量傳遞效率，以及營養較為豐富的系統。我們使用包含營養鹽-浮游植物-浮游動物的常微分模型進行模擬，測試食物網中掠食者對獵物體型選擇的廣度(雜食性)與環境營養供給量對群集動態與體型大小頻譜的影響。營養供給與雜食強度的增加皆會使此浮游生物系統不穩定，且浮游生物族群波動幅對會隨此兩項參數增加而放大。使用長期平均族群密度所建立的頻譜斜率大致隨掠食者雜食性與營養供給量而增加，而這主要是最高階掠食者因獲得較多能量，族群量上升造成。但是使用平均族群密度建構的頻譜斜率其斜率值範圍比實際水域環境觀察到的結果小得多。若我們觀察震盪系統內不同時間點的頻譜斜率，我們可以發現較平緩的斜率值。族群波動可解釋為何我們會在實際系統中觀察到較平緩的頻譜斜率。我們同時也觀察頻譜斜率與三項水域中常測量之環境因子:營養鹽濃度、浮游植物濃度與總初級生產率的相關性。本模擬結果確定環境營養鹽濃度與頻譜斜率的正相關性，但頻譜斜率在類似的營養豐度下的變化頗大。如要觀察到頻譜斜率與營養鹽濃度的正相關性，有必要進行長期且頻繁的採樣研究。

關鍵字

體型頻譜 ； 雜食行為 ； 營養鹽供給 ； 營養鹽-浮游植物-浮游動物常微分模型

並列摘要

Size spectra link the relationship between population density and organism body size. Empirical research revealed the connections of size spectrum with community structures and environmental conditions: a shallower spectrum and larger predator-prey size ratio corresponds to higher biomass transfer efficiency, and nutrient-rich systems. In this research, I use a nutrient-phytoplankton-zooplankton model to study the effects of omnivory and nutrient supply on the dynamics of the plankton system and structure of size spectrum. The increase of omnivory strength and new nutrient flux both destabilize the system, and the fluctuation amplitude of plankton populations increases with these two factors. Generally speaking, increase of omnivory strength and nutrient supply makes spectral slope constructed from long-term average plankton populations shallower, due to the increase of top predator. However, the range of slopes is smaller than observed in empirical research. When we take snapshots of size spectra in fluctuating systems, a wide range of slope values is observed and the range of slopes is similar to field observation if the system fluctuates regularly. The fluctuation of population offers an explanation to shallower spectral slopes in a plankton system. We also study the relationship between spectral slope and three frequently measured environmental factors: nutrient concentration, phytoplankton biomass and gross primary production. The result exhibits that nutrient concentration does increase with spectral slope, but the value of slope under similar nutrient condition is substantial. Long-term and frequent sampling is suggested if we want to observe the positive correlation between spectral slope and nutrient concentration.

並列關鍵字

size spectrum ； omnivory behavior ； nutrient supply ； nutrient-phytoplankton-zooplankton ODE model

參考文獻

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