東海橈腳類群集生長速率與體型大小、溫度及食物可得性的關係︰生態代謝理論之檢驗

Abstract

動物性浮游生物在海洋系統中扮演重要的角色，了解其在自然環境中群集尺度的生長速率如何變動對於海洋系統在環境改變下如何變動的預測工作十分重要。本研究使用人造年級群方式檢驗東海區域橈腳類群集單位重量生長速率受溫度、體型大小及葉綠素濃度（作為食物參考量）的影響，其中特別檢驗生態代謝理論將橈腳類生長速率時空變異與溫度及體型大小的關係作連結、藉以描述橈腳類群集生長速率之假說。結果顯示本研究區域之橈腳類群集單位重量生長速率大致與生態代謝理論相符、與溫度正相關而與體型大小負相關；然而其體型大小的迴歸係數與理論預測值不符，我們發現此偏誤可能來自於食物可得性的影響。此外，溫度及體型大小的迴歸係數在不同的分類群之間亦不同。綜合結果顯示欲了解自然環境的橈腳類生長速率應考慮食物受限及分類群差異的影響，而生態代謝理論衍生預測所受到的影響則有賴未來之深入探討。

Zooplankton play an essential role in marine food webs, and understanding how community-level growth rates of zooplankton vary in the field is critical for predicting how marine ecosystem function may vary in the face of environmental changes. Here, we used the artificial cohort method to examine the effects of temperature, body size, and chlorophyll concentration (a proxy for food) on weight-specific growth rates for copepod communities in the East China Sea. Specifically, we tested the hypothesis that copepod community growth rates can be described by the metabolic theory of ecology (MTE), linking spatio-temporal variation of copepod growth rate with temperature and their body size. Our results generally agree with predictions made by the MTE and demonstrate that weight-specific growth rates of copepod communities in our study area are positively related with temperature and negatively related to body size. However, the regression coefficients of body size do not approach the theoretical predictions. Furthermore, we find that the deviation from the MTE predictions may be partly attributed to the effect of food availability (which is not explicitly accounted for by the MTE). In addition, significant difference in the coefficients of temperature and body size exists among taxonomic groups. Our results suggest that considering the effects of food limitation and taxonomy is necessary to better understand copepod growth rates under in situ conditions, and such effects on the MTE-based prediction needs further investigation.