Effects of plankton community structure on energy pathways and tropic efficiency (PATH)

生态学家目前面临的一个挑战是预测水生食物网底部的成分变化如何传播到更高的营养水平。上层营养层的能量或资源可用性受食物链长度和调节初级生产者向消费者转移能量速率的因素的制约。本项目旨在验证浮游植物群落结构和物种组成是中浮游动物能量和食物质量转移的关键调节因子的整体预测。我们将(i)测试浮游植物-浮游动物界面之间脂肪酸特异性δ13C同位素的稳定性，这将是作为营养相互作用生物标志物的重要要求；（ii）操纵中生态系统中天然微生物物种组成和细菌活性，测量桡足类动物的碳和营养转移效率及其与尾尾动物的相互作用。桡足类是碳和营养流动的关键环节，尾虫是丰富的滤食性生物，预计随着气候变暖而增加。利用脂肪酸特异性δ13C同位素生物标志物，从产量、膳食来源和营养转移来估计营养效率。提高对食物网结构变化如何影响浮游生物食物网中的能量和碳通量的理解将是重要的，因为这些过程对渔业和气候有着深远的影响。

A current challenge to ecologists is to predict how compositional shifts at the base of the aquatic food web propagate up to higher trophic levels. Energy or resource availability for upper trophic levels is governed by food-chain length and by factors that regulate the rate of energy transfer from primary producers to consumers. The goal of this project is to test the overall prediction that phytoplankton community structure and species composition are key regulators of energy and food quality transfer to mesozooplankton. We will (i) test the stability of fatty acid-specific δ13C isotope between the phytoplankton-zooplankton interface, which will be an important requirement as biomarker for trophic interactions, and (ii) manipulate natural microbial species composition and bacterial activity in mesocosms and measure carbon and nutritional transfer efficiency to copepods and their interactive effects with appendicularians. Copepods are a key link for carbon and nutritional flux and appendicularians are abundant filter-feeding organisms that are expected to increase with climate warming. Trophic efficiency will be estimated from production rates, dietary sources and nutritional transfer using combined fatty acid-specific δ13C isotope biomarkers. An improved understanding on how shifts in food-web structure affects energy and carbon flux through the plankton food web will be important because these processes have profound influence on fisheries and climate.