Marine ecosystems are generally expected to have bottom-heavy trophic structure (more plants than animals) due to size-based constraints arising from increased metabolic requirements and inefficient energy transfer. However, size-based (allometric) approaches are often limited to confined trophic-level windows where energy transfer is predicted by size alone and are constrained to a balance between bottom-up and top-down control at steady state. In real food webs, energy flow is more complex and imbalances in top-down and bottom-up processes can also shape trophic structure. We expand the size-based theory to account for complex food webs and show that moderate levels of food web connectance allow for inverted trophic structure more often than predicted, especially in marine ecosystems. Trophic structure inversion occurs due to the incorporation of complex energy pathways and top-down effects on ecosystems. Our results suggest that marine ecosystems should be top-heavy, and observed bottom-heavy trophic structure may be a result of human defaunation of the ocean that has been more extreme than presently recognized.

中文翻译：

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食物网的复杂性削弱了对生命金字塔的大小限制

由于代谢需求增加和能量转移效率低下所产生的基于大小的限制，通常预计海洋生态系统具有底层重营养结构（植物多于动物）。然而，基于尺寸（异速生长）的方法通常仅限于有限的营养级窗口，其中能量转移仅通过尺寸预测，并且受限于稳态下自下而上和自上而下控制之间的平衡。在真正的食物网中，能量流动更为复杂，自上而下和自下而上过程中的不平衡也会影响营养结构。我们扩展了基于大小的理论以解释复杂的食物网，并表明中等水平的食物网连接允许比预测的更频繁地发生反向营养结构，尤其是在海洋生态系统中。由于复杂的能量途径的结合和对生态系统的自上而下的影响，发生了营养结构反转。我们的研究结果表明，海洋生态系统应该是头重脚轻的，观察到的底重营养结构可能是人类对海洋动物破坏的结果，这比目前认识到的更为极端。