An F-Ratio Model for Pelagic Marine Ecosystem

本研究将建立一个简单的生态系统模型，该模型将考虑在稳定状态和非稳定状态条件下观测到的中上层海洋生态系统的f比率。该模型的中心假设如下：(1)生产由单一营养物控制，该营养物的身份由浮游植物群落的营养需求和外来营养输入系统的比例决定。(2)浮游植物群落的大小谱是f比值的重要决定因素。大细胞与高f比相关联，小细胞与低f比相关联。(3)海洋中上层生态系统自然地向稳定性最大化的状态演化。迄今为止进行的工作表明，最大的稳定性与低f比率有关，即在0.05 - 0.1范围内。由于在稳态条件下，大细胞浮游植物总是以较低的相对生长速度生长，而小细胞浮游植物则以较高的相对生长速度生长，因此预计营养脉冲将使f比向更大的值移动。这项研究的主要长期目标是发展一个简单的f比率模型，该模型可以嵌入到更大的海洋-大气模型中，以解释来自于光带的有机碳的产生和输出。这项工作的第二个目标是发展一个理论框架，以协调各种测量远洋海洋生态系统的生产力和周转，即总光合作用和净光合作用产生颗粒碳之间的差异。

This research will develop a simple ecosystem model which will account for observed f ratios in pelagic marine ecosystems during both steady state and non steady state conditions. The central hypotheses of the model are as follows: (1) Production is controlled by a single nutrient, the identity of which is determined by the nutritional requirements of the phytoplankton community and the ratio of allochthonous nutrient inputs to the system. (2) The size spectrum of the phytoplankton community is a critical determinant of the f ratio. Large cells are associated with a high f ratio, and small cells are associated with a low f ratio. (3) Marine pelagic ecosystems naturally evolve toward a condition in which stability is maximized. Work carried out to date indicates that maximum stability is associated with low f ratios, i.e. in the range 0.05 0.1. Nutrient pulses are expected to shift the f ratio to larger values because under steady state conditions the large celled phytoplankton are always growing at a low relative growth rate, and the small celled phytoplankton are growing at a high relative growth rate. The principal long term goal of this research is the development of a simple model of the f ratio which can be embedded into much larger ocean-atmosphere models to explain the production and export of organic carbon from the euphotic zone. A secondary goal of this work is the development of a theoretical framework with which to reconcile various measures of the productivity and turnover of pelagic marine ecosystems, i.e., differences between gross photosynthesis and net photosynthetic production of particulate carbon.