The influence of the biological pump on ocean chemistry: implications for long-term trends in marine redox chemistry, the global carbon cycle, and marine animal ecosystems.
The influence of the biological pump on ocean chemistry: implications for long-term trends in marine redox chemistry, the global carbon cycle, and marine animal ecosystems.
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DOI：
10.1111/gbi.12176
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发表时间：
2016-05
期刊：
影响因子：
3.7
通讯作者：
Payne JL
中科院分区：
文献类型：
--
作者：
Meyer KM;Ridgwell A;Payne JL
海洋表层有机物的净输出及其在深层的呼吸作用造成了营养物和氧气供应的垂直梯度，这在构建海洋生态系统方面发挥了主要作用。这种“生物泵”性质的变化被假设为海洋生态系统结构的重要变化，包括寒武纪大爆发。然而，生物泵行为的变化对海洋生物化学的影响仍然很难量化，阻止了对生物泵在地质时期的变化如何影响海洋化学，生物化学循环和生态系统结构的长期变化的任何详细探索。在这里，我们使用一个中等复杂性的三维地球系统模型来定量探索生物泵对海洋化学的影响。我们发现，当下沉的有机物的呼吸是有效的，由于较慢的下沉或较高的呼吸速率，缺氧往往是更普遍的，并发生在较浅的沃茨。因此，在大陆架环境中，南极洲底层水缺氧减少的趋势可以通过营养循环的空间动态变化来解释，而不是通过海洋磷酸盐库存的任何变化来解释。模型的结果进一步表明，浮游生物的流行海洋缺氧的下降，在一定程度上，是一个后果的进化较大的浮游植物，其中许多产生矿化测试。我们假设，更大的动物丰度和代谢需求的古生界的趋势是由货架环境中的氧气浓度增加，而不是由更大的食物（营养）的可用性。事实上，在我们的封闭系统模型中，低于现代的海洋磷酸盐库存无法解释古生代普遍存在的底层水缺氧。总的来说，这些模型模拟表明，海洋中光合作用和呼吸作用的空间分布变化对整个中生代地球系统的演化产生了一阶控制作用。
The net export of organic matter from the surface ocean and its respiration at depth create vertical gradients in nutrient and oxygen availability that play a primary role in structuring marine ecosystems. Changes in the properties of this ‘biological pump’ have been hypothesized to account for important shifts in marine ecosystem structure, including the Cambrian explosion. However, the influence of variation in the behavior of the biological pump on ocean biogeochemistry remains poorly quantified, preventing any detailed exploration of how changes in the biological pump over geological time may have shaped long‐term shifts in ocean chemistry, biogeochemical cycling, and ecosystem structure. Here, we use a 3‐dimensional Earth system model of intermediate complexity to quantitatively explore the effects of the biological pump on marine chemistry. We find that when respiration of sinking organic matter is efficient, due to slower sinking or higher respiration rates, anoxia tends to be more prevalent and to occur in shallower waters. Consequently, the Phanerozoic trend toward less bottom‐water anoxia in continental shelf settings can potentially be explained by a change in the spatial dynamics of nutrient cycling rather than by any change in the ocean phosphate inventory. The model results further suggest that the Phanerozoic decline in the prevalence ocean anoxia is, in part, a consequence of the evolution of larger phytoplankton, many of which produce mineralized tests. We hypothesize that the Phanerozoic trend toward greater animal abundance and metabolic demand was driven more by increased oxygen concentrations in shelf environments than by greater food (nutrient) availability. In fact, a lower‐than‐modern ocean phosphate inventory in our closed system model is unable to account for the Paleozoic prevalence of bottom‐water anoxia. Overall, these model simulations suggest that the changing spatial distribution of photosynthesis and respiration in the oceans has exerted a first‐order control on Earth system evolution across Phanerozoic time.
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