National Oceanography Centre, University of Southampton Waterfront Campus, Southampton, UK.
Glob Chang Biol. 2017 Sep;23(9):3554-3566. doi: 10.1111/gcb.13680. Epub 2017 Apr 25.
Deep-water benthic communities in the ocean are almost wholly dependent on near-surface pelagic ecosystems for their supply of energy and material resources. Primary production in sunlit surface waters is channelled through complex food webs that extensively recycle organic material, but lose a fraction as particulate organic carbon (POC) that sinks into the ocean interior. This exported production is further rarefied by microbial breakdown in the abyssal ocean, but a residual ultimately drives diverse assemblages of seafloor heterotrophs. Advances have led to an understanding of the importance of size (body mass) in structuring these communities. Here we force a size-resolved benthic biomass model, BORIS, using seafloor POC flux from a coupled ocean-biogeochemistry model, NEMO-MEDUSA, to investigate global patterns in benthic biomass. BORIS resolves 16 size classes of metazoans, successively doubling in mass from approximately 1 μg to 28 mg. Simulations find a wide range of seasonal responses to differing patterns of POC forcing, with both a decline in seasonal variability, and an increase in peak lag times with increasing body size. However, the dominant factor for modelled benthic communities is the integrated magnitude of POC reaching the seafloor rather than its seasonal pattern. Scenarios of POC forcing under climate change and ocean acidification are then applied to investigate how benthic communities may change under different future conditions. Against a backdrop of falling surface primary production (-6.1%), and driven by changes in pelagic remineralization with depth, results show that while benthic communities in shallow seas generally show higher biomass in a warmed world (+3.2%), deep-sea communities experience a substantial decline (-32%) under a high greenhouse gas emissions scenario. Our results underscore the importance for benthic ecology of reducing uncertainty in the magnitude and seasonality of seafloor POC fluxes, as well as the importance of studying a broader range of seafloor environments for future model development.
海洋中的深海底栖生物群落几乎完全依赖于近表层浮游生态系统来提供能量和物质资源。阳光照射的水面的初级生产力通过复杂的食物网进行传递，这些食物网广泛地回收有机物质，但会有一小部分作为颗粒有机碳（POC）下沉到海洋内部。这种输出的生产力在深海中进一步被微生物分解，但最终仍有一部分会驱动海底异养生物群落的多样化。研究进展使人们认识到大小（体重）在构建这些群落结构中的重要性。在这里，我们使用耦合海洋生物地球化学模型 NEMO-MEDUSA 中的海底 POC 通量来驱动一个基于大小的海底生物量模型 BORIS，以研究全球海底生物量的模式。BORIS 解析了 16 个大小类别的后生动物，质量依次从大约 1μg 增加到 28mg，增加了一倍。模拟结果发现，POC 强迫的模式有很大的季节性响应范围，季节性变化减小，峰值滞后时间随身体尺寸增加而增加。然而，对于模型化的底栖群落，主导因素是到达海底的 POC 的综合量，而不是其季节性模式。然后，应用气候变化和海洋酸化下的 POC 强迫情景来研究底栖群落在不同未来条件下可能发生的变化。在表面初级生产力下降（-6.1%）的背景下，并且受浮游再矿化深度变化的驱动，结果表明，尽管在变暖的世界中，浅海的底栖群落通常表现出更高的生物量（+3.2%），但在高温室气体排放情景下，深海群落的生物量会大幅下降（-32%）。我们的研究结果强调了减少海底 POC 通量的幅度和季节性不确定性对底栖生态学的重要性，以及为未来模型开发研究更广泛的海底环境的重要性。
