Implications for the mesopelagic microbial gardening hypothesis as determined by experimental fragmentation of Antarctic krill faecal pellets

1. Detritivores need to upgrade their food to increase its nutritional value. One method is to fragment detritus promoting the colonisation­ of nutrient-rich microbes, which consumers then ingest along with the detritus; so-called microbial gardening. Observations and numerical models of the detritus-dominated ocean mesopelagic zone have suggested microbial gardening by zooplankton is a fundamental process in the ocean carbon cycle leading to increased respiration of carbon-rich detritus. However, no experimental evidence exists to demonstrate that microbial respiration rates are higher on recently fragmented sinking detrital particles.

2. Using aquaria-reared Antarctic krill faecal pellets we showed fragmentation increased microbial particulate organic carbon (POC) turnover by 1.8x, but only on brown faecal pellets, formed from the consumption of other pellets. Microbial POC turnover on un-and fragmented green faecal pellets, formed from consuming fresh phytoplankton, was equal. Thu...

1. 碎屑食性生物需对其食物进行提质，以提升食物的营养价值。其中一种手段为破碎碎屑，促进富营养微生物在碎屑表面定植，随后食腐生物会连同碎屑一同摄入这些微生物，该过程即所谓的微生物培育（microbial gardening）。针对以碎屑为核心的海洋中层带的观测与数值模型研究表明，浮游动物介导的微生物培育是海洋碳循环中的核心过程，可加速富碳碎屑的呼吸消耗。但目前尚无实验证据可证明，新近破碎的沉降碎屑颗粒上的微生物呼吸速率更高。
2. 本研究采用人工繁育的南极磷虾粪粒开展实验，结果显示：仅在由摄食其他粪粒形成的棕色粪粒上，破碎操作可使微生物介导的颗粒有机碳（particulate organic carbon）周转速率提升1.8倍；而对于由摄食新鲜浮游植物形成的绿色粪粒，无论是否经过破碎处理，其微生物POC周转速率均无显著差异。（原文后续内容截断）