College of Life and Environmental Sciences, University of Exeter , Exeter EX4 4QD, United Kingdom.
Plymouth Marine Laboratory , Plymouth PL1 3DH, United Kingdom.
Environ Sci Technol. 2016 Mar 15;50(6):3239-46. doi: 10.1021/acs.est.5b05905. Epub 2016 Feb 23.
Plastic debris is a widespread contaminant, prevalent in aquatic ecosystems across the globe. Zooplankton readily ingest microscopic plastic (microplastic, < 1 mm), which are later egested within their faecal pellets. These pellets are a source of food for marine organisms, and contribute to the oceanic vertical flux of particulate organic matter as part of the biological pump. The effects of microplastics on faecal pellet properties are currently unknown. Here we test the hypotheses that (1) faecal pellets are a vector for transport of microplastics, (2) polystyrene microplastics can alter the properties and sinking rates of zooplankton egests and, (3) faecal pellets can facilitate the transfer of plastics to coprophagous biota. Following exposure to 20.6 μm polystyrene microplastics (1000 microplastics mL(-1)) and natural prey (∼1650 algae mL(-1)) the copepod Calanus helgolandicus egested faecal pellets with significantly (P < 0.001) reduced densities, a 2.25-fold reduction in sinking rates, and a higher propensity for fragmentation. We further show that microplastics, encapsulated within egests of the copepod Centropages typicus, could be transferred to C. helgolandicus via coprophagy. Our results support the proposal that sinking faecal matter represents a mechanism by which floating plastics can be vertically transported away from surface waters.
塑料碎片是一种广泛存在的污染物，普遍存在于全球的水生生态系统中。浮游动物很容易摄入微小的塑料（<1 毫米，微塑料），随后这些微塑料会随着粪便颗粒排出体外。这些颗粒是海洋生物的食物来源之一，并作为生物泵的一部分，促进海洋垂直输送颗粒有机物质。目前尚不清楚微塑料对粪便颗粒性质的影响。在这里，我们检验了以下假设：（1）粪便颗粒是微塑料运输的载体；（2）聚苯乙烯微塑料可以改变浮游动物排泄物的性质和沉降速率；（3）粪便颗粒可以促进塑料向食粪生物的转移。在暴露于 20.6 μm 的聚苯乙烯微塑料（1000 个微塑料 mL(-1)) 和天然猎物（~1650 个藻类 mL(-1)) 后，桡足类 Calanus helgolandicus 排出的粪便颗粒的密度显著降低（P < 0.001），沉降速率降低了 2.25 倍，并且更容易碎裂。我们进一步表明，被桡足类 Centropages typicus 排出的微塑料，可以通过食粪作用转移到 Calanus helgolandicus 体内。我们的研究结果支持这样的假设，即沉降的粪便物质是漂浮塑料从水面垂直输送的一种机制。
