面对来势汹汹的微塑料纤维污染，壳菜如何行动？

在全球的海洋中，从热闹的沿海城市到没有人类接触的偏远地区，人造微粒塑料到处可见。微粒塑料的影响非常广泛：它们是浮游生物食物，是细菌群落的增长土地，甚至能够改变能量和营养穿过海洋生态系统的方式。

这项研究的其中一位作者，来自Bigelow实验室的高级研究科学家Paty Matrai说：“你在沙滩上能看到明显的大块塑料，但是微粒塑料同样无处不在。我们迫切需要一些方式来精确测量它们在海洋中的数量。”

数量最多的微粒塑料是容易从毯子，衣服等物质中脱落的纤维。由于其尺寸甚小，连浮游生物都可以把微塑料纤维当食物。不过，到现在依然有极少的研究项目在关注这类海洋污染。Matrai女士与Bigelow实验室高级科学家David Fields以及来自Shaw机构的研究院进行合作，来调研海洋生物会对这些纤维做出什么样的反应。这些工作有助于我们了解微塑料如何从食物链底层网上传递。当动物吃塑料的时候，不仅它们自己的身体会受到影响，同时也会使得他们的捕猎者（包括人类）在身体内积累塑料。

Fields先生说，“我们知道贝类能吃微纤维，不过具体速率以及累积时间依然不确定。”通过一系列的实验，研究团队发现，大多数被壳菜吸进身内的纤维能够被粘液覆盖，快速排出。凭这个做法，它们可以高效率地去掉纤维而不用完全吸进身内。

不过，10条纤维里大概有一条会被壳菜完全吃进去，累积在其身体组织里。科学家们发现，把壳菜转移到清洁水中，可以使得他们把身体里大多数累积的纤维排掉。

Shaw机构海洋研究协调员和这项研究的带领作者Madelyn Woods说：“我们的微粒塑料工作是准确模拟物种的自然环境的实验室研究。对各个物种及其颗粒选择机制进行详细研究能帮助我们明白在更大的范围内，微粒塑料如何影响生态系统。”

这项研究的初期实验是把壳菜放在微纤维浓度与海洋一样的水里。不过，在检测这些条件对壳菜的影响的时候，研究院面领着很大的挑战：如何数纤维。大多数微塑料研究要么是用工作量特别大的做法，要么是把实验条件做得太夸张、不像真实环境，这些都有可能使得研究结果跑偏。为了更容易地数纤维，Matrai女士的团队利用FlowCam，即在Bigelow实验室研发出来的光学仪器。这个新做法大量扩展了未来做微粒塑料纤维未来的潜能。

Matrai女士说：“就是因为海洋很广阔，所以微粒塑料的浓度并不高。但是，我们还不知道它们到底有多大的影响。所以我们一定要依靠数据，才能做出充沛的决策。”

发布时间：2018年12月4日

来源：Bigelow海洋科学实验室

翻译：凯瑟琳·奥尔森

Human-made microplastics exist throughout the global ocean, from busy coastal areas to remote regions far from human habitation. They have myriad impacts: microplastics are eaten by tiny animals called zooplankton, play host to bacterial colonies, and can even change how energy and nutrients flow through ocean ecosystems.

"The big pieces of plastic you find on the beach are in your face, but microplastics are everywhere," said Bigelow Laboratory Senior Research Scientist Paty Matrai, one of the study's authors. "We desperately need ways to accurately and precisely measure their numbers in the ocean."

The most abundant type of microplastics are fibers, which shed readily from materials as common as carpets and fleece clothing, and whose small size makes them edible by marine life as small as zooplankton. However, few studies to date have focused on this type of ocean pollution. Matrai worked with Bigelow Laboratory Senior Research Scientist David Fields and researchers from the Shaw Institute to learn how marine animals handle fibers -- which has important implications for understanding how microplastics move up the food web. Plastic can both directly affect the animals that ingest it and accumulate in the animals that feed on them, including humans.

"We know that microfibers can be consumed by shellfish, but at what rate and how long they are retained by the animals remains unclear," Fields said. Through a series of laboratory experiments, the team found that the mussels quickly rejected most of the fibers they took up by coating them in mucus and expelling them. This method allowed them to efficiently rid themselves of some of the fibers without taking them fully into their bodies.

However, the mussels did ingest nearly one in 10 fibers, accumulating them in their body tissues. Moving those mussels to clean water, the scientists found, allowed them to flush most of the accumulated fibers from their bodies.

"Our work with microplastic fibers emphasizes the need for laboratory studies that accurately mimic an organism's natural environment," said Madelyn Woods, marine research coordinator at the Shaw Institute and lead author on the study. "Detailed studies of individual species and their mechanisms for particle selection will be important for understanding how microplastics affect ecosystems on a larger scale."

The primary experiments used for this research placed mussels into water containing fibers at levels equivalent to those in the ocean. However, measuring the effect of those conditions presented the researchers with a major challenge: how to count the tiny plastic fibers. Most other microplastic experiments have used methods that are exceedingly laborious or do not resemble natural conditions, potentially skewing results. Matrai's team used a FlowCam, an optical instrument originally developed at Bigelow Laboratory, to more easily enumerate the particles. Establishing this new method opens the door for future experiments into microplastic fibers.

"Because the ocean is so vast, microplastics aren't actually that concentrated," Matrai said. "But no one knows the full impact they have. The bottom line is, we need data to help us make informed decisions."