CESAM - Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Campus Universitário de Santiago 3810-193, Aveiro, Portugal.
CESAM - Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Campus Universitário de Santiago 3810-193, Aveiro, Portugal.
Ecotoxicol Environ Saf. 2021 Jan 1;207:111375. doi: 10.1016/j.ecoenv.2020.111375. Epub 2020 Sep 25.
Freshwater sediments are a repository of microplastics (MPs) resulting from inland anthropogenic activities. Benthic invertebrates, particularly endobenthic sediment-ingesting species such as the annelid Lumbriculus variegatus (blackworm), are commonly found in contaminated sediments where they likely find and ingest MPs. In the present study, L. variegatus was exposed to concentrations between 0.51 and 20 g kg dry sediment of four size-classes of irregularly-shaped polyethylene MPs (PE-MPs; size-class A: 32-63, B: 63-125, C: 125-250 and D: 250-500 μm) for 48 h to assess their sub-cellular responses to particles ingested, and for 28 days to determine chronic effects on worm's reproduction and biomass. After the short-term exposure (48 h), number of PE-MPs in blackworms' gut were related to MPs concentration in the sediment. In general, PE-MPs ingestion by blackworms induced depletion of their energy reserves (e.g., sugars in all size classes and lipids in the size-classes of PE-MPs > 125 μm), concomitant with the activation of antioxidant and detoxification mechanisms (increased level of total glutathione in all size-classes, and increased glutathione-S-transferase activity in PE-MPs > 250 μm), preventing lipid peroxidation. In addition, it was observed a reduction of aerobic energy production (decreased activity of the electron transport system) and a slight increase in neurotransmission (cholinesterase activity). After a long-term exposure (28 d), the presence and ingestion of PE-MPs did not affect reproduction and biomass of L. variegatus. The activation and efficiency of the antioxidant and detoxification mechanisms allied with the anatomy and physiology of L. variegatus, its feeding strategy and potentially dynamic ingestion/egestion capacity seem to be key features preventing MP deleterious effects under short- and chronic-exposures. Considering the MPs levels reported for freshwater sediments, and despite evidence of MPs ingestion and some sub-organismal effects, our results suggest no adverse impacts of PE-MPs contamination on L. variegatus populations fitness. This study applies an integrative approach in which data concerning the ingestion of different sized MPs and subsequent sub-cellular and apical responses are delivered, raising knowledge on endobenthic invertebrates' strategies to potentially overcome MP toxicity in field contaminated sites.
淡水沉积物是内陆人为活动产生的微塑料 (MPs) 的储存库。底栖无脊椎动物，特别是像环节动物颤蚓 (Lumbriculus variegatus，黑蚯蚓) 这样的内栖性摄食沉积物的物种，通常在受污染的沉积物中被发现，它们在那里可能会发现并摄取 MPs。在本研究中，颤蚓被暴露于四种不同形状的聚乙烯 MPs（PE-MPs；A 尺寸级：32-63μm、B 尺寸级：63-125μm、C 尺寸级：125-250μm 和 D 尺寸级：250-500μm）的浓度范围为 0.51 至 20gkg 干沉积物中 48 小时，以评估它们对摄取颗粒的亚细胞反应，并在 28 天内确定对蠕虫繁殖和生物量的慢性影响。在短期暴露（48 小时）后，黑蚯蚓肠道中的 PE-MPs 数量与沉积物中的 MPs 浓度有关。一般来说，黑蚯蚓摄取 PE-MPs 会耗尽其能量储备（例如，所有尺寸级别的糖和大于 125μm 的 PE-MPs 尺寸级别的脂质），同时激活抗氧化和解毒机制（所有尺寸级别的总谷胱甘肽水平增加，以及大于 250μm 的 PE-MPs 尺寸级别的谷胱甘肽-S-转移酶活性增加），防止脂质过氧化。此外，还观察到有氧能量产生减少（电子传递系统活性降低）和神经传递略有增加（乙酰胆碱酯酶活性增加）。经过长期暴露（28 天）后，PE-MPs 的存在和摄取并不影响颤蚓的繁殖和生物量。抗氧化和解毒机制的激活和效率，以及颤蚓的解剖和生理学、摄食策略以及潜在的动态摄取/排泄能力，似乎是防止 MPs 在短期和慢性暴露下产生有害影响的关键特征。考虑到淡水沉积物中报道的 MPs 水平，尽管有证据表明摄取了 MPs 并产生了一些亚器官效应，但我们的研究结果表明，PE-MPs 污染对颤蚓种群适应性没有不利影响。本研究采用了一种综合方法，提供了关于摄取不同大小 MPs 以及随后的亚细胞和顶端反应的数据，提高了对内栖无脊椎动物在受污染的野外场地中潜在克服 MPs 毒性的策略的认识。
