Biological responses to disturbance from simulated deep-sea polymetallic nodule mining

Commercial-scale mining for polymetallic nodules could have a major impact on the deep-sea environment, but the effects of these mining activities on deep-sea ecosystems are very poorly known. The first commercial test mining for polymetallic nodules was carried out in 1970. Since then a number of small-scale commercial test mining or scientific disturbance studies have been carried out. Here we evaluate changes in faunal densities and diversity of benthic communities measured in response to these 11 simulated or test nodule mining disturbances using meta-analysis techniques. We find that impacts are often severe immediately after mining, with major negative changes in density and diversity of most groups occurring. However, in some cases, the mobile fauna and small-sized fauna experienced less negative impacts over the longer term. At seven sites in the Pacific, multiple surveys assessed recovery in fauna over periods of up to 26 years. Almost all studies show some recovery in faunal density and diversity for meiofauna and mobile megafauna, often within one year. However, very few faunal groups return to baseline or control conditions after two decades. The effects of polymetallic nodule mining are likely to be long term. Our analyses show considerable negative biological effects of seafloor nodule mining, even at the small scale of test mining experiments, although there is variation in sensitivity amongst organisms of different sizes and functional groups, which have important implications for ecosystem responses. Unfortunately, many past studies have limitations that reduce their effectiveness in determining responses. We provide recommendations to improve future mining impact test studies. Further research to assess the effects of test-mining activities will inform ways to improve mining practices and guide effective environmental management of mining activities.

商业规模的多金属结核（polymetallic nodules）开采或对深海环境造成重大影响，但当前学界对这类采矿活动的深海生态效应认知仍极为匮乏。全球首次多金属结核商业试采矿活动于1970年开展。自此之后，多项小规模商业试采矿或科学扰动研究相继实施。本研究借助元分析（meta-analysis）技术，对11项模拟或实际结核采矿扰动实验中测得的底栖生物群落的动物密度与多样性变化进行了评估。研究结果显示，采矿活动结束后短期内影响往往较为严重，多数类群的密度与多样性均出现显著负向变化。但在部分情形下，移动性动物与小型动物群落在长期观测中受到的负面影响相对更弱。在太平洋的7个采样点，已有多项调查对最长达26年的动物群落恢复过程进行了监测。几乎所有研究均表明，小型底栖生物（meiofauna）与移动性大型底栖生物（megafauna）的密度和多样性在一年内即可出现一定程度的恢复。但历经二十年之后，几乎没有任何动物类群能够恢复至基线或对照样地的水平。多金属结核采矿的生态影响大概率具有长期性。本研究的分析结果表明，即便在小规模试采矿实验的尺度下，海底结核采矿也会造成显著的负面生物学效应；不过不同体型与功能群的生物对扰动的敏感性存在差异，这对生态系统的响应过程具有重要影响。遗憾的是，过往多数研究均存在一定局限，削弱了其在解析生态响应方面的有效性。本研究针对未来采矿影响实验研究的优化方向提出了相关建议。后续针对试采矿活动影响的评估研究，将为采矿作业的优化提供科学依据，并为采矿活动的有效环境管理提供指导。