Megafaunal seafloor assemblages on the Monterey Fan in the NE Pacific (Station M, 4000 m depth) were studied between 2006–2018 using remotely operated vehicles (ROVs) as part of a continuing time-series study that began in 1989. Since 2006 we identified nearly 120,000 individual animals representing over 142 morphospecies, and observed continuous changes in the megafaunal assemblage. This study, which tracked variation in observed morphospecies over a 13-year period, is one of the most detailed long-term records of megafaunal change for abyssal depths. Our investigation shows that new variations continued to emerge, reinforcing the concept that the deep-sea is dynamic over short time scales, rather than static over long periods. Some species were uncommon, but later observed in high numbers, then decreased to very low or undetectable levels (e.g. Elpidia sp. A), while others (e.g. Psychropotes longicauda) exhibited a relatively persistent presence with less fluctuation in abundance. Decreasing total echinoderm density from 2013–2018 did not correspond with the continued occurrence of large episodic POC flux events between 2016–2018. This may be attributed to the quality of food supply arriving at the seafloor and the varied ability of organisms to utilize it. Long-term tracking (30 years) of 10 specific epibenthic echinoderm species originally quantified from camera-sled images shows a pattern of assemblage structure, perhaps returning toward the composition observed in the 1990s and early 2000s. Many questions remain as to how this abyssal site and others will change with continued, and potentially increasing, anthropogenic change in the upper ocean. For example, the marine heat anomaly known as the ‘Warm Blob’ may have influenced major ecological processes at the abyssal seafloor in terms of morphospecies and functional group composition due to changes in POC flux. The degree of dynamism continues to indicate that ad hoc or short-term investigations provide a limited perspective for assessing community structure in conservation or resource exploitation impact assessment studies in the deep sea.

作为自1989年开始的持续时间序列研究的一部分，在2006年至2018年之间，使用远程操作车辆（ROV）对东北太平洋蒙特利扇（M站，深度4000 m）上的巨型动物海底组件进行了研究。自2006年以来，我们确定了代表142种形态的近120,000只动物，观察到大型动物群不断变化。这项研究追踪了13年间观察到的形态学的变化，是深渊巨型动物群落变化的最详细的长期记录之一。我们的调查表明，新的变化继续出现，强化了这样一种观念，即深海在短期内是动态的，而不是长期内是静态的。一些物种不常见，但后来被大量观察，然后下降到非常低或不可检测的水平（例如Elpidia sp。A），而其他（例如Psychropotes longicauda））表现出相对持久的存在，丰度波动较小。2013-2018年间总棘皮动物密度的下降与2016-2018年间持续发生的大型情节性POC通量事件并不相符。这可能归因于到达海底的食物供应质量以及生物利用海底食物的能力各异。最初从照相机雪橇图像中量化的10种特定表皮棘皮动物物种的长期追踪（30年）显示出一种组装结构的模式，也许回到了1990年代和2000年代初期观察到的组成。关于这个深渊位置以及其他问题将如何随着上层海洋的持续不断且可能不断增加的人为变化而改变的问题仍然存在。例如，由于POC通量的变化，被称为“暖滴”的海洋热异常可能影响了深海海底的主要生态过程，其形态种类和功能基团组成。充满活力的程度继续表明，临时或短期调查为评估深海养护或资源开发影响评估研究中的社区结构提供了有限的视角。