Data_Sheet_6_Functional Pattern of Benthic Epifauna in the Chukchi Borderland, Arctic Deep Sea.CSV

Assessment of Arctic deep-sea ecosystem functioning is currently an urgent task considering that ongoing sea-ice reduction opens opportunities for resource exploitation of yet understudied deep-sea regions. We used Biological Trait Analysis to evaluate ecosystem functioning and test if common paradigms for deep-sea fauna apply to benthic epifauna of the deep-sea Arctic Chukchi Borderland (CBL). We also investigated the influence of environmental factors on the functional structure of the epifauna. The analysis was performed for 106 taxa collected with a beam trawl and a Remotely Operated Vehicle from 486 to 2610 m depth. The most common trait modalities were small-medium size, mobile, benthic direct and lecithotrophic larval development, and predatory feeding, which mostly supports the current view of epifauna in the global deep sea. Functional composition of epifauna differed between two depth strata (486–1059 m and 1882–2610 m), with depth and sediment carbon content explaining most of the functional variability. Proportional abundances of the modalities free-living, swimming, suspension feeders, opportunists/scavengers, internal fertilization and globulose were higher at deep stations. Functional redundancy (FR) was also higher there compared to the mid-depth stations, suggesting adaptation of fauna to the more homogeneous deep environment by fewer and shared traits. Mid-depth stations represented higher functional variability in terms of both trait modality composition and functional diversity, indicating more variable resource use in the more heterogeneous habitat. Food input correlated positively with the proportional abundance of the modalities tube-dwelling, sessile and deposit feeding. Areas with drop stones were associated with higher proportional abundance of the modalities attached, upright, and predators. Comparatively low FR may render the heterogeneous mid-depth area of the CBL vulnerable to disturbance through the risk of loss of functions. Across the study area, high occurrence of taxa with low dispersal ability among adult and larval life stages may prevent rapid adaptation to changes, reduce ability to recolonize and escape perturbation.

鉴于海冰持续消退为此前尚未被充分研究的深海区域资源开发提供了契机，当前评估北极深海生态系统功能已是一项紧迫任务。我们采用生物学性状分析（Biological Trait Analysis）对生态系统功能进行评估，并检验深海大型底栖动物的通用范式是否适用于北极楚科奇边缘地带（Chukchi Borderland, CBL）深海的底栖表生动物群落。此外，我们还探究了环境因子对表生动物功能结构的影响。本次分析针对486米至2610米水深范围内，通过桁拖网与遥控水下机器人（Remotely Operated Vehicle）采集的106个分类单元展开。最普遍的性状类型为中小型体型、移动型、底栖直接发育与卵黄营养型幼虫发育，以及捕食性摄食，这一结果大体支持全球深海表生动物的现有认知。表生动物的功能组成在两个深度层（486–1059米与1882–2610米）间存在显著差异，水深与沉积物碳含量解释了大部分功能变异。在较深站位，自由生活、游泳型、悬浮摄食者、机会主义者/食腐者、体内受精以及球形体型这些性状类型的相对丰度更高。相较于中层站位，较深站位的功能冗余度（Functional Redundancy, FR）也更高，这表明大型底栖动物通过更少且共有的性状来适应更为均质化的深海环境。中层站位在性状类型组成与功能多样性两方面均表现出更高的功能变异，这意味着在异质性更强的生境中，生物对资源的利用方式更为多样。食物输入与管栖、固着以及沉积摄食这些性状类型的相对丰度呈正相关。存在坠石的区域，附着型、直立型以及捕食者这些性状类型的相对丰度更高。相对较低的功能冗余度可能使得楚科奇边缘地带异质性较强的中层区域面临功能丧失的风险，进而易受干扰影响。在整个研究区域内，成虫与幼虫阶段扩散能力较弱的分类单元占比偏高，这可能会阻碍其对环境变化的快速适应，降低其重新定植与躲避扰动的能力。