Nineteenth-century collapse of a benthic marine ecosystem on the open continental shelf
Nineteenth-century collapse of a benthic marine ecosystem on the open continental shelf
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十九世纪开放大陆架底栖海洋生态系统的崩溃
DOI：
10.1098/rspb.2017.0328
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
S. Kidwell
中科院分区：
文献类型：
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作者：
A. Tomašovỳch;S. Kidwell
开放大陆架的软沉积物海底是地球上最不为人所知的生物群落之一，尽管它具有高度的多样性和对渔业和生物地球化学循环的重要性。在现在泥泞的南加州大陆大陆架上，大量的脚底悬浮物捕食的陆生臂足类动物（Laqueus）和扇贝的死壳揭示了最近，以前没有人怀疑的广泛的近海贝壳-砾石生态系统的灭绝，显然是由人为淤积引起的。以前生活在陆架中部和外部镶嵌着各种营养丰富的泥块的附生上系动物种群，今天被限制在陆架边缘的岩石海底和近海岛屿的砂质陆架上。对190具腕足动物死亡壳的地质年代测定表明：(1)在过去的100年里，大陆陆架上没有产生过壳；(2)它们的壳产量在19世纪急剧下降；(3)它们以前至少连续存在了4年。这种迅速（少于或等于100年）和彻底的损失足以代表生态系统的崩溃，与19世纪冲积平原土地利用的加剧，特别是牲畜放牧的加剧相吻合。到20世纪城市化、气候变暖、海底捕捞和科学调查开始时，灭绝已经完成。这种滤食性动物的消失以及沉积物和碎屑食性动物新的空间同质性和优势将通过减少栖息地异质性和海水过滤来改变生态系统功能。这一发现证明了这种地质方法对近期生态转变的力量，也极大地增加了归因于淤积负面影响的空间范围，并表明它在其他地方的大陆架上被认为是沿海土地利用的遗产。
The soft-sediment seafloor of the open continental shelf is among the least-known biomes on Earth, despite its high diversity and importance to fisheries and biogeochemical cycling. Abundant dead shells of epifaunal suspension-feeding terebratulid brachiopods (Laqueus) and scallops on the now-muddy mainland continental shelf of southern California reveal the recent, previously unsuspected extirpation of an extensive offshore shell-gravel ecosystem, evidently driven by anthropogenic siltation. Living populations of attached epifauna, which formerly existed in a middle- and outer-shelf mosaic with patches of trophically diverse muds, are restricted today to rocky seafloor along the shelf edge and to the sandier shelves of offshore islands. Geological age-dating of 190 dead brachiopod shells shows that (i) no shells have been produced on the mainland shelf within the last 100 years, (ii) their shell production declined steeply during the nineteenth century, and (iii) they had formerly been present continuously for at least 4 kyr. This loss, sufficiently rapid (less than or equal to 100 years) and thorough to represent an ecosystem collapse, coincides with intensification of alluvial-plain land use in the nineteenth century, particularly livestock grazing. Extirpation was complete by the start of twentieth-century urbanization, warming, bottom fishing and scientific surveys. The loss of this filter-feeding fauna and the new spatial homogeneity and dominance of deposit- and detritus-feeders would have altered ecosystem functioning by reducing habitat heterogeneity and seawater filtering. This discovery, attesting to the power of this geological approach to recent ecological transitions, also strongly increases the spatial scope attributable to the negative effects of siltation, and suggests that it has been under-recognized on continental shelves elsewhere as a legacy of coastal land use.