东沙海区海丘发现多底栖方式深水珊瑚

东沙岛周围海区发育众多深水(200~2 000 m)海丘,其中一些显示了明显的泥火山活动特征。近年的取样调查在多个底质差异明显的海丘都发现了非常丰富的深水珊瑚。为什么这些海丘上深水珊瑚兴盛尚不清楚。根据样品形态分析,初步识别的珊瑚既有以基座紧密固着于碳酸盐岩结核硬底的Madrepora oculate(多眼筛孔珊瑚)、Lochmaeotrochus(灌丛珊瑚)、Enallopsammia(突出海沙珊瑚)、Solenosmilia variabilis、Dendrophyllia(树珊瑚)、 Bamboo Coral (竹节珊瑚)、Golden Gorgonians (金柳珊瑚),还新发现有以鸭蹼状凹凸不平形底壳贴附于海底砂泥级生物碎屑的Desmophyllum dianthus(葵珊瑚)和尖底浅植于碎屑沉积中的Flabellum(扇珊瑚)、Crispatotrochus(卷轮珊瑚)、Balanophyllia(栎珊瑚),还有饼形、杯形能在软质海底缓慢自由移动的Fungiacyathus(蕈杯珊瑚)、Deltocyathusi(角杯珊瑚),指示在底质硬度及海流强度迥异的东沙海丘环境中有多种属珊瑚生长。大量具有机动性的深水珊瑚栖居于弱水动力海底,应更多依赖于栖居地本地而非海流带来的丰富食物,意味着东沙海区的泥火山活动泄漏的烃类流体可能是深水珊瑚食物的主要来源。泥火山的流体活动与珊瑚的兴盛可能具有相互指示意义。

Deep-water coral of multiple benthal strategies discovered from mounds in Dongsha Waters,the South China Sea

The Dongsha Waters surrounding the Dongsha Island, northern South China Sea hosts populous deep-water mounds (200-2000 m), likely of mud volcanic origin. In recent years from a dozen dredging expeditions to many such mounds, skeletal as well as living deep-water corals have been collected in large quantity (~1000), yet the cause of such coral flourishment is not known. In terms of their life strategies judging by morphology, the corals included the common immobile ones which attached with their base steadfastly to hard carbonate-nodules (Madrepora oculate, Lochmaeotrochus, Enallopsammia, Solenosmilia variabilis, Dendrophyllia, Bamboo Coral and Golden Gorgonians), the ones that weakly attached with duck-webbed uneven base (Desmophyllum dianthus) to or rooted with conic base (Flabellum, Crispatotrochus and Balanophyllia) onto sandy-muddy biogenic clastics on the seafloor, as well as the newly discovered, mobile epifauna (Fungiacyathus and Deltocyathus vaughani). The co-occurrence of various corals of diverse life strategies reflected widely variable benthic environments—from hard to soft substrates, and from strong to weak bottom currents. As these mobile, weakly attached corals thrive on mounds with weak bottom current, they may take sufficient nutrients from local geofluids rather than relying on nutrients transported by current. This implies that hydrocarbon leaked from local mud volcanoes may be the main feeder for the deep-water corals. Thus mud volcanoes and deep-water corals may be mutually dicative.