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

doi:10.13745/j.esf.sf.2022.1.13

Abstract

Abstract:

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.

Key words: Dongsha Waters, subsea mound, deep-water corals, mobile coral, volcanism

CLC Number:

YAN Pin, WANG Yanlin, JIN Yongbin, ZHAO Meixia, ZHONG Guangjian. Deep-water coral of multiple benthal strategies discovered from mounds in Dongsha Waters, the South China Sea[J]. Earth Science Frontiers, 2022, 29(4): 202-210.

Figures/Tables 7

Fig.1 Bathymetric chart of the Dongsha Waters and locations of benthic sampling sites (basemap from [15])

Fig.2 Sub-bottom profiles LS5 (a) and SUB2502 (b) and multi-channel seismic profile DS84 (c), with subsea mounds indicated by arrows (water depths from two-way time-to-depth conversion using velocity of 1500 m/s)

Fig.3 Coral specimens from site #10 (water depth 666 m). (a) Collection of samples. (b1, b2) Madrepora oculata Linnaeus, 1758. (c1, c2) Madrepora oculata Linnaeus, 1758. (d1, d2) Madrepora oculata Linnaeus, 1758. (e) Bamboo coral. (f-h) Solenosmilia variabilis Duncan, 1873. (i1, i2) Javania insignis Duncan, 1876. (j1, j2) Caryophyllia horologium Cairns, 1977. (k1, k2) Anomocora fecunda Pourtalès, 1871. (l1, l2) Anomocora marchadi Chevalier, 1966. Scale bar 1 cm.

Fig.4 Coral specimens from site #5 (water depth 617 m). (a) Collection of samples. (b1, b2) Desmophyllum dianthus Esper, 1794, with bottom view in b2 showing attachment of specimen base to soft clastic sediment. (c1, c2) Flabellum pavoninum Lesson, 1831. (d1, d2) Dendrophyllia. (e) Flabellum sp. (f1, f2) Crispatotrochus sp. (g) unidentified. Scale bar 1 cm.

Fig.5 Coral specimens from site #4 (water depth 353 m). (a) Collection of samples. (b1, b2) Stephanophyllia fungulus Alcock, 1902. (c1, c2) Deltocyathus vaughani Yabe & Eguchi, 1937. (d1, d2) Australocyathus vincentinus Dennant, 1904. (e1, e2) Alatotrochus rubescens Moseley, 1876. (f1-f3) Tropidocyathus lessonii Michelin, 1842. (g1, g2) Cyathotrochus pileus Alcock, 1902. (h1, h2) Caryophyllia (Acanthocyathus) karubarica Cairns & Zibrowius, 1997. (i1, i2) Balanophyllia rediviva Moseley, 1880. (j1-j3) Rhombopsammia niphada owens, 1986. Scale bar 1 cm.

Fig.6 Coral specimens from waters near Weitan Bank. (a) Flagelligorgia gracilis Cairns, 2017. (b) Acanthogorgiidae. (c) Antipatharia. Scale bar 1 cm.

Table 1 Basic information of sampling sites

站位号	调查编号	水深	底质特征	珊瑚种类、丰度及其它生物
1	WT3	321 m	大块硬质碳酸盐岩	棘柳珊瑚、海葵及螺贝丰富
2	GT4B-4	335 m	大块硬质碳酸盐岩	鞭柳珊瑚丰富
3	MV70	338 m	大块硬质碳酸盐岩	角珊瑚丰富
4	W7	353 m	细粒生物碎屑	蕈/角杯珊瑚、网沙珊瑚丰富,固底珊瑚少量
5	202009DZ202	617 m	黑泥及细粒生物碎屑	叶片珊瑚、扇形珊瑚、角杯珊瑚丰富,固着珊瑚少量,螺贝丰富
6	S202-2013	960 m	钙质角砾及生物碎屑	丛珊瑚碎枝、蕈杯珊瑚、海绵碎片少量
7	MV8-201609	785 m	钙质结核及生物碎屑	木珊瑚、柳珊瑚少量,有孔虫丰富
8	MV10-201609	654 m	含泥级细粒生物碎屑	丛珊瑚枝、蕈杯珊瑚、海绵碎片少量,螺贝丰富
9	MZ8-2016	570 m	硬质碳酸盐岩	以多眼筛珊瑚、SV^*为主的多种丛珊瑚断枝丰富,螺贝少量
10	202009MV65	666 m	硬质碳酸盐岩	以多眼筛珊瑚、SV^*为主的多种丛珊瑚断枝丰富,螺贝少量

References 33

[1]	FREIWALD A, FOSSÅ J F, GREHAN A, et al. Cold-water coral reefs: out of sight: no longer out of mind[M]//UNEP-WCMC Biodiversity Series 22. Cambridge UK: Springer, 2004.
[2]	FREIWALD A, ROBERTS J M. Cold-water corals and ecosystems[J]. Crustaceana, 2005(10): 1279-1280.
[3]	ROBERTS J M, WHEELER A J, FREIWALD A. Reefs of the deep: the biology and geology of cold-water coral ecosystems[J]. Science, 2006, 312(5773): 543-547.
[4]	HOVLAND M. Do carbonate reefs form due to fluid seepage?[J]. Terra Nova, 1990, 2(1): 8-18.
[5]	HOVLAND M. Deep-water coral reefs, unique biodiversity hot-spots[M]. Dordrecht, Netherland. Springer. 2008.
[6]	FREIWALD A, ROGERS A, HALL-SPENCER J, et al. Global distribution of cold-water corals (version 5.0). Fifth update to the dataset in FREIWALD A, et al. (2004) by UNEP-WCMC, in collaboration with Andre Freiwald and John Guinotte[R]. Cambridge UK: UN Environment World Conservation Monitoring Centre, 2017.
[7]	邹仁林. 南海深水石珊瑚的研究: Ⅱ.种属记述及时空分布特点[J]. 热带海洋, 1988, (1): 74-83.
[8]	LATYPOV Y Y. A solitary deep-water corals of the scleractinian of the Vietnamese Shelf[J]. American Journal of Zoological Research, 2014, 2(1): 5-15.
[9]	LI J R, WANG P X. Discovery of deep-water bamboo coral forest in the South China Sea[J]. Scientific Reports, 2020, 9: 15453.
[10]	汪品先. 深水珊瑚林[J]. 地球科学进展, 2019, 34(12): 1222-1233. DOI
[11]	YAN P, WANG Y, LIU J, et al. Discovery of the southwest Dongsha Island mud volcanoes amid the northern margin of the South China Sea[J]. Marine and Petroleum Geology, 2017, 88(3): 858-870.
[12]	陈忠, 莫爱彬, 赵美霞, 等. 南海北部冷泉区深水珊瑚的发现及其特征[J]: 热带海洋学报. 2018, 37(1): 64-71.
[13]	DENG Y, CHEN F, LI N, et al. Cold-water corals in gas hydrate drilling cores from the South China Sea: occurrences, geochemical characteristics and their relationship to methane seepages[J]. Minerals, 2019, 9(12): 742.
[14]	阎贫, 王彦林, 于俊辉, 等. 东沙海区泥火山调查进展[J]. 热带海洋学报, 2021, 40(3): 34-43.
[15]	杨胜雄, 邱燕, 朱本铎, 等. 南海地质地球物理图系[M]. 天津: 中国航海图书出版社, 2015.
[16]	郝沪军, 施和生, 张向涛, 等. 潮汕坳陷中生界及其石油地质条件-基于LF35-1-1探索井钻探结果的讨论[J]. 中国海上油气, 2009, 21(3): 151-156.
[17]	张莉, 张光学, 王嘹亮, 等. 南海北部中生界分布及油气资源前景[M]. 北京: 地质出版社, 2014: 344-351.
[18]	阎贫, 王彦林, 郑红波, 等. 东沙群岛西南海区泥火山的地球物理特征[J]. 海洋学报, 2014, 36(7): 142-148.
[19]	YAN Y, LIAO J, YU J, et al. Velocity structure revealing a likely mud volcano off the Dongsha Island, the Northern South China Sea[J]. Energies, 2021, 15(1): 195( 1-17).
[20]	CAIRNS S D. CORDEIRO R T S. A new genus and species of golden coral (Anthozoa, Octocorallia, Chrysogorgiidae) from the Northwest Atlantic[J]. Zoo Keys, 2017(668): 1-10.
[21]	KITAHARA, M V, CAIRNS, S D. A revision of the genus Deltocyathus Milne Edwards & Haime, 1848 (Scleractinia, Caryophylliidae) from New Caledonia, with the description of a new species[J]. Zoosystema, 2009, 31(2): 233-248.
[22]	TAVIANI M, VERTINO A, ANGELETTI L, et al. Paleoecology of Mediterranean cold-water corals[M]//OREJAS C, JIMÉNEZ C. Mediterranean cold-water corals: past, present and future:understanding the deep-sea realms of coral. Cham: Springer International Publishing, 2019: 15-30.
[23]	KENYON N H, AKHMETZHANOV A M, WHEELER A J, et al. Giant carbonate mud mounds in the southern Rockall Trough[J]. Marine Geology, 2003, 195(1/2/3/4), 5-30.
[24]	DUINEVELD G C A, LAVALEYE M S S, BERGHUIS E M. Particle flux and food supply to a seamount coldwater coral community (Galicia Bank, NW Spain)[J]. Marine Ecology Progress Series. 2004, 277: 13-23
[25]	SANO Y, KINOSHITA N, KAGOSHIMA T, et al. Origin of methane-rich natural gas at the West Pacific convergent plate boundary[J]. Scientific Reports, 2017, 7: 15646.
[26]	罗中原, 李江涛, 贾国东. 深水珊瑚的食物及其地球化学意义[J]. 地球科学进展, 2019, 34(12): 1234-1242. DOI
[27]	MACKENZIE F T, LERMAN A. Isotopic fractionation of Carbon: inorganic and biological processes[M]//Carbon in the geobiosphere—Earth’s outer shell (2nd). Dordrecht: Springer, 2006: 165-191.
[28]	RINCÓN-TOMÁS B, DUDA J P, SOMOZA L, et al. Cold-water corals and hydrocarbon-rich seepage in Pompeia Province (Gulf of Cádiz): living on the edge[J]. Biogeosciences, 2019, 16(7): 1607-1627.
[29]	冯志强, 冯文科, 薛万俊, 等. 南海北部地质灾害及海底工程地质条件评价[M]. 南京: 河海大学出版社, 1996: 98.
[30]	LÜDMANN T, WONG H K, BERGLAR K. Upward flow of North Pacific Deep Water in the northern South China Sea as deduced from the occurrence of drift sediments[J]. Geophysical Research Letters, 2005, 32: L05614.
[31]	HUBBARD J A E B. Diaseris distorta, an “Acrobatic” Coral[J]. Nature, 1972, 236(5348): 457-459.
[32]	尹希杰, 周怀阳, 杨群慧, 等. 南海北部甲烷渗漏活动存在的证据: 近底层海水甲烷高浓度异常[J]. 海洋学报, 2008, 30(6): 69-75.
[33]	郝海燕, 赵静, 刘海生, 等. 海洋沉积物中芳香烃预测中国南海潮汕坳陷油气圈闭方法[J]. 石油学报, 2018, 39(5): 528-540. DOI