造礁珊瑚骨骼氮同位素研究进展

Research Progress on Nitrogen Isotope Study in Reef-building Coral Skeleton

造礁珊瑚这一生物碳酸岩作为珊瑚礁生态系统的主体,具有对环境变化十分敏感、文石骨骼年际生长纹层清晰、年生长率高、易于精准定年、能够可靠记录其生长环境变化等特点,是研究环境变化的重要载体之一。由于人类对沿海的过度开发,近几十年来,全球范围内的珊瑚在不断退化。氮作为营养元素之一,能够用作了解珊瑚生命生长活动的指标,氮同位素(δ^(15)N)能很好地反映氮源变化和氮的生物地球化学循环,如记录近岸氮排放和氮循环等。国内外已经发表了较多关于珊瑚骨骼δ^(15)N的研究,但尚缺少综述性文章。从氮源示踪、氮循环和骨骼δ^(15)N测试手段综述造礁珊瑚骨骼δ^(15)N的研究现状,认为目前多数研究集中在珊瑚记录氮源变化历史方面,且主要关注人为因素对珊瑚生态系统的影响。未来应该发挥珊瑚骨骼δ^(15)N示踪的能力,开展更多不同海域和不同时间尺度的珊瑚骨骼δ^(15)N研究,探索建立新的测试技术,结合其他地球化学指标以区分生理信号和环境信号的重叠。这对利用珊瑚骨骼δ^(15)N重建古海洋环境和研究现今的环境污染问题都有着重要意义。

Reef-building coral,as a biological carbonate and the main body of coral reef ecosystems,is sensitive to environmental changes,has a clear annual growth layer of aragonite skeleton,a large annual growth rate,is easy to date accurately,and can record changes in their growth environment reliably;hence,it is considered an essential carrier for studying environmental changes.Coral has been degraded worldwide in recent decades due to human overexploitation of the coast.Nitrogen is one of the major nutritional elements used to understand coral growth.Nitrogen isotopes can reflect variations in nitrogen sources and biogeochemical cycles,such as recording nearshore nitrogen loading and nitrogen cycles.Many studies on nitrogen isotopes in coral skeletons have been published worldwide;however,relevant reviews are still lacking.In this study,we focused on coral nitrogen source tracing,the nitrogen cycle,and nitrogen isotope analysis.Currently,most studies have been conducted on the history of variations in coral nitrogen sources and have mainly focused on the impact of human activities on coral ecosystems.In the future,coral skeleton δ^(15)N should be utilized to conduct more research on coral skeleton δ^(15)N in different seas and at different time scales and to explore new analytical techniques to distinguish the overlap of physiological and environmental signals in combination with other geochemical indicators,which is of great significance for the reconstruction of the paleoceanographic environment and research on current environmental pollution problems.