Wild Christian, Huettel Markus, Klueter Anke, Kremb Stephan G, Rasheed Mohammed Y M, Jørgensen Bo B
Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, D-28359 Bremen, Germany.
Nature. 2004 Mar 4;428(6978):66-70. doi: 10.1038/nature02344.
Zooxanthellae, endosymbiotic algae of reef-building corals, substantially contribute to the high gross primary production of coral reefs, but corals exude up to half of the carbon assimilated by their zooxanthellae as mucus. Here we show that released coral mucus efficiently traps organic matter from the water column and rapidly carries energy and nutrients to the reef lagoon sediment, which acts as a biocatalytic mineralizing filter. In the Great Barrier Reef, the dominant genus of hard corals, Acropora, exudes up to 4.8 litres of mucus per square metre of reef area per day. Between 56% and 80% of this mucus dissolves in the reef water, which is filtered through the lagoon sands. Here, coral mucus is degraded at a turnover rate of at least 7% per hour. Detached undissolved mucus traps suspended particles, increasing its initial organic carbon and nitrogen content by three orders of magnitude within 2 h. Tidal currents concentrate these mucus aggregates into the lagoon, where they rapidly settle. Coral mucus provides light energy harvested by the zooxanthellae and trapped particles to the heterotrophic reef community, thereby establishing a recycling loop that supports benthic life, while reducing loss of energy and nutrients from the reef ecosystem.
虫黄藻是造礁珊瑚的内共生藻类，对珊瑚礁的高总初级生产力有重要贡献，但珊瑚会将其虫黄藻同化碳的一半以黏液形式排出。我们在此表明，释放出的珊瑚黏液能有效捕获水柱中的有机物，并迅速将能量和营养物质输送到礁湖沉积物中，礁湖沉积物起到生物催化矿化过滤器的作用。在大堡礁，硬珊瑚的主要属——鹿角珊瑚，每天每平方米礁区可排出多达4.8升黏液。其中56%至80%的黏液溶解在礁湖水中，并通过礁湖砂进行过滤。在此，珊瑚黏液以至少每小时7%的周转率被降解。分离出的未溶解黏液会捕获悬浮颗粒，使其初始有机碳和氮含量在2小时内增加三个数量级。潮流将这些黏液聚集体集中到礁湖中，它们在那里迅速沉降。珊瑚黏液将虫黄藻捕获的光能和捕获的颗粒提供给异养礁群落，从而建立一个支持底栖生物生存的循环回路，同时减少礁生态系统中能量和营养物质的损失。
