Nitrogen biogeochemistry in the Caribbean sponge, Xestospongia muta: a source or sink of dissolved inorganic nitrogen?
Nitrogen biogeochemistry in the Caribbean sponge, Xestospongia muta: a source or sink of dissolved inorganic nitrogen?
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DOI：
10.1371/journal.pone.0072961
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Lesser MP
中科院分区：
文献类型：
--
作者：
Fiore CL;Baker DM;Lesser MP
长期以来，海绵一直被认为是珊瑚礁上底栖动物的重要生态成员。最近的研究表明，海绵也是珊瑚礁氮地球化学的重要贡献者。已经完成的研究表明，大多数海绵是溶解无机氮（DIN; NH 4+和NO3 −）的净来源，并且由共生原核生物介导的硝化作用是向邻近珊瑚礁提供DIN的主要过程。用来自三个不同地点（佛罗里达礁岛群，美国;巴哈马群岛的Lee Stocking岛和开曼群岛的小开曼岛）的加勒比海海绵Xestospongia穆塔进行天然实验。利用营养盐分析、稳定同位素比值和同位素示踪实验研究了海绵的DIN通量。结果表明，不同地点和X.穆塔可以是DIN的源或汇。海绵和共生细菌组分的稳定同位素值表明，原核生物群落能够吸收NH 4+和NO3 −，而NH 4+示踪实验中海绵和细菌组分之间的δ 15 N差异表明，标记N从共生细菌转移到宿主。X.穆塔似乎是更复杂的比以前的研究表明，我们的研究结果表明，厌氧过程，如反硝化或厌氧氨氧化发生在这些海绵除了好氧硝化。此外，这种海绵及其原核共生体的代谢可能会产生显着的影响，通过释放大量的DIN，包括较高的NH 4+浓度，以前报道的氮地球化学对加勒比海珊瑚礁。
Sponges have long been known to be ecologically important members of the benthic fauna on coral reefs. Recently, it has been shown that sponges are also important contributors to the nitrogen biogeochemistry of coral reefs. The studies that have been done show that most sponges are net sources of dissolved inorganic nitrogen (DIN; NH4 + and NO3 −) and that nitrification, mediated by their symbiotic prokaryotes, is the primary process involved in supplying DIN to adjacent reefs. A natural experiment was conducted with the Caribbean sponge Xestospongia muta from three different locations (Florida Keys, USA; Lee Stocking Island, Bahamas and Little Cayman, Cayman Islands). The DIN fluxes of sponges were studied using nutrient analysis, stable isotope ratios, and isotope tracer experiments. Results showed that the fluxes of DIN were variable between locations and that X. muta can be either a source or sink of DIN. Stable isotope values of sponge and symbiotic bacterial fractions indicate that the prokaryotic community is capable of taking up both NH4 + and NO3 − while the differences in δ 15N between the sponge and bacterial fractions from the NH4 + tracer experiment suggest that there is translocation of labeled N from the symbiotic bacteria to the host. Nitrogen cycling in X. muta appears to be more complex than previous studies have shown and our results suggest that anaerobic processes such as denitrification or anammox occur in these sponges in addition to aerobic nitrification. Furthermore, the metabolism of this sponge and its prokaryotic symbionts may have a significant impact on the nitrogen biogeochemistry on Caribbean coral reefs by releasing large amounts of DIN, including higher NH4 + concentrations that previously reported.