Syue Siang-Tai, Hsu Chia-Hsuan, Soong Keryea
Department of Oceanography, National Sun Yat-Sen University, Kaohsiung, 80424, Taiwan.
Sci Rep. 2021 Apr 7;11(1):7661. doi: 10.1038/s41598-021-87350-4.
An encrusting sponge, Terpios hoshinota, has the potential to infect all species of stony corals in shallow reefs and killing them. It caused a decline in coral coverage in two south-eastern islands of Taiwan. We proposed two hypotheses to examine how the sponges kill the corals, namely, light blocking and toxins, and tested by in-situ experiments. The results revealed that both light blocking, sponge toxins, and particularly the combination of both factors were effective at inducing tissue damage in stony corals over a short period. Second, to answer why the sponges killed the corals, we tested two hypotheses, namely, gaining nutrients versus gaining substrates for the sponge. By analyzing the stable isotopes C and N, as well as exploiting an enrichment experiment, it was possible to determine that only approximately 9.5% of the carbon and 16.9% of the nitrogen in the newly grown sponge tissues originated from the enriched corals underneath. The analysis also revealed that the control corals without isotope enrichment had higher δC and δN than the control sponges, which was an additional indication that T. hoshinota did not rely heavily on corals for nutrients. Therefore, our results support the hypothesis that the encrusting sponge did not kill corals for food or nutrients, but rather for the substrate.
一种覆盖性海绵——星状扁海绵（Terpios hoshinota），有可能感染浅海珊瑚礁中的所有石珊瑚物种并致其死亡。它导致了台湾东南部两个岛屿珊瑚覆盖率的下降。我们提出了两个假说，以研究这种海绵如何杀死珊瑚，即遮光和毒素，并通过现场实验进行了测试。结果表明，遮光、海绵毒素，特别是这两个因素的组合，在短时间内都能有效诱导石珊瑚组织损伤。其次，为了回答海绵为何杀死珊瑚，我们测试了两个假说，即获取营养物质与为海绵获取附着基质。通过分析稳定同位素碳和氮，并开展一项富集实验，得以确定新生长的海绵组织中只有约9.5%的碳和16.9%的氮来自下方富集的珊瑚。分析还显示，未进行同位素富集的对照珊瑚的δC和δN高于对照海绵，这进一步表明星状扁海绵在营养物质方面并不严重依赖珊瑚。因此，我们的结果支持了这样的假说，即这种覆盖性海绵杀死珊瑚并非为了获取食物或营养物质，而是为了获取附着基质。
