Grillo Ana C, Simancas-Giraldo Susana M, Steinel Nico, Longhini Cybelle M, Soares Marcelo O, Bejarano Sonia, Longo Guilherme O
Leibniz Centre for Tropical Marine Research, 28359, Bremen, Germany.
Department of Oceanography and Limnology, Federal University of Rio Grande do Norte, Natal, 59014-002, RN, Brazil.
Sci Rep. 2025 Aug 15;15(1):29937. doi: 10.1038/s41598-025-15683-5.
The combination of ocean acidification (OA) and eutrophication can undermine the physiological performance of reef-building corals during competition for benthic space, leading to shifts towards non-accreting organisms like soft corals. We conducted a 28-day laboratory orthogonal experiment to test if acidification (950 µatm pCO) and moderate to high nitrate enrichment (4 and 8 µmolL) negatively affect the hard coral Stylophora pistillata while physically competing with the soft coral Xenia spp. We measured photosynthetic efficiency (PE) in hard corals and growth rate, Symbiodiniaceae density, and chlorophyll-a concentration in both hard and soft corals as proxies for their condition and responses to competition. Competition with the soft coral reduced PE, Symbiodiniaceae and chlorophyll-a contents of S. pistillata, while acidification alone and coupled with nitrate enrichment mitigated endosymbiont responses. The growth and chlorophyll-a concentrations of Xenia spp. were decreased by competition, but the soft coral was consistently benefited under nitrate enrichment. These results highlight that competition alone has a stronger negative impact on hard corals than on soft corals. Our study provides experimental evidence on how OA and eutrophication interact and shape coral dynamics, an overlooked but urgent topic in predicting reef futures under environmental change.
海洋酸化（OA）和富营养化的共同作用，会在造礁珊瑚争夺底栖空间的过程中破坏其生理性能，导致向软珊瑚等非增生性生物的转变。我们进行了一项为期28天的实验室正交实验，以测试酸化（950微大气压pCO₂）和中度至高硝酸盐富集（4和8微摩尔/升）在硬珊瑚鹿角杯形珊瑚与软珊瑚异花软珊瑚进行物理竞争时，是否会对其产生负面影响。我们测量了硬珊瑚的光合效率（PE）以及硬珊瑚和软珊瑚的生长速率、共生藻密度和叶绿素a浓度，以此作为它们的状态及对竞争反应的指标。与软珊瑚的竞争降低了鹿角杯形珊瑚的PE、共生藻和叶绿素a含量，而单独的酸化以及酸化与硝酸盐富集共同作用则减轻了内共生体的反应。竞争降低了异花软珊瑚的生长和叶绿素a浓度，但在硝酸盐富集条件下，软珊瑚始终受益。这些结果突出表明，单纯的竞争对硬珊瑚的负面影响比对软珊瑚更强。我们的研究提供了关于海洋酸化和富营养化如何相互作用并塑造珊瑚动态的实验证据，这是预测环境变化下珊瑚礁未来时一个被忽视但紧迫的课题。
