Barott Katie L, Rodriguez-Mueller Beltran, Youle Merry, Marhaver Kristen L, Vermeij Mark J A, Smith Jennifer E, Rohwer Forest L
Biology Department, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA.
Proc Biol Sci. 2012 Apr 22;279(1733):1655-64. doi: 10.1098/rspb.2011.2155. Epub 2011 Nov 16.
Competition between reef-building corals and benthic algae is of key importance for reef dynamics. These interactions occur on many spatial scales, ranging from chemical to regional. Using microprobes, 16S rDNA pyrosequencing and underwater surveys, we examined the interactions between the reef-building coral Montastraea annularis and four types of benthic algae. The macroalgae Dictyota bartayresiana and Halimeda opuntia, as well as a mixed consortium of turf algae, caused hypoxia on the adjacent coral tissue. Turf algae were also associated with major shifts in the bacterial communities at the interaction zones, including more pathogens and virulence genes. In contrast to turf algae, interactions with crustose coralline algae (CCA) and M. annularis did not appear to be antagonistic at any scale. These zones were not hypoxic, the microbes were not pathogen-like and the abundance of coral-CCA interactions was positively correlated with per cent coral cover. We propose a model in which fleshy algae (i.e. some species of turf and fleshy macroalgae) alter benthic competition dynamics by stimulating bacterial respiration and promoting invasion of virulent bacteria on corals. This gives fleshy algae a competitive advantage over corals when human activities, such as overfishing and eutrophication, remove controls on algal abundance. Together, these results demonstrate the intricate connections and mechanisms that structure coral reefs.
造礁珊瑚与底栖藻类之间的竞争对珊瑚礁动态至关重要。这些相互作用发生在许多空间尺度上，从化学尺度到区域尺度。我们使用微探针、16S rDNA焦磷酸测序和水下调查，研究了造礁珊瑚环纹菊珊瑚（Montastraea annularis）与四种底栖藻类之间的相互作用。大型藻类巴氏网翼藻（Dictyota bartayresiana）和仙人掌藻（Halimeda opuntia），以及丝状藻类的混合群落，会导致相邻珊瑚组织缺氧。丝状藻类还与相互作用区域的细菌群落的重大变化有关，包括更多的病原体和毒力基因。与丝状藻类不同，与壳状珊瑚藻（CCA）和环纹菊珊瑚的相互作用在任何尺度上似乎都不是对抗性的。这些区域没有缺氧现象，微生物也不像病原体，并且珊瑚与CCA相互作用的丰度与珊瑚覆盖率呈正相关。我们提出了一个模型，其中肉质藻类（即某些丝状藻类和肉质大型藻类物种）通过刺激细菌呼吸和促进有毒细菌对珊瑚的入侵来改变底栖竞争动态。当过度捕捞和富营养化等人类活动消除了对藻类数量的控制时，这使肉质藻类比珊瑚具有竞争优势。总之，这些结果证明了构成珊瑚礁的复杂联系和机制。
