Bonaldo Roberta M, Hay Mark E
School of Biology, Georgia Tech, Atlanta, Georgia, United States of America ; Departamento de Ecologia, IB, Universidade de São Paulo, São Paulo, Brazil.
School of Biology, Georgia Tech, Atlanta, Georgia, United States of America.
PLoS One. 2014 Jan 22;9(1):e85786. doi: 10.1371/journal.pone.0085786. eCollection 2014.
Tropical reefs are in global decline with seaweeds commonly replacing corals. Negative associations between macroalgae and corals are well documented, but the mechanisms involved, the dynamics of the interactions, and variance in effects of different macroalgal-coral pairings are poorly investigated. We assessed the frequency, magnitude, and dynamics of macroalgal-coral competition involving allelopathic and non-allelopathic macroalgae on three, spatially grouped pairs of no-take Marine Protected Areas (MPAs) and non-MPAs in Fiji. In non-MPAs, biomass of herbivorous fishes was 70-80% lower, macroalgal cover 4-9 fold higher, macroalgal-coral contacts 5-15 fold more frequent and 23-67 fold more extensive (measured as % of colony margin contacted by macroalgae), and coral cover 51-68% lower than in MPAs. Coral contacts with allelopathic macroalgae occurred less frequently than expected by chance across all sites, while contact with non-allelopathic macroalgae tended to occur more frequently than expected. Transplants of allelopathic macroalgae (Chlorodesmis fastigiata and Galaxaura filamentosa) against coral edges inflicted damage to Acropora aspera and Pocillopora damicornis more rapidly and extensively than to Porites cylindrica and Porites lobata, which appeared more resistant to these macroalgae. Montipora digitata experienced intermediate damage. Extent of damage from macroalgal contact was independent of coral colony size for each of the 10 macroalgal-coral pairings we established. When natural contacts with Galaxaura filamentosa were removed in the field, recovery was rapid for Porites lobata, but Pocillopora damicornis did not recover and damage continued to expand. As macroalgae increase on overfished tropical reefs, allelopathy could produce feedbacks that suppress coral resilience, prevent coral recovery, and promote the stability of algal beds in habitats previously available to corals.
热带珊瑚礁正处于全球衰退状态，海藻通常会取代珊瑚。大型藻类与珊瑚之间的负面关联已有充分记载，但其中涉及的机制、相互作用的动态变化以及不同大型藻类 - 珊瑚组合的影响差异却鲜有研究。我们评估了斐济三个空间分组的禁捕海洋保护区（MPA）和非MPA中，涉及化感和非化感大型藻类的大型藻类 - 珊瑚竞争的频率、强度和动态变化。在非MPA中，食草鱼类的生物量低70 - 80%，大型藻类覆盖率高4 - 9倍，大型藻类与珊瑚的接触频率高5 - 15倍、范围广23 - 67倍（以大型藻类接触的群体边缘百分比衡量），珊瑚覆盖率比MPA低51 - 68%。在所有地点，珊瑚与化感大型藻类的接触发生频率低于随机预期，而与非化感大型藻类的接触则往往比预期更频繁。将化感大型藻类（细枝绿藻和丝状乳节藻）移植到珊瑚边缘，对粗糙鹿角珊瑚和平顶珊瑚造成的损害比对柱形多孔珊瑚和叶状多孔珊瑚更快、更广泛，后两者似乎对这些大型藻类更具抗性。指状蔷薇珊瑚受到的损害程度居中。对于我们建立的10种大型藻类 - 珊瑚组合中的每一种，大型藻类接触造成的损害程度与珊瑚群体大小无关。在野外去除与丝状乳节藻的自然接触后，叶状多孔珊瑚恢复迅速，但鹿角珊瑚没有恢复，损害继续扩大。随着过度捕捞的热带珊瑚礁上大型藻类数量增加，化感作用可能会产生反馈，抑制珊瑚的恢复力，阻止珊瑚恢复，并促进以前珊瑚栖息的生境中藻床的稳定性。
