Martín Blanco Félix, Clero Alonso Lídice, González Sansón Gaspar, Amargós Fabián Pina
Centro de Investigaciones de Ecosistemas Costeros, Ministerio de Ciencia, Tecnología y Medio Ambiente, Cayo Coco, Morón, Ciego de Avila, CP 69400, Cuba.
Rev Biol Trop. 2011 Sep;59(3):1149-63.
The 1983-1984 mass mortality of Diadema antillarum produced severe damages on Caribbean reefs contributing to substantial changes in community structure that still persist. Despite the importance of Diadema grazing in structuring coral reefs, available information on current abundances and algal-urchin interactions in Cuba is scarce. We analyzed spatial variations in Diadema abundance and its influence on algal community structure in 22 reef sites in Jardines de la Reina, in June/2004 and April/2005. Urchins were counted in five 30 x 2m transects per site, and algal coverage was estimated in randomly located 0.25m side quadrats (15 per site). Abundances of Diadema were higher at reef crests (0.013-1.553 ind/m2), while reef slope populations showed values up to three orders of magnitude lower and were overgrown by macroalgae (up to 87%, local values). Algal community structure at reef slopes were dominated by macroalgae, especially Dictyota, Lobophora and Halimeda while the most abundant macroalgae at reef crests were Halimeda and Amphiroa. Urchin densities were negatively and positively correlated with mean coverage of macroalgae and crustose coralline algae, respectively, when analyzing data pooled across all sites, but not with data from separate habitats (specially reef crest), suggesting, along with historical fish biomass, that shallow reef community structure is being shaped by the synergistic action of other factors (e.g. fish grazing) rather than the influence of Diadema alone. However, we observed clear signs of Diadema grazing at reef crests and decreased macroalgal cover according to 2001 data, what suggest that grazing intensity at this habitat increased at the same time that Diadema recruitment began to be noticeable. Furthermore, the excessive abundance of macroalgae at reef slopes and the scarcity of crustose coralline algae seems to be due by the almost complete absence of D. antillarum at mid depth reefs, where local densities of this urchin were predominantly low.
1983 - 1984年，冠海胆大量死亡对加勒比珊瑚礁造成了严重破坏，导致群落结构发生重大变化，且这种变化至今仍然存在。尽管冠海胆的啃食对构建珊瑚礁很重要，但古巴目前关于其丰度以及藻类 - 海胆相互作用的可用信息却很少。我们于2004年6月和2005年4月分析了女王花园群岛22个珊瑚礁地点冠海胆丰度的空间变化及其对藻类群落结构的影响。每个地点在五条30×2米的样带中统计海胆数量，并在随机定位的0.25平方米的方形样方（每个地点15个）中估计藻类覆盖率。冠海胆的丰度在礁顶较高（0.013 - 1.553个/平方米），而礁坡上的种群数量低至三个数量级，并且被大型藻类覆盖（高达87%，局部值）。礁坡上的藻类群落结构以大型藻类为主，尤其是网胰藻、凹顶藻和仙掌藻，而礁顶最丰富的大型藻类是仙掌藻和双叉藻。在分析所有地点汇总的数据时，海胆密度分别与大型藻类和壳状珊瑚藻的平均覆盖率呈负相关和正相关，但与单独栖息地（特别是礁顶）的数据无关，这与历史鱼类生物量一起表明，浅海珊瑚礁群落结构是由其他因素（如鱼类啃食）的协同作用而非仅由冠海胆的影响所塑造。然而，根据2001年的数据，我们在礁顶观察到了冠海胆啃食的明显迹象以及大型藻类覆盖率的下降，这表明在这个栖息地啃食强度增加的同时，冠海胆的补充开始变得明显。此外，礁坡上大型藻类过多以及壳状珊瑚藻稀缺似乎是由于中深度珊瑚礁几乎完全没有冠海胆，该海胆在这些地方的局部密度主要很低。
