Cetz-Navarro Neidy P, Carpizo-Ituarte Eugenio J, Espinoza-Avalos Julio, Chee-Barragán Guillermina
El Colegio de la Frontera Sur, Chetumal, Quintana Roo, Mexico; Posgrado en Oceanografía Costera, Instituto de Investigaciones Oceanológicas-Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Ensenada, Baja California, Mexico.
Instituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California, Ensenada, Baja California, Mexico.
PLoS One. 2015 Feb 6;10(2):e0117936. doi: 10.1371/journal.pone.0117936. eCollection 2015.
Macroalgae and filamentous turf algae (FTA) are abundant on degraded coral reefs, and the reproductive responses of corals may indicate sub-lethal stress under these conditions. The percentage of gametogenic stages (PGS) and the maximum diameter of eggs (MDE; or egg size) of Orbicella annularis were used to evaluate the effect of long- (7-10 months) and short-term (2.5 months) FTA removal (treatments T1 and T2, respectively) at both the beginning (May) and the end (August) of gametogenesis. Ramets (individual lobes of a colony) surrounded by FTA (T3) or crustose coralline algae (CCA; T4) were used as controls. The removal of FTA enhanced the development of gametes (i.e., a larger and higher percentage of mature gametes (PMG)) of O. annularis for T1 vs. T3 ramets in May and T1 and T2 vs. T3 ramets in August. Similar values of PGS and MDE between gametes from T3 and T4 in both May and August were unexpected because a previous study had shown that the same ramets of T4 (with higher tissue thickness, chlorophyll a cm-2 and zooxanthellae density and lower mitotic index values) were less stressed than ramets of T3. Evaluating coral stress through reproduction can reveal more sensitive responses than other biological parameters; within reproductive metrics, PGS can be a better stress indicator than egg size. The presence of turf algae strongly impacted the development of gametes and egg size (e.g., PMG in ramets with FTA removal increased almost twofold in comparison with ramets surrounded by FTA in August), most likely exerting negative chronic effects in the long run due to the ubiquity and permanence of turf algae in the Caribbean. These algae can be considered a stressor that affects coral sexual reproduction. Although the effects of turf algae on O. annularis are apparently less severe than those of other stressors, the future of this species is uncertain because of the combined impacts of these effects, the decline of O. annularis populations and the almost complete lack of recruitment.
大型藻类和丝状草皮藻（FTA）在退化的珊瑚礁上大量存在，珊瑚的繁殖反应可能表明在这些条件下的亚致死应激。使用环纹杯形珊瑚（Orbicella annularis）的配子发生阶段百分比（PGS）和卵的最大直径（MDE；即卵大小）来评估在配子发生开始时（5月）和结束时（8月）长期（7 - 10个月）和短期（2.5个月）去除FTA（分别为处理T1和T2）的效果。被FTA（T3）或壳状珊瑚藻（CCA；T4）包围的分株（群体的单个叶）用作对照。去除FTA增强了环纹杯形珊瑚配子的发育（即，成熟配子（PMG）的比例更高且更大），5月时T1与T3分株相比，8月时T1和T2与T3分株相比。5月和8月T3和T4的配子之间PGS和MDE的相似值出乎意料，因为先前的一项研究表明，相同的T4分株（具有更高的组织厚度、叶绿素a cm-2和虫黄藻密度以及更低的有丝分裂指数值）比T3分株受到的压力更小。通过繁殖评估珊瑚应激比其他生物学参数能揭示更敏感的反应；在繁殖指标中，PGS可能比卵大小是更好的应激指标。草皮藻的存在强烈影响配子的发育和卵大小（例如，8月去除FTA的分株中的PMG与被FTA包围的分株相比增加了近两倍），从长远来看，由于草皮藻在加勒比地区的普遍存在和持久性，很可能产生负面的慢性影响。这些藻类可被视为影响珊瑚有性繁殖的应激源。尽管草皮藻对环纹杯形珊瑚的影响显然不如其他应激源严重，但由于这些影响的综合作用、环纹杯形珊瑚种群的减少以及几乎完全缺乏补充，该物种的未来仍不确定。
