Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America.
PLoS One. 2011;6(7):e21830. doi: 10.1371/journal.pone.0021830. Epub 2011 Jul 19.
Despite being one of the first documented, there is little known of the causative agent or environmental stressors that promote white-band disease (WBD), a major disease of Caribbean Acropora palmata. Likewise, there is little known about the spatiality of outbreaks. We examined the spatial patterns of WBD during a 2004 outbreak at Buck Island Reef National Monument in the US Virgin Islands.
METHODOLOGY/PRINCIPAL FINDINGS: Ripley's K statistic was used to measure spatial dependence of WBD across scales. Localized clusters of WBD were identified using the DMAP spatial filtering technique. Statistics were calculated for colony- (number of A. palmata colonies with and without WBD within each transect) and transect-level (presence/absence of WBD within transects) data to evaluate differences in spatial patterns at each resolution of coral sampling. The Ripley's K plots suggest WBD does cluster within the study area, and approached statistical significance (p = 0.1) at spatial scales of 1100 m or less. Comparisons of DMAP results suggest the transect-level overestimated the prevalence and spatial extent of the outbreak. In contrast, more realistic prevalence estimates and spatial patterns were found by weighting each transect by the number of individual A. palmata colonies with and without WBD.
As the search for causation continues, surveillance and proper documentation of the spatial patterns may inform etiology, and at the same time assist reef managers in allocating resources to tracking the disease. Our results indicate that the spatial scale of data collected can drastically affect the calculation of prevalence and spatial distribution of WBD outbreaks. Specifically, we illustrate that higher resolution sampling resulted in more realistic disease estimates. This should assist in selecting appropriate sampling designs for future outbreak investigations. The spatial techniques used here can be used to facilitate other coral disease studies, as well as, improve reef conservation and management.
尽管是最早记录的疾病之一，但对于导致加勒比海轴孔珊瑚（Acropora palmata）发生白带病（WBD）的病原体或环境压力源知之甚少。同样，对于疾病爆发的空间性也知之甚少。我们在 2004 年对美属维尔京群岛的比克岛礁国家纪念碑（Buck Island Reef National Monument）的 WBD 爆发进行了研究，以检验 WBD 的空间模式。
方法/主要发现：我们使用 Ripley's K 统计量来衡量 WBD 在各尺度上的空间依赖性。使用 DMAP 空间滤波技术来识别 WBD 的局部聚类。计算了以珊瑚虫（每个样带内有和没有 WBD 的 A. palmata 珊瑚虫数量）和样带（样带内有无 WBD）为单位的统计数据，以评估在每个珊瑚取样分辨率下空间模式的差异。Ripley's K 图表明 WBD 在研究区域内存在聚类现象，并且在 1100 米或更短的空间尺度上接近统计学意义（p = 0.1）。DMAP 结果的比较表明，样带水平高估了疾病爆发的流行程度和空间范围。相比之下，通过对每个样带进行加权，根据有和没有 WBD 的 A. palmata 珊瑚虫数量来计算患病率，可得到更为现实的流行率估计值和空间模式。
随着对病因的持续研究，对疾病空间模式的监测和正确记录可以为病因学提供信息，同时帮助珊瑚礁管理者分配资源来跟踪疾病。我们的研究结果表明，所收集数据的空间尺度会极大地影响 WBD 爆发的流行率和空间分布的计算。具体来说，我们表明，更高分辨率的取样会产生更现实的疾病估计值。这将有助于为未来的疾病爆发调查选择适当的取样设计。本文中使用的空间技术可用于促进其他珊瑚疾病研究，并改善珊瑚礁保护和管理。
