Lewis Bonnie, Lough Janice M, Nash Merinda C, Diaz-Pulido Guillermo
Griffith School of Environment and Australian Rivers Institute-Coast & Estuaries, Griffith University, Nathan, Australia.
ARC Centre of Excellence for Coral Reef Studies, Queensland, Australia.
PLoS One. 2017 Oct 4;12(10):e0185124. doi: 10.1371/journal.pone.0185124. eCollection 2017.
The presence of banding in the skeleton of coralline algae has been reported in many species, primarily from temperate and polar regions. Similar to tree rings, skeletal banding can provide information on growth rate, age, and longevity; as well as records of past environmental conditions and the coralline alga's growth responses to such changes. The aim of this study was to explore the presence and characterise the nature of banding in the tropical coralline alga Porolithon onkodes, an abundant and key reef-building species on the Great Barrier Reef (GBR) Australia, and the Indo-Pacific in general. To achieve this we employed various methods including X-ray diffraction (XRD) to determine seasonal mol% magnesium (Mg), mineralogy mapping to investigate changes in dominant mineral phases, scanning electron microscopy-electron dispersive spectroscopy (SEM-EDS), and micro-computed tomography (micro-CT) scanning to examine changes in cell size and density banding, and UV light to examine reproductive (conceptacle) banding. Seasonal variation in the Mg content of the skeleton did occur and followed previously recorded variations with the highest mol% MgCO3 in summer and lowest in winter, confirming the positive relationship between seawater temperature and mol% MgCO3. Rows of conceptacles viewed under UV light provided easily distinguishable bands that could be used to measure vertical growth rate (1.4 mm year-1) and age of the organism. Micro-CT scanning showed obvious banding patterns in relation to skeletal density, and mineralogical mapping revealed patterns of banding created by changes in Mg content. Thus, we present new evidence for seasonal banding patterns in the tropical coralline alga P. onkodes. This banding in the P. onkodes skeleton can provide valuable information into the present and past life history of this important reef-building species, and is essential to assess and predict the response of these organisms to future climate and environmental changes.
许多物种的珊瑚藻骨骼中都有环带存在的报道，主要来自温带和极地地区。与树木年轮相似，骨骼环带可以提供有关生长速率、年龄和寿命的信息；以及过去环境条件的记录和珊瑚藻对这些变化的生长反应。本研究的目的是探索热带珊瑚藻多孔石枝藻（Porolithon onkodes）中环带的存在并描述其性质，该藻类是澳大利亚大堡礁（GBR）以及整个印度-太平洋地区丰富且关键的造礁物种。为实现这一目标，我们采用了多种方法，包括X射线衍射（XRD）来测定季节性的镁（Mg）摩尔百分比，矿物学绘图以研究主要矿物相的变化，扫描电子显微镜-电子能谱仪（SEM-EDS），以及微计算机断层扫描（micro-CT）扫描来检查细胞大小和密度环带的变化，并用紫外线来检查生殖（生殖窝）环带。骨骼中Mg含量确实存在季节性变化，且与先前记录的变化一致，夏季MgCO3摩尔百分比最高，冬季最低，证实了海水温度与MgCO3摩尔百分比之间的正相关关系。在紫外线下观察到的一排排生殖窝提供了易于区分的环带，可用于测量生物体的垂直生长速率（每年1.4毫米）和年龄。微计算机断层扫描显示出与骨骼密度相关的明显环带模式，矿物学绘图揭示了由Mg含量变化产生的环带模式。因此，我们提供了热带珊瑚藻多孔石枝藻季节性环带模式的新证据。多孔石枝藻骨骼中的这种环带可以为这种重要造礁物种的当前和过去生活史提供有价值的信息，对于评估和预测这些生物体对未来气候和环境变化的反应至关重要。
