Reef shallowing is a critical control on benthic foraminiferal assemblage composition on nearshore turbid coral reefs
Reef shallowing is a critical control on benthic foraminiferal assemblage composition on nearshore turbid coral reefs
复制标题
DOI：
10.1016/j.palaeo.2019.109240
复制
发表时间：
2019-11
期刊：
影响因子：
--
通讯作者：
J. Johnson;C. Perry;S. Smithers;K. Morgan;S. Woodroffe
中科院分区：
文献类型：
--
作者：
J. Johnson;C. Perry;S. Smithers;K. Morgan;S. Woodroffe
水质下降对澳大利亚大堡礁（GBR）的珊瑚礁构成了重大威胁。由于靠近河流点源，人们普遍认为，位于GBR内陆架的珊瑚礁最容易受到沿海集水区营养物和沉积物排放增加的影响，其中许多自欧洲人定居以来已被修改。然而，水质变化对GBR内大陆架珊瑚礁的影响和程度仍不清楚。这种不确定性很大程度上可归因于缺乏长期记录，无法在适当的造礁时间尺度上评估生态和环境变化。在这里，我们介绍了位于GBR中心区域的三个近岸浑浊带珊瑚礁的底栖有孔虫古记录。贝叶斯年龄-深度模型用于确定与欧洲人在该地区定居的时间（约1850年 CE）相对应的岩心间隔，从而能够进行以下调查：(1)在珊瑚礁向海平面浅化期间底栖有孔虫组合的组成和变化；(2)在GBR中部的大多数近岸珊瑚礁上，是否可以识别出由于历史土地利用变化而增加的养分和沉积物输入的信号。多变量分析确定了两个组合组，由pararotaliaspp的相对丰度显著增加所描述。的核心。我们的研究结果表明，后欧洲定居相关的营养物质和沉积物输入的增加不太可能驱动底栖有孔虫组合组成的变化。相反，我们将底栖有孔虫组合组成的变化解释为与珊瑚礁向海平面浅化过程中水动力能、光可用性和珊瑚礁基质沉积物碳酸盐含量的变化有关。我们的研究结果支持了一个假设，即近岸浑浊带的珊瑚礁比那些位于GBR内/中陆架边界的更远的海域的珊瑚礁对增加的营养物质和沉积物输入具有更高的抵抗力。
Declining water quality represents a major threat to the coral reefs of Australia's Great Barrier Reef (GBR). Due to their close proximity to river point sources, reefs situated on the inner-shelf of the GBR are widely perceived to be most susceptible to the increased discharge of nutrients and sediments from coastal catchments, many of which have been modified since European settlement. However, the impact and magnitude of water quality change on the GBR's inner-shelf reefs remains unclear. Much of the uncertainty can be attributed to a paucity of long-term records with which to assess ecological and environmental change over appropriate reef-building timescales. Here, we present benthic foraminiferal palaeo-records from three proximal nearshore turbid-zone reefs located within the central region of the GBR. Bayesian age-depth modelling was used to identify the core intervals corresponding to the timing of European settlement in the region (c.1850 CE), enabling the investigation of: (1) the composition and variability of benthic foraminiferal assemblages during reef shallowing towards sea level; and (2) whether any signal of increased nutrient and sediment inputs, as the result of historical land-use change, can be discerned on the most nearshore reefs of the central GBR. Multivariate analyses identified two assemblage groups, delineated by a significant increase in the relative abundance ofPararotaliaspp. up-core. Our results suggest that post-European settlement associated increases in nutrient and sediment inputs are unlikely to have driven the observed shifts in benthic foraminiferal assemblage composition. Rather, we interpret changes in the composition of benthic foraminiferal assemblages as being linked to changes in hydrodynamic energy, light availability and the carbonate content of reef-matrix sediments during reef shallowing towards sea level. Our findings support the hypothesis that nearshore turbid-zone reefs have a higher resistance to increased nutrient and sediment inputs than those located further offshore, towards the inner/mid-shelf boundary of the GBR.