Carbonate and terrigenous sediment budgets for two inshore turbid reefs on the central Great Barrier Reef
Carbonate and terrigenous sediment budgets for two inshore turbid reefs on the central Great Barrier Reef
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DOI：
10.1016/j.margeo.2013.08.011
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发表时间：
2013-12-01
期刊：
影响因子：
2.9
通讯作者：
Perry, C. T.
中科院分区：
文献类型：
--
作者：
Browne, N. K.;Smithers, S. G.;Perry, C. T.
大堡礁 (GBR) 的近海浑浊带珊瑚礁出现在距大陆海岸 20 公里范围内，其海洋环境条件（就沉积率、浑浊度和水质而言）通常被认为对珊瑚礁生长来说是边缘的。尽管如此，来自各种底栖栖息地评估的数据报告，这些环境中的珊瑚覆盖率很高（>30%），而珊瑚礁核心记录显示，它们的特点是垂直增生速度相对较快（2-8毫米/年），这是一个长期趋势，表明高净碳酸盐生产力和原位碳酸盐框架积累。然而，由于缺乏陆源沉积物输入和通量速率以及碳酸盐生成速率的定量数据，阻碍了对碳酸盐生成的生态时间尺度速率和沉积物对珊瑚礁生长的长期净影响的理解。为了解决这一知识差距，在中礁和帕鲁马浅滩这两个近岸珊瑚礁开发了现代碳酸盐预算和陆源沉积物模型，该模型量化了礁石内、礁外的外来沉积物输入。两者均位于大堡礁中部地区，承受着高陆源沉积物负荷（>11,000 吨/年）和波动浊度（5 至 >100 毫克/升）的影响。根据沉积物动态模型，超过 81% 的沉积物被运离珊瑚礁，净沉积物积累仅限于受庇护的珊瑚礁栖息地。由于高珊瑚覆盖率（>30%）、高珊瑚钙化率（鹿角珊瑚平均 63 g/cm2/年）和低生物侵蚀率（0.3 至 5 kg/m2/年），净碳酸盐产量较高（>6.9 kg/m(2)/年），但在空间上存在差异，在深部（LAT >-2 m）迎风珊瑚礁区域内，净碳酸盐产量最高（>10 kg/m(2)/年）。高碳酸盐骨架产量使得中礁和帕鲁马浅滩能够快速垂直增生：中礁在-4 m 深度处形成，帕鲁马浅滩在-3 m 深度处形成，并且均在 2007 年达到海平面。
Inshore turbid zone reefs on the Great Barrier Reef (GBR) occur within 20 km of the mainland coast under marine environmental conditions (with respect to sedimentation rates, turbidity and water quality) that are generally considered marginal for reef growth. Despite this, data from various benthic habitat assessments report high (>30%) coral cover in these environments and reef core records show them to be characterised by relatively rapid rates of vertical accretion (2-8 mm/year), a long-term trend indicative of high net carbonate productivity and in-situ carbonate framework accumulation. However, the lack of quantitative data on terrigenous sediment input and flux rates, and on carbonate production rates has inhibited understanding of both ecological timescale rates of carbonate production and the aggregated long-term net impacts of sediments on reef growth. To address this knowledge gap a modem carbonate budget and terrigenous sediment model, that quantified allochthonous sediment inputs onto, within and off reef, was developed at two inshore reefs: Middle Reef and Paluma Shoals. Both are located within the central region of the GBR and are subjected to high terrigenous sediment load (>11,000 tonnes/year) and fluctuating turbidity (5 to >100 mg/L) regimes. Based on sediment dynamic modelling, over 81% of sediments delivered were transported off reef, with net sediment accumulation limited to sheltered reef habitats. Net carbonate production was high (>6.9 kg/m(2)/year) due to high coral cover (>30%), high coral calcification rates (Acropora average 63 g/cm2/year), and low bioerosion rates (0.3 to 5 kg/m2/year), but varied spatially with highest net carbonate production (>10 kg/m(2)/year) within deep (>-2 m at LAT) windward reef zones. High carbonate framework production has enabled Middle Reef and Paluma Shoals to vertically accrete rapidly: Middle Reef establishing at depths of-4 m, Paluma Shoals at -3 m depth and both reaching sea level in