Observations and a Model of Net Calcification Declines in Palau's Largest Coral Reef Lagoon Between 1992 and 2015
Observations and a Model of Net Calcification Declines in Palau's Largest Coral Reef Lagoon Between 1992 and 2015
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DOI：
10.1029/2020jc016147
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发表时间：
2020-08
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影响因子：
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通讯作者：
S. Lentz;A. Cohen;K. Shamberger;H. Barkley
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文献类型：
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作者：
S. Lentz;A. Cohen;K. Shamberger;H. Barkley
1992年至2015年间帕劳最大的泻湖和堡礁系统的净生态系统钙化率（NEC）是根据稀疏的总碱度（TA）和盐度测量以及潮汐交换模型估算的，在该模型中，落潮时向近海输送的表层泻湖水被在涨潮时进入泻湖后沉入底部的咸度较高（密度较大）的海水所取代。该模型可以准确地再现观测到的泻湖盐度，无需调整参数。为了准确再现观测到的泻湖TA，泻湖-堡礁系统的NEC从1992年至1998年为70 mmols m − 2 day − 1，从1999年至2012年为35 mmols m − 2 day − 1，从2013年至2015年为25 mmols m − 2 day − 1。这表明帕劳最大的泻湖截至 2015 年，堡礁系统尚未从 1998 年因严重白化事件导致珊瑚覆盖丧失而导致 NEC 下降 50% 的情况中恢复过来。 2012-2013年NEC进一步下滑的原因尚不清楚。泻湖停留时间从大潮期间的 8 天到小潮期间的 14 天不等，并导致泻湖 TA 发生显着的春季 - 小潮变化（约平均盐度 - 标准化海洋 - 泻湖 TA 差异的 25%）。不能解决这些春季-小潮变化的稀疏测量可能会表现出明显的碱度长期变化，而这些变化并不是由 NEC 的变化引起的。
Net ecosystem calci fi cation ( NEC ) rates of Palau's largest lagoon and barrier reef system between 1992 and 2015 are estimated from sparse total alkalinity ( TA ) and salinity measurements and a tidal exchange model in which surface lagoon water transported offshore on the ebb tide is replaced by saltier (denser) ocean water that sinks to the bottom after entering the lagoon on the fl ood tide. Observed lagoon salinities are accurately reproduced by the model with no adjustable parameters. To accurately reproduce observed lagoon TA , NEC for the lagoon ‐ barrier reef system was 70 mmols m − 2 day − 1 from 1992 to 1998, 35 mmols m − 2 day − 1 from 1999 to 2012, and 25 mmols m − 2 day − 1 from 2013 to 2015. This indicates that Palau's largest lagoon and barrier reef system has not recovered, as of 2015, from the 50% decline in NEC in 1998 caused by the loss of coral cover following a severe bleaching event. The cause of the further decline in NEC in 2012 – 2013 is unclear. Lagoon residence times vary from 8 days during spring tides to 14 days during neap tides and drive substantial spring ‐ neap variations in lagoon TA (~25% of the mean salinity ‐ normalized ocean ‐ lagoon TA difference). Sparse measurements that do not resolve these spring ‐ neap variations can exhibit apparent long ‐ term variations in alkalinity that are not due to changes in NEC .