Tide-salinity patterns reveal seawater-freshwater mixing behavior at a river mouth and tidal creeks in a tropical mangrove estuary
Tide-salinity patterns reveal seawater-freshwater mixing behavior at a river mouth and tidal creeks in a tropical mangrove estuary
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DOI：
10.1016/j.jafrearsci.2022.104684
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发表时间：
2022-08-19
影响因子：
2.3
通讯作者：
Ndondo, Gustave R. N.
中科院分区：
文献类型：
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作者：
Atekwana, Eliot A.;Ramatlapeng, Goabaone J.;Ndondo, Gustave R. N.
在多个半日潮中，每隔一分钟收集一次潮汐和盐度数据，用于调查在河口、河口中部潮汐溪和热带红树林河口头岸线潮汐溪混合时的水源（如海水、河流、地下水和雨水）及其相对时间。我们的目标是记录每个地点潮汐引起的水位变化和盐度的时间变化，并利用盐度和水位之间的关系来阐明水的来源和水文混合过程中不同水源的时间。河口的潮汐-盐度（T-S）图数据趋势显示涨潮时与海水混合，退潮时红树林的淡水稀释海水（微咸海水）排水。在河口中部红树林溪，升潮T-S图的数据趋势最初表现为盐度恒定，随后海水入侵导致盐度急剧上升至潮峰。在退潮开始时，由于红树林的淡水（雨水）稀释的微咸水涌入，盐度急剧下降。河口岸线潮溪的T-S图数据趋势为盐度恒定，仅在涨潮高峰附近因河水稀释而下降。退潮期间，地下水入潮后盐度进一步降低，后升高至本底盐度，直至退潮时保持不变。在潮下至潮尺度上建立红树林河口多个地点的T-S模式，确定海水-淡水混合的预期盐度变化，可用于(1)为时空评估建立基线水文和盐度（水化学）条件；(2)为科学研究和河口生态系统管理提供短期到长期采样制度的指导。
Tide and salinity data collected at minute intervals over multiple semidiurnal tides were used to investigate the source of water (e.g., seawater, river, groundwater and rain) and their relative timing in mixing at the mouth of a river, a tidal creek at mid-estuary and a tidal creek at the shoreline at the head of a tropical mangrove estuary. Our objectives were to document the temporal changes in tide induced water level changes and salinity at each location and to use the relationship between salinity and water level to elucidate the sources of water and the timing of different sources of water in the hydrologic mixing processes. The data trends in tide vs. salinity (T-S) plots for the river mouth revealed mixing with seawater during rising tides and freshwater diluted seawater (brackish) drainage from the mangrove forest during ebb tides. In the mangrove creek at mid-estuary, the data trends in the T-S plots for rising tides initially showed constant salinity, followed by sharp rises in salinity to peak tide caused by seawater intrusion. The salinity decreased precipitously at the start of tidal ebbing due to influx of freshwater (rain) diluted brackish water from the mangrove forest. The data trends in the T-S plots for the tidal creek at the shoreline located at the estuary head showed constant salinity which decreased only near peak rising tide because of river dilution. During tidal ebbing, the salinity further decreased from groundwater influx before increasing to background salinity, which stayed constant to low tide. Establishing T-S patterns for multiple lo-cations in mangrove estuaries over sub-tidal to tidal scales define the expected salinity variations in seawater-freshwater mixing which can be used to (1) establish baseline hydrologic and salinity (hydrochemical) condi-tions for temporal and spatial assessments and (2) serve to guide short to long-term sampling regimes for sci-entific studies and estuarine ecosystem management.