Tidal forcing is an important regulator of short-term variation in water properties and phytoplankton dynamics in estuaries. Tidal interactions with regulated freshwater discharge into estuaries that are affected by engineered structures such as sea embankments remain poorly understood. We examined tidal variations in the macrotidal (3–6 m) Yeongsan River estuary of South Korea, which receives regulated freshwater from a sea embankment. Semidiurnal variations in water properties and the phytoplankton community (size and taxonomic groups) were investigated fortnightly during four monitoring campaigns at a fixed station over daily cycles at neap and spring tides during both the dry (April–May 2012) and wet (August 2012) seasons. We calculated correlations and performed multivariate statistical analyses to identify the major factors affecting tidal variations. We found no consistent or predictable variations in water quality or the phytoplankton community over the fortnightly or semidiurnal tidal cycles. These parameters were more likely dependent on the extent of recovery from artificial freshwater discharge than on the tidal forcing, which is supported by the absence of any significant correlations between tidal height and water properties or phytoplankton features. Multivariate statistical analysis showed that tidal variation in the taxonomic community may be associated with freshwater discharge and was explained principally by water temperature and salinity, rather than tidal height. Diel tidal effects were in play only at a neap tide in the wet season after no freshwater had been discharged for 17 days, which is rare during the wet season. These findings imply that episodic anthropogenic freshwater discharge events disturb predictable macrotidal effects on water column processes, in turn enhancing the ecological complexity of estuaries such as the Yeongsan River estuary that have previously been altered by engineered structures.

中文翻译：

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河口系统水质和浮游植物群落中潮汐变化的人为干扰。

潮汐强迫是河口水质和浮游植物动力学短期变化的重要调节器。潮汐与受监管的淡水排放到受工程结构（如海堤）影响的河口的相互作用仍然知之甚少。我们检查了韩国荣山河河口巨潮（3–6 m）的潮汐变化，该河口从海堤接受了调节的淡水。在干旱（2012年4月至2012年5月）和潮湿（2012年8月）的潮汐和春季潮汐的每日周期内，在固定站进行的四个监测活动期间，每两周调查一次水质和浮游植物群落（大小和生物分类群）的半日变化。季节。我们计算了相关性并进行了多变量统计分析，以确定影响潮汐变化的主要因素。我们发现在每两周或半日的潮汐周期中，水质或浮游植物群落没有一致或可预测的变化。这些参数更可能取决于从人工淡水排放中恢复的程度，而不是取决于潮汐强迫，潮汐高度与水质或浮游植物特征之间不存在任何显着的相关性，这证明了这一点。多变量统计分析表明，生物分类学中的潮汐变化可能与淡水排放有关，并且主要由水温和盐度而不是潮高来解释。迪尔的潮汐效应只有在湿季的潮汐潮中才发挥作用，因为连续17天没有排出淡水，这在湿季中很少见。这些发现暗示，偶发的人为淡水排放事件扰乱了对水柱过程的可预见的巨潮影响，反过来又增加了诸如龙山河口等河口的生态复杂性，这些河口先前已被工程结构改变。