One of the significant aspects of estuarine water quality assessment is to discern the effect of tide on the environmental parameters. The variability of different physical, chemical, and biological parameters, in response to semi-diurnal tides, over a tidal cycle was investigated at contrasting salinity regimes of Mahanadi estuary. This estuary is formed at the mouth of Mahanadi River (the third largest river in peninsular India) that meets the Bay of Bengal on the east coast of India. Significant variability was observed in salinity, phosphate concentration, picophytoplankton biomass between upper and lower estuary irrespective of tides. Salinity and ammonium concentration varied significantly between high and low tide, irrespective of sites. A low salinity regime was observed in the upper estuary. Dissolved oxygen levels were higher at the lower estuary and relatively decreased at the upper estuary during high tide with increased tidal amplitude. The biochemical oxygen demand levels < 4 mg.l⁻¹ signified estuarine water quality in between fairly-clean and moderately polluted. Ammonium and phosphate distribution suggested anthropogenic influx at the lower/middle part of the estuary. Higher silicate content in upper estuary regardless of tides indicated prominent riverine source. Inorganic macronutrient molar ratios indicated a potential nitrogen limiting condition. Smaller phytoplankton size classes contributed predominantly to total phytoplankton biomass, irrespective of tides. This study highlighted the significance of continuous sampling over the tidal cycle to understand the effect of tides on estuarine water quality, which will aid in developing forecast models.

河口水质评估的重要方面之一是辨别潮汐对环境参数的影响。在马哈纳迪河口的对比盐度状况下，研究了潮汐周期内不同物理、化学和生物参数的变化，以响应半日潮。这个河口形成于马哈纳迪河（印度半岛第三大河）的河口，与印度东海岸的孟加拉湾汇合。无论潮汐如何，在上河口和下河口之间的盐度、磷酸盐浓度、微型浮游植物生物量方面都观察到了显着的变化。无论地点如何，高潮和低潮之间的盐度和铵浓度变化很大。在上河口观察到低盐度状态。高潮时河口下部溶解氧水平较高，而上河口溶解氧水平相对降低，潮幅增加。生化需氧量 < 4 mg.l^-1表示河口水质介于相当干净和中度污染之间。铵和磷酸盐的分布表明河口中下部有人为流入。无论潮汐如何，河口上游的硅酸盐含量较高，表明河流源头显着。无机常量营养素摩尔比表明潜在的氮限制条件。无论潮汐如何，较小的浮游植物大小类别主要对总浮游植物生物量做出贡献。这项研究强调了在潮汐周期内连续采样的重要性，以了解潮汐对河口水质的影响，这将有助于开发预测模型。