ABSTRACT

The Paciência river estuary (PRE) is an Amazonian estuary with relevant socio-economic importance; however, it is undergoing a continuous anthropogenic pressure such as the input of untreated domestic effluents. Hence, the phytoplankton community and trophic indices were analysed during three seasons in 2017 to assess the water quality and understand the degree of human influence in a macrotidal estuary. The trophic state of the PRE was determined by applying the trophic state index (TSI), trophic index, and Karydis trophic index, and ecological status by diversity metrics (diversity, evenness, richness, and dominance). Multivariate analysis indicated that TSI and dominance index were the most sensitive indices to changes in environmental conditions. The precipitation regime characterised the estuary in two different trophic scenarios. PRE was hypereutrophic in the dry season and mesotrophic in the rainy/transitional seasons based on the TSI. A high dominance index was recorded in the dry season with blooms of Thalassiosira rotula, reflecting an ecological disturbance. A higher phytoplankton diversity was recorded in the rainy/transitional seasons, indicating a tendency toward a lower stressed ecosystem. Therefore, understanding the trophic state variability in tropical estuaries and its response to changes in phytoplankton ecology is essential to support the management of coastal ecosystems.

摘要

Paciência 河口 (PRE) 是亚马逊河口，具有相关的社会经济意义；然而，它正在承受持续的人为压力，例如未经处理的生活污水的输入。因此，对 2017 年三个季节的浮游植物群落和营养指数进行了分析，以评估水质并了解大型潮汐河口的人类影响程度。PRE 的营养状态是通过应用营养状态指数 (TSI)、营养指数和 Karydis 营养指数来确定的，并通过多样性指标（多样性、均匀度、丰富度和优势度）来确定生态状态。多变量分析表明，TSI和优势指数是对环境条件变化最敏感的指标。降水制度在两种不同的营养情景中描绘了河口。根据 TSI，PRE 在旱季是富营养化的，而在雨季/过渡季节是中营养的。在旱季记录了高优势指数，开花Thalassiosira rotula，反映了生态干扰。在雨季/过渡季节记录到较高的浮游植物多样性，表明生态系统压力较低的趋势。因此，了解热带河口的营养状态变化及其对浮游植物生态变化的响应对于支持沿海生态系统的管理至关重要。