In the present study, it was analyzed the structure of mesozooplankton community, and their spatio-temporal variations along the Caeté River estuary (northeast of Pará, Brazil). Samples were collected during spring tides conducted in nychthemeral cycles, in three fixed sectors located along the studied estuary (inner-S1, middle-S2 and outer-S3), using conical plankton nets of 200 μm mesh size. Samplings were performed in September 2014 (dry season) and March 2015 (rainy season), totaling 54 samples. A total of 25 mesozooplankton species were recorded, being the copepods the most diversified group (21 species), mostly dominated by estuarine and coastal species. The most abundant mesozooplankton species presented significantly higher densities (p<0.0001) between the middle (Pseudodiaptomus richardi, 583.8±956.5 ind m⁻³, Paracalanus quasimodo, 108.9±181.4 ind m⁻³ and Pseudodiaptomus acutus, 23.4±66.6 ind m⁻³) and outer (Acartia tonsa, 476.9±1,298.8 ind m⁻³ and Acartia lilljeborgii (407.9±1,038.1 ind m⁻³ and Parasagitta tenuis, 59.9±117.1 ind m⁻³) sectors. The non-metric multidimensional ordination analysis highlighted that the average density of the main species varied mainly at a spatial scale, with density increasing toward the mouth of the estuary (except for P. richardi). Spearman's correlation (rs) demonstrated that the salinity, turbidity, dissolved nutrients and chlorophyll a concentrations were the prevailing environmental variables associated with significant spatial changes of mesozooplankton distribution in this area. Overall, the results showed that spatial variation in the water physicochemical characteristics of the Caeté Estuary have significant effects on the structure and succession of the mesozooplankton, which may potentially affect the functioning and biodiversity of this coastal ecosystem.

在本研究中，分析了Caeté河口（巴西帕拉州东北部）中型浮游生物群落的结构及其时空变化。样本是在大潮期间进行的，在位于研究河口的三个固定区域（内 S1、中 S2 和外 S3）中，使用 200 μm 网眼尺寸的锥形浮游生物网收集样本。采样时间分别为 2014 年 9 月（旱季）和 2015 年 3 月（雨季），共计 54 个样本。共记录了25种中型浮游动物，其中桡足类是最多样化的类群（21种），主要以河口和沿海物种为主。最丰富的中型浮游生物物种在中间（Pseudodiaptomus richardi, 583.8±956.5 ind m ^-3 , Paracalanus quasimodo, 108.9±181.4 ind m ^-3和Pseudodiaptomus acutus, 23.4±66.6 ind m ^-3 ) 和外部 ( Aca​​rtia Tonya, 476.9±1,298.8 ind m ^-3和Acartia lilljeborgii (407.9± 1,038.1 ind m ^-3和Parasagitta tenuis , 59.9±117.1 ind m ^-3 ) 扇区。非度量多维排序分析强调，主要物种的平均密度主要在空间尺度上变化，密度向着口部增加河口（ P. richardi除外）。Spearman 相关性（rs) 表明盐度、浊度、溶解养分和叶绿素a浓度是与该地区中型浮游生物分布的显着空间变化相关的主要环境变量。总体而言，结果表明，Caeté河口水理化特征的空间变化对中型浮游生物的结构和演替具有显着影响，这可能会影响该沿海生态系统的功能和生物多样性。