Hydromedusae are important components in the pelagic environment, which are influenced by abiotic variables such as salinity and water temperature. This study analyzed the hydromedusae community from the Amazonian Continental Shelf (ACS) region and its spatial and temporal variation. Sampling was carried out along a perpendicular transect to the coastline with six stations, where quarterly samplings occurred from April 2013 to January 2015, totalizing eight campaigns carried out through the INCT AmbTropic project.. Zooplankton was collected in oblique trawls with a 200μm net and a flowmeter coupled and the abiotic variables temperature (ºC), salinity, chlorophyll-a concentration (μg/L) and pH were measured with a CTD probe. The hydromedusae were counted and identified at the lowest taxonomic level with the aid of a stereomicroscope and adequate literature. Total density (org/m³), relative density (%), frequency of occurrence (%), richness, specific diversity, dominance and equitability of individuals were determined. A hierarchical grouping analysis was performed to evidence patterns. A Canonical Correspondence Analysis (CCA) was performed to verify the relationship between environmental variables, seasonality and taxa. In total, there were 34 taxa of hydromedusae identified. Liriope tetraphylla accounted for 91.76% of the community in the ACS region. The coast-ocean gradient influenced the hydromedusae community, which followed the pattern of higher individual densities and species richness in the stations closest to the coast, presenting a decrease toward the ocean. As the temperature did not show large variations in the coast-ocean gradient, salinity was the main variable that conditioned most individuals’ distribution. Seasonality did not presented considerable influence in the hydromedusae community, although the rainy season presented slightly higher values of density than the dry season.
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