Effects of climate, spatial and hydrological processes on shaping phytoplankton community structure and β-diversity in an estuary-ocean continuum (Amazon continental shelf, Brazil)

This study investigated the influence of the estuarine plume from the Maranhense Gulf on the phytoplankton community structure and beta-diversity. To understand the effects of the regulation mechanisms on shaping phytoplankton community structure and beta-diversity along an estuary-ocean continuum in the eastern sector of the Amazon shelf, this study considered spatiotemporal analyses of physical, chemical, and biological variables from May 2019 to June 2020. High temporal environmental heterogeneity was identified in Cuma similar to Bay and significant spatial environmental variability in the estuary-ocean continuum. Based on the thermohaline properties, an estuarine plume was observed alongshore at a distance of approximately 60 km from the coastline. Both phytoplankton community structure and beta-diversity varied in time and space. From 189 taxa, thirty-nine indicator species were selected based on their functional traits and indicator value. Skeletonema costatum was considered the best phytoplankton indicator of the estuarine water influence. Turnover was the main component responsible for boosting beta-diversity at spatial and temporal scales. The present study was the first performed on an Amazon estuary-ocean continuum which applied diversity metrics (beta-diversity) to generate new information about loss of taxon richness and provided important information about spatiotemporal changes in phytoplankton community and environmental heterogeneity.

Automated summary

This study investigated the influence of the estuarine plume on the phytoplankton community structure and beta-diversity in the Maranhense Gulf. Through spatiotemporal analyses, the study found high environmental heterogeneity in Cuma similar to Bay and significant spatial variability in the estuary-ocean continuum. An estuarine plume was observed approximately 60 km from the coastline. Phytoplankton community structure and beta-diversity varied in time and space. Indicator species, such as Skeletonema costatum, were identified, and turnover was found to be the main factor contributing to beta-diversity. The study provides important information about the changes in phytoplankton community and environmental heterogeneity in the Amazon estuary-ocean continuum.