Fig. 3: Microalgae communities at surface along the Amazon River plume.
From: Mixotrophy emerges as an optimal strategy in mature waters of the Amazon River plume
Structure of the pigmented plankton community derived by chemotaxonomy based on specific pigment markers during 2018 and 2021 cruises along the Amazon River plume. Pigments were collected at surface at 55 stations for a total of n = 55 individual samples. A Four distinct communities were identified by hierarchical cluster analysis and Manhattan distances as shown in the dendrogram (n = 55). B The separation of the clusters is not random, as confirmed by the principal component analysis (PCA), where the points are colored according to the clusters in the dendrogram, and it is possible to see clear clusters distributing along the first two principal components (Dim 1 and Dim2, n = 55). C Stacked bars represent the relative contribution of each group to total chlorophyll a in our stations for CSIA (n = 28, note that the sample in st 24.03 in 2018 was missed). Colors of the sample name in the stacked bars plot represent the different habitats defined by Pham et al.31 ordered by apparent age: Riverine Input (RI, gray), Young Plume Core (YPC, red), Outer Plume Margin (OPM, purple), Western Plume Margin (WPM, dark yellow), modified Oceanic Water (MOW, dark cyan) and Oceanic Water (OSW, blue). The stations where mixotrophy (TPGlu 1.5) was dominant are marked with a white asterisk. The gradient in the triangle illustrates the potential decreasing impact on the communities of the physicochemical forcing driven by the plume as the water ages.
