This picture and the caption tells us not only about the presence of toxins in the river, but also how they become visible through ecological patterns in the form of the algal bloom, and how they become invisble again through limited solutions related to social forces, such as religious practices.
I don'y have any suggestions to enrich the image, I think it communicates a lot as it is. If the presence of the figures taking the photographs was to be highlighted, perhaps the contrast could be increased. But that could take away from the focus of the photo and the caption, which is on the river, toxicity and the algae.
The image is a picture taken during ethnographic fieldwork by the author. The composition is really intereting - the figure scooping algae from the river divides the picture in two, with the polluted shore below and the algae above. One can see two people taking pictures through two shadows reflected in the river, and this seems to suggest the presence of the ethnographer in a way. The picture is taken from above, which anonimyses the figure and places the algal blooms as the centre of attention.
I think the caption could be elaborated to include more information about the consequences of the toxic sewage in the river, and also on the religious function of the river.
The visualisation communicates the temporary visibility of toxicity in the river through algal blooms, as well as the immediate yet incomplete solution: manual removal. The picture illustrates how an immediate 'solution' might in fact perpetuate the underlying problem.