Study sites by province, block and impact level based on anthropogenic activities (x = present).

Eutrophication level is indicated by the scores of PC axis 1 based on PCA of C/N ratios in seagrass tissue, chlorophyll concentrations in the water column, epiphytic and benthic annual algae biomass (see text for detail and Methods S1 for data).
1 - Peat Mining <5 km from site; 2 - agriculture <10 km upstream; 3 −85% agriculture within a 2 km radius of the site but still heavily forested 4–6 km upriver; 4 −95% agriculture within a 2 km radius of the site no forest left along the banks of the river; 5 −5% agriculture within a 2 km radius of the site, area still heavily forested; 6 −80% agriculture within a 2 km radius; 7 −45% agriculture within 2 km of site, heavy agriculture up river; 8 - Industrial forestry 3–4 km upriver.