Nutritional characterization of aquatic plants in different floodplain habitats of the Central Amazon

We conducted a study to characterize the nutritional composition of the main aquatic herbaceous plants in two protected areas within the Central Amazon. Our investigation aimed to evaluate possible nutritional variations in these plant species between two floodplains contrasting in fertility throughout the annual hydrological cycle and to examine if such differences might influence Amazonian manatee migration patterns. Plant samples were collected during high water levels (2007), receding water levels (2013), and low water levels (2008). Bromatological analysis was employed to characterize various nutritional parameters including dry matter, moisture, crude protein, fat, mineral matter, non-nitrogenous extract, and digestible energy. Our findings revealed no significant variations in nutritional contents between herbaceous plants from várzea and igapó environments. However, nutrient compositions varied within each floodplain type across different hydrological periods. High levels of fat and crude fiber observed in both environments during high and receding water periods suggest an energetic contribution to the manatee's reproductive, migratory, and feeding restrictions. Nonetheless, irrespective of hydrological periods and environmental types, Amazonian manatees appear to have assess to aquatic plants with adequate nutritional requirements. Thus, migrations may be more closely associated with physical constraints of the environments rather than solely driven by the animal's feeding demands.