Final answer:
The largest water fluxes among continental biomes come from Grassland and Rainforest biomes, with the tropical rainforests and temperate grasslands being the most productive.
Step-by-step explanation:
The two continental biomes that produce the largest water fluxes are the Grassland and Rainforest biomes, specifically the tropical rainforests and the temperate grasslands. These areas are characterized by high levels of precipitation and net primary productivity.
Rainforests, especially tropical ones, have abundant rainfall throughout the year and support diverse plant and animal life because of the warm temperatures and consistent moisture availability. Grasslands, particularly temperate varieties, also have high productivity and experience distinct seasons of growth, contributing significantly to water fluxes. In contrast, biomes like the tundra and desert have low primary productivity and limited water fluxes due to harsh temperatures and scarcity of water.