Regional and seasonal variation in nutrient limitation of river biofilms

Abstract

AbstractBenthic biofilms have multiple functions in stream and river ecosystems, and their growth and productivity are often limited by dissolved inorganic nutrient availability, particularly N or P. We deployed nutrient diffusing substrata (NDS) in 5 rivers in each of 3 regions: the Mountain West, the Arid West, and the Midwest, to assess regional and seasonal variation in nutrient limitation of river biofilms and to quantify which environmental factors control nutrient limitation. We constructed NDS with either inorganic or organic substrata to compare nutrient limitation of autotrophic and heterotrophic biofilms, and we explored inorganic N preference of biofilms by comparing results of NO3− and NH4+ amendments. During summer deployments, autotrophic and heterotrophic biofilms in Mountain Western rivers were commonly limited by N or colimited by N and P, whereas nutrient limitation was less common in Arid Western and Midwestern rivers. We deployed NDS seasonally in Midwestern rivers and found no obviou...