Role of agricultural land-use on mussel performance and trophic provisioning to stream food webs

The extent to which humans alter landscapes will have profound implications on how energy and nutrients move through ecosystems. These should be most pronounced in streams, which serve as conduits of material transport and ultimate buffer to lake and coastal ecosystems.    Through their filtering abilities, native freshwater mussels can influence ecosystems by moving materials from the water column to the benthos, which in turn, benefits local algal and invertebrate communities.  We asked how the trophic importance of these subsidies changes relative to local nutrient limiting conditions associated with an agricultural land-use gradient.  We selected 14 mussel beds in streams with varying agricultural land use (10-90% crop monoculture) and quantified variables relevant to ecosystem (shell algal pigment and elemental composition and macroinvertebrate community structure) and mussel performance (oxygen consumption, nutrient excretion).  Overall, freshwater mussel performance varied as a function of land-use with decreased oxygen consumption and increased excretion rates associated with high row-crop monoculture. Our results show that shifts in land-use may have cascading effects on the physiology and performance of freshwater mussels. Consequently these shifts may alter the nature of foodweb subsidies at adjacent and higher trophic levels.