Journal Article climate change 27YLU75U4W 7440-44-0 Carbon N762921K75 Nitrogen Phosphorus Research Support, U.S. Gov't, Non-P.H.S. temperature Research Support, Non-U.S. Gov't ecological stoichiometry N2-fixation Review activation energy benthic biofilms biogeochemistry body size carbon stable isotope community structure coupled biogeochemical cycles ecosystem ecosystem respiration energy demand gross primary production headwater streams metabolic theory metabolic theory of ecology metabolism nitrogen