Benthic community responses to lake eutrophication are poorly understood relative to pelagic responses. We
compared phytoplankton and periphyton productivity along a eutrophication gradient in Greenland, U.S., and Danish
lakes. Phytoplankton productivity increased along the phosphorus gradient (total phosphorus [TP] 5 2–430 mg
m23), but whole-lake benthic algal productivity decreased, substantially depressing increases in primary productivity
at the whole-lake scale. In shallow, oligotrophic Greenland lakes, periphyton was responsible for 80–98% of primary
production, whereas in Danish lakes with TP . 100 mg m23, phytoplankton were responsible for nearly 100% of
primary production. Benthic contributions ranged from 5 to 80% depending on morphometry and littoral habitat
composition in lakes with intermediate phosphorus concentrations. Thus, eutrophication was characterized by a
switch from benthic to pelagic dominance of primary productivity. Carbon stable isotope analysis showed that the
redistribution of primary production entailed a similar shift from periphyton to phytoplankton in the diets of zoobenthos.
Benthic and pelagic habitats were energetically linked through food web interactions, but eutrophication eroded
the benthic primary production pathway.