Autotrophic benthic systems, defined by the difference between the autotrophs net primary production over a year and the total community respiration, has been empirically measured and calculated for seagrass ecosystems. They are net autotrophic greater than an absolute total net primary production of benthic pelagic assemblage (NPP). However, even though it is regarded that seaweeds part of the benthic primary productivity can be greater than seagrass, I cannot find any reference to studies that have measured or calculated their NPP and community respiration i.e benthic animals, zooplankton, sediment respiration. If so, then as say kelps are lost during El niño years as upwelling and nutrient supply is lost at what point does the oligotrophic kelp ecosystem become heterotrophic in the manner as seagrass and phytoplankton lake communities.