Are streams often heterotrophic or autotrophic?

Huge contribution from alloctonus material. Most respiration happens on alloctonus material On an anual basis streams are heterotrophic. But there can be few days where the streams are autotrophic. Days with a lot of sun with high temp then they can be autotrophic. In mid summer basicly. Could also be streams with very little riparian imput - sourced with groundwater for instance.