Seasonal community metabolism in six Michigan headwater streams

Temperate headwater streams are generally considered heterotrophic with most production derived from allochthonous inputs. However, most studies have focused on a single season. Consequently contributions from autochthonous inputs during other times of the year may be underestimated on an annual basis. This study aimed to determine community metabolism and production in six Michigan headwater streams during three different seasons. Chambers were used to determine in-situ community metabolism during spring, summer, and fall. In general streams tended to be autotrophic in the spring, slightly heterotophic in the summer and were most heterotrphic in the fall. However, productivity varied among streams as well as among seasons with four of the streams exhibiting P/R ratios >1 on at least two sample dates whereas two streams were heterotrophic on all three dates. These data suggest that autochthonous inputs in these streams may contribute more to stream production than generally assumed.