Significance of pelagic and benthic metabolism for the carbon budget of a shallow lake

Abstract

Pelagic and benthic primary production and respiration were measured at an offshore station in the shallow, 1.2 m deep, polymictic Lake Gardno (Poland) to examine the role of the pelagic zone and the sediments in the overall carbon budget of this lake. The respiration rates in the sediments were within the same range of values as those in the pelagic zone. The results indicate that although the pelagic zone of the lake was net autotrophic (P:R = 2.46) based on annual cycles, total primary production to respiration (pelagic zone + sediments) was balanced, and the P:R ratio was 1.18. Thus, potentially only a small part of pelagic primary production is exported and buried in the sediments. The whole lake ecosystem does not act as an effective atmospheric CO2 sink. The balanced primary production to respiration ratio in the open water zone of the lake indicated that littoral production was most probably decomposed or buried within the littoral zone.