Degradation of macroalgae detritus: how does detritus from macroalgae cultivation affect carbon release from marine sediments?

Macroalgae cultivation can lead to loss of detritus before the algae are harvested, either from loss of whole thalli or erosion of tissue. When labile organic matter (LOM) is added to the sediment, a “priming effect” of the degradation of organic matter in the sediment can occur. A previous study found indications of microbial priming, as the mineralized carbon exceeded the amount of carbon in the added macroalgae. The aim of this study is to investigate microbial degradation of detritus from the species Ulva sp. and Saccharina latissima, and the potential priming effect in the sediment. Two laboratory experiments were conducted using sediment cores collected in Limfjorden. To start the flux experiment fresh algae tissue was added to each core. Measurements of O2, DIC and dissolved inorganic nutrient fluxes were taken at day 1, 5, 12, 20, 40 and 80 after the addition of algae. Results of the first lab experiment indicates significant effect of treatment and time on O2 flux. The results contribute to the discussion of whether macroalgae detritus from cultivation will contribute to carbon sequestration or stimulate increased degradation of carbon buried in the sediment.