Chlorophyll pigments: Subsamples of the top first cm of sediment were obtained using cut-off plastic syringes. Samples for chlorophyll pigment analyses were stored dark and frozen at -20°C until further analyses in the home laboratory. Chlorophyll pigments were extracted as described in Boetius et al. (1998, https://doi.org/10.1016/S0967-0637(97)00052-6). Briefly, pigments were extracted in 90% acetone, after addition of glass beads and grinding in a cell mill. Extracts were centrifuged and concentrations of chlorophyll a and phaeopigments (after acidification with HCl) were determined with a Turner Trilogy fluorometer. The sum of chlorophyll a and phaeopigments is expressed as chloroplast pigment equivalents (CPE). The proportion of chlorophyll a from CPE (% chla) is an indicator of the freshness of phytodetritus. Total organic carbon: Subsamples of the top first cm of sediment were also obtained using cut-off plastic syringes. Samples were stored frozen at -20°C until further analyses in the home laboratory. The total carbon content of sediment samples was determined by combustion and gas chromatography with a Carlo Erba NA-1500 CNS elemental analyzer. An aliquot of the sample was acidified to remove the fraction of inorganic carbon and to determine the total amount of organic carbon.