Virginia Institute of Marine Science
MARINE ECOLOGY PROGRESS SERIES
High nutrient loading to coastal bays is often accompanied by the presence of bloom-forming macroalgae, which take up and sequester large amounts of C and N while growing. This pool is temporary, however, as nuisance macroalgae exhibit a bloom and die-off cycle, influencing the biogeochemical functioning of these systems in unknown ways. The objective of this study was to trace the C and N from senescing macroalgae into relevant sediment pools. A macroalgal die-off event was simulated by the addition of freeze-dried macroalgae (Gracilaria spp.), pre-labeled with stable isotopes (C-13 and N-15), to sediment mesocosms. The isotopes were traced into bulk sediments and partitioned into benthic microalgal (BMA) and bacterial biomass using microbial biomarkers to quantify the uptake and retention of macroalgal C and N. Bulk sediments took up label immediately following the die-off, and macroalgal C and N were retained in the sediments for at least 2 wk. Approximately 6 to 50% and 2 to 9% of macroalgal N and C, respectively, were incorporated into the sediments. Label from the macroalgae appeared in both bacterial and BMA biomarkers, suggesting that efficient shuttling of macroalgal C and N between these communities may serve as a mechanism for retention of macroalgal nutrients within the sediments.
Stable isotopes; Macroalgae; Benthic microalgae; Bacteria; Biomarker; Coastal eutrophication
Hardison, Amber K.; Canuel, Elizabeth A.; Anderson, Iris C.; and Veuger, Bart, Fate of macroalgae in benthic systems: carbon and nitrogen cycling within the microbial community (2010). MARINE ECOLOGY PROGRESS SERIES, 414, 41-55.