Production and Utilization of Dissolved Organic Carbon During an Experimental Diatom Bloom

• Published in: Limnology and oceanography Vol. 40; no. 5; pp. 898 - 907
• Main Authors: Norrman, Bo, Zweifel, Ulla Li, Hopkinson, Charles S., Fry, Brian
• Format: Journal Article
• Language: English
• Published: Waco, TX American Society of Limnology and Oceanography 01-07-1995
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Bacillariophyceae; Bacteria; Biological and medical sciences; Carbon; Chlorophylls; Diatoms; Excretion; Fundamental and applied biological sciences. Psychology; Marine; Nucleic acids; Optical filters; Phytoplankton; Respiration; Sea water; Sea water ecosystems; Synecology; United States; North America; Massachusetts; America; ANW, USA, Massachusetts, Woods Hole, Woods Hole Harbor; Marine environment; Organic carbon; Isotope labelling; Algae; Bloom; Nutrient; Phytoplankton; Chrysophycophyta; Decomposition; Photosynthesis; Thallophyta
• ISSN: 0024-3590; 1939-5590
• DOI: 10.4319/lo.1995.40.5.0898

Stable isotope measurements of carbon were used to study the transfer of carbon from phytoplankton to bacteria during an experimental diatom bloom. A large-volume tank was filled with 900 liters of$10-\mum$-filtered seawater from Woods Hole Harbor, and N,P, and Si nutrients as well as13C-enriched NaHCO3were added. This resulted in a high nutrient system with an isotopelabel of +85%. in the dissolved inorganic carbon pool. Algal growth depleted nutrients to near-zero concentrations midway through the 2-week experiment with little net dissolved organic C (DOC) accumulation; algal chlorophyll concentrations peaked at$38 \mug liter^-1$near the time of nutrient depletion. Decline of the algal peak was associated with diatom sedimentation to the bottom of the tank and rapid accumulation of DOC. In 3 d, DOC increased from$\thicksim$130 to$250 \muM C$. The C:N ratio of this new DOC was > 22 vs. 14 in background harbor water.13Clabeling showed that bacteria preferentially assimilated the newly produced DOC in both the rapid growth and postbloom phases of the experiment, while DOC measurements indicated that very little if any of the background DOC from Woods Hole Harbor was metabolized by bacteria during the experiment. Overall, the experiment showed rapid DOC release following algal blooms, selective use of newly produced DOC by bacteria, and that DOC released during blooms is not rapidly or completely turned over following algal blooms.