The utilization of polysaccharides by heterotrophic bacterioplankton in the Bay of Biscay (North Atlantic Ocean)

• Published in: Journal of Plankton Research
• Main Authors: Piontek, Judith, Händel, Nicole, de Bodt, Caroline, Harlay, Jérôme, Chou, Lei, Engel, Anja
• Format: Text
• Language: English
• Published: Oxford University Press 2011
• Subjects: Article; North Atlantic
• Online Access: http://plankt.oxfordjournals.org/cgi/content/short/fbr069v1; https://doi.org/10.1093/plankt/fbr069

This study investigates the turnover of polysaccharides by heterotrophic bacterioplankton in the northern Bay of Biscay, a productive marine system on the continental margin of the temperate Atlantic Ocean. Bacterial biomass production (BBP) near the surface ranged from 0.5 to 25.7 nmol C L−1 h−1 during small phytoplankton blooms in May and June that occurred after the main spring bloom. A direct relationship between BBP and total polysaccharides strongly suggests the dependence of bacterial growth on the availability of semi-labile organic matter. Concentrations of combined glucose as well as rate constants of extracellular glucosidase activity and glucose uptake were determined to estimate the actual carbon fluxes from bacterial polysaccharide turnover. Results reveal that the degradation of polysaccharides in the upper 100 m of the water column sustained a glucose flux of 15.2–32.3 mg C m−2 d−1 that was available for bacterial consumption. The mean turnover time for polysaccharides was 170 and 165 days for α - and β -glycosidic linked polymers, respectively. Incorporation of free glucose supported 0.4–19.6% of BBP. The availability of nitrate plus nitrite (NO x ) was identified as one factor increasing bacterial incorporation of glucose in most samples. Our results demonstrate that the bacterial recycling of polysaccharides generated a significant flux of organic carbon in microbial food-webs and biogeochemical processes.