Low Contribution of the Fast‐Sinking Particle Fraction to Total Plankton Metabolism in a Temperate Shelf Sea. Issue 9 (6th September 2021)

• Record Type: Journal Article
• Authors: García‐Martín, E. E.; Davidson, K.; Davis, C. E.; Mahaffey, C.; McNeill, S.; Purdie, D. A.; Robinson, C.
• Is Part Of: Global biogeochemical cycles. Volume 35:Issue 9(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-06
• Subjects: microbial respiration -- bacterial production -- sinking particles -- carbon turnover -- seasonal variability; Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1029/2021GB007015
• Languages: English
• ISSNs: 0886-6236

Abstract

Abstract: Temperate shelf seas are productive areas with the potential to export high quantities of particulate organic carbon (POC), as sinking particles, to the sediments or off‐shelf to the open ocean. The amount of carbon which can be exported depends partly on the amount of POC produced and on the remineralization processes occurring on the sinking material. Here, we assessed the relative seasonal importance of microbial respiration and bacterial production associated with suspended, slow‐ and fast‐sinking particle fractions. The three fractions were collected in the Celtic Sea above and below the seasonal thermocline in November 2014, April and July 2015 using Marine Snow Catchers. The slow‐sinking fraction had higher microbial respiration and bacterial production rates than the fast‐sinking fractions, and these two fractions sustained rates of microbial respiration and bacterial production between 1 and 3 orders of magnitude lower than the suspended fraction. This low contribution of the slow‐ and fast‐sinking fractions was consistent with their low contribution to the POC concentration at the two depths sampled. The POC‐specific respiration rates associated with the slow‐ and fast‐sinking fractions were low (median 0.17 and 0.08 d −1, respectively), indicating low‐sinking particle degradation. Our results indicate that ∼5% of the POC in surface waters can be exported below the thermocline. Key Points: Higher microbial respiration and bacterial production rates estimated in slow‐sinking compared to fast‐sinking fractions in shelf waters Due to the low number of particles in the fast‐sinking fraction, their contribution to water column metabolism was low Slow‐sinking fraction made the greatest contribution to the potential export of particulate organic carbon to sediments or off‐shelf