Regional and temporal variability of sinking organic matter in the subtropical northeast Atlantic Ocean: a biomarker diagnosis

Abstract

Abstract. Sinking particles through the pelagic ocean have been traditionally considered the most important vehicle by which the biological pump sequesters carbon in the ocean interior. Nevertheless, regional scale variability in particle flux is a major outstanding issue in oceanography. Here, we have studied the regional and temporal variability of total particulate organic matter fluxes, as well as chloropigment and total hydrolyzed amino acid (THAA) compositions and fluxes in the Canary Current region, between 20-30 • N, during two contrasting periods: August 2006, characterized by warm and stratified waters, but also intense winds which enhanced eddy development south of the Canary Islands, and February 2007, characterized by colder waters, less stratification and higher productivity. We found that the eddyfield generated south of the Canary Islands enhanced by >2 times particulate organic carbon (POC) export with respect to stations (FF; far-field) outside the eddy-field influence. We also observed flux increases of one order of magnitude in chloropigment and 2 times in THAA in the eddy-field relative to FF stations. Principal Components Analysis (PCA) was performed to assess changes in particulate organic matter composition between stations. At eddy-field stations, higher chlorophyll enrichment reflected "fresher" material, while at FF stations a higher proportion of pheophytin indicated greater degradation due to microbes and microzooplankton. PCA also suggests that phytoplankton community structure, particularly the dominance of diatoms versus carbonate-rich plankton, is the major factor influencing the POC export within the eddy field. In February, POC export

234Th in different size classes of sediment trap collected particles from the Northwestern Pacific Ocean

“…Furthermore, Alonso-Gonzalez et al (2010) suggested that in regions of the ocean, such as in the tropical oligotrophic ocean under post bloom conditions, the slow sinking small particle pool contributes significantly to the POC flux. These field observations thus provide additional support that small sinking particles (<53 lm) are important for carrying carbon to the deep ocean.…”

Fronts at the Surface Ocean Can Shape Distinct Regions of Microbial Activity and Community Assemblages Down to the Bathypelagic Zone: The Azores Front as a Case Study

“…The origin of these particles could be both from the surface waters or advected from the more productive continental shelf. Analyses of organic biomarkers revealed that these particles have the same degradation state or are even fresher than rapidly sinking particles (Alonso-González et al, 2010). The large eddy activity in the region south of the AF could be responsible of the re-distribution of these slowly sinking particles in the deep ocean.…”

“…During the time of our study and the previous months, the region south of the AF would have been affected by strong advection of organic matter from the continental margins, explaining the lower beam transmission values, the association of heterotrophic prokaryotes to particles, and the increases in the LAPase:BGase and LAPase:AGase ratios, indicative of more labile material. Alonso-González et al (2010), using a sediment trap that separate particles as function of their settling velocity, found over a 1.5-year period deployment in the Canary Current region that more than 60% of total organic carbon is contained in small slowly settling particles (0.7-11 m d −1 ), at least during half of the year (from June to December). The origin of these particles could be both from the surface waters or advected from the more productive continental shelf.…”

Forcing of dissolved organic carbon release by phytoplankton by anticyclonic mesoscale eddies in the subtropical NE Atlantic Ocean

“…The dynamics of mesoscale eddies exert profound influences on the vertical fluxes of organic matter, nutrients and carbon (Owen, 1981;Arístegui et al, 2003;Martin and Richards, 2001;Mathis et al, 2007;Alonso-González et al, 2010;Benitez-Nelson and McGillicuddy, 2008) and may modulate the oceanic vertical pump (Oschlies and Garçon, 1998). Previous studies have indicated the importance of mesoscale eddies in ocean biogeochemistry by modulating the efficiency of the biological pump.…”