Bacterial vs. zooplankton control of sinking particle flux in the ocean's twilight zone

By D. K. Steinberg, B. V. Van Mooy, K. Buesseler, Philip W. Boyd, Toru Kobari, David M. Karl. 2008

413 citations recorded by the source corpus.

The downward flux of particulate organic carbon (POC) decreases significantly in the oceanÂs mesopelagic or ‘twilight’ zone due both to abiotic processes and metabolism by resident biota. Bacteria and zooplankton solubilize and consume POC to support their metabolism, but the relative importance of bacteria vs. zooplankton in the consumption of sinking particles in the twilight zone is unknown. We compared losses of sinking POC, using differences in export flux measured by neutrally buoyant sediment traps at a range of depths, with bacteria and zooplankton metabolic requirements at the Hawaii Ocean Time‐series station ALOHA in the subtropical Pacific and the Japanese times‐series site K2 in the subarctic Pacific. Integrated (150‐1,000 m) mesopelagic bacterial C demand exceeded that of zooplankton by up to 3‐fold at ALOHA, while bacteria and zooplankton required relatively equal amounts of POC at K2. However, sinking POC flux was inadequate to meet metabolic demands at either site. Mesopelagic bacterial C demand was 3‐ to 4‐fold (ALOHA), and 10‐fold (K2) greater than the loss of sinking POC flux, while zooplankton C demand was 1‐ to 2‐fold (ALOHA), and 3‐ to 9‐fold (K2) greater (using our ‘middle’ estimate conversion factors to calculate C demand). Assuming the particle flux estimates are accurate, we posit that this additional C demand must be met by diel vertical migration of zooplankton feeding at the surface and by carnivory at depth—with both processes ultimately supplying organic C to mesopelagic bacteria. These pathways need to be incorporated into biogeochemical models that predict global C sequestration in the deep sea.

Subfields: Ecology, Oceanography

View Paper: https://www.semanticscholar.org/paper/7eee11a9f17eed8c25b459c14ccf6a9787e5badf

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In Ecology

1. B. Popp
2. C. Choy
3. J. Drazen
4. D. Steinberg
5. C. Hannides
6. M. Landry
7. D. Hutchins
8. A. Atkinson

In Oceanography

1. D. Steinberg
2. Peter C. Davison
3. B. Popp
4. Philip W. Boyd
5. C. Choy
6. J. Drazen
7. J. Koslow
8. M. Landry

Citations in the corpus

• Zooplankton and the Ocean Carbon Cycle. (2017, background): “This carbon demand is partially met by DVM of zooplankton feeding at the surface and by carnivory at depth, both of which are independent of the consumption of sinking POC (Steinberg et al. 2008a).”
• Time series of vertical flux of zooplankton fecal pellets on the continental shelf of the western Antarctic Peninsula (2012, background): “Most of the sinking POC flux, however, does not reach the deep sea due to flux attenuation in the mesopelagic zone by bacteria, zooplankton, and nekton that degrade, consume, and respire the POC back to its inorganic form (Buesseler et al., 2007; Buesseler et al, 2008b; Steinberg et al, 2008b).”
• Variable food absorption by Antarctic krill: Relationships between diet, egestion rate and the composition and sinking rates of their fecal pellets (2012, methodology): “Even though sinking speeds of 100–200 m d 1 are faster than for most copepod pellets (Turner, 2002), krill pellets could provide concentrated sources of nutrient-rich food for protozoans, cyclopoids, harpacticoids, or other scavengers (Gonzalez et al., 1994; Turner, 2002; Poulsen and Iversen, 2008; ”
• Trophic structure and food resources of epipelagic and mesopelagic fishes in the North Pacific Subtropical Gyre ecosystem inferred from nitrogen isotopic compositions (2015, background): “…suspended particulate organic matter (POM) exported out of surface waters is rapidly utilized and degraded by microbial communities, or directly consumed by migrating zooplankton, which are in turn direct food resources for micronekton fishes, cephalopods, and crustaceans (Steinberg et al. 2008).”
• Microbial Surface Colonization and Biofilm Development in Marine Environments (2015, background): “Although some surface-colonizing bacteria may increase diatom aggregate formation, the particle sinking rate, and, thus, the potential efficiency of the marine biological pump (234, 235), it is commonly accepted that POC degradation by surface-colonizing microorganisms generally decreases the carbon”
• Emerging concepts on microbial processes in the bathypelagic ocean-ecology, biogeochemistry, and genomics (2010, background): “This zone receives organic inputs from overlying layers in the form of particulate (POM) and dissolved organic matter (DOM) after substantial remineralization and transformation via complex actions of epi- and mesopelagic biota (Steinberg et al., 2008; Robinson et al., 2010).”
• Evidence for aggregation and export of cyanobacteria and nano-eukaryotes from the Sargasso Sea euphotic zone (2010, background): “It is possible that fecal pellets may be fragmented into smaller particles by biological processes such as particle-attached microbial activity, zooplankton feeding, or zooplankton-induced shear (Steinberg et al., 2008).”
• Formation of Chromophoric Dissolved Organic Matter by Bacterial Degradation of Phytoplankton-Derived Aggregates (2018, background): “Additional phytoplanktonic DOM is released through viral infection, sloppy feeding by predators such as zooplankton, and cell death, with zooplankton contributing their own DOM through excretion of organic matter and fecal pellets (Urban-Rich et al., 2006; Steinberg et al., 2008; Saba et al., 2011).”
• Carbon export mediated by mesopelagic fishes in the northeast Pacific Ocean (2013, methodology): “A similar pattern was observed by Steinberg et al. (2008a) for vertically migratory zooplankton (Table 1), in which the more productive station (K2) had a higher incidence of DVM and more efficient active transport by zooplankton than was observed at the oligotrophic station (ALOHA).”
• Effects of phytoplankton community on production, size, and export of large aggregates: A world‐ocean analysis (2009, background): “Such processes could cause a significant reduction of the flux with depth (Stemmann et al. 2004; Steinberg et al. 2008).”
• Differential remineralization of major and trace elements in sinking diatoms (2014, background): “Proteins are also the major reservoir of N in phytoplankton (Sterner and Elser 2002).”
• Autotrophic picoplankton in mesozooplankton guts: evidence of aggregate feeding in the mesopelagic zone and export of small phytoplankton (2010, background): “There is also evidence that picoplanktonic cyanobacteria may be resistant to digestion by zooplankton, as viable cells have been observed in fecal pellets and deep-sea sediments (Silver & Alldredge 1981, Lampitt et al. 1993, Turner 2002 and references therein).”
• Diel vertical migration: Ecological controls and impacts on the biological pump in a one‐dimensional ocean model (2013, background): “A wealth of observations, ranging from in situ net captures to remote acoustic data, show regular DVM across a wide range of oceanographic provinces [e.g., Banse, 1964; Longhurst, 1976; Heywood, 1996; Luo et al., 2000; Steinberg et al., 2008a].”