Enhanced transfer of organic matter to higher trophic levels caused by ocean acidification and its implications for export production: A mass balance approach.

Boxhammer, Tim, Taucher, Jan, Bach, Lennart T., Achterberg, Eric P., Algueró-Muñiz, María, Bellworthy, Jessica, Czerny, Jan, Esposito, Mario, Haunost, Mathias, Hellemann, Dana, Ludwig, Andrea, Yong, Jaw Chuen, Zark, Maren, Riebesell, Ulf and Anderson, Leif G. (2018) Enhanced transfer of organic matter to higher trophic levels caused by ocean acidification and its implications for export production: A mass balance approach. Open Access PLoS ONE, 13 (5). e0197502. DOI 10.1371/journal.pone.0197502.

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Abstract

Ongoing acidification of the ocean through uptake of anthropogenic CO2 is known to affect marine biota and ecosystems with largely unknown consequences for marine food webs. Changes in food web structure have the potential to alter trophic transfer, partitioning, and biogeochemical cycling of elements in the ocean. Here we investigated the impact of realistic end-of-the-century CO2 concentrations on the development and partitioning of the carbon, nitrogen, phosphorus, and silica pools in a coastal pelagic ecosystem (Gullmar Fjord, Sweden). We covered the entire winter-to-summer plankton succession (100 days) in two sets of five pelagic mesocosms, with one set being CO2 enriched (~760 μatm pCO2) and the other one left at ambient CO2 concentrations. Elemental mass balances were calculated and we highlight important challenges and uncertainties we have faced in the closed mesocosm system. Our key observations under high CO2 were: (1) A significantly amplified transfer of carbon, nitrogen, and phosphorus from primary producers to higher trophic levels, during times of regenerated primary production. (2) A prolonged retention of all three elements in the pelagic food web that significantly reduced nitrogen and phosphorus sedimentation by about 11 and 9%, respectively. (3) A positive trend in carbon fixation (relative to nitrogen) that appeared in the particulate matter pool as well as the downward particle flux. This excess carbon counteracted a potential reduction in carbon sedimentation that could have been expected from patterns of nitrogen and phosphorus fluxes. Our findings highlight the potential for ocean acidification to alter partitioning and cycling of carbon and nutrients in the surface ocean but also show that impacts are temporarily variable and likely depending upon the structure of the plankton food web.

Document Type: Article
Keywords: Carbon dioxide; Mesocosms; Water columns; Particulates; Copepods; Food web structure; Phytoplankton; Sedimentation
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
AWI
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.1371/journal.pone.0197502
ISSN: 1932-6203
Projects: BIOACID, ASSEMBLE
Expeditions/Models/Experiments:
Date Deposited: 29 May 2018 07:13
Last Modified: 21 Jun 2018 12:45
URI: http://oceanrep.geomar.de/id/eprint/43165

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