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- Soares, Ana, et al.
(författare)
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New insights on resource stoichiometry : assessing availability of carbon, nitrogen, and phosphorus to bacterioplankton
- 2017
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 14:6, s. 1527-1539
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Tidskriftsartikel (refereegranskat)abstract
- Boreal lake and river ecosystems receive large quantities of organic nutrients and carbon (C) from their catchments. How bacterioplankton respond to these inputs is not well understood, in part because we base our understanding and predictions on "total pools", yet we know little about the stoichiometry of bioavailable elements within organic matter. We designed bioassays with the purpose of exhausting the pools of readily bioavailable dissolved organic carbon (BDOC), bioavailable dissolved nitrogen (BDN), and bioavailable dissolved phosphorus (BDP) as fast as possible. Applying the method in four boreal lakes at base-flow conditions yielded concentrations of bioavailable resources in the range 105-693 mu g CL-1 for BDOC (2% of initial total DOC), 24-288 mu g NL-1 for BDN (31% of initial total dissolved nitrogen), and 0.2-17 mu g PL-1 for BDP (49% of initial total dissolved phosphorus). Thus, relative bioavailability increased from carbon (C) to nitrogen (N) to phosphorus (P). We show that the main fraction of bioavailable nutrients is organic, representing 80% of BDN and 61% of BDP. In addition, we demonstrate that total C : N and C: P ratios are as much as 13-fold higher than C : N and C: P ratios for bioavailable resource fractions. Further, by applying additional bioavailability measurements to seven widely distributed rivers, we provide support for a general pattern of relatively high bioavailability of P and N in relation to C. Altogether, our findings underscore the poor availability of C for support of bacterial metabolism in boreal C-rich fresh-waters, and suggest that these ecosystems are very sensitive to increased input of bioavailable DOC.
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- Soares, Ana R.A., et al.
(författare)
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Bacterioplankton Responses to Increased Organic Carbon and Nutrient Loading in a Boreal Estuary-Separate and Interactive Effects on Growth and Respiration
- 2018
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Ingår i: Microbial Ecology. - : SPRINGER. - 0095-3628 .- 1432-184X. ; 76:1, s. 144-155
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Tidskriftsartikel (refereegranskat)abstract
- Increases in the terrestrial export of dissolved organic carbon (C) to rivers may be associated with additional loading of organic nitrogen (N) and phosphorus (P) to the coastal zone. However, little is known about how these resources interact in the regulation of heterotrophic bacterioplankton metabolism in boreal coastal ecosystems. Here, we measured changes in bacterioplankton production (BP) and respiration (BR) in response to full-factorial (C, N, and P) enrichment experiments at two sites within the A-re estuary, northern Sweden. The BR was stimulated by single C additions and further enhanced by combined additions of C and other nutrients. Single addition of N or P had no effect on BR rates. In contrast, BP was primarily limited by P at the site close to the river mouth and did not respond to C or N additions. However, at the site further away from the near the river mouth, BP was slightly stimulated by single additions of C. Possibly, the natural inflow of riverine bioavailable dissolved organic carbon induced local P limitation of BP near the river mouth, which was then exhausted and resulted in C-limited BP further away from the river mouth. We observed positive interactions between all elements on all responses except for BP at the site close to the river mouth, where P showed an independent effect. In light of predicted increases in terrestrial P and C deliveries, we expect future increases in BP and increases of BR of terrestrially delivered C substrates at the A-re estuary and similar areas.
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