Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: a <sup>13</sup>C pulse-chase experiment
Shallow coastal waters in many regions are subject to nutrient enrichment. Microphytobenthos (MPB) can account for much of the carbon (C) fixation in these environments, depending on the depth of the water column, but the effect of enhanced nutrient availability on the processing and fate of MPB...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2018-05-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/15/2873/2018/bg-15-2873-2018.pdf |
| _version_ | 1818446606407565312 |
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| author | P. M. Riekenberg P. M. Riekenberg J. M. Oakes B. D. Eyre |
| author_facet | P. M. Riekenberg P. M. Riekenberg J. M. Oakes B. D. Eyre |
| author_sort | P. M. Riekenberg |
| collection | DOAJ |
| description | Shallow coastal waters in many regions are subject to nutrient enrichment.
Microphytobenthos (MPB) can account for much of the carbon (C) fixation in
these environments, depending on the depth of the water column, but the
effect of enhanced nutrient availability on the processing and fate of
MPB-derived C (MPB-C) is relatively unknown. In this study, MPB was labeled
(stable isotope enrichment) in situ using <sup>13</sup>C-sodium bicarbonate. The
processing and fate of the newly fixed MPB-C was then traced using ex situ
incubations over 3.5 days under different concentrations of nutrients
(NH<sub>4</sub><sup>+</sup> and PO<sub>4</sub><sup>3−</sup>: ambient, 2 × ambient, 5 ×
ambient, and 10 × ambient). After 3.5 days, sediments incubated with
increased nutrient concentrations (amended treatments) had increased loss of
<sup>13</sup>C from sediment organic matter (OM) as a
portion of initial uptake (95 % remaining in ambient vs. 79–93 % for
amended treatments) and less <sup>13</sup>C in MPB (52 % ambient, 26–49 %
amended), most likely reflecting increased turnover of MPB-derived C
supporting increased production of extracellular enzymes and storage
products. Loss of MPB-derived C to the water column via dissolved organic C
(DOC) was minimal regardless of treatment (0.4–0.6 %). Loss due to
respiration was more substantial, with effluxes of dissolved inorganic C
(DIC) increasing with additional nutrient availability (4 % ambient,
6.6–19.8 % amended). These shifts resulted in a decreased turnover time
for algal C (419 days ambient, 134–199 days amended). This suggests that
nutrient enrichment of estuaries may ultimately lead to decreased retention
of carbon within MPB-dominated sediments. |
| first_indexed | 2024-12-14T19:50:24Z |
| format | Article |
| id | doaj.art-87968fbcf32c4d63a98d22f9497cf0e8 |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-14T19:50:24Z |
| publishDate | 2018-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-87968fbcf32c4d63a98d22f9497cf0e82022-12-21T22:49:26ZengCopernicus PublicationsBiogeosciences1726-41701726-41892018-05-01152873288910.5194/bg-15-2873-2018Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: a <sup>13</sup>C pulse-chase experimentP. M. Riekenberg0P. M. Riekenberg1J. M. Oakes2B. D. Eyre3Centre for Coastal Biogeochemistry, Southern Cross University, P.O. Box 157, Lismore, NSW, 2480, Australianow at: NIOZ Royal Netherlands Institute for Sea Research, Department of Marine Microbiology and Biogeochemistry, P.O. Box 59, 1790AB Den Burg, the NetherlandsCentre for Coastal Biogeochemistry, Southern Cross University, P.O. Box 157, Lismore, NSW, 2480, AustraliaCentre for Coastal Biogeochemistry, Southern Cross University, P.O. Box 157, Lismore, NSW, 2480, AustraliaShallow coastal waters in many regions are subject to nutrient enrichment. Microphytobenthos (MPB) can account for much of the carbon (C) fixation in these environments, depending on the depth of the water column, but the effect of enhanced nutrient availability on the processing and fate of MPB-derived C (MPB-C) is relatively unknown. In this study, MPB was labeled (stable isotope enrichment) in situ using <sup>13</sup>C-sodium bicarbonate. The processing and fate of the newly fixed MPB-C was then traced using ex situ incubations over 3.5 days under different concentrations of nutrients (NH<sub>4</sub><sup>+</sup> and PO<sub>4</sub><sup>3−</sup>: ambient, 2 × ambient, 5 × ambient, and 10 × ambient). After 3.5 days, sediments incubated with increased nutrient concentrations (amended treatments) had increased loss of <sup>13</sup>C from sediment organic matter (OM) as a portion of initial uptake (95 % remaining in ambient vs. 79–93 % for amended treatments) and less <sup>13</sup>C in MPB (52 % ambient, 26–49 % amended), most likely reflecting increased turnover of MPB-derived C supporting increased production of extracellular enzymes and storage products. Loss of MPB-derived C to the water column via dissolved organic C (DOC) was minimal regardless of treatment (0.4–0.6 %). Loss due to respiration was more substantial, with effluxes of dissolved inorganic C (DIC) increasing with additional nutrient availability (4 % ambient, 6.6–19.8 % amended). These shifts resulted in a decreased turnover time for algal C (419 days ambient, 134–199 days amended). This suggests that nutrient enrichment of estuaries may ultimately lead to decreased retention of carbon within MPB-dominated sediments.https://www.biogeosciences.net/15/2873/2018/bg-15-2873-2018.pdf |
| spellingShingle | P. M. Riekenberg P. M. Riekenberg J. M. Oakes B. D. Eyre Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: a <sup>13</sup>C pulse-chase experiment Biogeosciences |
| title | Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: a <sup>13</sup>C pulse-chase experiment |
| title_full | Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: a <sup>13</sup>C pulse-chase experiment |
| title_fullStr | Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: a <sup>13</sup>C pulse-chase experiment |
| title_full_unstemmed | Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: a <sup>13</sup>C pulse-chase experiment |
| title_short | Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: a <sup>13</sup>C pulse-chase experiment |
| title_sort | short term fate of intertidal microphytobenthos carbon under enhanced nutrient availability a sup 13 sup c pulse chase experiment |
| url | https://www.biogeosciences.net/15/2873/2018/bg-15-2873-2018.pdf |
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