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| Titel |
Microphytobenthos and benthic macroalgae determine sediment organic matter composition in shallow photic sediments |
| VerfasserIn |
A. K. Hardison, E. A. Canuel, I. C. Anderson, C. R. Tobias, B. Veuger, M. N. Waters |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 8 ; Nr. 10, no. 8 (2013-08-20), S.5571-5588 |
| Datensatznummer |
250085304
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| Publikation (Nr.) |
 copernicus.org/bg-10-5571-2013.pdf |
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| Zusammenfassung |
| Microphytobenthos and benthic macroalgae play an important role in system
metabolism within shallow coastal bays. However, their independent and
interactive influences on sediment organic matter (SOM) are not well
understood. We investigated the influence of macroalgae and microphytobenthos
on SOM quantity and quality in an experimental mesocosm system using bulk and
molecular level (total hydrolyzable amino acids, THAA; phospholipid linked
fatty acids, PLFA; pigment) analyses. Our experiment used an incomplete
factorial design made up of two factors, each with two levels: (1) light
(ambient vs. dark) and (2) macroalgae (presence vs. absence of live
macroalgae). Over the course of the 42-day experiment, total organic carbon
(TOC) and total nitrogen (TN) increased under ambient light by 173 ± 14
and 141 ± 7%, respectively, compared to in the dark (78 ± 29
and 39 ± 22%). THAA comprised a substantial fraction of SOM
(~ 16% of TOC, 35% of TN) and followed TOC and TN
accumulation patterns. Mole percent composition of the THAA pool indicated
that SOM was composed of more labile organic material (e.g., L-glutamic acid,
phenylalanine) under ambient light conditions while SOM in dark treatments
was more degraded, with higher proportions of glycine and D-alanine. PLFA
content, which represents viable biomass, made up ~ 1% of TOC and
contained high levels of algal fatty acids in the light, particularly PLFA
derived from diatoms. In the presence of microphytobenthos (i.e., light and
macroalgae treatments), SOM lability increased, resulting in the observed
increases in bacterial PLFA concentrations. Macroalgae, which were added to
half of the light treatments, decreased SOM accumulation compared to light
treatments without macroalgae, with TOC and TN increasing by only
130 ± 32 and 94 ± 24%, respectively. This decrease likely
resulted from shading by macroalgae, which reduced production of
microphytobenthos. The presence of macroalgae decreased SOM lability as well,
which resulted in diminished buildup of bacterial biomass. By the final day
of the experiment, principal component analysis revealed that sediment
composition in treatments with macroalgae was more similar to dark treatments
and less similar to light treatments without macroalgae. Overall,
microphytobenthos and benthic macroalgae fundamentally altered SOM quality
and quantity, which may have notable ecological consequences for
shallow-water systems such as increased hypoxia/anoxia, sulfide accumulation,
enhanced mineralization and/or stimulated denitrification. |
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