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| Titel |
Intertidal foraminifera (Protista) and carbon-nitrogen cycling: combined effects of temperature and diet quality |
| VerfasserIn |
Julia Wukovits, Annekatrin Julie Enge, Max Oberrauch, Margarete Watzka, Wolfgang Wanek, Petra Heinz |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250141590
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| Publikation (Nr.) |
 EGU/EGU2017-5120.pdf |
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| Zusammenfassung |
| Benthic foraminifera (eukaryotic protists) are to a large extent acting as detrivores, feeding on
microalgal detritus. Phytodetritus constitutes a main component of the intertidal carbon (C)
and nitrogen (N) pool, thus making foraminifera important players in intertidal nutrient
fluxes. These fluxes are strongly dependent on interactions between biotic and abiotic
environmental factors, as e.g. the energetic value or the quality of phytodetritus that depends
on environmental nutrient availability. Increased inorganic C concentrations in coastal water
bodies (e.g. due to increased atmospheric CO2) can have a negative effect on the phytodetrital
quality by increasing microalgal C:N ratios. Simultanous warming of the environment can
cause increased metabolic rates of exposed heterotrophic organisms, like foraminifera. The
combination of lower food quality and increased metabolic rates is supposed to
cause cascading effects on organismic C cycling, potentially diminishing the role of
detrivorous food as a C sink in marine food webs by increased discharge of excess
C.
In this study, the above described scenario was tested in laboratory feeding experiments on a
common and abundant intertidal foraminiferal species (Haynesina germanica, collected in
the German Wadden Sea). Two batches of artificially produced and dual isotope labeled (13C
and 15N) chlorophyte detritus (1.5 gDW m-2) with different C:N ratios (5.5 and 7.6) and one
batch of isotopically labelled diatom detritus (C:N 5.6) were fed under controlled
conditions at three different temperatures. Results were extrapolated to the in situ
abundance of live H. germanica individuals in the sampling area (sediment core
data), to estimate the magnitude of the effect on an areal basis within the natural
habitat.
The study revealed significant, temperature induced variations in the carbon and nitrogen
processing of H. germanica. The food source with an increased C:N ratio doubled the release
of carbon from the H. germanica community at 20∘C in relation to 15∘C, causing a
theoretical carbon loss of 1000 μg m-2 within 24 hours. The uptake of diatom detritus was
higher relative to chlorophyte detritus uptake, though the carbon release did not differ from
the chlorophyte food source of similar C:N (C:N 5.5). The results illustrate the impact of
altered environmental factors on benthic nutrient fluxes in foraminiferal communities, an
important but often overlooked component of intertidal microfauna associations. |
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