In:
Biogeosciences, Copernicus GmbH, Vol. 18, No. 4 ( 2021-02-23), p. 1395-1406
Abstract:
Abstract. Foraminifera are unicellular organisms that play an important role in marine
organic matter cycles. Some species are able to isolate chloroplasts from
their algal food source and incorporate them as kleptoplasts into their own
metabolic pathways, a phenomenon known as kleptoplastidy. One species showing
this ability is Elphidium excavatum, a common foraminifer in the Kiel
Fjord, Germany. The Kiel Fjord is fed by several rivers and thus forms a
habitat with strongly fluctuating salinity. Here, we tested the effects of
the food source, salinity and light regime on the food uptake (via 15N
and 13C algal uptake) in this kleptoplast-bearing foraminifer. In
our study E. excavatum was cultured in the lab at three salinity
levels (15, 20 and 25) and uptake of C and N from the food source
Dunaliella tertiolecta (Chlorophyceae) and Leyanella arenaria (Bacillariophyceae) were measured over time (after 3, 5 and 7 d). The species was very well adapted to the current salinity of the
sampling region, as both algal N and C uptake was highest at a salinity of 20. It seems that E. excavatum coped better with lower than with
higher salinities. The amount of absorbed C from the green algae
D. tertiolecta showed a tendency effect of salinity, peaking at a
salinity of 20. Nitrogen uptake was also highest at a salinity of 20 and
steadily increased with time. In contrast, C uptake from the diatom
L. arenaria was highest at a salinity of 15 and decreased at higher
salinities. We found no overall significant differences in C and N uptake from
green algae vs. diatoms. Furthermore, the food uptake at a light–dark rhythm
of 16:8 h was compared to continuous darkness. Darkness had a
negative influence on algal C and N uptake, and this effect increased with
incubation time. Starving experiments showed a stimulation of food uptake
after 7 d. In summary, it can be concluded that E. excavatum
copes well with changes of salinity to a lower level. For changes in light
regime, we showed that light reduction caused a decrease of C and N uptake by
E. excavatum.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-18-1395-2021
DOI:
10.5194/bg-18-1395-2021-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2021
detail.hit.zdb_id:
2158181-2
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