The effect of the salinity, light regime and food source on carbon and nitrogen uptake in a benthic foraminifer

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