Response of shallow water benthic foraminifera to a <sup>13</sup>C-labeled food pulse in the laboratory
Abstract
In recent years, stable isotope techniques have been applied successfully directly on the sea floor to follow the fate of carbon in the marine carbon cycle. Feeding experiments using <sup>13</sup>C-labeled food enable the tracking of ingested tracer material in the cytoplasm of foraminifera to study phytodetrital carbon uptake in situ. Here we introduce first results of a <sup>13</sup>C-labeled food pulse in the laboratory. Benthic foraminiferal species Ammonia tepida and Bolivina variabilis were studied to analyze their response. Marked green algae Dunaliella tertiolecta were added at the beginning of the experiment and the foraminiferal reaction was followed for 42 days. In order to assess the uptake of labeled material with time, foraminiferal specimens were subsampled at 2, 7, 21, and 42 days and analyzed for their carbon signals. Culture conditions (T, salinity, O<sub>2</sub>) were monitored and kept stable during time. Both species showed fast and strong ingestion of the added food material after 2 days, followed by a decreasing isotopic signal in the biomass with time. Additionally, the isotopic signals in the overlying water of the experimental dishes and in the foraminiferal tests were measured, but these values were difficult to interpret
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