Species-specific ingestion of organic carbon by deep-sea benthic foraminifera and meiobenthos: In situ tracer experiments

Abstract

We measured organic carbon uptake rates by deep-sea benthic foraminifera and studied differences among species, living depth, and seasons to investigate how these protists contribute to carbon consumption on the deep-sea floor. In situ feeding experiments using 13 C-labeled algae were carried out in the central part of Sagami Bay from 24 to 29 November 2001 and 1 to 12 April 2002. Our results indicate that carbon assimilation rates were higher in shallow infaunal species (Uvigerina akitaensis, Bulimina aculeata) and lower in intermediate (Textularia kattegatensis) and deep infaunal species (Chilostomella ovoidea). Some shallow and intermediate infaunal species showed higher carbon uptake in spring than in autumn. In total, benthic foraminifera assimilated C at 5.8 Ϯ 4.8 mg m Ϫ2 and 2.0 Ϯ 1.3 mg m Ϫ2 (in spring and in autumn, respectively) of labeled algae within 2 d, which was more than that by total metazoans (1.5 Ϯ 0.4 mg m Ϫ2 and 0.4 Ϯ 0.1 mg m Ϫ2 , respectively). Deep-sea benthic foraminifera rapidly ingest large amounts of carbon and may play an important role in carbon consumption on the deep-sea floor. Different responses to algal carbon among species may explain foraminiferal assemblages and shifts after environmental changes, such as seasonal pulses of organic matter supply.

Algal pigments in Southern Ocean abyssal foraminiferans indicate pelagobenthic coupling

“…Niche separation between different surface-sediment feeding foraminiferans is demonstrated by the composition of algal pigments in the cytoplasm, confirming previous experimental results (Heinz et al, 2001;Nomaki et al, 2005Nomaki et al, , 2009Witte et al, 2003). The high ratios of chlorophyll a and Pheo a pigments in Miliolinella 1 and Miliolinella 2 shows that they were feeding on fresh phytodetritus.…”

“…But it has also been shown that many deep-sea foraminiferans are associated with phytodetrital aggregates (Cornelius and Gooday, 2004) and can give a fast response to pulses of phytodetritus (Gooday, 1988(Gooday, , 2002. The response of foraminiferans to phytodetritus exposure has been extensively documented both in situ and experimentally (Enge et al, 2011;Heinz et al, 2001;Nomaki et al, 2005Nomaki et al, , 2009Witte et al, 2003). Indirectly, the distribution of benthic foraminiferal faunas, e.g., dominated by Epistominella exigua (Brady, 1884) in various Southern Ocean environments are a reflection of the importance of phytodetritus pulses (Mackensen et al, 1993(Mackensen et al, , 1995.…”

Uptake of algal carbon and the likely synthesis of an "essential" fatty acid by <i>Uvigerina</i> ex. gr. <i>semiornata</i> (Foraminifera) within the Pakistan margin oxygen minimum zone: evidence from fatty acid biomarker and <sup>13</sup>C tracer experiments

“…In situ experiments at a mildly oxygen-depleted bathyal site in Sagami Bay, Japan (1450 m depth) suggest that broad differences exist in the trophic preferences of different deep-sea foraminiferal species, as well as the degree to which they respond to pulses of labile food. Thus, some species (including Uvigerina akitaensis) in Sagami Bay consume only fresh algae and are particularly active in the short-term processing of algal-derived organic matter, while others will ingest sedimentary organic matter as well as more labile material (Nomaki et al, 2005a(Nomaki et al, , 2006(Nomaki et al, , 2011. Subsequent experiments in which labelled carbon was tracked into specific fatty acids within foraminiferal cells suggested that some species (again including U. akitinensis) are able to degrade and/or synthesise some fatty acids (Nomaki et al, 2009).…”

Sedimentary membrane lipids recycled by deep-sea benthic archaea

“…The experiment was performed on the seafloor at the central part of Sagami Bay, Japan (3500.8'N, 13921.6'E; 1453 m depth) 17 for 0-405 days (Supplementary Figure 1). 50…”