Abstract
Abstract. Foraminifera are an important component of benthic communities in oxygen-depleted settings, where they potentially play a significant role in the processing of organic matter. We tracked the uptake of a 13C-labelled algal food source into individual fatty acids in the benthic foraminiferal species Uvigerina ex. gr. semiornata from the Arabian Sea oxygen minimum zone (OMZ). The tracer experiments were conducted on the Pakistan margin during the late/post monsoon period (August–October 2003). A monoculture of the diatom Thalassiosira weisflogii was 13C-labelled and used to simulate a pulse of phytoplankton in two complementary experiments. A lander system was used for in situ incubations at 140 m water depth and for 2.5 days in duration. Shipboard laboratory incubations of cores collected at 140 m incorporated an oxystat system to maintain ambient dissolved oxygen concentrations and were terminated after 5 days. Uptake of diatoms was rapid, with a high incorporation of diatom fatty acids into foraminifera after ~ 2 days in both experiments. Ingestion of the diatom food source was indicated by the increase over time in the quantity of diatom biomarker fatty acids in the foraminifera and by the high percentage of 13C in many of the fatty acids present at the endpoint of both in situ and laboratory-based experiments. These results indicate that
Highlights
Benthic foraminifera are a highly successful and diverse group of heterotrophic protists in all marine environments
Within the framework of this broader investigation, we focused on the calcareous foraminifera Uvigerina ex. gr. semiornata, the dominant (72–77 % of assemblage in > 300 μm fraction) macrofaunal species at 140 m depth (Larkin and Gooday, 2009)
Our experiments were conducted during the post-monsoon season, when the site was within the oxygen minimum zone (OMZ) and strongly hypoxic
Summary
Benthic foraminifera are a highly successful and diverse group of heterotrophic protists in all marine environments. Some species are carnivorous (Suhr et al, 2008; Dupey et al, 2010), but many typically feed at a low trophic level on algae, bacteria, sedimentary organic matter, and phytodetritus (e.g. Gooday et al, 2008 and references therein). Phytodetritus derived from primary productivity in the euphotic zone provides an important source of fresh organic matter for benthic organisms. Gooday and Rathburn, 1999; Koho et al, 2008; Gooday et al, 2010 and references therein). Based on these observations, it has been suggested that foraminifera are important in the processing of organic carbon on the ocean floor (Gooday et al, 2008)
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