Photosynthetic activity in Devonian Foraminifera

Abstract. Photosynthetically active foraminifera are prolific carbonate producers in warm, sunlit, surface waters of the oceans. Foraminifera have repeatedly developed mixotrophic strategies (i.e., ability an organism or holobiont to both feed and photosynthesize) by facultative obligate endosymbiosis with microalgae sequestering plastids (kleptoplasts) ingested algae. Mixotrophy provides access essential nutrients (e.g., N, P) through feeding while providing carbohydrates lipids produced photosynthesis, resulting substantial energetic advantage sunlit environments where food dissolved scarce. Our morphological as well stable carbon isotope data provide, now, earliest (Mid-Devonian) evidence for photosynthetic activity first advanced, multichambered, calcareous foraminifera, Semitextularia, from tropical shelf Laurussia paleocontinent. This adaptation likely influenced evolutionary radiation Devonian (“Givetian revolution”), one most important events foraminiferal history, that coincided worldwide development diverse calcifying marine communities inhabiting linked stromatoporoid coral reefs.