Food supply and size class depending variations in phytodetritus intake in the benthic foraminifer Ammonia tepida

Abstract

Ammonia tepida is a common and abundant benthic foraminifer in intertidal mudflats. Benthic foraminifera are primary consumers and detritivores and act as key players in sediment nutrient fluxes. In this study, laboratory feeding experiments using isotope-labeled phytodetritus were carried out with A. tepida collected at the German Wadden Sea, to investigate the response of A. tepida to varying food supply. Feeding mode (single pulse, constant feeding; different incubation temperatures) caused strong variations in cytoplasmic carbon and nitrogen cycling, suggesting generalistic adaptations to variations in food availability. To study the influence of intraspecific size to foraminiferal carbon and nitrogen cycling, three size fractions (125–250 µm, 250–355 µm, >355 µm) of A. tepida specimens were separated. Small individuals showed higher weight specific intake for phytodetritus, especially for phytodetrital nitrogen, highlighting that size distribution within foraminiferal populations is relevant to interpret foraminiferal carbon and nitrogen cycling. These results were used to extrapolate the data to natural populations of living A. tepida in sediment cores, demonstrating the impact of high abundances of small individuals on phytodetritus processing and nutrient cycling. It is estimated that at high abundances of individuals in the 125–250 µm size fraction, Ammonia populations can account for more than 11% of phytodetritus processing in intertidal benthic communities.

Species composition and habitat preferences of benthic ostracod and foraminifera in seagrass and non-seagrass systems within a tropical estuary

“…Its presence also indicates a preference for higher nutrient inputs represented by refractory organic matter (Jorissen, 1988); the presence of seagrass may have enhanced the accumulation of organic matter in the sediment and provides a suitable habitat for this species. In such a high productivity estuarine environment, A. tepida play an important role in sediment nutrient fluxes and phytodetrital carbon and nitrogen processing (Wukovits et al ., 2018). These observations raise questions about the mechanisms that enable foraminifera to influence sediment carbon and nitrogen fluxes.…”

The distinct roles of two intertidal foraminiferal species in phytodetrital carbon and nitrogen fluxes – results from laboratory feeding experiments

“…Carbon loss, e.g., due to organismic respiration or OM remineralization to CO 2 , reduces the availability of organic carbon sources in the heterotrophic food web. As mentioned above, in the heterotrophic coastal zone, 30 % of the carbon pool is lost via respiration, whereas dissolved organic carbon sources from organismic excretion can serve as an important nutrient source for bacteria (Kahler et al, 1997;Snyder and Hoch, 1996;Zweifel et al, 1993). Therefore, the fast processing of OM in A. tepida might be an important sink for inorganic carbon (CO 2 respiration) and at the same time a link for dissolved organic carbon sources in intertidal carbon and nitrogen fluxes.…”

Conservation Paleobiology as a Tool to Define Reference Conditions in Naturally Stressed Transitional Settings: Micropaleontological Insights from the Holocene of the Po Coastal Plain (Italy)

“…The composition of benthic foraminifer assemblages is rather stable with dominant A. tepida and subordinate H. germanica, taxa characteristic of partially barred environments enriched in organic matter and with reduced salinity [85,86]. Specifically, the former is able to rapidly consume high rates of both fresh and refractory organic matter, whereas the latter tolerates moderate organic enrichments, showing lower consumption rates of organic material [87]. The upward increasing concentrations of taxa commonly reported from lagoons but with a relatively low tolerance to organic enrichment, such as H. depressula and A. parkinsoniana [86], suggests lower organic matter levels.…”