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

Abstract

Abstract. Benthic foraminifera play a major role as primary consumers and detrivores redistributing organic carbon and nitrogen in intertidal environments. Here we compared the differences of phytodetrital carbon and nitrogen intake and turnover of two dominant intertidal foraminifera, Ammonia tepida and Haynesina germanica. Their lifestyles in relation to feeding behavior (feeding preferences, intake and turnover of phytodetrital carbon and nitrogen) and temperature adaptations were compared to obtain a closer definition of their specific roles in intertidal organic matter processing. For this comparison, we carried out a series of short-term laboratory incubations with stable-isotope-labeled (13C and 15N) detritus as the food source. We compared the response of the two species to diatom detritus at three different temperatures (15, 20, 25 ∘C). Ammonia tepida showed a very high, temperature-influenced intake and turnover rates with more excessive carbon turnover, compared to nitrogen. The fairly low metabolic nitrogen turnover in H. germanica was not affected by temperature and was higher than the carbon turnover. This might be related with the chloroplast husbandry in H. germanica and its lower demands for food-derived nitrogen sources. Ammonia tepida prefers a soft chlorophyte food source over diatom detritus, which is harder to break down. In conclusion, A. tepida shows a generalist behavior that links with high fluxes of organic matter (OM). Due to its high rates of OM processing and abundances, we conclude that A. tepida is an important key player in intertidal carbon and nitrogen turnover, specifically in the short-term processing of OM and the mediation of dissolved nutrients to associated microbes and primary producers. In contrast, H. germanica is a highly specialized species with low rates of carbon and nitrogen budgeting.

Enrichment of intracellular sulphur cycle –associated bacteria in intertidal benthic foraminifera revealed by 16S and aprA gene analysis

“…Despite the challenging conditions, foraminifera can thrive in these environments due to their ability to survive long periods of anoxia 5,50,51 and tolerate sulphidic conditions 52 . In the Wadden Sea, all three species are commonly encountered and contribute significantly towards benthic biomass 1,22,42 . Under anoxia, the metabolic rate of foraminifera decreases 53 and their cytoplasm gets thinner 41 .…”

Organic Heterogeneities in Foraminiferal Calcite Traced Through the Distribution of N, S, and I Measured With NanoSIMS: A New Challenge for Element-Ratio-Based Paleoproxies?

“…The δ 15 N signature, located in the organic test parts of planktic foraminifera, is correlated to δ 15 N of the foraminiferal cytoplasm (Ren et al, 2012). In benthic foraminifera, δ 15 N of the biomass is also influenced by the food source, the availability of different food sources, and the position within the food chain (Nomaki et al, 2008;Wukovits et al, 2018). It might thus be possible to identify past changes in food sources or benthic ecology by analyzing δ 15 N in the organic heterogeneities enclosed in tests of fossil benthic foraminifera.…”

Benthic Foraminiferal Salinity index in marginal-marine environments: A case study from the Holocene Guadalquivir estuary, SW Spain

“…A. tepida is a euryhaline species tolerating brackish waters (Murray 2006; Blázquez and Usera 2010; Pérez-Asensio and Aguirre 2010). This species can thrive in environments with low oxygen content and/or high organic matter fluxes (Martins et al 2013;Wukovits et al 2018). According to Jorissen et al (2018), A. tepida is a second-order opportunist, which highly increases when organic matter supply is maximal.…”