Partitioning benthic nitrogen cycle processes among three common macrofauna holobionts

Abstract

effect). Taken together, these functions promoted a reuse of nutrients at the benthic level, limiting net losses (e.g. denitrification) and effluxes to bottom water. Finally, the detection of multiple N transformations in macrofauna holobionts suggested a community-associated versatile microbiome, however, its role was of minor importance as compared to the activity of sediment-associated microbial communities. The present study highlights hidden and interactive effects among microbes and macrofauna, which should be considered analysing benthic functioning.

Spatial and seasonal pattern of microbial nitrate reduction in coastal sediments in the Vistula River plume area, Gulf of Gdańsk

“…Denitrification rates in coastal systems exhibit significant spatial and seasonal variability influenced by various factors. These include the fluctuating availability of NO 3 in the water column, which tends to be higher during colder periods, variations in macrofauna diversity, abundance, and biomass, diverse organic matter inputs from the water column, and varying water temperatures (Bonaglia et al, 2014b;Bartoli et al, 2021;Zilius et al, 2022). Results from this study suggest that the rise in water temperature played a significant role in the elevated denitrification rates observed during the summer in the Vistula plume area (Figure 4).…”

“…In comparison, the contribution of D w to total denitrification was relatively minor at the study site due to relatively low NO 3 concentrations in bottom water, never exceeding 10 μM. In other coastal areas, the large dilution of riverine nitrate inputs results in limited rates of D w and the dominance of D n (Hietanen and Kuparinen, 2008;Zilius et al, 2022). D n has a complex regulation that depends on the availability of O 2 and NH 4 + in the pore water, which impacts nitrification rates and the proximity of the denitrification zone.…”

“…Benthic macrofauna has also a demonstrated important role in the biogeochemical functioning of sediments, particularly in regulating the N cycle (Kristensen et al, 2012). Macrofauna affects benthic N biogeochemical processes directly through its physiology (e.g., via respiration, feeding or excretion) (Berezina et al, 2019;Zilius et al, 2022). Additionally, benthic animals can influence sediment through their activity (movement, burrowing or ventilation), stimulating microbial and meiofauna communities and N transformations (Gilbertson et al, 2012;Bonaglia et al, 2014a;Moraes et al, 2018).…”

“…Additionally, benthic animals can influence sediment through their activity (movement, burrowing or ventilation), stimulating microbial and meiofauna communities and N transformations (Gilbertson et al, 2012;Bonaglia et al, 2014a;Moraes et al, 2018). Laboratory experiments have demonstrated that burrowing macrofauna stimulates permanent N loss via denitrification, either by increasing sediment nitrification or by directly enhancing the availability of NO 3 in sub-surface sediments via burrow ventilation and irrigation (Samuiloviene et al, 2019;Zilius et al, 2022). Comparatively, a few studies have analyzed the effects of macrofauna on nitrate ammonification (Bonaglia et al, 2013).…”

Allometric and Stoichiometric Traits Predict Nutrient Excretion Rates by Benthic Consumers

“…However, several studies report a positive relationship between macrofaunal biomass and sediment NH 4 + effluxes (e.g. Gibbs et al, 2005;Norkko et al, 2013), and benthic excretion and activity have been shown to stimulate macrobenthic (Norkko et al, 2001), meiobenthic, and microbial activity and enhance sediment biogeochemical cycling (Henriksen et al, 1983;Stief, 2013;Zilius et al, 2022). In our case, the high excretion rates of NH 4 -N in comparison to sediment efflux emphasize that the benthic fauna likely enhances nitrification, as indicated by the effluxes of nitrate and nitrite from the sediments (Figure S3).…”