Abstract
Coastal lagoons display a wide range of physico-chemical conditions that shape benthic macrofauna communities. In turn, benthic macrofauna affects a wide array of biogeochemical processes as a consequence of feeding, bioirrigation, ventilation, and excretion activities. In this work, we have measured benthic respiration and solute fluxes in intact sediment cores with natural macrofauna communities collected from four distinct areas within the Sacca di Goro Lagoon (NE Adriatic Sea). The macrofauna community was characterized at the end of the incubations. Redundancy analysis (RDA) was used to quantify and test the interactions between the dominant macrofauna species and solute fluxes. Moreover, the relevance of macrofauna as driver of benthic nitrogen (N) redundancy analysis revealed that up to 66% of the benthic fluxes and metabolism variance was explained by macrofauna microbial-mediated N processes. Nitrification was stimulated by the presence of shallow (corophiids) in combination with deep burrowers (spionids, oligochaetes) or ammonium-excreting clams. Deep burrowers and clams increase ammonium availability in burrows actively ventilated by corophiids, which creates optimal conditions to nitrifiers. However, the stimulatory effect of burrowing macrofauna on nitrification does not necessarily result in higher denitrification as processes are spatially separated.
Highlights
Bioturbation by benthic macrofauna—which includes a wide set of different processes among which burrow construction, ventilation, bioirrigation, sediment reworking, and biodeposition—makes sedimentary processes variable and complex [1,2,3,4,5]
We demonstrate that the relationships between biodiversity and benthic functioning can be tackled with multiple approaches on natural, undisturbed sediments collected along estuarine gradients
The analysis of benthic N-cycling conducted at a larger scale, grouping cores collected from the same site, allows to analyze how the interactions among different macrofauna groups determine different net effects on multiple microbial process
Summary
Bioturbation by benthic macrofauna—which includes a wide set of different processes among which burrow construction, ventilation, bioirrigation, sediment reworking, and biodeposition—makes sedimentary processes variable and complex [1,2,3,4,5]. Macrofauna communities display different adaptations to live within or on the surface sediment and produce sometimes contrasting effects on microbial processes, depending upon functional traits and tolerance to environmental stress. Depending on the species and their vital habitats, associated bacterial processes can be accelerated or slowed down (e.g., anaerobic ammonium oxidation—anammox) [8,9]. Bioturbating macrofauna communities are responsible for the rearrangement of the original microbial stratification within the sediment by creating and destroying the oxic and anoxic microenvironments in the sediment, and by direct action on the physical properties of colonized substrates [4].
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