Short-term effects of nereid polychaete size and density on sediment inorganic nitrogen cycling under varying oxygen conditions

Abstract

Chronic eutrophication and expanding seasonal hypoxia (O 2 < 63 µM) in estuaries like Chesapeake Bay have altered benthic faunal communities in favor of opportunistic species that can quickly populate organic-rich sediments following hypoxic events. It has been suggested that the biogenic activity of polychaetes can stimulate microbial ammonification, nitrification, and/or denitrification in estuarine sediments as well as increase the fluxes of inorganic nitrogen (NH 4 + , NO 2 − , NO 3 − , N 2 ) across the sediment−water interface. Results of 2 laboratory experiments with the opportunistic polychaete Alitta (Neanthes) succinea were used to quantify the short-term influence of density and size of surface-feeding polychaetes on denitrification and sediment− water fluxes of inorganic nitrogen under varying oxygen conditions. This study shows that polychaete enhancements of O 2 and nitrogen fluxes were strongly correlated with total animal biomass. Fluxes of O 2 , NH 4 + and N 2 were stimulated by presence of animals for both larger and smaller worms, but per capita effects were greater for the deep-burrowing larger polychaetes. With the onset of hypoxic conditions, all density treatments had reductions in O 2 , NH 4 + and N 2 fluxes, with the high-density treatment showing the greatest change. Denitrification efficiency was 33% higher for experiments with large worms than for smaller worm treatments, suggesting that the former were more effective in removing fixed nitrogen.

Below‐ground ecosystem engineers enhance biodiversity and function in a polluted ecosystem

“…Either way, these changes can be due to increased remineralisation rates and/or increased animal consumption of detritus. These results are similar to those of another study where a deposit-feeding polychaete worm was found to increase oxygenation and denitrification rates in sediments ex-situ, suggesting potential for nutrient remediation (Bosch et al, 2015). Moreover, we observed a stronger effect of worms in-situ than ex-situ, with organic content reduced up to 50% in-situ accompanied by increases in biodiversity at the location with medium levels of pollution.…”

Mediation of macronutrients and carbon by post-disturbance shelf sea sediment communities

“…In such environments there tends to be a predominance of small species with opportunistic reproductive modes that are able to respond quickly post-disturbance and can reach high abundances, but these species are more likely to have a low bioturbation potential (Solan et al 2004a;Queirós et al 2013). As per capita effects on sediment-water nutrient fluxes are disproportionately greater for larger polychaetes (Bosch et al 2015), there is less capacity for most of the resident infauna to influence biogeochemical processes. A similar effect is also true for non-cohesive sediments which, due to their inherent mobility, host a high proportion of opportunistic species (Collie et al 2000), but these communities also harbour large deep-burrowing fauna (e.g.…”

Partitioning benthic nitrogen cycle processes among three common macrofauna holobionts

“…Deep burrowing macrofauna, during ventilation, pump N-and O 2 -rich bottom water downward (Nielsen et al 2004;Mermillod-Blondin and Rosenberg 2006;Renz and Foster 2013;Murphy and Reidenbach 2016). This stimulates microbial N-cycling pathways, including ammonification, nitrification and denitrification (Tuominen et al 1999;Bonaglia et al 2013;Stief 2013;Bosch et al 2015;Moraes et al 2018). Therefore, in macrofauna bioturbated sediments, the abundance and the activity of microbial communities often exceed those of surrounding, non-bioturbated sediments (Gilbertson et al 2012;Laverock et al 2014;Yazdani Foshtomi et al 2018;Samuiloviene et al 2019).…”