Meiofauna increases bacterial denitrification in marine sediments

Abstract

Denitrification is a critical process that can alleviate the effects of excessive nitrogen availability in aquatic ecosystems subject to eutrophication. An important part of denitrification occurs in benthic systems where bioturbation by meiofauna (invertebrates <1 mm) and its effect on element cycling are still not well understood. Here we study the quantitative impact of meiofauna populations of different abundance and diversity, in the presence and absence of macrofauna, on nitrate reduction, carbon mineralization and methane fluxes. In sediments with abundant and diverse meiofauna, denitrification is double that in sediments with low meiofauna, suggesting that meiofauna bioturbation has a stimulating effect on nitrifying and denitrifying bacteria. However, high meiofauna densities in the presence of bivalves do not stimulate denitrification, while dissimilatory nitrate reduction to ammonium rate and methane efflux are significantly enhanced. We demonstrate that the ecological interactions between meio-, macrofauna and bacteria are important in regulating nitrogen cycling in soft-sediment ecosystems.

Ecological effects of Irgarol 1051 and Diuron on a coastal meiobenthic community: A laboratory microcosm experiment

“…Since all treatments started with a similar community composition and the experimental units were closed systems, changes in composition were probably due to species loss, as detected in the univariate analysis. These community effects of Irgarol and Diuron are particularly relevant given the intimate link that has been increasingly observed between composition and diversity of benthic communities and key ecosystem processes (Snelgrove et al, 1997;Bonaglia et al, 2014).…”

Influence of Natural Oxygenation of Baltic Proper Deep Water on Benthic Recycling and Removal of Phosphorus, Nitrogen, Silicon and Carbon

“…Triplicate cores were sampled directly after the addition of the 15 NO were performed in order to estimate the anammox contribution to total N 2 production (Thamdrup and Dalsgaard, 2002;Risgaard-Petersen et al, 2003). Our experiments followed the procedure described in Bonaglia et al (2014). Briefly, the top 2 cm of two sediment cores (9 cm inner diameter) were extruded, homogenized and 100 ml of this sediment was transferred to a glass bottle filled with 900 mL filtered and anoxic bottom water.…”

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

“…Due to their high abundance and diversity, their widespread distribution, their rapid generation time and fast metabolic rates, meiofaunal organisms are vital contributors to ecosystem function, including nutrient cycling and the provision of energy to higher trophic levels (Woodward 2010). These characteristics make meiofaunal organisms excellent candidates to test general ecological hypotheses and theories (Jessup et al 2004;Nascimento et al 2011Nascimento et al , 2012Bonaglia et al 2014). However, this group represents an often neglected component of marine biodiversity (Curini-Galletti et al 2012) and is generally poorly studied (particularly in the deep sea) because most applied programmes target the larger macrofauna, which are more readily identifiable and countable than meiofauna (Schratzberger et al 2000).…”