Bioturbation and bioirrigation extend the open exchange regions in permeable sediments

Abstract

Large-scale experimental exclusion of lugworms (Arenicola marina) from 400 m 2 intertidal fine sand revealed significant effects of their bioturbation and bioirrigation on sediment characteristics, benthic infauna composition, and the dominant mineralization and benthic-pelagic exchange processes in the sediment. Absence of lugworms resulted in sediment clogging with organic-rich fine particles, an eightfold decrease in sediment permeability, low oxygen penetration depths, and accumulation of reduced mineralization products in the pore water. The sand flat inhabited by lugworms had low fine-particle and chlorophyll contents and low sulfide and nutrient concentrations in the pore water. The effects were not limited to the vicinity of lugworm burrows but extended throughout the entire sediment down to ,20-cm depth. Sediments with the lugworm shared the characteristic of low-organic, advection-driven permeable sand rather than of muddy, diffusion-dominated sediments in the absence of lugworms. Areal oxygen uptake rates depended strongly on hydrodynamic conditions: under calm conditions, sedimentary oxygen uptake was slightly higher at the exclusion site. Experimental flushing using controlled hydrodynamic conditions showed that oxygen uptake at the lugworm site would be higher during more dynamic conditions (e.g., storms) due to significantly deeper oxygen penetration permitted by higher sediment permeability. Our results indicate an interactive effect of bioturbating organisms and hydrodynamics on water-sediment exchange processes and highlight the importance of benthic infauna for sedimentary processes even in physically dominated systems.

Bioturbating shrimp alter the structure and diversity of bacterial communities in coastal marine sediments

“…In support of this, Bertics and Ziebis (2009) found that as the combined bioturbation activities of thalassinidean shrimp and fiddler crabs increased, so did the in situ microbial abundances and oxidationreduction potential. Such effects have also been observed in sediments inhabited by lugworms, which resulted in changes in the pore-water chemistry of the entire permeable sediment (Volkenborn et al, 2007). Nevertheless, recent investigations have noted the differences between sediment characteristics in situ and mesocosm sediments (Papaspyrou et al, 2007), and it would be beneficial to confirm the conclusions of this study by comparison with in situ exclusion studies.…”

Sediment destabilizing and stabilizing bio-engineers on tidal flats: cascading effects of experimental exclusion

“…Thus, engineering by these species potentially ampliWed the eVects of lugworm absence. In 2004, sediment permeability on experimental exclusion plots in the low intertidal had fallen below the critical value where lugworms can thrive (Volkenborn et al 2007b). The contrasting eVects of both functional types of benthic bio-engineers suggest that mutual exclusion may not only be a product of localised disturbance or sediment binding, but involve long-lasting, sediment-mediated processes.…”

Statistical Modeling of Variability in Sediment-Water Nutrient and Oxygen Fluxes

“…These include solute transport processes (e.g., Jørgensen and Revsbech, 1985;Huettel and Gust, 1992;Janssen et al, 2005;Bühring et al, 2006), temperature (e.g., Pamatmat and Banse, 1969;Banta et al, 1995;Thamdrup et al, 1998), hydrodynamic forces (e.g., Jørgensen and Des Marais, 1990;Søndergaard et al, 1992;Almroth et al, 2009;Holmroos et al, 2009), macrofauna and microbial community (e.g., Jørgensen, 1977;Volkenborn et al, 2007;Na et al, 2008), organic matter sources (e.g., Banta et al, 1995;Conley and Johnstone, 1995;Stephens et al, 1997) and oxygen saturation in the overlying water column (e.g., Rasmussen and Jørgensen, 1992) and its penetration into the sediment (e.g., Huettel and Gust, 1992;Cardenas et al, 2008).…”