Nitrification potentials of benthic macrofaunal tubes and burrow walls:effects of sediment NH4+ and animal irrigation behavior

Abstract

We examined the natural variation of nitrification potentials (NPs) of surface sediments and macrofaunal tubes and burrow walls in relation to sediment NH,' level, season, and macrofaunal species. NP (the ability of a unit of sediment to oxidize NH,' when NH,+ and O2 are not limting) is an index of the abundance and activity of nitrifying bacteria which we measured in slurries with the chlorate block technique (nmol NO2--N produced g-' dry weight sediment h -' ) . The NP of the tubes of the polychaete Loimia medusa was positively related to sediment NI I<+ (KC]-extractable) concentration at 3 sites where tubes were collected in June 1990 (Spearman rank correlation coefficient rs 0.90. p = 0.03), as was the NP of surface (0 to 1 cm) sediment (r2 = 0.92, p = 0.002). The degree to which tube NP exceeded the NP of surface sediment was, however, negatively associated with sediment NH4+ (rS = -0.84, p = 0.05). Tube NP of L. medusa did not vary significantly with date (February, April, and June 1990). Tubes or burrow walls of Macoma balthjca (bivalve), Leptocheirusplumulosus (amphipod), and the polychaetes Macroclymene zonalis, Pectinaria gouldll, L. medusa, and Diopatra cuprea had NPs significantly greater (2 to 20 times) than that of adjacent sediment from the same depth interval, indicating that these species stimulated nitrification. Except for burrows of M. balthjca, the NPs of these structures were significantly (p 2 0.05) greater (1.5 to 61 times) than that of surface sediment. The duration of macrofaunal irrigation activity, but not irrigation rate, was positively associated (rS = 0.72, p = 0.01) with the enhancement of NP in tubes and burrow walls relative to surface sediment. These findings indicate that macrofaunal tubes and burrows tend to be sites of enhanced NP and that this enhancement varies among species due to variations in irrigation behavior. The NP of macrofaunal structures also varies among sites in relation to sediment NH,' concentrations.

Anaerobic Metabolism: Linkages to Trace Gases and Aerobic Processes

“…In the absence of physical mixing, burrowing, or radial 0 2 loss, the depth of 0 2 penetration into saturated soils and sediments is a few millimeters. The influence of plants and animals on anaerobic metabolism is similar in the sense that both effectively increase the aerobic-anaerobic surface area (Mayer et al, 1995;Armstrong, 1964). In addition, plants are a source of labile organic carbon compounds that fuel anaerobic metabolism.…”

Marine benthic faunal successional stages and related sedimentary activity

“…The authors concluded that bioturbation increases the rates of both nitrification and denitrification. Similarly, Mayer et al (1995) found that macrofaunal burrows and tubes greatly enhanced the nitrification potential compared to that of oxidised surface sediments. Experiments conducted in situ in the Mediterranean demonstrated a 160 to 280% greater denitrification potential with infauna compared to in defaunated sediments (Gilbert et al, 1998).…”

The influence of macrofaunal burrow spacing and diffusive scaling on sedimentary nitrification and denitrification: An experimental simulation and model approach

“…Bioturbation of sedimentary deposits typically generates close juxtapositions of oxic and anoxic microenvironments around biogenic structures and strongly influences both nitrification and denitrification. There is often a general stimulatory effect of macrobenthic activity, and particularly bioirrigation, on sedimentary nitrification and denitrification (Sayama and Kurihara, 1983;Kristensen and Blackburn, 1987;Henriksen and Kemp, 1988;Pelegri et al, 1994;Mayer et al, 1995;Rysgaard et al, 1995;Gilbert et al, 1998). Field measurements have demonstrated that denitrification rates can also vary inversely with bioirrigation intensity at the highest irrigation rates (Berelson et al, 1998).…”