Short-term influence of recolonisation by the polycheate worm Nereis succinea on oxygen and nitrogen fluxes and denitrification: a microcosm simulation
M. Bartoli et al., Short-term influence of recolonisation by the polycheate worm Nereis succinea on oxygen and nitrogen fluxes and denitrification: a microcosm simulation, HYDROBIOL, 431(2-3), 2000, pp. 165-174
The short-term effects of sediment recolonisation by Nereis succinea on sed
iment-water column fluxes of oxygen and dissolved inorganic nitrogen, and r
ates of denitrification, were studied in microcosms of homogenised, sieved
sediments. The added worms enhanced oxygen uptake by the sediments, due to
the increased surface area provided by the burrow walls and the degree of s
timulation was stable with time. Similarly, ammonium fluxes to the water co
lumn were stimulated by N. succinea, but declined over the 3 day incubation
in all microcosms including the controls. Nitrate fluxes were generally gr
eater in the faunated microcosms, but highly variable with time. Denitrific
ation rates were positively stimulated by N. succinea populations, denitrif
ication of water column nitrate was stimulated 10-fold in comparison to den
itrification coupled to nitrification in the sediments. Rates of denitrific
ation of water column nitrate were not significantly different from rates i
n undisturbed sediment cores with similar densities of N. succinea, whereas
rates of coupled nitrification-denitrification were 3-fold lower in the ex
perimental set-up. These results may reflect the relative growth rates of n
itrifying and denitrifying bacteria, which allow more rapid colonisation of
new burrow surfaces by denitrifier compared to nitrifier populations. The
data indicate that recolonisation by burrowing macrofauna of the highly red
uced sediments of the Sacca di Goro, Lagoon, Italy, following the annual dy
strophic crisis, may play a significant role in the reoxidation and detoxif
ication of the sediments. The increased rates of denitrification associated
with the worm burrows, may promote nitrogen losses, but due to the low cap
acity of nitrifying bacteria to colonise the new burrow structures, these l
osses would be highly dependent upon water column nitrate concentrations.