Influence of Spartina detritus enrichment on exchange of nutrients between sediment and water in an intertidal area of Bay of Fundy

Abstract

The influence of Spartina alterniflora detritus on exchange of nitrate + nitrite, ammonia, and phosphate between sediment and water was studied after burial of plant litter in a muddy intertidal sediment in Cobequid Bay, Bay of Fundy. The enriched area in general showed higher flux rates than the control area. Dissolved inorganic nitrogen (DIN) flux was dominated by ammonium. Ammonium was normally only released from the sediment and maximum release rates were 300 and 180 pm01 NH:-N m-2 h-' in the enriched and control plot, respectively. In contrast, both uptake and release of nitrate + nitrite by the sediment was found; maximum uptake rates were 43 and 25 and release rates 98 and 51 pm01 NO;+NO;-N m-2 h-' in the enriched and control plot, respectively. Very low phosphate fluxes were observed in both plots. Initial C/N and C/P ratios of the Spartina material were 24 : 1 and 117 : 1, respectively. The C/N ratio showed a n initial decrease followed by a slow increase. The C/P ratio showed the opposite pattern. Only 8.8 % of the N and 2.7 % of the P initially added to the sediment remained after 4 mo decomposition as Spartina material (> 1 mm). The loss of N and P was larger than the cumulated release of DIN and DIP to the overlying water; thus 33 % of the N and 72 % of the P lost from the particulate detritus was retained in the sediment or lost in other ways. Flux rates of nitrate and ammonium in the enriched area were the only variables correlated. Exchange rates of nutrients were not correlated with in situ temperature. However, laboratory incubations at 7.5 and 17.5 "C showed Qlo-values of up to 10, indicating that short term changes of temperature in the field, e.g. die1 variation, may be significant. The nutrient concentration of the water was low during the summer period and increasing during the fall.

The importance of benthic macrofauna in decomposition of microalgae in a coastal marine sediment

“…Both bioturbated and control sediments seemed to retain [ 14C]DOC equally well. Andersen and Hargrave (1984) found a similar low release of DOC from plant material buried in intertidal sediments, although a 14% loss of C as DOC occurred during a 6-d laboratory leaching experiment without sediment. Kepkay and Andersen (198 5) found that most of the DOC produced from 14C-labeled detritus actually was mineralized in the sediment and released to overlying water as 14C0…”

“…3) Aller 1978;Henriksen et al 1980Henriksen et al , 1983Kristensen 1984Kristensen , 1985Andersen and Kristensen 1988). The influence of ventilation on pore-water alkalinity is clearly evident, with much lower concentrations measured in deeper layers of bioturbated sediment than in defaunated controls (Fig.…”

“…Oxygen uptake and CO2 production are generally accepted as reliable measures of the total organic matter decomposition in sediments (Andersen and Hargrave 1984;Kelly and Nixon 1984;Kepkay and Andersen 1985;Kristensen and Blackburn 1987). Oxygen and CO, fluxes alone, however, do not allow qualitative and quantitative separation of microbial degradation of new vs. old organic matter components.…”

“…Two cores from each group were sliced into O-l, l-2, 2-3, 3-5, 5-7, and 7-g-cm intervals. Pore water was obtained by centrifuging sediment samples for 10 min at 2,000 rpm in double centrifuge tubes (Andersen and Kristensen 1988). Subsamples of 0.5 ml were diluted to 10 ml with distilled water and treated as described for the seawater samples to determine labeled DIC and DOC concentrations.…”

Decomposition processes of Spartina maritima in a salt marsh of the Basque Country

“…Other studies show different dynamics (Hackney & de la Cruz, 1980 ;Buth & Wolf, 1985 ;Andersen, 1986) and interpretations are difficult .…”