ISSN:
1573-5125
Keywords:
Sediment
;
nitrogen release
;
phosphorus release
;
core incubation
;
enclosure
;
low-moor peat ditches
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The release of N and P from the sediment of two ditches, one (A) dominated by filamentous algae and the other (B) by water-lilies, was estimated by core and enclosure experiments. The release rates for ditch A tended to be higher than those for ditch B. Sediment cores covered by a filamentous algae layer released about 1.5 times more N and P than those from which the layer had been removed. During the incubation of the cores in the dark at 20°C for 2–3 weeks, about 10% of the N in the filamentous algae layer was mineralized. The mineralization could be described as a first-order reaction with a rate constant of about 0.2 d−1. On average the cores of ditches A and B released about 40 mg mineral N and 3 mg.m−2.d−1 soluble reactive phosphorus. Defining the release from the sediment in the enclosures as the net increase of N and P in the water phase and in the vegetation minus the input, a negative net release,i.e. net accumulation of N and P in the sediment, was found over the summer half of the year. The negative values were due to the significant N and P input, resulting from pumping ditch water into the enclosures in order to compensate for downward seepage. From the enclosure experiments a downward seepage rate of 14 mm.d−1 and an external load of about 6 g.m−2 total N and 0.6 g.m−2 total P during the summer half of the year —i.e. 33 mg.m−2.d−1 N and 3 mg.m−2.d−1 P. respectively — was calculated for the ditches. Tentative gross release rates — based on the sum of the positive net release of N and P into the water phase over 1–2 weeks intervals and the net increase of N and P in the vegetation — converted to 20°C and allowing for underestimation of the primary production by a factor of 5, amounted to 58 mg mineral N and 7 mg.m−2.d−1 soluble reactive phosphorus during the summer half of the year. Combining the rates estimated by cores and enclosures and converting them to rates at the mean water temperature during the summer half of the year, the release of mineral N and soluble reactive phosphorus roughly amounted to 40 and 4 mg.m−2.d−1, respectively. The release rates as well as the external load indicated a relatively low eutrophication of the ditches.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02256729
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