A Field Study on the Hydrochemistry of Land/Inland Water Ecotones with Reed Domination

Abstract

The hydrochemistry of land/water ecotones dominated by a reed (Phragmites australis) community was studied in a eutrophic shallow lake in China. The ecotones are composed of reed beds divided by many artificial ditches and serve as a connecting link between the upstream Fuhe River mouth and the downstream central lake. This lake-side ecotone exhibited a strong chemical buffering function and high nutrient removal processes. In the subsurface water of reed beds, the partial CO 2 pressure was 23…704 times of that in the atmosphere and the partial O 2 pressure was 5…34 % of atmospheric O 2 pressure. The change of hydrochemical type and greatest nutrient reduction occurred at 0.5 m landward from the reed-bed/ditch boundary. The dominant cations in ditch water and subsurface water were Na + and Ca 2+ , respectively. The nutrient level in the reed-bed subsurface water maintained low and stable despite the variable high concentrations of nutrients in the ditch water. The crisscrossed reed-bed/ditch landscape greatly increases the active area between eutrophic river mouth water and subsurface water. Since the area of reed fields in the lake occupies 22 % of the lake area, the exchange between the subsurface water of reed beds and ditches can act as a huge buffer to reduce allochthonous nutrient input and the nutrient concentrations in the lake.Thus, the self-purification capacity of the lake ecosystem increased with the presence of an active ecotone. Eine Feldstudie zur Hydrochemie von Land/Binnengewässer-Übergangsgebieten, dominiert von Röhricht Untersucht wird die Hydrochemie eines Land/Wasser-Ökotons, dominiert von einem Röhricht (Phragmites communis), in einem eutrophen Flachsee in China. Die Ökotone bestehen aus Röhrichtbeeten, geteilt durch künstliche Gräben, und dienen als Bindeglied zwischen der Mündung des River Fuhe und dem Zentrum des Sees. Diese Übergangsregion zwischen Land und See zeigt eine stark puffernde Funktion mit hohem Nährstoffrückhalt. Im Bodenwasser der Röhrichtbeete betragen die Partialdrücke des CO 2 das 23…704fache und des O 2 5…34 % der atmosphärischen Drücke. Die Änderung des hydrochemischen Typs und stärkste Reduzierung der Nährstoffe tritt 0.5 m landwärts der Grenze zwischen Beet und Kanal ein. Die dominanten Kationen im Kanalwasser bzw. Bodenwasser sind Na + bzw. Ca 2+. Der Nährstoffgehalt des Bodenwassers innerhalb des Röhrichts bleibt niedrig und stabil unabhängig von den wechselnd hohen Konzentrationen in den Kanälen. Die Landschaft aus dem Gewirr von Kanälen und Röhrichtbeeten vergrößert die aktive Zone zwischen dem eutrophen See und dem Bodenwasser erheblich. Da das Gebiet der Röhrichtfelder 22 % der Seefläche beträgt, arbeitet der Austausch zwischen Bodenwasser und Kanälen als sehr großer Puffer zur Reduzierung des allochthonen Nährstoffeintrages auf die Nährstoffkonzentration im See. Dadurch nimmt die Selbstreinigungskapazität des Gesamtökosystems See mit derartig aktiven Ökotonen zu.

A Late Glacial to Holocene record of environmental change from Lake Dojran (Macedonia, Greece)

“…Extensive reed beds in the littoral areas of Lake Dojran could have also restrained allochthonous clastic supply by filtering and organic sediment supply by nutrient consumption (cf. Yin and Lan, 1995;Wang et al, 2002). This could have limited the productivity in the lake center although temperatures increased rapidly in the Mediterranean region during the early Holocene (Allen et al, 1999;Bordon et al, 2009;Kotthoff et al, 2011).…”

Spatio-temporal distribution of nitrogen in the undulating littoral zone of Lake Taihu, China

“…TN and NO 3 --N concentrations in subsurface water were less than those in the reed belt water column in the growing and non-growing seasons. Moreover, NO 3 --N concentrations decreased from the lakeside to the hill and was lowest in the saturated area, which indicates (1) subsurface flow can carry little NO 3 --N to the inundated littoral zone; and (2) water column NO 3 --N may infiltrate into the supralittoral zone; and (3) the littoral reed belt may remove NO 3 --N efficiently from infiltrated lake water, as found in Lake Baiyangdian (Wang et al, 2002).…”

Sedimentary Enzyme Kinetics of Land/Water Ecotones with Reed Domination

“…In previous studies it was shown that the partial pressure of CO2 in the subsurface water progressively increased with distance and the CO2 pressure was 23-704 times larger than the atmospheric pressure of CO2 (as seen in Fig. 6 of Wang et al [13]). A tendency for O2 to increase occurred from 0.5 to 8 m. This result indicated that littoral zones had well developed microorganisms and abounded in soil enzymes.…”

“…this area was the hot zone, where significant changes in nutrient content occurred and the 1 m spot was the hot point. The transition zones between the reed beds and ditches were particularly active areas, as a result of a physical mechanism [13], and caused changes in the nutrient spatial distribution. That simultaneously led to the microbial response.…”

“…Triska et al [12] found that some important biogeochemical processes occur in littoral zones and Wang et al [13] inferred that soil enzymes abound in littoral zones, where oxygen and carbon dioxide cause great change.…”