Conference Proceedings - IAD

39th IAD Conference, August 2012, Szentendre, Hungary
second included all canal sites together with the Torfata (marsh from Orsoya
floodplain). The Srebarna Lake took an intermediate position while the Maluk
Preslavets Lake was isolated far away due to its geological nature and distinct
elevation above the Danube River level.
The spatial ordination of wetland sites and the Danube River samples by PCA
regarding thetheir chemistry variables wetland sites and the Danube River
samples distinguished between canal sites, lake sites and river samples
according to their chemistry variables. The Danube samples have higher oxygen
and NO3-N concentrations and smaller variability (only due to seasonal
differences) than the wetlands where more intense NO3-N uptake and
denitrification seemed to occur.
We do not present the last dDiscussed PCA ordination, first, due to space
shortage and second because the RDA of the same data set (reduced by
Danube samples) provided the same spatial separation between lake and canal
sites for chemistry data significantly explained by variable “wetland type” (lake or
canal) and macrophyte surface cover. The canal sites were more turbid, with a
thick silt bottom layer, richer in nutrients and with lower oxygen than the sites of
lake type (Table 2). This can be explained with both the canals location in
proximity or within arable lands, and with their past and recent functionality as
drains. In opposite, the lake type sites are either isolated from agricultural activity
due to their protection status (Srebarna lake reserve), or they are located in the
middle of the river (Belene island). The macrophytes had an obvious contribution
in phosphate uptake and as a second explanatory variable they separated the
wetlands to phosphate rich and poor.
Table 2. Arithmetic means (AM) and coefficient of variation (CV) of data from three main
water types measured in spring, summer and autumn of year 2011
Water body
type
Lake
Canal
Statistics
Oxygen g m -3
Oxygen
saturation %
pH
Conductivity
µS cm -1
76
NO3-N mg/l)
NO2 -N mg/l
NH4-N mg/l
PO4-P mg/l
Turbidity
absorbance at
550nm
AM 8.798 94.981 8.444 598.651 0.126 0.048 0.405 0.167 0.230
CV, % 38.727 33.169 6.646 47.758 75.161 100.917 104.289 104.713 55.057
AM 2.485 26.151 7.529 708.111 0.210 0.027 0.905 0.286 0.898
CV, % 84.701 90.235 6.558 22.572 117.711 119.886 102.321 102.080 152.380
Danube AM 10.487 105.223 8.070 403.000 1.333 0.015 0.035 0.133 0.126
River CV, % 16.473 22.579 3.853 9.261 11.456 27.555 59.211 18.875 70.118