Abstract ID
nutdyn24
Type
Oral
Theme
nutdyn
Full title
Fate of nutrients in floodplain lakes under the hydrological regime of a temperate climate zone in central Europe
Abstract text
The ultimate characteristic of floodplain lakes is their exceptional hydrological and hydrochemical
variability. Any floodplain ecosystem undergoes hydrological processes, which together with management
practices at a catchment level, regulate nutrient loading reaching aquatic ecosystems. A defining characteristic
of temperate floodplain lakes in central Europe, opposite to e.g. the tropics, is their seasonal but generally
unpredictable hydrological cycle underpinned by relatively variable meteorological conditions. Rivers in
northern Poland represent the mixed type of hydrological regime (sensu Pardè, 1933) with the annual pattern
of two periods of high flows separated by two periods of lower activity of water. The first period – the main
one, occurs in mid-winter (January-February) or spring (March-April) due to snow melt and is responsible for
the highest peak flows, whereas the second period is the result of intensive rains during summer (June-July).
Summer floodplain inundations are relatively rare and when they appear, they are superimposed by other factors
e.g. channel overgrowth. This cycle can range from isolated, very shallow or even desiccated water bodies
during the dry season, to much deeper water bodies inundated by a major river, local runoff and precipitation. A
lake’s dimensions can increase orders of magnitude in volume and surface area, to become indistinguishable
from waters inundating the floodplain. Nevertheless, the two genetic types of flood have different and individual
consequences for the water quality in floodplain ecosystems. We assumed that the variable hydrological
conditions imposed by the flood pulse on floodplain lakes underpin a pronounced seasonal response in chemical
composition of water. The results of the 4-year research (2005-2008) conducted on 23 floodplain lakes located
along meandering sections of three young-glacial river valleys (Lyna, Drwęca and Slupia) in northern
Poland, showed that the flood pulsing alters both morphometry and water quality of floodplain lakes. The
comparison of the following parameters: water temperature, dissolved oxygen, electrical conductivity, and pH
as well as N03-N, NO2-N, NH4-N, SRP (soluble reactive phosphorus), TP-total phosphorus as well as cations
(Ca2+, Mg2+, Na+, K+), anions (Cl-, SO42-, HCO3-) and total dissolved matter exhibited significant
differences between water examined during spring and summer floods.
Nonetheless on a genetic type of
flood, high water levels (floods) contributed to the increase of water aeration and the dilution of the majority of
ions in floodplain lake water. At all sites during spring inundations, we observed more significant aeration of
water (even oversaturation) than during summer. Although the flood water is a significant source of nutrients,
the ions of geochemical origin (Ca2+, Mg2+, SO42-, HCO3-) showed statistically lower concentrations during
spring inundations when compared to summer floods. Biotic components of the floodplain ecosystems
significantly changed response of overgrown lentic ecosystems to summer flood waters. A permanent
hydrological connectivity to the river channel diminished the effects of flood on water quality in lakes of
permanent water exchange.
Submission date
2009-10-13
Keywords
floodplain lake, hydrological regime, flood, temperate climate, aeration, nutrients
Will be submitting paper?
Yes