Abstract ID
nutdyn22
Type
Oral
Theme
nutdyn
Full title
Testing the Flood Pulse Concept in high latitudes: an example from the Baltic Region
Abstract text
This study is the first application of the Flood Pulse Concept (FPC) in hydroecological research of floodplain
lakes in the Baltic Region (North East Europe). The floodplain of the Daugava River at Daugavpils in South
East Latvia was selected as the study site in 2004 and 2005 because of its natural hydrology and numerous
floodplain lakes.In order to clarify whether the hydrological connectivity has any detectable impact on the
aquatic chemistry, the phytoplankton, zooplankton and zoobenthos communities and aquatic vegetation, 24
floodplain lakes of the Daugava River were selected for this study at first. In July 2004, the morphometric and
physicochemical parameters, vegetation cover and the amplitude of water level fluctuation of these lakes were
determined. Simultaneously, the samples of water, phytoplankton, zooplankton and zoobenthos were collected
and composition of macrophyte vegetation was explored. The Daugava River upstream and downstream from
Daugavpils and its four largest floodplain lakes were selected for seasonal observations. In 2005, these sites
were monitored 11 times, from March till October. At every field trip, physicochemical parameters of these sites
were determined and samples of water, phytoplankton and zooplankton were collected. In addition, weather
conditions were monitored and water level observations within the floodplain were performed. The data series
were analysed statistically by applying the Rank Correlation and Factor Analysis methods.During this study, the
long-term mean annual flooding frequency of the selected floodplain lakes was determined; original
hydrological classification of these floodplain lakes was proposed; ecological role of the spring floods and the
flash floods was evaluated; significance of an interaction between the flood pulse and the ice cover was stated;
the Intermediate Disturbance Hypothesis was tested; the concept of nutrient and energy cycling within the large
river floodplain was modified according to local conditions; and main factors, which accounts for the spatial
variability in physicochemical parameters and phytoplankton, zooplankton, zoobenthos communities and
macrophyte vegetation during the summer isolation, were identified.According to this study, the Flood Pulse
Concept is suitable for further hydroecological studies in the Baltic Region after some local conditions are taken
into account. In contrast to other river floodplains studied before, floodplains of this region are quite new and
are characterised by much colder climate, and by a prolonged seasonal cover of ice, which restricts development
of the phytoplankton and aquatic vegetation. During the spring floods, the rivers might have ice jams, which
significantly transform the flood pulse in terms of its amplitude, timing and dynamics. An interaction between
the flood pulse and the ice cover, however, could be regarded as a stimulating ecological factor, which
accelerates the nutrient and energy cycling within the floodplain lakes of this region. On the other hand, it slows
down overgrowth by reeds and other macrophytes. In contrast to tropical river floodplains, phytoplankton
communities probably play a central role in nutrient and energy cycling within these floodplains during the
annual floods whereas the growth of terrestrial and aquatic vegetation determines the cycling during the summer
droughts.
Submission date
2009-10-07
Keywords
Flood Pulse Concept, floodplain lakes, phytoplankton, nutrients
Will be submitting paper?
Yes