500 years of trophic-state history of a hypertrophic Dutch dike-breach lake

Abstract

We present a palaeolimnological study encompassing five centuries of trophic-state change of the dike-breach lake De Waay located on the RhineMeuse delta (the Netherlands). Diatom-inferred total phosphorus (TP) concentrations indicate hypertrophic epilimnetic conditions ([300 lg l -1 TP) since the formation of the lake in the fifteenth century until the end of the eighteenth century. Cladocera data support the reconstructed trophic state and indicate turbid conditions in lake De Waay during this period. High inferred TP concentrations as well as the amount of Ti in the sediment reflect numerous flooding events. From the nineteenth century onwards reconstructed TP concentrations decreased to 40-150 lg l -1 due to improvements in sewage and dike systems that considerably diminished direct river flooding and seepage-derived nutrients. As a consequence, the increased stability of littoral habitats led to an increased diversity of the Cladocera assemblages.The most significant decrease in TP concentrations to *40 lg l -1 occurred between about 1900 and 1930. This mesotrophic phase was a consequence of the isolation of the lake from catchment drainage and the introduction of a highly elaborate flood control during this period. However, since the mid twentieth century a eutrophication trend is preserved in the record, likely related to increased agricultural activity in the vicinity of the lake. Our results emphasize that landuse and trophic-state history must be taken into account when evaluating the ecological status of lakes for water management and protection actions, especially for lakes in landscapes that are strongly modified by human action.

Younger Dryas Cladocera assemblages from two valley mires in central Poland and their potential significance for climate reconstructions

“…3) could be explained by its position: this lake was isolated from direct fluvial influence. A similar situation has been reported from Dutch lakes formed after breaching of river dikes (Krilova et al, 2010).…”

Eutrophication of moderately deep Dutch lakes during the past century: flaws in the expectations of water management?

“…Between fifteenth and eighteenth century, the background DI-TP concentrations were around 300 lg l -1 . However, since the beginning of the twentieth century the direct nutrient sources, which were connected to the lake and the river floods were not affecting the lake anymore (Kirilova et al, 2009b). Consequently, our reconstructions show mesotrophic conditions and DI-TP of 40 lg l -1 since the mid-twentieth century.…”

“…When determining the ecological development of dike-breach lakes, we have to keep in mind that they are highly dependent on flooding frequency and river groundwater supply, and that the catchment of these lakes often consists of cultivated areas (Kirilova et al, 2009b;Hudson et al, 2008). The three dike-breach lakes examined in this study (Ammerzoden, Empel A, and Emel B) are located within the delta flood-plain of the River Meuse.…”

“…Moreover, the lakes are highly influenced by groundwater of riverine origin. Lake De Waay is located between the rivers Rhine and Linge and was created in 1496 as a consequence of a dike-breach (Kirilova et al, 2009b). All study lakes are dimictic.…”

“…A recent palaeolimnological study showed eutrophic to hypertrophic conditions in a Dutch floodplain lake at least since the fifteenth century, caused primarily by human activities (Kirilova et al, 2009b). On a shorter time-scale Cremer et al (2009a) showed that the artificially created Lake IJsselmeer, a former bay of the North Sea, has high phosphorus concentration since its formation in 1932.…”