Multi-lake studies in The Netherlands: trends in eutrophication

Citation
Dt. Van Der Molen et R. Portielje, Multi-lake studies in The Netherlands: trends in eutrophication, HYDROBIOL, 409, 1999, pp. 359-365
Citations number
26
Categorie Soggetti
Aquatic Sciences
Journal title
HYDROBIOLOGIA
ISSN journal
00188158 → ACNP
Volume
409
Year of publication
1999
Pages
359 - 365
Database
ISI
SICI code
0018-8158(1999)409:<359:MSITNT>2.0.ZU;2-K
Abstract
The relation between (inter)national programs aiming at nutrient load reduc tion and changes in eutrophication has been studied for 231 Dutch lakes ove r the period 1980-1996. Trends in total-phosphorus (P) and total-nitrogen ( N) were negative, as determined by analysis of both individual lakes and th e complete data set. The relative trends in the nutrient concentrations as well as in the N/P ratio correspond with the significantly reduced P emissi on and the limited reduction of N emission in The Netherlands since the beg inning of the 1980s. Negative trends in chlorophyll-a and positive trends i n Secchi-disc transparency may be partly explained by reduced nutrient conc entrations. Perspectives for the nearby future are discussed. Lake characte ristics had only a minor impact on the trends. The improvement of the water quality was found for all subsets of average depth, surface area, hydrauli c retention time and soil type. Furthermore, the effect of restoration meas ures and meteorological conditions on the trends were studied. Biomanipulat ion resulted in an additional improvement of several water quality variable s compared to lakes that were only subject to (inter)national programs on n utrient load reduction. Specific measures resulting in additional P load re duction resulted only in lowered P concentrations. Severe winters resulted in lower chlorophyll-a concentrations in the following summer and dry condi tions in spring were favourable for all eutrophication variables in the fol lowing summer.