Original paper
Changes in Secchi disk depth with eutrophication
Seip, Knut L.; Sas, Hein; Vermij, Steven
Archiv für Hydrobiologie Volume 124 Number 2 (1992), p. 149 - 165
37 references
published: Mar 31, 1992
DOI: 10.1127/archiv-hydrobiol/124/1992/149
ArtNo. ESP141012402001, Price: 29.00 €
Abstract
We examine changes in Secchi disk depth, SD (m), represented by the lake water attenuation coefficient, k = 1/SD, as a function of eutrophication. We do this by calculating moving median slopes S = Δk/ΔTP in k = f (TP) graphs (TP is total phosphorus). This work shows that the slope of the attenuation coefficient varies with trophic state. Median slopes for oligotrophic and mesotrophic lakes (TP < 30 mg • m-3) and hyper-eutrophic lakes (TP > 120 mg • m-3) are 0.004 and 0.003, respectively. For eutrophic lakes (30 mg • m-3 < tp < 120 mg • m-3) there is practically no relation between TP and k. This is in contrast to results obtained by derivation of normal logarithmic regressions for k = f (TP) graphs which give slopes in the range 0.005-0.007 for all trophic states. The background attenuation coefficient, defined as the Y-intercept in k = f (TP) graphs (TP is in the range 5 to 420 mg TP m-3) increases with trophic state from 0.06 to 0.78. For hypereutrophic lakes with TP > 250 mg • m-3 it contributes more than 50 % to the total attenuation coefficient. Results are also shown for variations in k caused by bluegreen algae and by TP and total nitrogen, TN, in combination.
Keywords
Secchi disk depth • eutrophication • logarithmic • algae