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Effects of ice cover on sediment resuspension and phosphorus entrainment in shallow lakes: Combining in situ experiments and wind‐wave modeling
Author(s) -
Kleeberg Andreas,
Freidank Andreas,
Jöhnk Klaus
Publication year - 2013
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2013.58.5.1819
Subject(s) - sediment , entrainment (biomusicology) , oceanography , hydrology (agriculture) , transect , wind speed , particulates , geology , shear velocity , environmental science , atmospheric sciences , geomorphology , turbulence , chemistry , meteorology , geotechnical engineering , philosophy , rhythm , aesthetics , physics , organic chemistry
In situ experiments on sediment resuspension were carried out along a depth transect in shallow polytrophic Lake Langer See, northeast Germany (area = 1.27 km 2 , Z max = 3.8 m), in winter under ice and in summer 2006, using a hydrodynamically calibrated erosion chamber (diameter 20 cm). Shear velocity U * was incrementally increased 11 times for 10 min each (0–2.57 cm s −1 ) to initiate resuspension. Entrainment rates ( E ) of suspended particulate matter ( E SPM ) and total P ( E TP ) were determined by a mass balance. Sandy nearshore sediments at 1–2 m depth showed low E SPM (0.01–6.64 g m −2 h −1 ) and E TP (0.2–2.96 mg m −2 h −1 ). There was no difference in critical shear velocity ( U *crit ) of incipient resuspension between winter and summer. Muddy offshore sediments at 2–3.8 m depth showed higher E SPM (0.09–106.1 g m −2 h −1 ) and E TP (0.06–532.3 mg m −2 h −1 ). Under ice, U *crit was 0.9–1.1 cm s −1 higher than in summer, indicating that the wave‐unaffected sediment had ample time for consolidation and biostabilization. Wind‐wave modeling, using measured E SPM and E TP , revealed that resuspension is primarily (90%) restricted to the nearshore sediments (17% lake area). Our scenarios show that annual entrainment of SPM and TP increased linearly with the duration of ice‐free period. Since ice coverage increased shear resistance, climate‐driven absence or shortening of ice‐cover would reduce the period for settling of particles and their integration into sediments, lowering their biostabilization, thus facilitating resuspension and phytoplankton recruitment in spring after ice thaw.