『Abstract
A combination of field measurements, modelling and laboratory
experiments was used to evaluate the potential impact of sediment
resuspension on phosphorus (P) dynamics. The study was carried
out in two adjacent shallow coastal lakes (lake Honda and Lake
Nueva) which, due to their geographic proximity (only 200 m apart),
are subject to equal meteorological forcing and represent ideal
systems to study how morphometry and sediment properties relate
to wind events. The focusing factors (a measure of the fluxes
of sediment into the water column through resuspension) estimated
by comparing settling fluxes measured in surface sediment traps
with those measured in bottom traps, were significantly larger
(approximately 34％ larger) in Lake Honda (LH; 1.18) than in Lake
Nueva (LN; 0.88). Our model estimates of resuspension fluxes (E)
were also ca. 40％ larger in LH than in LN, in agreement with the
observed focusing factors. The larger resuspension fluxes encountered
in LH, in comparison with LN, can mainly be explained by differences
in lake morphometry. Still, they could arise from differences
in grain size distribution or in benthic algae concentration encountered
in the lake sediments. By means of adsorption experiments in the
laboratory, we show that resuspension events will have different
effects on P-dynamics in LH and LN. While the resuspended material
from LH tends to adsorb phosphate (PO43-),
removing it from the water column, in LN the resuspended sediments
tend to increase the availability of PO43-
in solution. These differences arise from (1) higher concentrations
of PO43- in water in LH compared
to LN; and (2) larger PO43- adsorption
capacity of the LH sediments as a result of the more abundant
iron oxyhydroxides and clay.
Keywords: Resuspension; Shallow lakes; Phosphate; Wind action;
Sediment』
Introduction
Materials and methods
Study site, lake morphometry and meteorological observations
Sediment analysis
Sedimentation and resuspension fluxes
A modelling framework to analyze differences in resuspension
Adsorption experiments
Statistical analysis
Results and discussion
Sediment composition
Settling fluxes and focusing factor
Resuspension fluxes: physical and biological mechanisms controlling
differences between lakes
Resuspension and phosphate dynamics
Conclusions
Acknowledgments
References