Mr. Penn et Mt. Auer, SEASONAL VARIABILITY IN PHOSPHORUS SPECIATION AND DEPOSITION IN A CALCAREOUS, EUTROPHIC LAKE, Marine geology, 139(1-4), 1997, pp. 47-59
Settling particulate matter was collected in sediment traps from the m
ajor depositional basin of Onondaga Lake, a calcareous, eutrophic lake
in Syracuse, New York, U.S.A. Sediment traps were deployed at three d
epths from July to November and for a brief period under ice cover in
February to investigate both vertical and seasonal variations in sedim
entation. A sequential chemical extraction (fractionation) method was
applied to the collected material to quantify the following phosphorus
(P) fractions, or forms: loosely bound-P (sorbed-P, CaCO3 associated-
P, and Fe and Al bound-P), extractable biogenic-P (easily degradable o
rganic-P and biogenic inorganic polyphosphates), calcium mineral-P (e.
g., apatite), and refractory organic-P. Extractable biogenic-P and ref
ractory organic-P were strongly correlated, suggesting a common, autoc
hthonous origin in plankton. Calcium mineral-P appears to be of terrig
enous origin. A dramatic increase in the loosely bound-P content of th
e particulate matter was observed during fall turnover when dissolved
Fe2+, which had accumulated in the anoxic hypolimnion, mixed with the
surface waters and oxidized with attendant adsorption of P. We estimat
e that the labile-, or exchangeable-P (i.e. loosely bound- and extract
able biogenic-P forms) content of the settling particulates constitute
s similar to 50% of the total P influx to the sediments over the perio
d of study. The labile-P flux over the July-November study period was
11 mg P m(-2) day(-1) and the labile-P flux estimated from sediment tr
aps deployed under ice cover was 6 mg P m(-2) day(-1). From these valu
es the annual average labile-P flux to the sediments was estimated to
be 9 mg P m(-2) day(-1), only slightly less than the estimated annual
average sediment P release rate of 10 mg P m(-2) day(-1). This indicat
es that the sediments are approximately at steady state with respect t
o current external P loadings to the lake. (C) 1997 Elsevier Science B
.V.