VERTICAL DISTRIBUTION OF PHOSPHORUS IN LINSLEY POND MUD

VERTICAL DISTRIBUTION OF PHOSPHORUS IN
LINSLEY POND MUD

D. A. Livingstow and J. C. Bogkin

Zoology Dcpartmcnt, Duke University

ABSTRACT

Acid extraction, digestion, and water dilution cxpcriments disclose the prcsencc of large
quantities of phosphorus in the basal third of the scdimcntary section from Linslcy Pond,
Connecticut. The results suggest, but do not prove, that scdimcntary phosphorus is bound
largely by sorption reactions with mineral material. If this is so, then changes in pro-
cluctivity of the dcvcloping lake, and diffcrcnccs in lake productivity gcncrally, may be
determined by sorption reactions in the surface mud. For any kincl of sorption reaction the
productivity would be inversely proportional to the sorptivc capacity of the mud, and for
ion cxchangc it would also bc directly proportional to the total ionic activity of the water.

INTRODUCTION the phase of increase were not elucidated,

Because of the richness and complctcness but it was suggested that the ultimate limit
of their fossil record, lakes present a unique was imposed by self-shading of the seston.
opportunity for the study of ecological proc-
esses over long periods of time. This oppor- Later work demonstrated that the rate of
tunity has been exploited most fully for Lins- change and its extent were less than had
ley Pond in Connecticut, and several limnol- appeared ( Livingstone 1957)) and that the
ogists, aided by taxonomic specialists, have change had taken place at a time when the
attempted to decipher the information pre- external environment of the lake was chang-
served in its sedimentary column (Decvey ing in a manner to decrease the rate of de-
1939,1942,1955; Hutchinson 1942; Hutchin- livery of allochthonous inorganic sediment
son and Wollack 1940; Austin 1942; Patrick to the lake. This suggested that the phenom-
1943; Vallcntyne 195513; Vallentync and enon of biomass growth-or its time differ-
Swabey 1955; Livingstone 1957 ) . cntial, productivity change-might not be
the general one expected of all developing
One conclusion of importance emerged ecological systems, but a special one result-
from the early work of Deevey and of ing from the changing rate of mineral sedi-
Hutchinson and Wollack, and has been sup- mentation. This suggestion was supported
ported by later studies: the productivity of by failure to find any evidence for a corrc-
Linslcy Pond was low when the pond was sponding phase of biomass increase in the
young, then rose slowly to a high level, and history of arctic lakes (Livingstone, Bryan,
has remained at the high level ever since. and Leahy 1958).
This change in productivity is attested by
changes in the species composition and areal The doubts led to a suggested mechanism
distribution of the biota within the pond, for the control of the rate of increase in pro-
and by changes in the rate of deposition of ductivity during the time that it was rising
organic matter, of sedimentary chlorophyll, to its ultimate equilibrium value. It was sug-
of zooplankton carapaces, and of larval gested that the large quantities of alloch-
midge remains. thonous mineral material being delivered to
the lake during its early history might have
The early workers viewed the change in limited productivity by interfering with the
productivity as a result of the internal work- release of phosphorus from the mud to the
ings of the ecosystem. They believed that water. In such a case, one would expect that
they were dealing with a case of determinate
growth of the biomass inhabiting the lake the phosphorus that had not been released
from the mud during the early history of the

that was analogous to the determinate lake would still bc trapped in the sediment.
growth displayed by many individual organ- In fact, when the ratio of phosphorus to
isms and single-species populations. The organic matter was plotted against depth,
factors governing the rate of growth during using the original analytical data of Hutch-

57

58 D. A. LIVINGSTONE AND J. C. BOYKIN

inson and Wollack, it was found to be high DRY WEIGHT IN MGM PERCENT LOSS OF
near the bottom of the column, and to fall as
the productivity rose ( Livingstone 1957). OF ONE ML. WEIGHT ON IGNITION

Such a change in the efficiency of phos- FIG. 1. Dry weight and per cent loss on ignition
phorus release is not the only thing that of LL-58, a complete core through the sediments of
might lead to the observed vertical distribu- Linsley Pond, Connecticut. Note that the increase
tion of phosphorus. It has been suggested to in dry weight occurs at a lower lcvcl in the core than
us by Prof. Hutchinson that the lower layers the increase in organic matter.
of sediment may contain much primary apa-
tite that has never entered into the phos- a mixture of equal parts of 50% nitric acid
phorus cycle of the lake. Partly to test this and 70% perchloric acid. A few samples
specific suggestion, and partly to provide were dry ashcd by simple heating to dull red
more information about the amount and na- without addition of carbonate.
ture of the phosphorus in Linsley Pond mud,
we undertook the present investigation. GROSS STRATIGRAPI-IY

This research was supported principally The core, which WC have designated LL-
by grants G-2679 and G-8234 from the Na- 58, had a total length of 14 m. The bottom
tional Science Foundation. The Duke Re- 70 cm consisted of a coarse unsorted gravelly
search Council helped to provide the boring sand, with pieces up to 3.5 cm in maximum
apparatus, and Mr. Ted Brown and Mr. dimension. Larger pieces than this may have
Shoji Horie assisted in its use. The American been present in the deposit, but they would
Academy of Arts and Sciences provided the hcdve been too large to enter the sampling
calorimeter used for phosphorus detcrmina- tube. This material was probably ice-con-
tion, and the manuscript was prepared dur- tact stratified drift, perhaps redeposited by
ing tenure of a John Simon Guggcnhcim slumping into the kettlehole at the time the
Memorial Fellowship by the senior author. ice block melted. We do not regard it as lake
sediment, nor were we able to treat it as we
METHODS treated the rest of the core. For example,
after it was mixed in the Waring blendor it
A complete section, ending in gravelly immcdiatcly settled out of suspension, and
sand, was taken in the deep water OFLins- the aliquots taken from the blended sam-
ley Pond with a modified Vallcntyne (1955a) ples for further analysis consisted mostly of
sampler 1.5 in. in diameter. The sample water, with a very small amount of mineral
tubes were corked in the field and brought material that was fine enough to enter the
back intact to the laboratory, where they bore of the 5-ml automatic pipette. For this
were extruded, scraped clean, and examined. reason the bottom two points on the three
Samples of 20 ml were taken at X-m inter- stratigraphic curves ( Figs. 1,2, and 3) have
vals, diluted to 200 ml with deionized water, very little meaning.
and mixed in a Waring blcndor. The sam-
ples were stored in rubber-stoppcrcd Pyrex Above the gravelly sand lay more than 2 m
flasks in a refrigerator, and 5-ml aliquots of clay. In its lower part this clay member
wcrc taken from them with an automatic
pipette for the various dilution, desiccation,
extraction, and ashing experiments. Phos-
phorus analyses were by the molybdenum
blue method as outlined in Standard Meth-
ods for the Examination of Water and Sew-
nge (American Public Health Association
1955). Filtration was through HA Millipore
filters and commonly took more than an
hour. Wet ashing was by preliminary oxida-
tion with concentrated nitric acid, followed
by digestion in a micro-Kjcldahl flask with

PIIOSPIXORUS IN LINSLEY POND MUD 59

0.0 0.2 0.4 0.6 0.8 I.0 1.2 1.4 I.6

hydrogen peroxide digestion --mm 011 N HCL exfrocfion
-L Nitric-perchloric acid digestion
-+ Nifric-perchloric acid diges fion

a Gytfjo --4
--6
a Cloy

q Gravel/y sond

-8

--IO

--I2

l@kj@kj-+, --T. =r-- I--- -r. 0.0 0.2 0.4 0.6 0.8 I.0 I.2 I.4 1.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 - 1.k MILLIGRAMS OF PHOSPHATE PER MILLILITER MUD

MILLIGRAMS OF PHOSPHATE PER MILLILITER MUD

FIG. 2. Phosphorus content of Linslcy Pond FIG. 3. Effect of increasing the acidity of the
mud as dctermincd by digestion with hydrogen cxtrncting fluid on the amount of phosphorus rc-
peroxide and with perchloric acid. leased by Linslcy Pond mud.

contained layers of sand; at 12 m it contained gyttja, though also containing considerable
a short series of obscure black bands and in mineral material, contain it in the form of
its upper part it graded insensibly into the water-holding finely divided clay.
overlying Syttja. Yin our diagrams we h ave
placed the clay-gyttja boundary at 11 n-4 STRATIGRAPIIIC DISTRLRUTION
but it might almost as well have been placed
at any level within % m of this point. The Ol? PI-IOSPEIORUS
black bands were the only feature in this
core that bore any resemblance to the very The stratigraphic distribution of phos-
fine series of bands that Vallcntync and phorus liberated from our core by wet ash-
Swabcy (1955) found in their LV core. In ing is shown in Figure 2. For comparison,
LL-58 the bands were far too indistinct to Hutchinson and Wollack’s ( 1940) results
permit counting or measuring, and we could have been recalculated and are shown on the
see no tract of the Gray Zone of the LV core. same graph, but it must be realized that
These features must be of limited horizontal these cores cannot be correlated meter for
extent. meter along their entire length. Hutchin-
son and Wollack’s L-10 core was not a com-
Above the clay member the sediment con- plete section and, although it is shorter than
sisted of gyttja all the way to the surface. LL-58, it was probably taken from a place
Between 8.5 and 11 m this gyttja was black where the total section was a little thicker.
or almost black in color, and above 8.5 m it Correlation of the loss-on-ignition curves of
was dark brown. There were no other visible the two cores suggest that the base of the
features in this part of the core. clay mcmbcr probably lay a little more than
a meter deeper at the site of L-10 than it did
Figure 1 shows the dry weight and per in LL-58.
cent loss on ignition of the core. For Lins-
ley Pond mud, which is not very calcareous, Even when this correlation is borne in
loss on ignition may be taken as a measure of mind it is quite evident that there is much
the relative abundance of organic matter in more phosphorus in the lower part of the
the dry sediment. It is interesting to note Linsley Pond section than had previously
that a large part of the decrease in dry been realized. A large part of the phos-
weight occurs below the increase in organic phorus in the mineral sediment was appar-
matter. This is presumably because the ently not released by the hydrogen peroxide
lower part of the clay member contains much digestion of Hutchinson and Wollack, al-
silt and sand which will not hold water, though this method was slightly more effec-
while the upper part and the overlying tivc than perchloric digestion in releasing

PERCENT OF TOTAL PHOSPHORUS FROM
IO-METER LEVEL IN AQUEOUS PHASE

PERCENT OF TOTAL PHOSPHORUS FROM
IO-CM. LEVEL IN AQUEOUS PHASE

PHOSPHORUS IN LINSLEY POND MUD 61

ing it in water. If phosphorus in the falling water, We suggest that these factors well
seston had been bound in the same way as it may be the most important ones, and that
is in the sediment, then a large part of the they could be very easily measured, the ex-
phosphorus would never have been precipi- change capacity by the standard methods of
tated in the first place. The seston, however, pedology, the ionic activity by conductivity,
consists in large part of organisms, and part with perhaps a correction for different bind-
of the phosphorus that they contain is bound ing affinities of the common ions in lake
in large organic molecules and is not re-
moved readily by water. After these same water.
organisms have been incorporated in the Such speculations-though they would, if
sediment their bodies are dccomposcd by
bacteria, and at least part of the contained correct, have wide limnological significance
phosphorus is released to take part in the -are not essential to the problem at hand.
sedimentary binding reactions. Regardless of what the mechanism may be
that binds phosphorus to lake mud, it is quite
Regardless of the nature of the binding evident that it was much more effective dur-
reactions, one might expect the ratio be- ing the early stages of the development of
tween the bound phosphorus and the bind- Linsley Pond than it has been since. High
ing agent to be constant at all depths. We phosphorus binding capacity is correlated
have computed the ratio of phosphorus to with high mineral content of the lake mud.
organic matter, to inorganic matter, and to Thus, as the rate of mineral sedimentation
total dry weight throughout the sedimentary falls, so dots the phosphorus content of the
column, and find that the ratio of phos- mud, presumably because phosphorus is bc-
phorus to inorganic matter is the most nearly ing released from the mud and recycled
constant of the three. It departs from con- through the ecosystem. This appears to have
stancy most in the layer between 8.5 and been the mechanism that limited the rate of
10.5 m, where the core is particularly rich growth during the phase of sigmoid increase
in water-retaining, and hence presumably in the Pond’s history.
finely divided, mineral material. Such a
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Effects of an arctic enviromnent on the origin