Oxygen uptake kinetics at the sediment

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Oxygen uptake kinetics at the sediment
Oxygen uptake kinetics
at the sediment-sea
O C E A N O L O G IA , No. 30
water interface in the
Puck Bay*
pp.
5 7 -7 5 , 1991.
PL ISSN 0078 3234
Oxygen
Sediments
Chamber experiments
Puck Bay
J erzy B o la le k
Institute o f Oceanography,
Gdansk University,
Gdynia
A n d r e y V e r s h in in
Institute of Oceanology,
USSR Academy of Sciences,
Moscow
Manuscript received October 03, 1990, in final form April 05, 1991.
Abstract
The paper presents the parameters o f oxygen exchange at the sea water-sediment
interface in Puck Bay. The calculations were based on data on oxygen concentration
changes in water, obtained at two stations in chamber experiments in June 1989.
Oxygen consumption in the processes of respiration and mineralization o f organic
matter was determined on the basis of oxygen concentration changes, data on the
plankton biomass in water, and data on the biomass of macro- and meiobenthos in
the sediment.
The following parameters of oxygen exchange at the water-sediment. interface
were calculated using the quasi-stationary model of oxygen uptake: oxygen con­
sumption in the benthic water A w, oxygen uptake by the sediment at the begin­
ning o f the experiment Jo, oxygen penetration depth into the sediment x j, diffusive
sublayer height h, oxygen concentration in the diffusive sublayer Cwo, oxygen con­
centration at the bottom of the diffusive sublayer at the initial moment.
The parameters obtained agreed very well with the character of the sediments,
as well as the number of meiobenthic organisms and their biomass in the sediment,
and plankton biomass in water.
* The investigations were carried out under the research programme C PB P 03.03.C,
co-ordinated by the Institute o f Oceanology of the Polish Academy of Sciences.
1. Introduction
E xchange o f chem ical substances through the w ater-bottom interface
is a com pon en t o f element circulation between the hydrosphere and the
lithosphere. A s a result investigations into various processes taking place at
the w ater-bottom interface are im portan t. Investigation o f oxygen uptake
by sediments is significant with respect to m eiobenthos existence and the
diagenetic reactions which occu r (H argrave, 1969, 1972; H opkinson and
W etzel, 1982; P am atm at, 1971; Sm ith, 1974).
T h e m ost frequently used technique to measure oxygen uptake by sedi­
ments are based on incubation o f a certain am ount o f w ater and sedim ent
and subsequent m onitoring o f oxygen concentration changes in w ater above
, the sediment as a function o f tim e (B agander, 1977; Hall, 1984; R ozan ov
et al., 1988; Rutgers van der L oeff et al., 1984). O xygen uptake b y the
sediments can also be estim ated from the oxygen profiles in sedim ents m ea­
sured w ith m icroelectrodes (Reim ers et al., 1984; Reimers and Sm ith, 1986;
R evsbech et al., 1980a,b). Numerous experim ents have revealed that oxygen
uptake b y the sediment depends on tem perature (D u ff and Teal, 1965; Hall,
1984), m eiobenthos biological activity (E dw ards and R olley, 1965), turbulance and currents in the water ab ove the sediment (B oy n ton et al., 1981).
T h e effect o f the initial oxygen concentration on its uptake b y the sedim ent
is not entirely recognized. For instance, Pam atm at and Banse (1969) found
that these tw o param eters are independent, while K now les et al. (1 9 6 2 ), as
well as E dberg and H ofsten (1973) established that the oxygen uptake by
the sediment is low er at low er initial oxygen concentrations. A nother group
o f researchers thinks that oxygen concentration in w ater does not influence
its uptake b y the sediment until its concentration falls below a certain level.
A ccordin g to M artin and Bella (1971) this concentration is o f the order o f
6 0 -9 0 /im ole · d m - 3 .
This paper aims at presenting a m eth od o f calculation o f the param e­
ters o f oxygen exchange processes at the w a ter-b ottom interface, as well as
discussion o f the param eters o f this exchange in Puck Bay, and attem pts to
determ ine oxygen uptake in the benthic water and sediment (respiration o f
organisms and m ineralization o f organic m atter).
2 . Materials a n d methods
2 .1 . Field and lab oratory w orks
Em ployees o f the Institute o f O ceanography o f Gdansk University and
o f the Institute o f O ceanology o f the USSR A cadem y o f Sciences (M o sco w )
took part in the experim ents carried out in Puck Bay between 7th and 21st
June, 1989, within the ‘ M irovoy O k e a n ’ C O M E C O N p roject. T h e ex p er­
iment was carried out at tw o stations o f different b o tto m sedim ent charac­
teristics and different depth. Station location description o f the cham bers
and their param eters, the manner o f settling at the b o tto m , sam pling p ro ­
cedure, as well as m ethods o f sea water and sediment analysis, have been
described previously (Bolalek et al., 1991). O xygen in sea w ater was deter­
mined by the W inkler m ethod. Organic m atter content in the sedim ents
was determined as the loss on roasting.
T he ph yto- and zooplankton com position was determ ined at each sta­
tion in the n ear-bottom w ater sam pled by scuba divers, using m eth ods rec­
om m ended b y B M B 1 (E dler, 1979). T h e num ber o f specim ens has been
recalculated to biom ass.
Samples o f b o tto m sediments were drawn at the end o f the experim ent
from below the cham bers and' from the adjacent area. T h e samples were
divided into 1 cm segm ents, in which the m eiobenthos classification units
were determined (Elm gren and Radziejow ska, 1989).
2 .2 . C alculation m eth od s
The results obtained during the experim ent were elaborated on the basis
o f the quasi-stationary m odel described by Y egorov and Vershinin (1 9 9 0 ).
The m odel is based on the follow ing four equations (Berner, 1971; Hall
1984 et al., 1989; Lerm an, 1979; R evsbech et al., 1980b):
1. Sediment diagenesis equation:
„
d 2C
F,
dx2 ~
4
x > 0)
2. Equation describing the change o f the concentration in the cham ber
as a function o f time:
dCw
Ql
J
~~jj
K WC W
—H
<
x
<
—
h 't
3. Equation describing the flux o f the substances through the sedim ent
surface (first F ick ’s law ):
f l . e g
x = 0;
4. Equation describing the diffusion through the diffusive sublayer:
T — n ^ w ~ ^0
L
------1--------------- h < x < 0;
where:
- vertical coordinate (w ith positive sense in to the sedim ent x > fl­
at the sediment surface * = 0 ),
’
1Baltic Marine Biologists.
D, D ,
- tim e,
- m olecular diffusion coefficients o f a substance dissolved in water
n, m
and in the sedim ent, respectively,
- order o f reaction o f utilization or excretion o f the dissolved sub­
t
stance in the sedim ent and in w ater, respectively,
K a, K w - equilibrium constants o f reactions o f utlization or excretion o f the
dissolved substance in the sedim ent and in w ater, respectively,
Ca
Cw
h
- concentration o f the dissolved substance in the interstitial w ater,
- concentration o f the dissolved substance in the cham ber (in the
turbulent m ixing zon e),
- diffusive sublayer thickness, equal to 1 -2 m m (B ou d rea w and
G uinasso, 1982; Hall et al., 1989). In this sublayer the m olec­
ular diffusion prevails over the turbulent m ixing,
C0
- con cen tration o f the dissolved substance at the b o tto m o f the dif­
H
J
fusive sublayer (or at the sediment surface),
- range o f turbulent m ixing, equal to the height o f the cham ber,
- dissolved substance flux through the w ater-sedim ent interface.
Similar equations or a part o f these equations were considered in the
papers b y B agander (1 9 7 7 ), Hall et al. (1 9 8 9 ), Jones and M urray (1 9 8 5 ),
Rutgers van der L oeff e t al. (1 9 8 4 ), Ullmann and Aller (1 9 8 2 ). O nly zero
order reactions (n = 0) were considered in papers taking in to accou n t equa­
tion (2 ), (B agander, 1977; Hall, 1984; Hall et al., 1989; H olm , 1978; R utgers
van der L oeff et al., 1984). M oreover, oxygen uptake b y the n ea r-b ottom
water layer has not been taken in to account in the second equation - there
was no K WC™ term . This resulted from the fact that the authors o f these
papers did n ot use the reference ch am ber, allowing for the changes occu rrin g
in the n ea r-b ottom water.
T h e system o f equations presented above describes a quasi-stationary
process o f a change in con cen tration o f a chosen substance dissolved in the
cham ber, in w hich water con ta cted the sedim ent. Solving this equation
system using the experim entally determ ined concentration changes in tim e
C w(t) allows not only the m agnitude o f the flux across the w ater-sedim ent
interface, but also the reaction constants K w and K , to b e determ ined,
as well as the vertical distribution o f a given substance in the sedim ent.
It additionally enables the selection o f the reaction order m and n, and
the evaluation o f the size o f the diffusive sublayer, penetration depth o f
a substance in to the sediment ( x i ) , tota l uptake (o r excretion ) intensity
o f the soluble form o f a substance in the sedim ent at the initial m om ent o f
locatin g the cham bers ( A so = K 3C™). A part from the previously m entioned
param eters o f exchange the m odel allows the follow ing con centrations to be
evaluated:
• C wo ~ initial concentration in the diffusive sublayer,
• C ' - initial concentration o f the dissolved substance (ox y g en in this
case) at the b o tto m o f the diffusive sublayer,
a C ‘ - C wo - C'0 - initial concentration difference in the diffusive sub­
layer.
A m ethod o f data analysis obtained in cham ber experim ents was developed
on the basis o f the above equations (Vershinin et a/., 1990). T h e calculations
were carried out in the U SSR A cadem y o f Sciences (M oscow ) using an E C
1061 com puter (program w irtten in Fortran language).
The experim ental C w as a function o f time dependences obtain ed in the
N o. 2 cham ber, isolated from the b o tto m , have been utilized in the first stage
o f calculations. T h e values o i K w( K w ^ 0) have been determ ined from the
present values o f m (m = 0 , 1 ,2 ,3 ,4 ) . T h e K w and m values obtain ed are
the kinetic param eters o f oxygen uptake in the n ea r-b ottom w ater layer.
O xygen uptake is equal K WC % . This is the am ount o f oxygen consum ed b y
1 m 3 o f water in 1 s. This value has been used in further calculations.
A curve reflecting the continous process o f the reduction o f oxygen con ­
centration in water contained in the cham bers was draw n inthe second
stage. T h e follow ing were the input param eters: d, D 9, H , 0 , K w, C w;, t,·, m ,
a = 0.5(n + 1), and h - where C w%and t,· are the experim ental data obtained
in the No. 1 cham ber. T h e h param eter was changed in the calculations.
It has been assumed in the final calculations that the real process corre­
sponded to this value o f h, at which the m agnitude o f the m inim um risk
function (S M ) was the smallest (T aylor, 1985). T h e D and D , param eters
are interrelated by the D , — D / k dependence (Lerm an, 1978). T h e val­
ues o f the k param eter (1 .4 ) and the 0 param eter (0 .9 ) were adop ted on
the basis o f literature data (M ancheim and W aterm an, 1979; Y egorov and
Bolshakov, 1988). T h e J0, h, n and K a param eters were the ou tpu t values
obtained at this stage o f the calculations. T h e flux obtained represents the
initial total oxygen uptake for the mineralization o f the organic m atter in
the sediment and the respiration o f the organisms at the beginning o f the
measurements.
3. Results and discussion
Changes o f dissolved oxygen concentration in cham bers, in w hich water
directly con tacted the sediment (cham ber N o. 1), were very rapid (T abl. 1).
In general, oxygen contained in the water was used up during the second
week o f the observations. A t ST I, where the sediments were a few times
richer in organic m atter com pared to ST II, a com plete exhaustion o f
T a b le 1. Changes in oxygen concentration (ml · dm -3 ) in the Puck Bay during the
chamber experiments performed in June, 1989
Station II - ST II
Station I - ST I
Data
3
2
1
3
2
1
7.73
7.70
7.74
7.12 7.33 7.92
7
3.45 7.25 6.23 6.45 7.47 7.66
8
2.55 5.93 7.62 5.15 7.35 7.04
9
1.05 4.30 8.64 1.55 6.67 4.50
12
5.41
3.80 7.97 1.43
13
6.45 7.65
0.39 3.27 7.03
14
6.28 6.31
6.83
15
7.88 0.63 6.19 7.32
0.26
16
0.08 3.02 7.75 0.56 5.81 6.65
19
0.00 2.39 7.09 0.33 5.57 6.97
21
1 - chamber No. 1,
2 - chamber No. 2,
J - chamber surroundings.
oxygen was observed after 12 days. N o com plete exhaustion, o f ox yg en
was observed untill the end o f the m easurem ents, i.e. w ithin 15 days,
at ST II.
T a b le 2. Selection o f the h and n parameters on the example o f ST II
h [cm]
n= 1
SM
87.50
(a = 1)
88.81
9.613
*
1
o
(a = 0.5)
Jo · lO“ 4
6.646
6.695
6.549
6.617
6.928
7.706
H
0.01
0.0125
0.025
0.0375
0.05
0.075
n= 0
SM
480.5
456.5
409.7
347.5
290.5
184.6
9.828
ri = 2
SM
47.92
38.55
32.64
33.26
36.83
52.10
(a = 1.5)
J o · lO "4
22.02
19.21
16.77
15.00
13.86
11.14
Jo expressed in ml · dm 3 · cm · s 1.
Determined for the following data:
H = 0.47 m,
D = 1.45 10“ 5 cm s " 2,
Cwi
oxygen concentration in the No. 1 chamber in time i,
0
= 0.9,
K w = 0.6219 · lO“ 8 m l" 2 · d m '6 · s - 1.
A slow reduction o f oxygen concentration was observed in w ater iso­
lated from the b o tto m (cham ber N o. 2 ). T h e changes ranged from 0.08 to
1.32 m l-d m -3 d a y - 1 . C oncentration o f oxygen dissolved in w ater at S T I
decreased within 15 days from 7.46 to 2.39 m l · d m - 3 , while at S T II - from
7.73 to 5.57 m l · d m - 3 .
T able 3. Results of calculations of the oxygen exchange parameters at the water.
Parameter
M
n
a
Kw
Aw
h
D
Jo
B
K.
C'o
Cwo
c
A ,o
*1
where:
i
___·
t
_____ m o n
Dimension
(ml · dm - 3 )1-m · s-1
10-6 m m ole-m ~3 s_1
nm
10~5 cm2 s“ 1
mmole · m -2 · day-1
10-4 (ml · dm-3 ) -0 5 · cm · s-1
m3 · mmole-1 · day-1
mmole · dm -3
mmole · dm -3
mmole · dm -3
mmole · m -3 · day-1
nm
Station I
1
2
1.5
1.379 10"6
439
0.50
1.65
55.31
3.09
28.93
124
318
194
444823
2.63
Station II
3
2
1.5
0.6219· 10“ 8
143
0.25
1.45
64.91
1.445
7.21
230
359
129
381409
5.14
c;
CW0 = (J0 - B ~ 1) - a + h J 0 D - \
C
— Cwo — Cot
K, = B 2 a t i - D - 1 - 0 - 2,
K . r^X1J™
W — IYW
J>
1 _ 1
\Jc(x i
VC0
*1 = —-------- 1----C (x i) = 0.05 ml dm -3 - the lowest oxygen concentration determinable by the
Winkler’s method (Vershinin ei al., 1990).
Table 2 illustrates an exam ple o f the choice o f the values o f the h and
m param eters at ST II, based on the equation system presented. From the
various preliminary adopted values o f h and m those for w hich the m agni­
tude o f the m inim um risk function was the lowest were chosen. T h e results
presented in Tables 1 and 2 can also b e illustrated graphically. Figures l a
and 2a present the results o f determ ination o f oxygen concentration in water
from the cham bers. T h e solid lines depicted in Figures l a and 2a correspond
to theoretical curves obtained on the basis o f the m odel. Figures l b and
2b illustrate an exam ple o f selection o f the optim al value o f the diffusive
sublayer h, expressed in cm .
All the calculated param eters o f oxygen exchange betw een the near­
b ottom water and the sediment at b o th the stations are listed in Table 3.
In general, all the param eters m ore or less in agreement with the literature
data.
F ig. 1. a empirical data and theoretical approximation o f oxygen distribution
in the chambers at ST I, b —graphical illustration o f the selection o f the h and n
parameters at ST I; 4- experimental data from chamber No. 1, © experimental
data from chamber No. 2
fu K' u ‘
ernp,rical data and theoretical approximation o f oxygen distribuiion in
the chambers at ST II, b - graphical illustration o f the selection o f the h and n
parameters at ST II. Denotations as in Figure 1
É
Plankton content at b o th stations differed significantly.
A t S T I the
num ber o f specim ens in 1 dm 3 was 1967313, while at ST II it was 922822,
which corresponds to 16.804 and 1.519 m g -d m -3 in term s o f biom ass, re­
spectively. These differences are reflected in the ox yg en uptake constants
in the near- -b o tto m water layer (ch am ber N o. 2 ). T h e K w constants span
tw o orders o f m agnitude. T h e K w param eter is related to the intensity of
oxygen uptake A w (T ab l. 3 ). T h e decrease in oxygen con cen tration in the
N o. 2 cham ber is due to tw o processes:
• respiration and decom position o f organic m atter (p h y to- and 7,00 plank to n ),
• m ineralization o f organic substances contained in water.
A t the beginning o f the m easurem ents w ater at the tw o stations can be
considered equal w ith respect to the chem ical substance con ten t (B olalek et
al., 1991). A ssum ing that oxygen con su m ption for the second kind o f the
described processes (let us denote it as A w0„ - oxygen con su m p tion for the
m ineralization o f the organic m atter in w ater) was similar at b o th stations,
while the uptake for the respiration processes and the d ecom p osition o f the
indigenous organic m atter ( A wr was prop ortion al to the plankton biom ass
( B P ) , it is possible to calculate what part o f the uptake is due to the first
and w hat to the second process:
A wj — A woaj -I- A tvfii,
A wi i = A wosn + A wr h ,
A Wosi = A W03u — A wos,
A wr i _ B P j
A wr i i
B P 11
Using the a bove considerations, data from Table 3 and data on biom ass,
it was calculated that A woa = 114 10- 6 m m ole O 2 -m - 3 -s - 1 ). Using sim­
ple prop ortion s it has been calculated that at ST I 26% o f the ox yg en is
consum ed in the processes o f m ineralization o f organic substances, while the
remaining 74% (325 · 10- 6 m m ole O 2 · m - 3 · s- 1 ) is used up in the processes
o f respiration and decom position o f the indigenous organic m atter.. A t S T II
these values are 80% and 20% (29 ■10- 6 m m ole O 2 · m ~ 3 · s- 1 ), respectivelyHall (1 984) determ ined that the size o f the diffusive sublayer was 1.0 m m
in tw o cham bers placed in autum n, and 1.7 m m in the cham ber placed in
winter. T h e value o f h obtained b y Hall et al. (1 9 8 9 ), using M n , Fe, Zn
and Hg isotopes as indicators, ranged from 0.7 to 1.9 m m . In our case the
thickness o f the diffusive sublayer was slightly smaller (T a b l. 3 ), m easur­
ing 0.5 m m at ST I and 0.25 at ST II. M ost probab ly the value o f this
param eter is related to biotu rbation processes, which depend am on g other
things on tlie am ount and num ber o f m eiofauna, and its m igrations. These
will be discussed later on.
Rutgers van der LoefF et al. (1984) revealed that oxygen p e r o r a t i o n
depth into the sediment ( x i ) is a few m m and depends on the season o f
a year. Hall et al. (1989) determ ined that at the beginning o f the experim ent
x i was 0.6 m m in autum n and 2.7 m m in winter. T hey found that this
was due to a greater oxygen uptake by the sediment in autum n. Slightly
higher values o f the depth o f oxygen penetration depths in to the sedim ent
were obtained using m icroelectrodes - ca. 2 m m (J0rgensen and R evsbech ,
1985). R evsbech et al. (19 80 b), examining oxygen concentration in the
sediments with the use o f m icroelectrodes, obtained differentiated values o f
the X* param eter depending on water tem perature (3 °C — 10 m m r 0 °C —
7 m m , 18°C - 5.5 m m ). Helder and Bakker (1985) obtained a value o f
10 m m with the use o f m icro- and m illielectrodes. T h e depths o f oxygen
penetration into the sediment in Puck Bay are close to the literature data.
A t ST I x x was 2.63 m m , while at ST II it was 5.14 m m T he differences
in the obtained values o f x x should be related to the different character o f
the b o tto m and to the bioturbation processes. A t ST I the m eiobenth ic
organisms occurred in the sediment to the depth o f 5 cm , while at S T II —
to 7 cm . T he conditions o f oxygen penetration in to the sediment are better
for sandy sediments (S T II), due to greater porosity and interstitial spaces.
A t the beginning o f the investigations the oxygen concentration in the
diffusive sublayer (C wo) slightly exceeded 300 /zmole · d m -3 T h e (C wo - C'a)
difference in this sublayer was larger at ST I (194 /xmole · d m - 3 ). This could
be due to the different character o f the b o tto m , and to the greater num ber
o f m eiobenthos, requiring oxygen. At ST I the organic m atter content in
the 0—5 cm layer was 2.48% , while at ST II 0.69% (Boialek et al., 1991).
The m eiofauna biom ass was approxim ately equal to 21.7 and 6.4 g - m - 2 ,
respectively.
Measurements o f oxygen concentration m icrogradients, diffusive sub­
layer thickness and oxygen penetration depth into the sediment are ex ­
tremely difficult to analyse because o f the instability and spatial n on ­
uniform ity o f these param eters. The problem is additionally com plicated
by the activity o f m acro- and m icrofauna, which loosens the sedim ent and
pumps water inside the ‘ burrows
B ioturbation by benthic animals plays
an im portant role in the distribution and exchange o f substances dissolved in
the sediment, particularly o f oxygen (A ller, 1982). J0rgensen and R evsbech
(1985) presented three vertical oxygen profiles within the sedim ent-w ater
interface (F ig. 3). O xygen concentration in the upper part o f the diffusive
sublayer was o f the order o f 250 /xmole · d m - 3 , while in the low er part it was
50-80 /x m o le -d m -3. O xygen penetration depth slightly exceeded 1 m m .
F ig. 3. An example o f the vertical oxygen distribution in the sediment (J 0 rgensen
and Revsbech, 1985)
A n on -typical oxygen distribution at the water sedim ent interface is illus­
trated in Figure 3c. Such a distribution occurred when the sedim ent was
cut with oblique channels drilled by m eiobenthos. W ithin the channels the
concentration continously changed according to the ‘ pum pin g ’ rhythm o f
the organism s.
3
17
37
33
1 - below the No. 1 chamber,
2 - below the No. 2 chamber,
3 - in the chamber surroundings.
11
1
II
Tardterada
Tola)
II
I
hopoda
204
1 97
1
14
II
J
Uarpacttcoda
1
5
15
27
II
1
Oslracoda
9
3
99
16
9
2
61
133
II
1
II
I
17
37
1
1
90
31
6
II
I
II
I
I
H
II
1
II
I
Bivalvta
Ohqocnaeia
Polychaela
NemaXoda
Gaslroincha
Turbeliarta
—jr— ---------------^
82
50
82
50
8
12
8
12
I
4
1
2
55
336
5
18
10
18
1 - 5
1
52
320
8
-
151
73
1
2
151
70
cm
1-2 *a
; -------- - -------------- ? --------------2--------------i ------------- 2
rorammijera
l
1
1
1
1
1
2
12
2
12
3
3
Lay«
2-3 cm
3
1
■
1
1
15
50
15
46
2
8
8
2
2
2
4
2
3
-
1
1
l
4
_
9
2
179
3 = 4 Ï 5 -------- 4 = 5 7 5 ---- 5 = 6 7 5 ---- 6 = ? 7 5 ---3
1
2
3 1 2 3 1 2 3
------- —------------- ——---------- —-
Table 4. The number of meiobenthic organisms in the Puck Bay sediments in the 2.25 cm2 section
188
121
-
1
8
1
25
119
1
-
11
2
—
-
25
57
-
-
-
2S1
57
2
Total
1
427
fifU
1
576
1
4
100
16
10
13
5
15
27
17
5
1
2
15
1
33
On the other hand, oxygen penetration depth is im portant for small ani­
m als, which require oxygen for respiration. These organism s are adapted to
m igration in the direction o f water m ore abundant in oxygen and fo o d . For
exam ple, Jorgensen and R evsbech (1 985) found ou t, using m icroelectrodes,
that P olych eta elegans form s channels protruding a few millimeters above
the sediment and assuring m ore oxygenized water for respiration.
A shift from aerobic to anaerobic or alm ost anaerobic conditions at the
end o f the m easurements within the sediment under the N o. 1 cham ber
(T abl. 1) caused drastic changes in the classification units and num ber o f
m eiobenthos (T abl. 4 ). A t the beginning o f the experim ent the m ost num er­
ous groups in the 0 -1 cm sedim ent layer at S T I were Oligocheta (4 8 .5 % ),
N em atoda (2 9 .9 % ) and H arpacicoida (1 3 .2 % ). In the deeper layers p racti­
cally the only group was Nem atoda. A t S T II N em atoda prevailed in all
the layers, although other groups also occurred.
Such a distribution o f
m eiofauna is prob ab ly determ ined b y the character o f the sedim ent and
the related possibilities o f oxygen penetration and m igration o f organism s.
A decrease in w ater aeration was accom panied by a com plete disappear­
ance o f aerobic organism s. Such a tendency m anifested itself at b o th the
stations. Distinct m igrations o f N em atoda from the deeper layers upwards
are noticeable in the exam ple o f ST I, where 113 specim ens were found in
the upper 2 cm o f the sedim ent at the beginning o f the experim ent, the
num ber increasing to 172 at the end. It is possible that the organism s liv­
ing initially in the upper layer o f the sediment died and were replaced by
the organism s from the deeper layers, accustom ed to anaerobic or alm ost
anaerobic conditions.
In P u ck B ay oxygen uptake by the sedim ent was equal to 53.31
m m o le -m -2 -d a y -1 (S T I) and 64.91 m m o le -m -2 -d a y -1 (S T II). T hese
values are higher than those obtained b y Hall (1984) for the B altic on the
Swedish coast (from 6.1 to 16.2 m m ole m -2 · d ay - 1 ). T h e Swedes obtained
their results for a b o tto m o f a different character and in the au tu m n -w in ter
season, when the rhythm o f biological life was slower, hence oxygen was
consum ed m ainly in the processes o f mineralization o f the organic m atter
contained in the sediment.
T h e entire oxygen uptake can be divided, with g o o d approxim ation,
into the part used up for the mineralization o f the organic m atter in the
sediment ( Jog), the part used for the respiration o f m acrobenthic organism s
( Jr b ) and m eiobenthic organism s (J r m b )'
h — Jaoi + J r b i + Jr m b i ,
J i i = Jsoi 1
+ J r b i i + Jr m b i i ■
It has been assumed that:
Jr - Jr b + Jr m b ,
Jr b i _ B B i
Jr b i i
Jr i _
BBh ’
BBi + BM Bi
J r ii
B B u + B M B ji ’
Jr m b i _ B M B i
Jr m b i i
Jaol
Jsoli
_
B M Bu ’
C orgi
C OTglJ
where:
BB
- m acrobenthos biom ass,
B M B - m eiobenthos biom ass,
C OTg - organic m atter content in the sediment,
I, II - ST I, ST II.
U nfortunately the m acrobenthos biomass in the region o f the measuring
stations was not determ ined during the experim ent. It follow s from the
literature (Legezyriska and W ik tor, 1981) that the m acrobenthos biom ass
in the ST I region is o f the order o f 150 g - m ~ 2, while in the S T II region
it is 550 g · m - 2 . T he approxim ate values o f the total benthos biom ass were
obtained by summing the m acro- and m eiobenthos biom ass. A fter solving
the above system o f equations it has been calculated that Jaoi = 38.62,
Jto'n = 10.73, Jr b i = 14.45, Jr b i i = 53.52, Jr m b i = 2.24 and Jr m b i i =
0.66 m m ole · m -2 · d ay - 1 . T h e obtained values o f oxygen uptake b y the
sediment equate to 38.62 and 10.73 m m ole · in-2 · d ay -1 and are close to the
literature data.
4, Conclusions
The results o f calculation o f the param eters o f oxygen exchange at the
water-sediment interface in Puck Bay, obtained on the basis o f the quasi-stationary m odel, remained in close agreement with the literature data for
the Baltic. On the basis o f the results o f oxygen concentration changes
during the cham ber experim ent, as well as the data on plankton biomass
in water and benthos biomass in the sediment it was possible to divide the
total oxygen uptake into those parts used up for the respiration processes
and those used for organic m atter m ineralization. T h e oxygen dem and in
water (A w) was 439· 10~6 (S T I) and 143 · 10~6 (S T II). These num bers
agreed with the phyto- and zooplankton biomass (16.8 and 1.5 m g - d r a '3,
respectively). This agreement allowed us to determine that at S T I 74% o f
the oxygen was consum ed in the processes related to plankton respiration,
while the remaining 26% was used up for the m ineralization o f the organic
m atter contained in w ater (at ST II these num bers were 20 and 80% , re­
spectively). A fter recalculating it has been found that 1 g o f plankton uses
69 //m ole oxygen per hour for respiration processes. L aboratory determ ined
oxygen consum ption b y the plankton (D onelly and Torres, 1987; G orsky
et al., 1987; Hirche, 1987) ranged from 4.5 to 2450 /zmole · g -1 · h -1 and
depended on the plankton type.
T he discussed param eters o f oxygen exchange at the water-sedim ent
interface rem ained in g o o d agreement with the character o f the sedim ent
and the m agnitude o f biotu rbation , as well as the num ber and biom ass o f
the m eiobenthic organisms.
O xygen uptake by the sediment was equal to 55.3 m m ole · m -2 · d a y -1
at ST I and 64.9 m m ole · m -2 · d ay -1 at ST II. This data is consistent with
the total m acro- and m eiobenthos biom ass (S T I - 172 g - m - 2 , S T II 55 g - m - 2 ) and the organic m atter content in the sedim ent (S T I - 2.48% ,
ST II - 0.69^6). This consistency allowed us to divide oxygen consum ption at
the water-sedim ent interface in to part used for m ineralization o f the organic
m atter in the sediment (J 0f>), that part used for m acrobenthos respiration
( Jr b )> and the part used for m eiobenthos respiration ( J r m b )· T h e follow ing
values o f the particular com ponents o f oxygen uptake were obtained at S T I:
J0, = 38.6, J r b = 14.5, Jr m b — 2.2 m m ole · m -2 · d a y - 1 ; at S T II these
values were JOB = 10.7, Jr b = 53.5 and Jr m b = 0.7 m m ole · m -2 · d a y - 1 .
It has been determ ined that the am ount o f oxygen consum ed b y the ben­
thos is 104 /zmole g -1 -h - 1 . For instance, Policheta N ereis virens uses
155 n m o le - g -1 - d a y -1 (K irstensen, 1989).
T h e high level o f agreement betw een the values o f oxygen uptake for the
respiration o f plankton and benthos obtained in this w ork, and in the liter­
ature data, allowed us to establish that the m ethod o f cham ber experim ents
can be applied for the approxim ate in situ determ ination o f the values o f
oxygen uptake by particular organism s, provided that the num ber o f the
measuring stations and o f the biological determ inations is increased.
A ck n o w led gem en ts:
The authors wish to thank Dr. M aria Szymelfing for the m eiobenthos anal­
yses, and M . Sc. M ałgorzata Przybylska for the analyses o f p h y to- and
zooplankton.
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